340 dyno chart thoughts

[roccodart440]

In ran a holley black forever. Now I run an aeromotive A1000 submersible.

 

[moper]

Carter M6866 mechanical.

 

[AJ/FormS]

I believe I understand all of what's being said, so perhaps to make this easier on the OP, riddle me this;

Let's say a guy needed an HFT of around 230/237/110cam (.050). Installed at 108, this makes the .050 intake events look like this; opens at 7 before and closes at 43 after. The advertised SAE @.006 might be 276/284. Since we know that flows below .050 are minimal we don't much care about them. However, these specs are useful to determine Dcr and idle quality. So again in at 108 the SAE intake events now are 30before and 66after. The 66 after can be plugged into a Dcr calculator and the result can indicate a lil something about how the engine will idle and how it will behave at low revs. The exhaust side events are open at 74,closed at 30.
So to recap,
the .050s numbers are;
int;opens at 7*before closes at 43*after for total 230*
Exh;open at 50.5* before,closes at 6.5* after for 237*
and overlap of 7+6.5=13.5*
The SAE numbers are;
intake opens 30before,closes 66after,for total 276*
exh opens 74before,closes 30after,for total of 284*
and overlap of 30+30=60*
What this shows us about the intake lobe, is that from SAE to .050 is a difference of 276-230=46degrees and 23 of 'em are on either end. That means the ramps are climbing; (.050 less .006) =.044 in 23 degrees or .044/23=.001913inch per degree,average.

Now let's say you want that same cam size, cuz the engine needs it, in actual valve event specs, but you don't want the 66* of ICA that comes with the HFT. So the thought of using a SFT enters your head, on account of their faster ramps.

This is where the confusion comes in.Because of the two different ways these cams are rated, it is impossible to directly relate them.
So now what's a guy to do? You gotta call somebody, and it better be somebody who has actually done it and has measured it, or the guy that builds cams, or the guy who builds engines and knows this stuff.
Am I wrong?

 

[yellow rose]

Nope.


But once both lifters get to .050 lift, it's all about acceleration rate. You can't say a SFT is 10* less at .050 because of the ramps.

That was one of the remarks in this thread.

The other thing there is confusion on is reversion. Which is not the same as over scavaging. Two separate things that get lumped together.

One is the result of late intake closing. The other is an exhaust issue. But we call them both by the same issue, and crutch over scavaging with LSA.

By the way....naw I think I'll start a thread!

That makes jpar happy. And I live for that.

 

[AJ/FormS]

I hear you on scavenging and reversion. But on a typical streeter neither of these really become issues.
Even the 292/508/108 is not a big deal,as to reversion. and with typical headers and street pipes,"over scavenging" should not be a problem. I ran twin full-length 3inchers with that cam, in about an 11.3- 367, and while it liked it's gas allrighty, I blamed it on my driving style.lol. I only had that cam one summer, finding it waaay too big for me. With 3.55s it was soft off the line and by the time she woke up I was speeding in first gear. Fun?heck ya! But too soft below 30ish MPH;even with 11.3 Scr. I moved it three times at least, with little to no improvement. It was pretty good with 4.88s tho. Finally, I yanked it.
Don't laugh,but I replaced it with a 223/230/110. I loved that cam.I had to swap out that thin head gasket tho. I loved that cam.It was a beast.lol

 

[roccodart440]

Many, MANY times, a smaller or milder cam in a well matched combo and chassis is far more fun to drive and enjoy on the street.

 

[273]

Many, MANY times, a smaller or milder cam in a well matched combo and chassis is far more fun to drive and enjoy on the street.

I don't understand this need for some to push the cam size and even CR especially when they want to be stingy on stall and gears. Obviously max acceleration isn't you primary concern.

I figure if your willing to gear it and stall it then build it if not go bigger cid or in this case less cam.

 

[JBurch]

Many, MANY times, a smaller or milder cam in a well matched combo and chassis is far more fun to drive and enjoy on the street.

Yeh...........not every build has to be for Top Fuel or Pro-Stock............

 

[yellow rose]

I don't understand this need for some to push the cam size and even CR especially when they want to be stingy on stall and gears. Obviously max acceleration isn't you primary concern.

I figure if your willing to gear it and stall it then build it if not go bigger cid or in this case less cam.

Exactly. If you like 3.23's and a stock converter, why are you buying other than a stock cam?

 

[frosty_the_punk]

Exactly. If you like 3.23's and a stock converter, why are you buying other than a stock cam?

I think there are performance gains to be made in a stock application. when a manufacturer builds an engine they have to take into account things which a motoring enthusiast might have less concern for, like emissions, fuel economy, expected service life and most of all the almighty dollar!

let's face it, in stock form your average 1970's V8 engine isn't built with any kind of performance in mind, they had cubes and that was enough to make them satisfactory for their intended purpose.

These days there are plenty of cam kits available for a variety of vehicles which will provide a modest increase in performance in an otherwise stock application, especially by owners of later model vehicles who wish to retain their factory fuel injection instead of going for a standalone engine management system.

The same thing applies to our old mills too, Even when you order a "stock cam" you will almost always get something better than OEM.

So I'd say the opposite to you, there's really no reason to run a camshaft designed in circa 1968 on a fresh build.

 

[yellow rose]

I think there are performance gains to be made in a stock application. when a manufacturer builds an engine they have to take into account things which a motoring enthusiast might have less concern for, like emissions, fuel economy, expected service life and most of all the almighty dollar!

let's face it, in stock form your average 1970's V8 engine isn't built with any kind of performance in mind, they had cubes and that was enough to make them satisfactory for their intended purpose.

These days there are plenty of cam kits available for a variety of vehicles which will provide a modest increase in performance in an otherwise stock application, especially by owners of later model vehicles who wish to retain their factory fuel injection instead of going for a standalone engine management system.

The same thing applies to our old mills too, Even when you order a "stock cam" you will almost always get something better than OEM.

So I'd say the opposite to you, there's really no reason to run a camshaft designed in circa 1968 on a fresh build.

No, that's what I say.

I never say to run an off the shelf cam.


BUT, because people are cheap asses, and most don't give a **** about making power, I say to hell with it, run a 68 340 cam and be happy.


There even a thread on here where guys are arguing about making too much power!

 

[AJ/FormS]

Yeah, I got carried away with the desk-top dyno. Chasing a horsepower number on a streeter is um for the rich and weekend warriors, not so much for the average Joe who likes to drive everywhere,all the time.I was quite happy with that lil 223. When it dropped two lobes I moved up to a 230/237/110 and while it's ok now with a 10.97 starter gear, and the overdrive, there was a time I wondered if I hadn't made a mistake.......

 

[yellow rose]

Yeah, I got carried away with the desk-top dyno. Chasing a horsepower number on a streeter is um for the rich and weekend warriors, not so much for the average Joe who likes to drive everywhere,all the time.I was quite happy with that lil 223. When it dropped two lobes I moved up to a 230/237/110 and while it's ok now with a 10.97 starter gear, and the overdrive, there was a time I wondered if I hadn't made a mistake.......

Hind sight is always 20/20. You did at the time what was best.

 

[AJ/FormS]

What no Hockey-stick Humor?
That's the nicest thing you ever said to me..........I'm almost touched.

 

[yellow rose]

What no Hockey-stick Humor?
That's the nicest thing you ever said to me..........I'm almost touched.

Well ****, I let one slip by.

Its freaking cold here, and cold where you are.

Yeah, that's it, the cold made me forget. I won't let that happen again.

 

[fez440]

[/QUOTE]

You can port match it, but it is different. It will never be the LD340.

I know you won't like to hear it, but when the port is small, then you make it big at the flange, it's a pretty good flow loss. It's counterintuitive but, you are better off if the intake manifold is bigger than the port. Ideally the port at the plenum should be bigger than the port at the flange. And the port at the flange should should be the same size as the port. BUT, if you have to have a mismatch, the intake should be bigger than the cylinder head, without the hour glass shape from a port match.

Can anyone elaborate on this ? I was assuming that port matching this intake to the heads would make it the same as a ld340.isn't that the only differance between a ld4b and a ld340? Would a different intake make that much of a differance?

 

[273]

The ld4b is has 273/318 runners a performer has 360 runners but narrows to 318 port size.

So you can port out a lb4b but the weakest link wins but on the other hand performer wins cause the runners are 360 size so a little porting is needed.

 

[Lustle]

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.

Advertised duration was created to be just that. An advertisement. Many many moons ago, guys would advertise their cams in catalogues and magazines. But there was no standard as to how things were measured. Like you mentioned, now there is. But guess where it came from? Advertisements. It forced all cam companies to measure the same way for advertisments, so guys couldn't claim more duration but not mention they were measuring it differently than their competitor. It's really that simple.

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!

Not confused. I'm just right. You obviously don't understand valve events. How do you calculate duration? You use valve events. How do you calculate valve events? By measuring the cam. How do you calculate LSA? You use valve events. How do you calculate valve events? Once again, by measuring the cam. Valve events are GROUND INTO THE CAM. They happen at the same point on the cam NO MATTER WHAT. The only way to change them, is to regrind the cam. Even if the cam is installed advanced or retarded, those valves STILL open and close at the same time relative to each other. Can you figure out valve events with out knowing the duration? Yes. Can you figure out the duration without knowing the valve events? No. So guess which determines which.

And no, duration, LSA, advance, etc etc, don't tell you EVERYTHING about valve timing events. They give you a good estimate of how that cam will perform. But obviously they don't tell you everything. Hence why a cam with the same duration, same lift, same LSA - can have different valve events and different drivability.

I really don't know how else to explain that to you.

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?

I don't care about flow. I care about events. Hence I put them on the same playing field.

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!

And if you don't know valve events, can you determine duration? No. Valve events determine duration. Without knowing valve events, you don't know duration. Therefore duration does not influence valve events. Duration is a product of how long that certain valve event is occurring. No valve event? No duration.

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.

Uhhhh right from the manufacturer. So, you're wrong.

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.

Once again. This is why I calculated them both at .006. To reduce it right down to almost base circle. To get the FULL valve event. This is what DCR calculators use to find out DCR. Hence this is why I use it. And yes. I understand they are measured differently. Hence why I calculate them both at .006. To get the full angle. I don't know how else to explain that to you but I can't understand it for you.

 

[Mattax]

I'm thinking for now I would use a mech.

Mechanical will work fine. The Carter M6866 is a stock replacement but IF the free flow fuel volume posted on the S*mmit website is correct, then that not keep up on full throttle 1/4 mile run. A 340 with a cc280 cam will need about 28 gal/hr peak. You can calc the exact number for your engine at any rpm since you have the lbs/hr from the dyno data. Just divide by 6, it will be close enough for this purpose. The nice thing about the M6866 pump is the max pressure (aka cutoff pressure) 5.5 psi
Carter's M6902 may be a good alternative. There seems to be some internet talk, for whatever its worth, that the cutoff pressure is over 7psi. That would be a problem if true. However they were originally set with a spring that relieved pressure at 6psi, which most carbs can handle.
The M6270 carb is 7.5 psi and definately would need a regulator.
I've had good luck with a Holley mechanical, 12-360-11, 110 gph series, no regulator.

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?

My opinion is spend time on tuning what you have. Looking at the dyno data, the manifold pressure didn't go up during the runs. However the AFR dropped .4, so get that flat and then work it for max power. Whether max power is going to be at 12.5 or 12.9 or something else only will be found by testing. Use the same fuel if possible. Take it to the drag strip and have fun.

i have a question about the ld4b that i have on the engine. this intake has smaller ports then the 340 intakes. is the full chamber smaller on the ld4b or is it just at the opening where it enters the heads? i ask because i was told he port matched the intake to the heads so would that not make it the same as the ld340 intake or no?

The LD340 has bigger runners than the LD4b. I did very similar to you, same cam in a 340, had a Street Dom port matched to the 340. Now have a different cam in it but with the LD340 intake. In retrospect would suggested using the 4b without porting up, but its too late. Small runners help on the street (autocross rally, etc) by keeping velocity up at lower rpms so less fuel drops out and less volume needed to keep the walls wet. The discontinuity of the intake to head port *might* have helped reduce reversion at idle and low rpm (ie under 2500).

For the rpm range this cam gets happy at, I'd not use a plain ole performer. The Ld4b was a good choice for street/strip, the only one that might do better at both lower rpm and higher rpm is the Performer RPM . If you start trying taller intakes, keep an eye on hood clearance.

As to your initial question, Since it was mostly a break-in excercise, keep the data as a baseline.
If there were some weird divergences on the VE, BSFC, Fuel to AFR etc, then that would be a flag for something being off. The EGTs and the spark plugs will let you know if the WOT distribution was fairly even.

 

[mopowers]

Carter's M6902 may be a good alternative. There seems to be some internet talk, for whatever its worth, that the cutoff pressure is over 7psi. That would be a problem if true. However they were originally set with a spring that relieved pressure at 6psi, which most carbs can handle.

Unfortunately, Carter no longer makes the M6209 pump. It's too bad, because that was a good pump.

 

[fez440]

Thanks for the replies

 

[frosty_the_punk]

Advertised duration was created to be just that. An advertisement. Many many moons ago, guys would advertise their cams in catalogues and magazines. But there was no standard as to how things were measured. Like you mentioned, now there is. But guess where it came from? Advertisements. It forced all cam companies to measure the same way for advertisments, so guys couldn't claim more duration but not mention they were measuring it differently than their competitor. It's really that simple.

That's what i just said. Advertisements used to be all over the place until a standard duration measurement was implemented. Now they all advertise at the standard. The standards came from SAE. you DO know what SAE is don't you?

Lustle, you need to get it through your skull that a camshaft's specs are determined long before you install that camshaft into an engine with valves. They design a camshaft using specs and they produce the camshaft using specs.

One day if you ever care to look, you will find that duration is measured as a specified lift for a specified number of degrees and this is measured @ the lobe/lifter, NOT the valve.

Think about that for a second. I'll just repeat it. Camshaft duration spec has nothing to do with the valve. It is simply measuring... the camshaft. you know.. the long bumpy thing? It actually still exists when it's not installed in an engine and can even be measured that way! Fancy that!

Now, getting back to those SAE standards we talked about.

The standard for measuring duration on hydraulic cams is 0.006" of lift AT THE LOBE.

The standard for measuring duration on Solid cams is 0.020" lift AT THE LOBE.

I know that thinking isn't your strong point, I've explained the difference lash makes in how a solid cam's duration specs translates to actual valve timing TWICE now and still you don't get why you can't compare a hydraulic to a solid using the same 0.006" specs. So this time i drew you a picture, Good luck!

 

[frosty_the_punk]

Hughes STL5054AS-8 250/254 -108ºLSA - Intake valve closing angle 64.

Uhhhh right from the manufacturer. So, you're wrong.

This is the manufacturer's description of that cam?
Hughes Engines

Show me where it says IVC 64 ABDC on this page please.

All the values on this page are correct for the duration and lobe separation with 4 degrees advance.

To get IVC 64 ABDC you will need 11 degrees retard. good luck with that.

 

[Lustle]

That's what i just said. Advertisements used to be all over the place until a standard duration measurement was implemented. Now they all advertise at the standard. The standards came from SAE. you DO know what SAE is don't you?

I literally just said that. Thanks for repeating me?

Lustle, you need to get it through your skull that a camshaft's specs are determined long before you install that camshaft into an engine with valves. They design a camshaft using specs and they produce the camshaft using specs.

You mean like how I said valve events are ground into a cam? Camshaft specs are VALVE EVENTS. And yup, they are determined before the cam is ground. Just like I mentioned before. You do know what camshaft grinding is, right? You do know what they use to determine the grind, right? I've been mentioning this in my posts, are you sure you are reading them? Here it is again:

How do you calculate duration? You use valve events. How do you calculate valve events? By measuring the cam. How do you calculate LSA? You use valve events. How do you calculate valve events? Once again, by measuring the cam. Valve events are GROUND INTO THE CAM.

Here you are with that comprehension thing again:

One day if you ever care to look, you will find that duration is measured as a specified lift for a specified number of degrees and this is measured @ the lobe/lifter, NOT the valve.

You mean how I just mentioned that duration is determine by valve events as ground into the cam? I'm starting to notice a pattern here, I think it's with your comprehension. ONCE more now here:

By measuring the cam.

LOOK AT THAT. I mention measuring the cam, before you did! Gee, repeating me again?

Think about that for a second. I'll just repeat it. Camshaft duration spec has nothing to do with the valve. It is simply measuring... the camshaft. you know.. the long bumpy thing? It actually still exists when it's not installed in an engine and can even be measured that way! Fancy that!

Are they bumpy for a reason? OH maybe it's because things are GROUND INTO THEM. And measuring the cam? What a radical... wait, you mean like I mentioned. Here it is again for you:

By measuring the cam.

So now this.

View attachment 1715001683 View attachment 1715001684 View attachment 1715001685
Now, getting back to those SAE standards we talked about.

The standard for measuring duration on hydraulic cams is 0.006" of lift AT THE LOBE.

The standard for measuring duration on Solid cams is 0.020" lift AT THE LOBE.

I know that thinking isn't your strong point, I've explained the difference lash makes in how a solid cam's duration specs translates to actual valve timing TWICE now and still you don't get why you can't compare a hydraulic to a solid using the same 0.006" specs. So this time i drew you a picture, Good luck!

Awww, is someone getting frustrated cause they are wrong?

It's ok to admit when you are wrong frosty.

I understand lash. I understand how it takes up. I get all that. You seem to be the one with the comprehension problem here.

Also. I noticed how you forgot to quote a large part of my post. Is that perhaps cause you were wrong? Things like "can you determine duration without knowing valve events". BTW the answer is no. Easy to skip over stuff you got wrong, right?

This is the manufacturer's description of that cam?
Hughes Engines

Show me where it says IVC 64 ABDC on this page please.

All the values on this page are correct for the duration and lobe separation with 4 degrees advance.

To get IVC 64 ABDC you will need 11 degrees retard. good luck with that.

I notice something here. You once again leaving something out that you got wrong. Let's quote your original post again, shall we?

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.

So are we talking ABDC? OR ATDC? They are different. You, you do know that right? When I quoted the valve closing figures earlier, I said:

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

Now. I maybe made the "mistake" of not mentioning ABDC here. I assumed it was pretty clear what I was talking about. Considering the intake valve only closes ABDC. So I'll just assume you meant ABDC (even if you didn't. I did).

So I said. I got them from the manufacturer. You then say "hughes website doesn't say that". Completely forgetting about the Comp cams website. What did the Comp say? Oh that right. It said 63. Right from the manufacturer. How ever you came up with 45, you're wrong. By a lot. Once again easy to skip stuff that you were wrong about, isn't it?

Now lets look at your intake valve closing angle on the hughes. You insist it is 53 ABDC, right? So you are telling me. A cam shaft with 250/254 @.050 duration, .588/.600 lift, with a lash of only .010/.012. Closes the intake valve 10 degrees sooner than a cam with 230/236 @.050 duration, .488/.491 lift? Interesting.

One reason I like to use valve events. Is to calculate DCR. DCR calculators use seat to seat measurements. You know what seat to seat is, right? Is .020 seat? Hmm nope, but .006 is about as close as you can get. So. Lets punch that Hughes cam (as measured by you) into the DCR calculator. We will use my engine as an example. It's simple. 10:1 compression. .040 overbore/stock stroke. KB243 pistons. J heads with a valve job, minor cleanup, and some work on the turn. Pretty basic setup. Also I am at 3000 feet.

Now, DCR with the current XE274H cam:
Your dynamic compression ratio is 7.44:1 .
Your dynamic cranking pressure is 145.44 PSI.
And DCR with the hughes cam (again as measured by you):
Your dynamic compression ratio is 8.01:1 .
Your dynamic cranking pressure is 160.14 PSI.

So. If I put that hughes cam, with its 250/254 duration, and .588/600 lift. I will have MORE cranking pressure? And MORE DCR? Over a smaller cam?

Wow, maybe I should just stick the biggest cam I can in there. Obviously according to your calculations. It will work!

But hey, lets try my calculation of 64 degrees:
Your dynamic compression ratio is 7.38:1 .
Your dynamic cranking pressure is 143.90 PSI.

WHOA! The cam with MORE duration has LESS DCR and cranking pressure? That doesn't make sense. Does it? I mean, it's not much different, but 63 to 64 isn't huge. But obviously some of that is because of lash (yes I'm aware of what it is), LSA, and lobe design. I think we all (except maybe you frosty) know that LSA closes that intake a little sooner. Letting you get more cylinder pressure. And the XE274H is from what, 78? There have been numerous camshaft design improvements since then.

I hope you are realizing at this point, that your calculations are incorrect.

In the end. This is going to be my last hijack post on this thread. Obviously OP didn't intend for this conversation. If you wish to continue to be proven wrong frosty, please feel free to start another thread and I will feel free to debate further with you.

 

[frosty_the_punk]

omg for heaven's sake!

Look at this website and scroll down to the part where it says
"Cam timing @ 0.050 tappet lift"
Hughes Engines

Now go to this website and look at where it says "Valve Timing @ 0.006 Lift"
20-224-4 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts

Do you realise that duration @ 0.006 is ALWAYS going to be a higher duration figure than the same camshaft measured @ 0.050". You DO know that they're different right? why are you trying to compare two cams but using different methods to measure them? Seems pretty silly right?

Congratulations, you're measuring a big cam with a big ruler (duration @ 0.050") and coming up with a numerical measurement for the result.

Then you're comparing it to a much smaller cam, but instead of using the same ruler, you're making the ruler smaller as well (Duration @ 0.006") and then getting the same/similar numerical measurement as a result.

Seriously, If you MUST compare this solid cam to this hydraulic cam, Use the same type of measurement for both. go to a cam calculator website and type in the comp cam's 0.050" specs for 230/236 duration, along with the 110 lobe separation and the 4 degrees of advance. Let me know if you still think that the IVC is 63 ABDC.

Even still, the lash will make the solid cam have less duration @ the valve than it has at the lobe due to lash. So like i keep saying the entire comparison is pointless.

Newsflash, you will NEVER see a solid cam advertised as seat duration. or @ 0.006". The closest thing you are going to get is probably going to be duration @ 0.020" lobe lift. Makes it pretty freaking hard to compare a hydraulic to a solid doesn't it?

If you want to talk about dynamic compression ratio, you are going to need the hughes cam's specs @ 0.020", the website doesn't give these. only the 0.050" specs

And yes, earlier I did state "ATDC" for the IVC when I should have written ABDC. You knew that's what we were both talking about since there is no such thing as an IVC ATDC. Sincere apoligies there.

This was fun, I honestly feel like you will soon where you went wrong in this example. You have the right idea about most things. I'm sure you will have a clearer understanding soon. No hard feelings. Let's do it again some time.