That's an interesting point I don't remember the boys from Engine Master's covering. How much actual power is it worth to degree a cam vs going "dot-to-dot"?
CK5
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All things Drag Racing.
- Thread starter 500$k5
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Not sure I agree with that one, It feel like I'm the redneck that degrees the cam, not the preppy guy.
And that depends on how far off it is how much it matters. Many times its dead on and it wouldn't change a thing, sometimes its off 2 degrees, sometimes 4. I would guess 80% of the time I don't move it because it's as close as it will get. I use 9 keyway sprockets with 2 degree increments.
It shifts the whole curve toward peak power (retarded) or low end torque (advanced).
Many cams are ground with 4 degrees advance built in (the ICL is 4 degrees smaller than the LSA). In those instances when you put it straight up, it should be 4 degrees advanced, if not, you move it until it is.
But if I have one that degrees in at 5 degrees advanced and I could move it to 3, most of the time I would leave it at 5 unless it's a high RPM race setup.
And that depends on how far off it is how much it matters. Many times its dead on and it wouldn't change a thing, sometimes its off 2 degrees, sometimes 4. I would guess 80% of the time I don't move it because it's as close as it will get. I use 9 keyway sprockets with 2 degree increments.
It shifts the whole curve toward peak power (retarded) or low end torque (advanced).
Many cams are ground with 4 degrees advance built in (the ICL is 4 degrees smaller than the LSA). In those instances when you put it straight up, it should be 4 degrees advanced, if not, you move it until it is.
But if I have one that degrees in at 5 degrees advanced and I could move it to 3, most of the time I would leave it at 5 unless it's a high RPM race setup.
Same. I’ve degreed every cam I put in and never saw the need to change it.
The funny thing is, I have never had to move the cam timing on a stock crank engine build. But with aftermarket cranks it's more like 1/3 of the time I have to move it. Which, its usually the opposite, the aftermarket quality engine pieces like pistons and rods are usually more precise. But for some reason not the keyway on the balancer or something in the tolerance stackup. And this is true for both high end cranks that are over $2,500 for one crank and budget cranks that are $300.
And for reference, even my solid roller cam in my 632 that I have the rev limiter set to 7500 RPM, even that cam with 315/328 duration is still ground 4 degrees advanced. It's rare to leave the cam truly straight up on the cam grind.
And for reference, even my solid roller cam in my 632 that I have the rev limiter set to 7500 RPM, even that cam with 315/328 duration is still ground 4 degrees advanced. It's rare to leave the cam truly straight up on the cam grind.
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We had to move a Comp Thumper in a 67 307. The Comp in my Camaro was 4°+ just as it was ground. And a lot of the ground in advance is for eventual timing chain wear/stretch as I understand it.
The ground in advance is for performance, the vehicle is faster with the advance. If you chain stretches even close 4 degrees that's extremely sloppy, that would be enough to skip a tooth I would guess. Even when I can move the chain 1/4" it's less than a degree of slop, but I would still replace that chain, I don't like any slop of possible, which it is with an old BBC or SBC and a good chain. Although most LS chains are sloppy and then there is the tensioner to prevent chain slap when you let off.
And good true roller chains don't stretch much. Like the ProGear from Avon Gear, better than a Cloyes no doubt.
And good true roller chains don't stretch much. Like the ProGear from Avon Gear, better than a Cloyes no doubt.
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They sorta do, but they don’t go wheeling. Nothing against them, they got go fast toys.
Rally mode
I'm going from what I've read in performance books over the years and from my Dad who was a GM tech and built budget street engines in the 70s and 80s.
He always said advance 2° for stretch and 2° for the added low end on a street engine vs "straight up". But he was putting together street engines that didn't get constant tear downs and inspections. I would think purpose built or competition engines would need different considerations same as deck height and other factors.
That sounds way off to me, like a myth, but you got me curious now, and I happen to be degree-ing a 502 cam this week. The factory chain is so sloppy I replaced it, but I am going to degree the sloppy one both directions to see what the difference is in ICL and see how many degrees of slop it is. You can move this chain about a 1/4" side to side in the middle.
You have me curious, so am going to run a test, I'll let you guys know what I find out.
My guess is the slop will be less than 1 degree, but I could be wrong.
You have me curious, so am going to run a test, I'll let you guys know what I find out.
My guess is the slop will be less than 1 degree, but I could be wrong.
Well, I did it so I can put the new chain on. First I measured the chain how much I could move it in the middle, worse than I thought, 7/16"of "flop" in the chain with my finger moving it back and forth. I consider this a lot of slop, out it goes.
Anyway, I degreed it both ways twice because once you have it setup its easy.
It was 110 ICL one way, and 110.75 ICL the other way. I did that twice, same result. The interesting thing was, both times it was off 1 degree on one side of the lobe, and .5 degrees on the other side of the lobe. So the cam lobe is either stretch the chain a little more or a little less depending on whether its going up or down the lobe, interesting. Of course it was only one lifter, but still.
So it had .75 degrees of slop at 7/16" of flop. That means if it had ~1.5 degrees or more it would be rubbing on the block or the timing cover. So I feel like the 2 degrees for stretch is a little bit of a myth, but it's plausible, with a very warn chain, that should be replaced a long time ago, and is rubbing on the block.
Also, it was supposed to be 108, so I have to eat my words on not moving a factory crank engine, now I likely will. It was only advanced 2 degrees.
So I will install the new 9 keyway set likely at 2 degrees advanced to try it first and hope it is dead on at 108 ICL, but I'll find out, it will be later this week or early next week.
Anyway, I degreed it both ways twice because once you have it setup its easy.
It was 110 ICL one way, and 110.75 ICL the other way. I did that twice, same result. The interesting thing was, both times it was off 1 degree on one side of the lobe, and .5 degrees on the other side of the lobe. So the cam lobe is either stretch the chain a little more or a little less depending on whether its going up or down the lobe, interesting. Of course it was only one lifter, but still.
So it had .75 degrees of slop at 7/16" of flop. That means if it had ~1.5 degrees or more it would be rubbing on the block or the timing cover. So I feel like the 2 degrees for stretch is a little bit of a myth, but it's plausible, with a very warn chain, that should be replaced a long time ago, and is rubbing on the block.
Also, it was supposed to be 108, so I have to eat my words on not moving a factory crank engine, now I likely will. It was only advanced 2 degrees.
So I will install the new 9 keyway set likely at 2 degrees advanced to try it first and hope it is dead on at 108 ICL, but I'll find out, it will be later this week or early next week.
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Car science.
What timing set were you using? I wonder how much difference a 70k mile fiber gear set would make?
Anyways, thanks for checking that out and getting us some data on these "old ways"!
well......crap!
That was a factory GMPP 502 timing set, it was a single roller chain. I think regardless of what timing set you use, it would be rubbing on the block or timing cover if it was stretched 2 degrees, which wouldn't be good.
I am replacing it with a 9 keyway Howard's true double roller.
I am replacing it with a 9 keyway Howard's true double roller.
So I degreed it in with the new timing set and I could not see a difference in degree no matter which way I turn it, it read the same. The new one is nice and snug, you can move the chain a little with your finger but it goes right back straight again like it should when its snug. Sometimes I can't even move it at all and I wonder if it's too tight but it has always worked fine.
Also, I had to advance it 4 degrees with that timing chain to get it at 108.5 ICL as 2 degrees advanced with the new timing set was still 110.5. I did it 3 times and confirmed TDC again to make sure. I always double check and then triple check when I have to move it.
So now I have moved a factory crank if GMPP counts as factory.
Also, I had to advance it 4 degrees with that timing chain to get it at 108.5 ICL as 2 degrees advanced with the new timing set was still 110.5. I did it 3 times and confirmed TDC again to make sure. I always double check and then triple check when I have to move it.
So now I have moved a factory crank if GMPP counts as factory.
