340 dyno chart thoughts

[skep419]

We're all at hogwarts learning magic. Comp cams aka Lord Voldemort............

This is great stuff

 

[Lustle]

Looks like you're referring only to seat duration specs when looking at overlap, which will tell you when there is .006" of valve lift having a negative effect on vacuum. Think hard now, how much do you actually suppose this amount of valve lift effects things? It isn't very much

This is the main reason why the common spec of "0.050" exists. it is used as a point of reference where it can be considered that valve lift actually starts to perform it's function, allowing gases from the intake runner to enter the cylinder and for pressures between the two to equalize.

Put in simpler terms, how long the valve overlap period occurs can be seen with duration numbers alone. But how far they are open requires both seat duration AND duration @ .050"

We know that more degrees of overlap will reduce vacuum.
We also know that you lose more vacuum through a big hole than a small hole (like a completely open valve compared to a nearly shut valve. for an extreme example)

So if we have two camshafts with the same degrees of overlap as measured by seat-to-seat specs, but one having more overlap at 0.050". The one with more degrees of overlap @ 0.050" is reaching higher valve lifts earlier as they open and keeping them open for longer as they are on the closing side of the ramp, even if the total duration is the same. Since overlap happens at the beginning of one valve and the end of the other, this is an important factor.

Even with the same seat duration, a higher spec @ 0.050" will have the valves be open FURTHER during the overlap period and as such will have less vacuum at idle.

Uh no. When I calculate overlap. I use the valve events. That's how overlap is calculated.

Obviously you missed the entire point of my post. And it is this.

20-30 years ago - big duration/lift = late valve events = **** idle, **** streetability, **** daily driver.

Today - big duration/lift =/= late events =/= **** idle, **** streetability, **** daily driver.

Cams have come a long way in the last 20/30 years. You can have a bigger duration cam, with more lift, with better valve events. And that makes them street able, compared to the cams of past.

 

[frosty_the_punk]

Uh no. When I calculate overlap. I use the valve events. That's how overlap is calculated.

Obviously you missed the entire point of my post. And it is this.

20-30 years ago - big duration/lift = late valve events = **** idle, **** streetability, **** daily driver.

Today - big duration/lift =/= late events =/= **** idle, **** streetability, **** daily driver.

Cams have come a long way in the last 20/30 years. You can have a bigger duration cam, with more lift, with better valve events. And that makes them street able, compared to the cams of past.

Gotta remember that cam designs are much better now. Valve events and such aren't nearly as drastic compared to duration/lift as they once were. For example. Look at the mopar P4120655 cam. 252 @ 50 duration. 110 LSA. Yet the overlap is 76. Very similar duration to the hughes. Yet much higher overlap. And lift is down!

Uh no. When I calculate overlap. I use the valve events. That's how overlap is calculated.

Obviously you missed the entire point of my post. And it is this.

20-30 years ago - big duration/lift = late valve events = **** idle, **** streetability, **** daily driver.

Today - big duration/lift =/= late events =/= **** idle, **** streetability, **** daily driver.

Cams have come a long way in the last 20/30 years. You can have a bigger duration cam, with more lift, with better valve events. And that makes them street able, compared to the cams of past.

I did read your post. and i do get what you're trying to say. modern lobe design has a faster rate. ie more duration @ 0.050" relative to seat/advertised duration.

This is fantastic for getting lots of performance, but it doesn't change the fact that more duration @ 0.050 will still affect your idle vacuum. (everything else being equal)

Let me show you a picture i quickly made up which demonstrates this in an easy to understand visual way. The shaded area is valve overlap.

Note how Both camshafts have 60 degrees of overlap @ seat duration (each graph is 60 deg wide).

Also note the where horizontal 0.050" line intersects with the RED closing of the exhaust valve, and then again with the BLUE opening of the intake valve line. these intersections are 10 degrees apart on the first camshaft and 30 degrees apart on the second.

The shaded area is overlap. As you can see, even though both of these cams have "60 degrees" overlap according to advertised duration numbers... the second camshaft has a crapload more valve lift during that entire 60 degrees. This increases the effect of overlap and reduces idle vacuum. Any questions?

 

[frosty_the_punk]

It's definitely possible. For example. Looking at hughes STL5054AS-8. It has 250/254 duration. 108LSA. Guess what the overlap is? 66. Very mild compared to the duration. My XE274H has an overlap of 60. And it's 230/236 duration with 110LSA.

There's a very simple explanation for this.

By my calculations. if the STL5054AS-8 camshaft is 60 degrees overlap on 108 LSA with 250/254 @ 0.050" as you mentioned, that means it must be 274/278 advertised duration (i couldn't find them listed on their webpage).

So you probably think that the hughes cam is way faster ramp rate than the comp cam, right?

Hughes, 278/282 advertised duration, 250/254 @ 0.050"
Comp, 274/278 advertised duration 230/236 @ 0.050"

Not so fast.

The hughes STL5054AS-8 camshaft is a solid cam, the COMP XE274H is a hydraulic.

The standard for measuring Solid cams is 0.020" for advertised duration.
The standard for measuring Hydraulic cams is 0.006" for advertised duration.

if you get a camshaft, ANY camshaft.. and measure it's duration by both these specs. you will have more degrees at 0.006" compared to 0.020".

In the example you gave, it has little to do with how aggressive the lobe is and is almost entirely because of the difference between how each one is being measured in a different way.

 

[frosty_the_punk]

Then install the ****** 4-6* ahead. What don't you get? What I'm saying is exactly what you are either too stupid to understand or you don't want to LEARN.

This doesn't change the overlap period. Are you going to try to tell everyone that overlap has no effect on idle vacuum now as well?

We are talking two cams with relatively low overlap. If you can't make a 284 MP idle and be streetable you need to quit and go golfing.

No we are talking about two cams with completely different overlap values to each other when you consider how much valve lift is occuring during that overlap period. I'm not saying I can't make either cam idle and be streetable, but the smaller duration cam with the wider lobe separation will idle better and be more streetable every single time. You're the one saying it won't.

You still have NOT explained why I can use 255 at .050 and get idle and vacuum that YOU can't? I posted my numbers. It's even on a 105 LSA. That's at least 5* ahead of what you think is the greatest thing since pussy.

I have explained EXACTLY why you can get a 255 solid cam on 105LSA to idle similarly to much smaller hydraulic cam. VALVE LASH. IT'S A THING.

Cams have come miles and miles and it's stupid to contend that a ******* passenger car head needs anything wider than a 108 is pure ignorance. And YOU continue to preach ignorance. Youre so ate up by the numbers that you can't see the numbers. ******* crazy.

anything over 108 lobe separation is no good for a passenger car? In that case maybe you should write a letter to all the major camshaft companies, as well as all vehicle manufacturers telling them they should never run a wider LSA than 108. Clearly you must know something they don't.

Now I'm going to post WHY comp, the crap company that it is, decided 110 LSA was the best thing since pussy and it had ZERO to do with performance.


As comp grew in size to the monolithic sloth it is today, they had to do what crane had already done...own a company that made cores. If you are grinding cams at the rate comp does, you can't wait on cores. I don't recall all the machinations that went on, but comp ended up either buy a core company or went into an exclusive contract with a supplier. Now comp had all the cores it needed, all the time.


Since most HFT and SFT cores are cast iron, they are EXACTLY THAT.....cast. The lobes, and therefore POTENTIAL LSA's are already there. We all KNOW that there are times when a 100*LSA or maybe even a 98* LSA is called for. On the other end of the spectrum, especially with the onslaught
of power adders, and specifically turbos, the LSA naturally has to get wider. A mild BB turbo engine may call for 113-114 LSA. I've seen as high as 120 LSA on a turbo alky deal, but it was well over 500 CID.

So, between, let's say, 102 and 114 LSA is where most cams will fall. To make a core that will take that spread is very expensive. And, it takes longer to grind. Unless you are somewhere in the middle. So the marketing jerks got with the engineering nerds and THEY decided for COST and PRODUCTION that 110 LSA would be the de facto standard. Comp had now birthed, blessed and baptized the living abortion of the production LSA.

It saves money because the cores can be made with less LSA split between them. It took less time to grind. They could make bank. Now the marketing pukes had to sell it, and so a media blitz raised from the pits of the marketing sewer. And all the sheep went to the slaughter. With them , they brought multiplied sheep, ripe for the killing by regurgitating this vile lie. But who cares? Money is made, they average guy is happy with "what he has" because he doesn't test, and engine builders are happy because they can stock a few generic junk **** cams and the customer will swallow them down like a 2 dolla ***** on a three piece suited John.

In 2016 and beyond, it has become almost impossible to get a core that will go tighter than 107. 106 is a push. Anything narrower than 106 and you are pretty much **** out of luck, unless you are somebody who is somebody. Engine builders no longer want to spend time trying to reeducate the customer from 3 decades of marketing stupidity. So they give the customer what he wants, even though the customer, most of whom are just casual with the hobby, have no ******* idea what they want, let alone what they need.


So engines are underachievers, and all the fools applaud and say bravo to an engine that is down on power, down on torque, has the torque curve too wide and makes RPM like a flat head ford. Yes, bravo indeed.


The facts are it's not just me bitching about guys giving up power. I PAY for power. It's what I expect. Many people for years have been trying to overcome the inertial ignorance that comp has blow right up our collective asses. It's not just me.


But just like the church of Scientology, it's hard for folks to admit that what they are doing is wrong, at least from theperspective of performance. All leave the religion of it to the rest of the Gentiles to argue out.

I would say that 99% of all aftermarket performance camshafts fall between 107 and 114 LSA because that's what suits most applications best. not because of anyone's marketing campaign or some kinda brainwashing by comp's evil henchmen. if you want something unusual, you might have to pay a bit more and go billet if you think the gains will be worth the expense.

The LSA triangle is the single most misunderstood, misapplied and abused function of cam timing I can think of. And that's because it starts with your CYLINDER HEADS. Nothing else. If you can't make that connection, I can't help you. Every single cam event is based on YOUR cylinder heads, induction and exhaust system.

What's there to misunderstand or abuse?? it's a graph which shows a camshaft's lift for both lobes relative to crank degrees of rotation. my picture was just an example generateed by a computer. but when ordering a custom camshaft you can get these created using an actual camshaft's lift values throughout it's full rotation, with the numerical values for reference. It's literally telling you EVERYTHING about the size and shape of your camshaft.

Sorry for the long, sometimes gruff rant. But it is stupid to keep hashing over numbers when ONE guy takes everything LITERAL and types a tome on the nuances of his pet theories.

No need to apologize, It really doesn't bother me. However, i have no pet theories. What i do have is a modest understanding of camshaft theory.

With that in mind, I take BACK my comment for the OP to use the 284 MP cam. F-T-P says it will never work, so therefore, it is so.

I didn't say it will never work, i said it wouldn't make the same idle vacuum as the much smaller cam which OP is already using.

I will go back to what I always have said. Buy a CUSTOM CAM. Don't get ate up by the LSA if it is more narrow that what the brainwashed masses claim is de facto. Rise above their ignorance. The earth is NOT flat. Never was. You have been duped by production oriented manufacturing and Madison Avenue pukes.

It's time to leave the dark ages of cam timing and get to the light.

Keep fighting the good fight, brother. They may take our lives, but they can NEVER take our narrow lobe separation angles!

 

[crackedback]

The dick swinging contest continues... LMAO

 

[txstang84]

If nothing else, I get to read some more fun entertaining and educational stuff...between this one and the "don't understand cams" thread, they're pure gold.

 

[JBurch]

MAKE IT STOP!!!!...........MAKE IT STOP!!!!!........MY EYES, MY EYES!!!!!!!...............................................

Little did the OP know what kind of **** storm he was inviting when he asked......"What do you think?"

It's been 27 posts since the OP commented and its been little more than esoteric mental masturbation of cam profiles, LDA's, centerlines, installed centerlines bla, bla, bla, bla, bla!

To those who felt he left so much on the table; crowd source/crowd fund WHAT YOU desperately feel HE NEEDS, SO YOU, CAN FEEL GOOD, ABOUT HIS BUILD. Get in you car, get on a plane, take it to him, GIVE IT to him.

I stand by what I said back in post 43: Street only engine, it will be fun to drive any where, any time he wants. Strong torque curve low in the rpm band says to me, rear tire wear may be an issue. I want to know where he buys tires so I can invest. Should deliver a strong dividend.

To Fez440: Drop that sucker into a car, have fun, be careful, nice build!!

 

[fez440]

Lol thanks. yes things seemed to get out of control here not what I was looking for when i 1st ask about my build. some people really know their cams I was a bit lost in what they were discussing. I did learn some stuff though so all is good. in the end I think it's sweet engine. This is my 1st mopar so I'm happy regardless. It has good vacuum for my power brakes. torque curve is good to me. sounded great when running. we are always wanting more power aren't we lol but to much and things get out of control especially in a older car. I appreciate all the comments though. will be posting more once I get the car back from paint. to share my build. hopefully I don't raise a ruckus then to lol. might be good info to for some else that what's to build something similar or where to improve on it

 

[MOPAROFFICIAL]

Lol thanks. yes things seemed to get out of control here not what I was looking for when i 1st ask about my build. some people really know their cams I was a bit lost in what they were discussing. I did learn some stuff though so all is good. in the end I think it's sweet engine. This is my 1st mopar so I'm happy regardless. It has good vacuum for my power brakes. torque curve is good to me. sounded great when running. we are always wanting more power aren't we lol but to much and things get out of control especially in a older car. I appreciate all the comments though. will be posting more once I get the car back from paint. to share my build. hopefully I don't raise a ruckus then to lol.

As long as you like it... that's all the matters, making the customer happy with the end result should always come first.

 

[yellow rose]

This doesn't change the overlap period. Are you going to try to tell everyone that overlap has no effect on idle vacuum now as well?


No we are talking about two cams with completely different overlap values to each other when you consider how much valve lift is occuring during that overlap period. I'm not saying I can't make either cam idle and be streetable, but the smaller duration cam with the wider lobe separation will idle better and be more streetable every single time. You're the one saying it won't.



I have explained EXACTLY why you can get a 255 solid cam on 105LSA to idle similarly to much smaller hydraulic cam. VALVE LASH. IT'S A THING.



anything over 108 lobe separation is no good for a passenger car? In that case maybe you should write a letter to all the major camshaft companies, as well as all vehicle manufacturers telling them they should never run a wider LSA than 108. Clearly you must know something they don't.



I would say that 99% of all aftermarket performance camshafts fall between 107 and 114 LSA because that's what suits most applications best. not because of anyone's marketing campaign or some kinda brainwashing by comp's evil henchmen. if you want something unusual, you might have to pay a bit more and go billet if you think the gains will be worth the expense.



What's there to misunderstand or abuse?? it's a graph which shows a camshaft's lift for both lobes relative to crank degrees of rotation. my picture was just an example generateed by a computer. but when ordering a custom camshaft you can get these created using an actual camshaft's lift values throughout it's full rotation, with the numerical values for reference. It's literally telling you EVERYTHING about the size and shape of your camshaft.



No need to apologize, It really doesn't bother me. However, i have no pet theories. What i do have is a modest understanding of camshaft theory.



I didn't say it will never work, i said it wouldn't make the same idle vacuum as the much smaller cam which OP is already using.



Keep fighting the good fight, brother. They may take our lives, but they can NEVER take our narrow lobe separation angles!

View attachment 1714997122

Just so someone doesn't come along and read this **** and actually THINK that LSA is a vacuum killer, and idle killer and all that silly ****, I'll spell it out one more ******* time.


The biggest killer of low speed torque, idle and vacuum is seat to seat duration. If you have a cam with 314 degrees of seat timing, but has an at .050 of 220 that cam has SLOW ramps. It will RPM to the moon with an LSA wide enough but it will RPM slow and be a pig. This is what GM did with the JUNK 30-30 cam that some GM guys think is the best thing since Pussy. Junk is junk.


Now, take that same 220 at .050 and make the seat timing 270. You can pull the LSA in a bit, it will still idle and have vacuum. Seat to seat duration is the biggest killer there is.

The next biggest killer, and just as important is the INTAKE VALVE CLOSING point. The later you close the intake , the shittier the idle and the lower the vacuum is. This is the number ONE killer of all things guys ***** about. Yet all the heros blame LSA when it isn't LSA that is causing the issue.

Soooooooo, if you take the same cam, and change the INTAKE CENTER LINE, you change the INTAKE VALVE CLOSING point.

One more time. If you can't make the MP 284/.484 cam idle well and run power brakes, hit the links. It's not the cams fault. It's the tuners fault.

Unreal.

 

[yellow rose]

As long as you like it... that's all the matters, making the customer happy with the end result should always come first.

Educating the customer SHOULD come first, but some of them ain't teachable.

 

[Lustle]

I did read your post. and i do get what you're trying to say. modern lobe design has a faster rate. ie more duration @ 0.050" relative to seat/advertised duration.

This is fantastic for getting lots of performance, but it doesn't change the fact that more duration @ 0.050 will still affect your idle vacuum. (everything else being equal)

Let me show you a picture i quickly made up which demonstrates this in an easy to understand visual way. The shaded area is valve overlap.

Note how Both camshafts have 60 degrees of overlap @ seat duration (each graph is 60 deg wide).

Also note the where horizontal 0.050" line intersects with the RED closing of the exhaust valve, and then again with the BLUE opening of the intake valve line. these intersections are 10 degrees apart on the first camshaft and 30 degrees apart on the second.

The shaded area is overlap. As you can see, even though both of these cams have "60 degrees" overlap according to advertised duration numbers... the second camshaft has a crapload more valve lift during that entire 60 degrees. This increases the effect of overlap and reduces idle vacuum. Any questions?

View attachment 1714997120

So you're agreeing with me then? Or maybe you didn't understand what I'm trying to say. I have no idea why you keep using advertised duration, when I use valve events. Advertised duration is just that an ADVERTISEMENT.

As I said. Valve events determine idle quality. Not duration. Not LSA. Yes, generally with more duration idle is worse. And with tighter LSA idle is worst. BUT that's because of valve events, they determine idle. Period. Part of my point with that, is that as cam technology got better, you could have larger duration with better idle because of improved valve events.

There's a very simple explanation for this.

By my calculations. if the STL5054AS-8 camshaft is 60 degrees overlap on 108 LSA with 250/254 @ 0.050" as you mentioned, that means it must be 274/278 advertised duration (i couldn't find them listed on their webpage).

So you probably think that the hughes cam is way faster ramp rate than the comp cam, right?

Hughes, 278/282 advertised duration, 250/254 @ 0.050"
Comp, 274/278 advertised duration 230/236 @ 0.050"

Not so fast.

The hughes STL5054AS-8 camshaft is a solid cam, the COMP XE274H is a hydraulic.

The standard for measuring Solid cams is 0.020" for advertised duration.
The standard for measuring Hydraulic cams is 0.006" for advertised duration.

if you get a camshaft, ANY camshaft.. and measure it's duration by both these specs. you will have more degrees at 0.006" compared to 0.020".

In the example you gave, it has little to do with how aggressive the lobe is and is almost entirely because of the difference between how each one is being measured in a different way.

Well the overlap on the solid was 66.

And I use intake valve closing angle at zero (ok well .006") to find overlap. Because that's how you should do it. Yes, I calculated that on the hughes cam.

So once again, my point is that valve events are what you need to look at. Not advertised duration. Because that's an ADVERTISEMENT.

STOP focusing on advertised duration. And start focusing on WHEN the valves actually open and close.

The next biggest killer, and just as important is the INTAKE VALVE CLOSING point. The later you close the intake , the shittier the idle and the lower the vacuum is. This is the number ONE killer of all things guys ***** about.

This was exactly my point. To bring up the cams I mentioned before?

Hughes STL5054AS-8 250/254 -108ºLSA - Intake valve closing angle 64.
Comp XE274H - 230/236 - 110 LSA - Intake valve closing angle 63.

Which just proves that you can have a crazy big duration, but still have mild valve events. Pay attention to valve events. They tell you what the cam is doing and when it's doing it.

 

[fez440]

so.. based on my setup if i were to change the cam which hydraulic one would you recommend. and what size of carburetor to go with it? i assume if i wanted more power from my engine later on these 2 things would be the best place to start. everything else should be fine?

 

[yellow rose]

So you're agreeing with me then? Or maybe you didn't understand what I'm trying to say. I have no idea why you keep using advertised duration, when I use valve events. Advertised duration is just that an ADVERTISEMENT.

As I said. Valve events determine idle quality. Not duration. Not LSA. Yes, generally with more duration idle is worse. And with tighter LSA idle is worst. BUT that's because of valve events, they determine idle. Period. Part of my point with that, is that as cam technology got better, you could have larger duration with better idle because of improved valve events.



Well the overlap on the solid was 66.

And I use intake valve closing angle at zero (ok well .006") to find overlap. Because that's how you should do it. Yes, I calculated that on the hughes cam.

So once again, my point is that valve events are what you need to look at. Not advertised duration. Because that's an ADVERTISEMENT.

STOP focusing on advertised duration. And start focusing on WHEN the valves actually open and close.



This was exactly my point. To bring up the cams I mentioned before?

Hughes STL5054AS-8 250/254 -108ºLSA - Intake valve closing angle 64.
Comp XE274H - 230/236 - 110 LSA - Intake valve closing angle 63.

Which just proves that you can have a crazy big duration, but still have mild valve events. Pay attention to valve events. They tell you what the cam is doing and when it's doing it.

There are too many people that are getting mixed up in my answers. In going to try and stop doing that. Wish I knew how to quote just part of a post and then answer it. Copy and paste is too tedious for me.


Anyway, I agree not to get all caught up in advertised numbers, but they do matter. Once the valve is off the seat about .020-.025 you start getting some flow. If you up the pressure it happens earlier. We know that at overlap, the pull on the intake port can be as high as 120 inches on a decent prepped street head. So with long slow ramps you get into issues with reversion. That's why GM in the aforementioned 30-30 Duntove junker and some other junk GM cams that I can't recall the nomenclature on, had LSA's as wide as 116. It was to help with the bi seat to seat numbers. They were **** cams.

 

[Lustle]

so.. based on my setup if i were to change the cam which hydraulic one would you recommend. and what size of carburetor to go with it? i assume if i wanted more power from my engine later on these 2 things would be the best place to start. everything else should be fine?

I wouldn't recommend hydraulic. They are really just OK. And there's really no price advantage to either.

If you are fine with popping the valve covers off once or twice a year. Go with a solid. It's seriously not that hard to check lash. Take the car, pickup a couple buddies from their places, stop at the beer store and grab beer. Come back home and check them. It's a 2 beer job at most. The driving around get's it nice and warm. If you **** hundreds, go with a solid roller. You've got the heads for it.

What cam you get depends ENTIRELY on what you want. Off idle throttle and lots of torque? 230's duration, .550 area lift. Hot street cam with low gears and a 4 speed/high stall convertor? 240's duration, .550-600 lift. High RPM, screamer 340? 250's duration, .600+ lift. Honestly your heads can support all 3. And I'm oversimplifying the choice. A lot.

The best thing to do? Call the cam guys. Your cam choice will be determined by (in no order):

Rear gears
Convertor/4 speed
Car weight
Engine static/dynamic compression
Head flow
Intake
Driver style
Street vs track time
And a whole wack of things.

Take a look at this - Page Title

That will give you an idea of what goes into picking a cam.

As for carb? That will also depend on cam. The more RPM's you're pulling, the more carb you need. But a solid START on a stock stroke 340 is the 750 double pumper. 8 out of 10 times that carb is a drop on with minor adjustment. BUT the more you pull out of the engine, the more you need. There are guys running 950 carbs on their setups. I think someone on here is running a 1050 dominator on his 340 and loves it.

 

[Lustle]

There are too many people that are getting mixed up in my answers. In going to try and stop doing that. Wish I knew how to quote just part of a post and then answer it. Copy and paste is too tedious for me.


Anyway, I agree not to get all caught up in advertised numbers, but they do matter. Once the valve is off the seat about .020-.025 you start getting some flow. If you up the pressure it happens earlier. We know that at overlap, the pull on the intake port can be as high as 120 inches on a decent prepped street head. So with long slow ramps you get into issues with reversion. That's why GM in the aforementioned 30-30 Duntove junker and some other junk GM cams that I can't recall the nomenclature on, had LSA's as wide as 116. It was to help with the bi seat to seat numbers. They were **** cams.

To quote part of a post, just delete between the quote boxes (those little [ symbols that say quote inside. Then it'll only show what's in that area. Try messing around with it.

As for cams, advertised numbers do matter. I'm not trying to imply they don't. Obviously they come into play. BUT I'm saying calculating things like overlap, and trying to determine idle quality off something that can be measured in several different ways (.0006, .050, etc etc). Is not the way to go about it. Looking only at duration, advertised or not, is a great way to overlook a lot about the cam. As you said, some people look at a 250 duration cam and say "That's way to big". But it's not that simple.

As for GM? I try not to touch that stuff! lol

 

[fez440]

i enjoyed reading thought this tread in the link as well. some good info for people. somewhat comparable to mine i think. its great to see actual dyno numbers to me cuz then you are getting proof not just talk
340 Head/Cam upgrade before vs after with results

this was also a good read
RustyRatRod's Guide To Hot Rod Bliss

what would you recommend for a fuel pump for this engine ?

 

[crackedback]

Since answers to questions don't seem to be forthcoming...

The tune is miles off is my guess.

Back to the dick swinging contest

 

[frosty_the_punk]

Just so someone doesn't come along and read this **** and actually THINK that LSA is a vacuum killer, and idle killer and all that silly ****, I'll spell it out one more ******* time.

The biggest killer of low speed torque, idle and vacuum is seat to seat duration. If you have a cam with 314 degrees of seat timing, but has an at .050 of 220 that cam has SLOW ramps. It will RPM to the moon with an LSA wide enough but it will RPM slow and be a pig. This is what GM did with the JUNK 30-30 cam that some GM guys think is the best thing since Pussy. Junk is junk.


Now, take that same 220 at .050 and make the seat timing 270. You can pull the LSA in a bit, it will still idle and have vacuum. Seat to seat duration is the biggest killer there is.

Oh, Gee. Don't you think maybe the reason why increasing duration screws up your idle might be because it increases overlap?

I mean, really. Take a step back and think about what "increase duration" means.

It means the lobes open earlier and close later.

If the exhaust is still closing while the intake is opening. that means more duration means they are both simultaneously open for more crank degrees and are also at higher lifts.

Newsflash, pretty much all street/strip cams have a positive overlap figure in degrees @ 0,050" lift. that means the valves are simultaneously open to 0.050" of lift or more for a certain number of degrees of the crankshaft.

Don't you think that is just a little more telling than how many degrees the valves are both open 0.006"? where they don't actually FLOW anything?

The next biggest killer, and just as important is the INTAKE VALVE CLOSING point. The later you close the intake , the shittier the idle and the lower the vacuum is. This is the number ONE killer of all things guys ***** about. Yet all the heros blame LSA when it isn't LSA that is causing the issue.

Soooooooo, if you take the same cam, and change the INTAKE CENTER LINE, you change the INTAKE VALVE CLOSING point.

I disagree. Let's use an example.

Cam 1, 230/230 on 105LSA IVC 40 ABDC
compared to
Cam 2, 230/230 on 115LSA IVC 50 ABDC

IF the first important thing is duration, we eliminated that by keeping them equal.

If the second most important thing is having an early IVC for a good idle with high manifold vacuum, why is it that Cam 2 has a LATER IVC but actually idles better and has more vacuum?

I'll give you a hint

Cam 1, EVC 10 ATDC. IVO 10 BTDC.
Cam 2, EVC 0 ATDC, IVO 0 BTDC.

 

[frosty_the_punk]

So you're agreeing with me then? Or maybe you didn't understand what I'm trying to say. I have no idea why you keep using advertised duration, when I use valve events. Advertised duration is just that an ADVERTISEMENT.

When i say "more duration", most people can understand that this will "Open both the intake and exhaust several degrees earlier and close them several degrees later"

Just as they understand that "wider lobe separation" means "open and close the exhaust several degrees earlier and open and close the intake several degrees later".

As for the word "advertised" in "advertised duration". That actually gives a manufacturer license to use any arbitary lift value to spec their cam in degrees of duration. But typically it's SAE, which is 0.006" for a hydraulic cam and 0,020" for a solid..

If you don't believe me about the 0.020 duration being less than 0.006. by all means, purchase a solid camshaft and dial it up on some V-blocks. I'll guarantee that the duration they advertised you will be at a lift of 0.020" and whatever duration you are able to measure at 0.006" will be much greater.

The reason why there is SAE standards for measuring duration is that it's important for a customer to be able to compare one manufacturer's camshaft specs to another's without it being a "250 degrees from brand X is about the same as 240 from brand Y" type deal.

As I said. Valve events determine idle quality. Not duration. Not LSA. Yes, generally with more duration idle is worse. And with tighter LSA idle is worst. BUT that's because of valve events, they determine idle. Period. Part of my point with that, is that as cam technology got better, you could have larger duration with better idle because of improved valve events.

You seem largely confused by this so I'll spell it out for you. duration, lobe separation and installed advance determine the valve events, not the other way around.

These three numbers tell us EVERYTHING about the valve timing events.

More duration is worse because it causes a later exhaust closing and/or an earlier intake opening (depending on whether the duration is greater on just one or both lobes). Since these events overlap. (they creatively called this "overlap"!)

PS, "more overlap" is also easier to say!

Well the overlap on the solid was 66.

And I use intake valve closing angle at zero (ok well .006") to find overlap. Because that's how you should do it. Yes, I calculated that on the hughes cam.

again, how much flow do you think a valve is capable of when it is open 0.006"?

How much flow do you think a valve is capable of when it is open 0.050"?

If you think one flows crap-nothing and the other flows quite a bit, Don't you think maybe overlap is going to have a bigger effect at the lift value where the valve flows quite a bit compared to the one flowing crap-nothing?

So once again, my point is that valve events are what you need to look at. Not advertised duration. Because that's an ADVERTISEMENT.

STOP focusing on advertised duration. And start focusing on WHEN the valves actually open and close.

mmk, You DO realise that duration is a measurement of how many degrees of crankshaft rotation the cam is keeping the valve open for. right? Hence, duration is a major influence on valve events. You can't look at one and not be looking at the other. You may as well be telling me to stop looking at the floods and concentrate on the water!

This was exactly my point. To bring up the cams I mentioned before?

Hughes STL5054AS-8 250/254 -108ºLSA - Intake valve closing angle 64.
Comp XE274H - 230/236 - 110 LSA - Intake valve closing angle 63.

Which just proves that you can have a crazy big duration, but still have mild valve events. Pay attention to valve events. They tell you what the cam is doing and when it's doing it.

Where did you get these figures from?
The intake closing angle for a 250/254 - 108 LSA is 53 ATDC
The intake closing angle for 230/236 - 110 LSA is 45 ATDC.

Also, again, the solid cam will have less duration @ the valve on both the intake and exhaust because 10-12 degrees will be taken up by lash.

If they give an advertised duration it will be at 0.020" giving a lower duration figure relative to 0.050"

Let me try to explain it another way.

0.020" is closer to 0.050" than 0.006" is to 0.050"

Therefore the duration specs at 0.020" are going to be closer to the specs at 0.050 than the 0.006 specs will be.

This isn't a faster ramp rate, this is measuring the ramp rate two different ways.

Again, on the hydraulic cam when lobe is opening the lifter moves, the pushrod moves, the rockers move and the valve moves.

On a solid cam, the lifter moves, the pushrod moves. the rocker moves, but the valve doesn't move until the other end of the rocker arm has moved enough to take up the lash, whatever that number is. about 0.020 or somewhere in that ballpark. The lash is taken up and THEN the valve moves. ie the valve moves a lot later than the lifter.

The same is true when a valve closes, it happens earlier than the lifter. Together, they eat about 10-12 degrees. there's just no getting around this.

That is why they're measured differently. I can explain it for you but I can't understand it for you.

 

[moper]

so.. based on my setup if i were to change the cam which hydraulic one would you recommend. and what size of carburetor to go with it? i assume if i wanted more power from my engine later on these 2 things would be the best place to start. everything else should be fine?

Crane 693511 cam
340/360 Performer intake
Edelbrock 650 Thunder AVS 1806

 

[fez440]

Crane 693511 cam
340/360 Performer intake
Edelbrock 650 Thunder AVS 1806

What about a fuel pump? Any suggestions?

 

[roccodart440]

What about a fuel pump? Any suggestions?

Do you want electric or Mechanical? I'd recommend electric but I know there are some people that are passionate about their mech pumps.

 

[fez440]

I'm thinking for now I would use a mech. But what is a good electric pump since we are talking about it?