What effect does Advance and Retarded Cam install have on the Engine

[Blown&Injected]

A friend is telling me that everybody says it must be done to realize the full potential. He cites many magazine articles that suggest it is crazy to install a cam without dergeeing it in.

So say one chooses a cam, installs it straight up, just aligns the dots. Lets also say it happens to be right on the money; engine runs great. OK, now do nothing other than lets say a 4* retard on the cam, then a 4* advance set up on the cam?

I read about cranking cylinder pressure and RPM range, but it looks like it does not change things that much.

So while some say it must be done to be right, they omit the part about what will happen, what problems the engine will exhibit, if the cam is out +/- a few degrees.

So What's Up?

 

[John Larkin]

Have him cite you articles that pertain to degreeing TURBO cams. That will end the argument since he won't be able to find any.

 

[Ormand]

In general, advancing and retarding the cam will move the peak power/torque up and down in rpm. Advancing the cam gives a little more torque at low rpm, as I remember, and retarding will give more power at higher rpm. (I may have that backward) Either way, it's not a big change, and most turbo Buicks run a fairly mild cam which is best installed "straight up". With other engines, degreeing the cam is more essential, since there may be valve/piston interference if the cam is not installed just right, but that's not usually a problem with our motors.

 

[n20junkie]

the first question i ask everyone prior to checking something like bearing clearances or cam orientation is " are you going to pay to fix it" its not an easy task to get a cam exact unless you have a aftermarket set with bushings that can adjust it by very small degrees, 1 and 2 degrees is about all they are ever off, advancing the cam brings the power in lower, retarding brings it in higher, but 99.999 percent of the time the cam isn't off more than 1 degree, and thats not going to show a noticable difference in any engine, and pretty much no matter what engine you have the cam being off by 2 degrees isn't going to cause valve/piston interfearance problems, if it does you need more clearance in that combo, but the big difference between a blown vs NA engine is that in a NA engine the cam timing helps build the ineria in the fuel air mixture so that it gts proper cylinder filling, in a forced induction engine it has positive intake pressure, so that cylinder filling is not an issue, hope that helps
Grant

 

[Blown&Injected]

Thanks guys!

Yeah, that is what I thought too, it will just move the range up or down a bit. The IVC being way retarded only created about 15 extera psi difference in cranking pressure. That is within 10% of the starting point?

 

[gofstbuick]

IMHO, I would not advance cam timing on your engine. Yes it will move the power band, giving you more low end by advancing cam timing and more top end by retarting cam timing. But it will also limit the power band based on the limitations of the cam. When I build an engine, I lock myself in the garage and don't let any one bother me. I made the mistake of allowing a buddy into my garage while building my 383 SBC. He talked me into advancing cam timing (to account for timing chain stretch). Granted a 383 inherently produces torque, but now with the cam timing advanced, it gave more torque than was needed and narrowed the powerband. The engine felt like it was straining past 5200 rpms (and with 6 inch rods ). So one day, I took the timing cover off and set the cam timing back to straight up. It was like night and day. The engine pulled just as hard as before, but it did not strain at the top end and went straight to 6200 rpms. Now this isn't a turbo engine, but I believe the mechanics and theory behind changing cam timing will still apply (with regards to powerband). Just like the factory, most cam manufacturers spend a lot on R and D to make the cam work for your requirements. So I would just follow their recommendations.