Degreeing in a cam

I could use a little advice from Pat or Richard or Dave or any other of the knowledgeable engine guys who make their presence known on this forum.

I have a degree wheel hanging on a nail in my little shop that I have owned for probably thirty years. I have never tried to use it, even when we were running our modified roadster.

With the server down and the temperature outside at a brisk fifteen degrees, and with nothing else to do, I decided to try to degree in the mid-range cam in my yet unstarted '76 Cadillac (500ci) engine. After tinkering for a while I have decided to ask for help before I mess around and do something dumb or expensive, or both.

Can somebody advise me on this procedure?

Thanks -

Jim

Yeah, that would be a great thread. I've read magazine articles on it, and still don't understand what you have to do.

Good question.

Don

Ah!

Many thanks, Denny.

This is what I was looking for. Good stuff. I appreciate it.


Jim

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Originally Posted by Big Tracks

I could use a little advice from Pat or Richard or Dave or any other of the knowledgeable engine guys who make their presence known on this forum.

I have a degree wheel hanging on a nail in my little shop that I have owned for probably thirty years. I have never tried to use it, even when we were running our modified roadster.

With the server down and the temperature outside at a brisk fifteen degrees, and with nothing else to do, I decided to try to degree in the mid-range cam in my yet unstarted '76 Cadillac (500ci) engine. After tinkering for a while I have decided to ask for help before I mess around and do something dumb or expensive, or both.

Can somebody advise me on this procedure?

Thanks -

Jim

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I am not trying to say don't degree your cam.
Before I even think about trying to "degree" a cam I make sure that the customer has a good timing chain set.
The $25 set you at the local Auto Zon- won't work well.
If you are serious about doing this you need a set that has the larger .250 roller along with good steel gears top and bottom.
Say you decide to degree the cam as soon as you start the engine it won't be correct due to timing chain stretch.
Comp. has some of their cams ground with 4* advance in them to compensate for timing chain stretch.
If we do a dyno pull even after using a good $100 set the cam timing will still be off a little after several hard pulls.
If it where a SBC or a BBC what we do is "degree" the cam at first and then after several hard pulls we will either advance or retard the timing to make the most hp.
When you are playing with cam timing always make sure you have enough piston to valve clearance.

You mention something else. When I just got my new Cloyes double roller set for the 350. it offered 4 degrees advance, zero, and 4 retard. I just put it at zero to be safe, but what advantages would it give to do the other two?


Don

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Originally Posted by Itoldyouso

You mention something else. When I just got my new Cloyes double roller set for the 350. it offered 4 degrees advance, zero, and 4 retard. I just put it at zero to be safe, but what advantages would it give to do the other two?


Don

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If you advance the cam it will begin to work earlier starting your power band at a lower rpm.
If you retard it it will begin to work later and make your cam come on at a higher rpm.

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Originally Posted by erik erikson

I am not trying to say don't degree your cam.
Before I even think about trying to "degree" a cam I make sure that the customer has a good timing chain set.
The $25 set you at the local Auto Zon- won't work well.
If you are serious about doing this you need a set that has the larger .250 roller along with good steel gears top and bottom.

When you are playing with cam timing always make sure you have enough piston to valve clearance.

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Erik, you are forcing me to admit that I bought a Melling timing chain and gear set. There are two reasons that I did that:

1. The cost of a roller set for a Cadillac. (The cost of ANYTHING for a damn Cadillac, for that matter.)

2. Ignorance.

I don't anticipate valve clearance problems but since you suggest it, I'll definitely check it out.

On another subject, I was in Clive late last June and enjoyed a long visit with some old friends. The bad deal attached to the visit was that my wife and I were on the way up to Hampton for the funeral of another old friend. At my age those occasions are popping up pretty frequently.

Anyway, Thanks for the input. It is appreciated.

Jim

So then, would the chain stretching retard the cam timing moving the power band up? After a few hard pulls how far off would the cam timing be?

I read somewhere that while advancing the cam timing does improve low speed/rpm performance, retarding cam timing doesnt really have any beneficial effects. Wish I could cite the source, but I'm 90% sure it was one of the Engine Masters series mags from last year. The issue had a section on understanding cams, timing and such.

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Originally Posted by 46yblock

I read somewhere that while advancing the cam timing does improve low speed/rpm performance, retarding cam timing doesnt really have any beneficial effects. Wish I could cite the source, but I'm 90% sure it was one of the Engine Masters series mags from last year. The issue had a section on understanding cams, timing and such.

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I've never installed a cam retarded, so have no direct experience but I've read the same thing.

Hey I found the magazine! "Engine Masters" fall of 2006. " Most aftermarket cams are ground with some advance built in, typically about 4 degrees. Advancing the cam makes all the valve train events happen earlier, and genrerally favors low rpm operation, helping idle quality, cylinder pressure, vacuum, and lower speed torque. Retarding the cam deteriorates these characteristics, though in some cases high rpm power may be enhanced. The real score here is that ... most of the time retarding the cam will gain little if anything, even up top"

Question: What size degree wheel would do the job?

I'll just add a little detail to Erik's response:

Advancing or retarding the cam moves the engine's torque band around the rpm scale by moving the valve events further ahead of or further behind the movement of the piston.

Advancing the cam clockwise in relation to the crankshaft improves low-end power and response.
Begins and ends all valve opening and closing events sooner in relation to piston position.
The engine builds torque quickly, then lays down on the top end. Makes the motor "peaky".
Decreases piston to intake valve clearance.
Increases piston to exhaust valve clearance.

Retarding the cam counter-clockwise in relation to the crankshaft improves high-end power.
Delays all valve opening and closing events in relation to piston position.
Increases piston to intake valve clearance.
Decreases piston to exhaust valve clearance.

As has been stated, cam grinders will grind in a little advance when they manufacture the camshaft. You can figure the amount of ground-in advance by subtracting the intake lobe centerline in degrees from the lobe separation angle in degrees. Here's an example. Look at the bottom of this cam card. It shows that the intake lobe centerline is at 105* after top dead center and that the exhaust lobe centerline is 115* before top dead center. To get the lobe separation angle of this cam, add those 2 figures together and divide by 2.....
105 plus 115 equals 220, divided by 2 equals 110*. So this cam is ground on a lobe separation angle of 110*. If we subtract the intake lobe centerline (105) from the lobe separation angle (110), we find that the manufacturer has ground in 5 degrees of advance.
http://www.cranecams.com/?show=brows...tType=camshaft

Pretty neat stuff, huh?

In a local oval track series, with a spec cam requirement, We routinely play with the camshaft timing. All engines (chevy-ford-mopar) distinctly benefit from 4 deg. retard setting over a straight-up engine.

Having said that, we do run at a pretty narrow RPM band and I cant really speak for their flexability.

MIZ

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Originally Posted by ceh383

So then, would the chain stretching retard the cam timing moving the power band up? After a few hard pulls how far off would the cam timing be?

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As much as 8 degree's.
At it's worse it could mean 30 less hp.
One area I would like to mention is cam speed is different than crank speed.
My advice is always put the crank sprocket on "straight up" and try to adjust the cam timing.
In all the drag engines we build in SBC or BBC we will try and run a two piece timing chain cover or a belt drive and either advance or retard the timing to make the car go faster.
One idea is if you have a car that won't "hook -up" you can try and retard the timing to try and lessen the low end shock and make the engine pull harder up above.
Like I said before always make sure you have enough piston to valve clearance.

Posted by 46yblock:
"Question: What size degree wheel would do the job?"

I've used this Moroso unit for years:
http://store.summitracing.com/partde...5&autoview=sku

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As has been stated, cam grinders will grind in a little advance when they manufacture the camshaft.

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Is this advance to compensate for timing chain stretch?
What I'm trying to get at is, when you install a new cam in a street motor and you want it "straight up" would you give it some advance knowing the chain will stretch? or Install it "straight up" knowing that the grinder has allowed for this?

Install the cam on the centerline advised on the timing card that comes with the cam. The guys who grind these sticks know more than we do. If you need to alter the cam very much from the straight-up point on the cam card, then you probably have stuck the wrong grind cam in the motor.

I'm with Tech. When I buy a cam, I fill out the tech data completely and accurately, and go with the manufacturer's recomendation. On race or hot street engines, I usually wind up calling Comp Cams, giving them all the information about the engine and the rest of the car and have one custom ground.... Yeah, I know I spend a bit more for a cam, but when it's installed in the engine I know it's the right one. Used to play with a lot of cams, cam settings and everything else on the dyno. Discovered it's really tought, as in almost impossible, to out engineer the engineer's!!!!!

PS---Notice I said talk to the Cam Company Tech's, not some dummy working the phone bank at Jeg's!!!!!

When I've put motors together that's what I've done.....follow the manufacturer's recomendations, it generally works out best that way.
But the question remains unanswered....
Is this (built in) advance to compensate for timing chain stretch?
Let's say you were going to build two idendical motors....with one minor difference. One uses a timing chain and the other uses a gear drive.
Would you install the cam the same way? Or would it be different?

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Originally Posted by ceh383

When I've put motors together that's what I've done.....follow the manufacturer's recomendations, it generally works out best that way.
But the question remains unanswered....
Is this (built in) advance to compensate for timing chain stretch?
Let's say you were going to build two idendical motors....with one minor difference. One uses a timing chain and the other uses a gear drive.
Would you install the cam the same way? Or would it be different?

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Hmmm. not really a question for me seeing as how I would never put a gear drive in an engine. If I used anything other then a chain, it would be a belt drive....

In answer to your question, there is minimal stretch on quality double roller chains, doubt you could see the difference on a dyno....

In Denny W's post above, there is a pic apparently decribing the positive stop method of finding TDC. I seem to recall some expert(s) writing to find true TDC, use a dial indicator, and note on the degree wheel wheel where .010 BTDC was, and .010 ATDC, and TDC would be the in between point.
They said, if I remember correctly, that using the equivalent of the positive stop method could give an error of several degrees.
Sure dont mean to be an ass here, just trying to learn. I have been doing a lot of reading trying to get ready for my try at degreeing a cam, coming soon.

A dial indicator would be more accurate then a positive stop. Unless you are actually going to change the cam setting, the positive stop is probably plenty accurate for just checking the actual specs against the cam card......

Another post stated...

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As much as 8 degree's.
At it's worse it could mean 30 less hp.

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So, if using a chain would you compensate for this?

No. Use a dial indicator to get absolute TDC. A positive stop bolt is little more then a WAG. If it's the right cam for the engine you won't need to change a thing on the advance. If it's the wrong cam, no amount of advance degree change is going to make it right. A quality double roller timing chain and gears will be dead on. Trying to compensate for something you can't measure is over thinking the whole operation.