timing chain question

[Willowbilly3]

I'm putting a new chain and gears into my 260 anf got to wondering if I should take advantage of the 3 notch gear and advance/retard the valve timing. Engine is stock, stickshift car with 4'11s and weighs maybe 1800. rpm in 5th with the tires I'm running should be around 2600 at 65.

 

[Old Iron]

Not on a stock cam/engine combo.
You will gain more by dialing in the cam with a degree wheel to what the cam specs are designed at.
Advancing the cam causes the combustion chamber pressure to be raised which can cause detonation from the junk fuels we run.
You can also run into problems with valve to piston clearance when advancing the cam.
You need a minimum of .080 on the intake at 10 degrees after top dead center and .100 on the exhaust at 10 degrees before top dead center.
Advancing the cam will close the clearance on the intake at 10 degrees after top dead center and open the exhaust clearance at 10 degrees before top dead center.
One last thing, if you have to advance the cam to get the torque you want at lower rpms, then the cam is most likely too big. This is the number one biggest mistake made when building an engine.

 

[donsrods]

When we had the cam degreed in my Son's 455 Olds the guy found it was 4 degrees retarded so we were able to take advantage of the 4 degree advance notch and it put him dead on. But I think to just arbitrarily advance or retard the cam without knowing where you are is not wise.

So on a stock rebuild where I am not having the cam degreed, I just install it straight up to be safe.


Don

 

[Studebaker]

It all depends on cam company as well, some are built at 4 degrees advanced setting at zero, while others seem to retard them for a certian aplication. Just larger than stock with a fresh stock rebuild will give ya a good power all around. If u need more-just talk with ur local machinist and he'll give some good ideas

 

[Willowbilly3]

It's just a stock old 260 with about 80,000 miles on it. I was cleaning it up and putting in new seals and decided the timing chain should get replaced while I was in there. Best tl leave the tining alone then, thanks.

 

[earthman]

At least we know you are still working on it

 

[Gastrick]

It's just a stock old 260 with about 80,000 miles on it. I was cleaning it up and putting in new seals and decided the timing chain should get replaced while I was in there. Best tl leave the tining alone then, thanks.

Replacing the timing chain on an engine with 80 grand on the odometer is a good idea in my opinion. Stock rebuild.....just install the gear straight up and let it fly.

 

[Willowbilly3]

At least we know you are still working on it

You'd be proud. Before I got sick I got a lot done. I'll post up a progress report soon.

 

[jfg455]

degreeing a cam is always a good idea even in a stock build. There was a couple of studies done that found mass produced cam grinds to be 2-4 degrees off either way on identical cams from the same manufacturer. If you degree it then you know it is "straight" up.