Advancing Cam Question

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SpeedThrills

SpeedThrills

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I've degreed a couple cams when I installed them. You "gots to know".

Now I'm advancing my MP 292-508 cam from straight up (108 ICL), to 104. It has a double roller chain with the 3 keyways; 4* advanced, 0, and 4* retarded. I don't know what chain and gears they are, as I bought the engine used. However, I have had the cam (and everything else) out of the engine, and checked it when I re-installed it.

My questions are: are the keyways in these gears prone to being machined inaccurately? Do I need to check and see if it actually moved 4*? I know the best answer is, "check it". But if the answers are overwhelmingly in favor of them being accurate, I'll just move it and put it back together.
 
That's a huge hydraulic cam. If I were to degree it in anything under an honest 10:1, I'd put it in down around 102-100.
 
RustyRatRod said:
Is that true "as told" or true "as measured"?
Click to expand...
Measured it meself. Don’t have the numbers handy.
.030 KB190’s, 915 heads I don’t remember the cc’s right now.
I do remember using a thicker hg than planned, cuz I had to pull the heads when I discovered some dirt, and I already had some thicker ones for when I put them back.
Actually, I’ll post the numbers later, I need to refresh me ol memory anyway.
 
On “Most” of the 3 key way timing sets I’ve used, the +/- 4 is advancing the “cam” +/-4 *………which ends up being +/-8* at the crank(on the degree wheel).
That’s almost always more than I want/need to move the cam, so I basically don’t buy those anymore.
I use the 9 way sets where each notch is a 2* move.
On a SBM, you can use the offset keys in the cam for finer than 4/8* adjustments.
 
Average cc chamber volume: 64.6
Bore: 4.030
Dome cc: -1.2
Gasket: .040 (estimate, was .057 before install)
Gasket bore diameter: 4.125 (scaled)
Deck: .018 (below)

Compression ratio (Wallace): 10.9:1

Looks like I lied. I think when I figured it before, I used the smallest chamber. It's been a few years, and my notes ain't perfect. (Darn, 11.1:1 sounds cooler.)
 
Have you ever run a compression test on it? I'd like to see some numbers.
 
SpeedThrills said:
I knew the answer before I finished typing the question, lol.
I’m going to check it.
@RustyRatRod, the engine is a true 11.1:1.
Click to expand...
If a true 10.9 or thereabouts lol, what do you expect to gain by advancing it?
You should have lots of cylinder pressure already, so it can't be that......
The Wallace points to 160 psi. With iron open-chamber heads that's about the limit for pumpgas.
advancing to 104 is pointing to 169 psi. almost a sure recipe for detonation on pumpgas.
I'm with @RustyRatRod ; highly recommend a compression test.
 
AJ/FormS said:
If a true 10.9 or thereabouts lol, what do you expect to gain by advancing it?
You should have lots of cylinder pressure already, so it can't be that......
The Wallace points to 160 psi. With iron open-chamber heads that's about the limit for pumpgas.
advancing to 104 is pointing to 169 psi. almost a sure recipe for detonation on pumpgas.
I'm with @RustyRatRod ; highly recommend a compression test.
Click to expand...
Thank you. See post #12. Comp test has been done.
This thread is getting convoluted with my "How To Measure Fuel Volume" thread. Sorry for the mix up.
 
SpeedThrills said:
I'll try to address all of the ideas that have been posted!

First, I did a compression test (warm, throttle open), but haven't done a leakdown yet.
1) 180
2) 170
3) 185
4) 185
5) 170
6) 180
7) 170
8) 170
Click to expand...
You mean this?
With iron heads?
and quench-pad pistons?
And you still want to advance the cam more?

Your numbers are pointing way more than 10.9Scr
Lets go look at them again
see post 18
 
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SpeedThrills said:
Thank you. See post #12. Comp test has been done.
This thread is getting convoluted with my "How To Measure Fuel Volume" thread. Sorry for the mix up.
Click to expand...
Post 13. Are those numbers with the 508 camshaft? If so, I would degree it 4 degrees advanced and leave it. Those are pretty good numbers.......really good numbers if that's with the 508 cam.
 
AJ/FormS said:
You mean this?
With iron heads?
and quench-pad pistons?
And you still want to advance the cam more?

Your numbers are pointing way more than 10.9Scr
Lets go look at them again
Click to expand...
I'm just going by what Wallace Calculators says. The idea is to get it to pull a little harder because the convertor isn't loose enough. All info is in the fuel volume thread. It doesn't ping now on 93. I didn't consider if advancing it 4* would change that.
RustyRatRod said:
Post 13. Are those numbers with the 508 camshaft? If so, I would degree it 4 degrees advanced and leave it. Those are pretty good numbers.......really good numbers if that's with the 508 cam.
Click to expand...
Yes, with the .508
 
SpeedThrills said:
Average cc chamber volume: 64.6
Bore: 4.030
Dome cc: -1.2
Gasket: .040 (estimate, was .057 before install)
Gasket bore diameter: 4.125 (scaled)
Deck: .018 (below)
Click to expand...
At 4.03 x 3.58, your swept is 748.3 cc

Total chamber, per to match your numbers is;
64.6 -1.2+ 8.6gasket +3.76 deck=75.76 and so
(748.3+75.76)/75.76=10.9 alrightee, but 185psi is pointing to 11.4 at sealevel.
to hit 185psi at 10.9, you'd have to be ~2200ft below sealevel .......
The point is, something is not correlating, and I trust the Wallace.
My guess is that One of Us did some creative math .......... lol, or your compression gauge is real optimistic.

BTW
I ran that cam back in year 2000, with KB107 Flat-Tops, and alloy heads; at 11.3Scr.
She was a real snorter. But not very streetable until she gets to 4.30s, and I ran a clutch.
At 900ft elevation, and in 4* advanced, I was getting only 175psi and my gauge more or less matches what the Wallace predicts.
 
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I'm going to give 4* a shot. I''l update how it runs in a week or so. Life keeps getting in the way. Plus, I'm gathering parts and making a balancer installer. Not to mention the new speedo cable adapter that sheared the o-ring and now lets the red stuff out. :rolleyes: :mad:
I won't make it to the track until September or October, but I'll update then how it goes.
 
If you are advancing 4* to improve the c'ter hit, I doubt you will feel the difference.

img389.jpg
 
It will make more tq that he will feel? Every engine is different, & in my opinion, the change will not be worth the effort.
I am going to be generous & use the 2500 rpm tq figures from post #21. Generous, because the tq difference at 2500 from 0* to 4* adv is 5.0 ft/lbs. At 4250, the change is a whopping.....0.3ft lbs.

The tq increase at 2500 is......1.48%.
 
I just traced out the angles of a Cloyes 9 way crank sprocket and measured each with a protractor to see if it was accurate. Everyone I checked was within one half degree, as good as my method and cheap tools could check. This verified the need to check the cam installed centerline as I’m getting 4 advanced using the 2A slot. Either original crank or new cam was off.
 
Bewy said:
If you are advancing 4* to improve the c'ter hit, I doubt you will feel the difference.

View attachment 1716288974
Click to expand...
That's about what I found as well;
The biggest improvement was at low rpm with a manual trans, due I supposed, to the higher cylinder pressure.
And retarded, I felt it at the top, like all the way to about 6800, which I wanted to attribute to the overlap period being possibly "better".
The midrange seemed about the same.
Exactly what your chart shows.
But that was 25 years ago.
In the end;
on the street with 3.55s, which is as high as I wanted to run;
Power at 6800 was not really useful to me, being almost 60 mph in First/ 80 in Second/110 in Third.
and, advanced, even 8*, the boost at low rpm wasn't enough to impress me,
so I pulled it out and sold it.

Then I got me a 223@050 and hotdaymn, at 195psi, that was a wicked combo. If that cam had not dropped lobes on me, it would still be in there.
I retarded it, to straight up. and still had a better bottom than the 292, and at the top, while noticeably less powerful, it was still enough to initiate tirespin at 45 mph from a footstomp, and sometimes even50 mph. Mind you, at that time I was only running 275s. 245s were a joke. Soon I had 295s on it, cuz I kept wiping out in traffic and ending up on the median, or facing backwards, yes with 3.55s.
I think everybody should have a fun-combo like that, at least for a few weeks in their life, lol.
Can you do it with a 318?
Yeah/Sure with skinny tires, lotsa cylinder pressure and the right gears, which is gonna kill hi-way fuel-economy.
But if said 318 only makes 95psi pressure, then;
not with 295s,
not with a factory stall, and
certainly not with 3.55s.
But I digress, lol.
that combo had so much bottom end, that eventually, I installed one of them A833 super wide-ratio overdrives, AND a GVod behind that, which got me final drive of 1.97, which got me, 65=1600 rpm. This promptly pegged the fuel-economy meter at over 30 mpgs, I kid you not. Allbeit Not with the 750DP, lol. I shouldda tried it I suppose, lol. Naw, that was done with a modified 600, blocked secondaries, and a dash-mounted, dial-back, timing module, set to stun.
 
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