Camshaft question

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AJ/FormS said:
That is a metering rod carb, right? ; make sure that the metering rods are staying down at idle, and also at low rpm/ modest throttle. That takes manifold vacuum; and if your idle-timing is retarded, or if the Vcan has been disconnected, good luck.
The stock convertor will also make this just a bit of a chore.

To see how much Part Throttle timing your engine wants , rev it up in Neutral/Park to just below your stall-rpm and hold the rpm there while;
You advance the timing a lil. Keep advancing, and dialing back the rpm, until additional timing produces NO additional rpm.
Now, put a light on it at the rpm that you were keeping it at. Subtract THREE degrees, and write it down. That is the Part Throttle timing that she will want, at that rpm.
Suppose your stall is 2400.
Choose 2200 for your target rpm.
Suppose your engine tops out there at 50 degrees.
How are you gonna get it?
Typically, your base-timing will be in the range of 14 to 20 degrees.
Typically your Power-Timing will be 36 degrees after say 3600.
That leaves about 20 degrees to be brought in by the centrifical system.
Typically, you bring it in at the rate of ~.8 degree per 100rpm, beginning around 1000rpm.
Thus, those 20 degrees will not be "all-in" until (20/.8)+ ( the start point of say 16*@1000)=3600
Therefore, at 2200; the centrifical will be; (2200 less 1000)/100, times .8degree,=9.6 degrees
So then, your all-in, before Vacuum advance will be 16 + 9.6= 25.6 degrees.
From the target of 50*, you are thus 24.4 degrees short, which HAS to come from the Vacuum Advance system.
Well, the Vcan is able to be modified out to 22* for sure ( I have done that), to possibly 24* ( Trailbeast has done that). Suppose you can get all 24. Then Badboom, yur in business.
But if your can only makes 20*, then you gotta get the rest from somewhere else. The easiest place is to just advance your base timing to 4* from 16 to 20* Badaboom. But hang on, if you do that, then your Power-Timing will also jump up 4 degrees to 40*, which, in a Mope, is practically guaranteed to cause detonation. So then, you gotta go back inside the D and limit the centrifical to 4* less, which would be 16*.
Badaboom, now you have a starter curve.
Now you get to fine tune it.
Happy HotRodding.

PS, someone mentioned to disconnect the Vcan until you get your PowerTiming bugged out. This is probably a good idea if this is your first tune.
Sometimes the engine will except 36* of Power-Timing at 3200 rpm, sometimes not until 3800, so you gotta hunt around to find the switch-point that your engine likes. Once you find it, write it down.
Sometimes you can/ sometimes you have to; swap some base-timing with the PowerTiming, either way to keep the combo, under load, from detonating. When you do that, you always gotta go back and re-engineer the Idle-Timing. And finally, Once the Power-Timing switch point is established, and the centrifical advance has been selected to establish the Idle-Timing, you still get to play with the "rate of advance" in-between those two points. Usually but not always, it sorta depends on your stall, you want to bring it "all-in" as fast as she will accept it without detonating. This will energize low rpm operation.
However;
Since WOT operation is NOT gonna be your primary mode of operation, at least it is not mine,lol, IMO, if you have choices to make, it is always better to bias them for your mode of operation, which typically, will be at 50% throttle or less. To help me with this, after I have selected the PowerTiming, I disable the secondaries, and do the rest of the timing-tuning on the Primaries only. This just takes the guess work out of it, and keeps your speeds down during testing. Your 3.23s and tires will get you about 60mph @3800 in SECOND gear, which is about where you can stop your Power Testing. Keep an eye out for JohnnyLaw.

It might help you to know that your engine, any engine, has exactly one perfect crank position that it wants peak cylinder pressure to occur at. This is said to be between ~25 and 28 degrees AFTER TDC. All your timing systems are designed to try and achieve that. Your job is to target that window and hit it as often as you can, and for as many load sttings as you can. Trying is about the best that you can do.
And finally; your WOT butt-dyno will not be able to tell the difference in the first two gears, if you are "bang-on", or up to three degrees short of optimum, so don't sweat the last three degrees. To actually find it, your dyno operator probably found it, and your top speed will point to it, but with 3.23s, that will be really really dangerous. The qtr-mile trapspeed is also a good guide.
Most of us just slap 34 to 36 degrees on it, and good enough........ especially with a stroker, lol. It will save you mucho time .
Somebody said to get your idle-engineered First before anything else. I agree, because if you don't, you will never be happy, and the car will spend too much time in the garage. I know it might sound daunting to get the tune into her, but when you finally do, you'll forgive her; I guarantee it.
Yknow, my wife complained everyday about being pregnant, but the truth is, as soon as she was healed up, she forgot all about it, and she went on to have more babies, lol. You'll forget all about the hassles too.
If it makes you feel better, I have a 367/4speed/with 3.55s. She will idle down to 550 in first gear, pulling herself around all day. and with the 750DP up top, will take WOT anytime, exploding in a noisome cloud of fury. And this, with 11/1 Scr and a 230/237/110 cam. Edit; and it does this with just 5* of advance.
I never begrudge her the time it took to make that happen.
You also will forget, lol.
Click to expand...
Wow, thanks for the tutorial! I will start digging into this very soon.
 
Killer6 said:
Right, so far no idea what the mystery cam is, or idle vacuum..
Click to expand...

Here is the Mopar 340 Cam specs that I use as a baseline to compare other cam specs to.
It's a good basic cam, with good performance and a decent idle.

Rpm Range: Idle to 5000 rpm.
114* Lobe Centers (less valve overlap)

As camshaft selections move up the rpm scale, the valve overlap increases giving the choppy idle.
(as the cam centerline numbers decrease, the valve overlap increases)

Mopar340Cam.png
 
George Jets said:
Here is the Mopar 340 Cam specs that I use as a baseline to compare other cam specs to.
It's a good basic cam, with good performance and a decent idle.

Rpm Range: Idle to 5000 rpm.
114* Lobe Centers (less valve overlap)

As camshaft selections move up the rpm scale, the valve overlap increases giving the choppy idle.
(as the cam centerline numbers decrease, the valve overlap increases)

View attachment 1715997792
Click to expand...
That LSA will suck the life outta that stroker, & I'm not sure exactly why the OP feels the current unidentified cam is a bit too large, idle quality only or....? "torque like crazy" sounds like it ain't too big for the engine, I'll wait for the OP to dial in the tune & reveal what the current cam specs are, before judging what if any cam change would be an improvement.
 
^^^^^Exactly right. You put a 114 LSA cam in a turbo engine....maybe.
 
Until you come across people who make power with wide LSA's that don't follow everyone else.......
 
And where are the examples, the tests of LSA comparison testing where wider 114 LSA make more power. Not interested in opinions, facts please.
 
Bewy said:
And where are the examples, the tests of LSA comparison testing where wider 114 LSA make more power. Not interested in opinions, facts please.
Click to expand...
You mean magazine articles set up to sell camshafts.........:lol:
 
The way you tell is you advance or retard the cam at the track and that tells you where it wants to be the combo matters
why listen to anyone else thats about as usefull as a sunroof in a submarine
before someone tells me the lsa is ground into the cam everyone knows that as well as what a tighter or wider lsa does
some just will say oh i dont trust that test on there happy dyno yada yada
 
No, I mean tests. Valid tests.....
And even if a magazine [ or any other entity ] presented the test results, why would it matter if the object of the test was to show how LSA changes power, by having identical cams ground, changing only the LSA.
 
there are videos ive watched them std na motor 450 hp there abouts tighter added torque with very lil loss up top
101 106 110 114 121
110 stole the show
plenty of articles as well
drag motor 108 106
test aslo showed nitrous did not want a wide lsa as well as more exhaust duration and lift epic fail
my nitrous motor had a 108 lsa
the track is still the place to do it or tighten or loosen the lash
combo dependent as well as matching the intended use
 
Bewy said:
No, I mean tests. Valid tests.....
And even if a magazine [ or any other entity ] presented the test results, why would it matter if the object of the test was to show how LSA changes power, by having identical cams ground, changing only the LSA.
Click to expand...
You think that just changing the LSA and running a test is valid? You think that that some how proves something to be able to make blanket statements like 106 is better than 114?

There are far too many variables in a running engine to make blanket statements like a tight LSA always makes more power, what if the Duration. Lift. ICL or any other metric isn't ideal to begin with..............

Maybe the Prostock guys need to get Vizard on board because they have no idea on this stuff nor do guys like Mike Jones and Harold Berkshire who grind them for them on 118 LSA's
 
Hysteric said:
You think that just changing the LSA and running a test is valid? You think that that some how proves something to be able to make blanket statements like 106 is better than 114?

There are far too many variables in a running engine to make blanket statements like a tight LSA always makes more power, what if the Duration. Lift. ICL or any other metric isn't ideal to begin with..............

Maybe the Prostock guys need to get Vizard on board because they have no idea on this stuff nor do guys like Mike Jones and Harold Berkshire who grind them for them on 118 LSA's
Click to expand...

Oh brother.
 
I forget which cam MP produced in both 108 and 114 variations 484 or 508. All I know is the 114 wasn't even good to use as a doorstop. JUNK

Don't know what they did for ignition timing on those test, but, I'd bet all three of them would like a different initial timing setting. No mention of that in the article, IIRC.
 
crackedback said:
I forget which cam MP produced in both 108 and 114 variations 484 or 508. All I know is the 114 wasn't even good to use as a doorstop. JUNK

Don't know what they did for ignition timing on those test, but, I'd bet all three of them would like a different initial timing setting. No mention of that in the article, IIRC.
Click to expand...
as i recall the 484 was 108 moons ago then changed to 110
 
Hysteric,
Yes, quite valid to just compare LSAs. Your example just adds to the number of tests that I have seen that tighter LSA is better, & my comment was for this build.
However, as a general comment on NA engines built by the average hot rodder, tighter is better & is born out by numerous tests. [ tighter being 104-110 LSA]. There are engines where wider is better, & if you actually bothered to read Vizard's stuff, he quotes instances/engines that require wider LSAs. He states this: '..all out race engine with 582 ci & a 15.5:1 CR. The CR is four ratios higher than the 11.5 base number, so you need to spread the LCA by 8 degrees'. And...'LCAs from 112 to 116 were tested in 1 degree increments.'
Even the cam grinders are getting the message.....
My 1984 Crane catalog has 13 HFT cams listed for the SB Chev; only 2 are 110 or tighter. My 2010 catalog has 47 HFT cams listed. 27 are 110 LSA or tighter; & the tightest, which is 104 LSA, also has the shortest duration 184 @ 050. Hmmmm.
I never take much notice of Jones...
And by the bay it is Brookshire, not Berkshire.....
Finally, I would like a dollar for every hot cam installed & the new owner heralding the success...'Runs great'. 'More power than ever'. And the list goes on.... But never compared to anything else in an objective comparison.
 
Bewy said:
Hysteric,
Yes, quite valid to just compare LSAs. Your example just adds to the number of tests that I have seen that tighter LSA is better, & my comment was for this build.
However, as a general comment on NA engines built by the average hot rodder, tighter is better & is born out by numerous tests. [ tighter being 104-110 LSA]. There are engines where wider is better, & if you actually bothered to read Vizard's stuff, he quotes instances/engines that require wider LSAs. He states this: '..all out race engine with 582 ci & a 15.5:1 CR. The CR is four ratios higher than the 11.5 base number, so you need to spread the LCA by 8 degrees'. And...'LCAs from 112 to 116 were tested in 1 degree increments.'
Even the cam grinders are getting the message.....
My 1984 Crane catalog has 13 HFT cams listed for the SB Chev; only 2 are 110 or tighter. My 2010 catalog has 47 HFT cams listed. 27 are 110 LSA or tighter; & the tightest, which is 104 LSA, also has the shortest duration 184 @ 050. Hmmmm.
I never take much notice of Jones...
And by the bay it is Brookshire, not Berkshire.....
Finally, I would like a dollar for every hot cam installed & the new owner heralding the success...'Runs great'. 'More power than ever'. And the list goes on.... But never compared to anything else in an objective comparison.
Click to expand...
Vizard on 106* LSA vs 112* LSA in a BBC - Don Terrill’s Speed-Talk

Mike Jones:

Pretend the story was written by someone you've never heard of.
How does it match what you've seen in the real world.

I've done many dyno tests were we change nothing but LSA, and then move each cam around to where it runs the best. I've come to different conclusions then David.
Click to expand...

And Harold:

My opinion is that you should buy whatever Dave Vizard recommends, because you probably deserve it.......
Tell your cam man what LSA you want, and he will grind it for you.
This way, your car will run its' fastest.
However, I recommend everywhere from 107 to 118, just depending.
Click to expand...

Too many variables........
 

Hysteric,
How many cams did Harold actually compare & where are the test results??
The problem as I see it is that people like Harold & Jones grind cams that they have designed/recommended. Owner[ s ] install cam[ s ] & reports back that engine is making more hp. So that means it is a 'winner' right? But other cams may have done better, but we will never know....
That is why a huge number of combinations need to be tested to get meaningful & accurate data. And that is exactly what DV did....
 
Probably wasn't Vizards 25000.......
 
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