Technical cam timing

wondering if any one has tried advancing the stock cam 1 tooth and what was the result and if it was worth the effort

 

Need to know how many decrees = 1 tooth.
Advanced = more torque

 

Gains power at low end, loses at the top end. A full tooth is way too much, just a few degrees is what most try.

 

Usually when you advance or retard cam timing it's in a matter of 4 or maybe 8 degrees, if you go one entire tooth, the engine will most likely not even run. At the worst depending on engine, you could have piston to valve contact


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Back in the late 70's Ford started retarding their cam timing for emissions which made them run like crap, get bad mileage and reduce power. I worked at a Ford dealership and customers would come in with their pickups and say I can't pull my horse trailer with this new truck.
We would put the 69 351 Cleveland timing chain and gears in the 351 M and 400 M motors. 70 429 Cobra Jet timing set in the 460's . They would gain 3-4 mpg and increase torque.
The cams and timing sets stock were about 8 degrees retarded from the earlier models. All of the ranchers said money well spent. I was in Arizona at the time working in a dealership at high altitude where power was down to start with because of the elevation.

 

^^ I've heard Chevy did the same thing. I have a stock cammed '79 305 and need to check/replace the timing chain. Can anyone confirm, and is it worth advancing the cam?

 

advance it a few deg. (4-8) a full tooth way too much

 

If a camshaft worked better advanced or retarded, it would probably be ground that way.

Are you going to degree the cam to see where you're at, or just advance it. I'm pretty sure a cam works about as well as possible straight up 99% of the time.

The reason the cam advance worked on the Fords is because it was put back where it was originally timed, before the government got involved. I guess that if it's one of those situations, you will pick up some drivability by advancing the cam timing back to the original settings. You'd need to do a little research and see if your vehicle was one that was altered at the factory to start with.

 

How does a cam actually get advanced, or retarded just a few degrees??Interesting stuff.

 

You can use different timing sets(as in the Ford deal or multi indexed crank gears, like pictured), drill the cam gear and install offset bushings, or stepped crank keys.

Something else, advancing the cam reduces intake valve to piston clearance and retarding the cam reduces exhaust valve to piston clearance.

 

That crank gear has 21 teeth so the corresponding cam gear would have 42. Interesting. If I had the engine that used that set and it was just an old, tired, stocker I'd be tempted to advance the cam one tooth just to see what changes it would make, if the valves stayed clear of the pistons. 360* / 42 = 8.57*. Might be good for a couple laughs.

 

Larry T -

There's very few factory cams ground..."straight up"..! Even many of the factory performance cams. While I doubt ALL cams were done this way, very many were.
As another said, many were ground retarded 2 to 4 degrees, mostly for emissions, some just because the original grind wasn't working as thought it would. As in the Studebakers, there was little to no concern for emissions back in 54-60 but they did grind their cams retarded, as did Chevy, Chrysler and Ford, V-8's. Not sure about I-6's.
Don't know about the foreign brands.

And as for the original question...would be nice to hear about the brand, the model, the engine itself to be able to help with a responsible answer..!?

Mike

 

- Make camcard using zero installation or compare Your camcard and decrees You get with decree wheel and dial gauge
- Make camcard using 1teeth advanced installation

That tells everything. Now You do not know what is Basic situation and how much is change.

 

I realize that some cams are ground advanced or retarded for different reasons (emissions come to mind). I also said that I usually installed the timing chain straight up, because the manufacturers have done a lot more homework than I'll ever do to make the cams work with standard timing sets. If I think the camshaft is far enough off that it needs major advance or retard to work in my application, I look at other camshafts that might work better without the advanced or retarded timing in the timing set.

I'll agree that we would need a lot more information about the engine the OP is working on to even make a WAG about advancing or retarding the cam in his engine. I'm gonna guess that advancing the cam one tooth might not get the optimum results though.

 

Not intentionally.

The best way is to use the proper cam for the application.

You need to degree your cam first to find out what you have, then make the necessary adjustment. Here is a good video for Comp Cams...
https://video.search.yahoo.com/sear...9620ef07f96b974b87d76df8b77c964c&action=click

 

ok for information 1 eng is 239 flathead so v/p clearance is not a problem 2 eng has stock grind cam that has intake opening at 0DEG as per factory specs eng is in good nick overall just seems lazy low down 3 intake 2X 97 strombergs 4 exhaust fenton cast headers

 

PS 1 tooth is about 8 cam deg

 

Without knowing what it will do internally, I would check piston to valve clearance when advancing or retarding any cam.

One tooth is too much, unless the cam was made wrong.

I do tend to run cams 3º to 4º advanced on street engines that I spec. It pushes the torque peak down, were the engine is most often used, but that depends on the specific application.

 

Yes, and in that case, run it 3º advanced.

 

the old school way is to use an offset bushing on the index pin, and slightly over-drilling the bolt holes in the gear, if needed.

 

If you do use one of those multi keyway gears make sure you use the right dot to time it with

 

You didn't mention you were working on a flathead, but the principles are all still the same. Only the methods used to achieve the outcome are different.

Generally speaking, if you advance the intake timing, you get a lower rpm torque increase by increasing cylinder pressure, unless of course you were already at peak pressure.

If you retard the exhaust timing, you get an increase in power by an increase in rpm. If you can do both at once like on a DOHC application, you can get the best of both worlds. It's all relative of course.

If you have a single cam you usually defeat the purpose by moving it very much, because it moves both (IN & EX) the same amount at the same time. One or the other is in the opposite direction needed and is always compromised.

If you move it more that 6-8 crankshaft degrees in either direction it is usually best to grind another cam. That costs more, but that is usually the best way.

I know stock flatheads are lazy, but there are plenty of cams available that can wake them up a little.

 

On second thought, maybe.

If this is still in a vehicle that has to be smog checked, you probably shouldn't.

 

find someone with a real loose chain that jumps all by itself

 

It seems that in the early 60s if I remember right, the super stockers with a auto. trans. would advance the cam 3-4 deg. to help bottom end. To help the top end they ran a lot of dual point dist. with the points wired throught 2 switchs and as the rpm built up in high gear kill the switch leading to the lead set of points, in effect retarding the timing 2-3 deg. pulling better on the top end.

 

I like the dual point trick, never thought of that one!

In my drag race days, we used to advance the intake cam as much as mechanically possible for bottom end and retard the exhaust for best mph. In effect giving it a wider lobe separation angle. If it spun the tire too much we'd back a couple degrees out of the intake.

Now a days everything is computer controlled to do what we did mechanically.

 

Dual point trick Grumpy Jenkins if i remember correctly.

 

On a flathead , you can file the bolt slots a little in one direction to do what you need .

 

Install a 69 chain and sprocket this gives be for smog cam timing.

 

Thanks Gimpy.

On another note (different engine), if a cam has an intake centerline of 95* and exhaust centerline of 105* does that mean it is 5* advanced?