Do I really need a roller cam for TBI? As long as the LSA is 112 or bigger, what's the advantage? I'm buying the 350HO engine which has a hydraulic cam for my 92RS. I'd like to keep the TBI system (after upgrading to the larger TBI and vortec manifold).

:hail:

 

No you don't need a roller cam for that motor. The purpose behind a roller cam is less friction (wheel rolling on the lobe of the cam as apposed to a chunk of steel dragging along over that lobe). Also, a roller can get to max lift quicker that a flat tappet cam can. They run steeper ramp angles on a roller cam than on a flat tappet cam, because the flat tappet cam (hydraulic) will tend to dig in to the face of the cam lobe if the face is too steep. The roller will not do this. Quicker lift = more time under lift = more air and fuel in the cylinders = more power.

:rockon: :rockon: :rockon:

 

Sorry, for not being more clear. I'm asking if it's necessary to have a roller cam to get the computer to perform correctly or if it really cares whether the cam is a roller or regular as long as the LSA is within a range it can compute for.

 

The computer on a TBI car is plenty forgiving enough to be able to use a flat tappet cam. Now if you get a 'giant' cam with a very lopey idle, andvery high lift, this will cause the engine to have little vacuum at idle, which would cause the computer to show a code. I would recommend keeping a roller cam though, because you can make more power with it, and a roller engine will rev much faster.

 

Thanks. The cam is actually pretty mild from what I've seen some guys on this board running: 212/222 degrees, .435/.460. It's what comes stock on the 350HO, so it's good for a bunch of HP and torque and, while I'd like a roller, I don't want to add more expense to this swap...maybe when this one wears out...

 

I just remembered that my friends 93 Chevy pickup is a TBI 305, and it came stock with a flat tappet cam. We noticed this when we pulled the intake off to clean it. We were expecting to see a roller cam in it. It is a roller block, but the bosses for the spider were not drilled. The TBI looks identical to camaro/firebird TBI systems, and probably has the same ECM.

 

Thanks for the follow up. Now that you mention it, GM didn't start putting roller cams into the trucks until the vortec engines debuted...I think. Lower emission standards for trucks and some dollar savings as well probably.

 

I was under the impression that roller cams only went into the 350 engines, not the 305's. If anyone has info, please let me know.

I can say this for sure:
My 87 305 tbi pickup did not have a roller cam.
The 93 350tbi caprice motor I just rebuilt does have a roller.

Am open to any info on this-
Thanks,
S-D

 

My 91 305 TBI WAS a roller.

Brian

 

Wow- I didn't know that 305's came w/ rollers. I just pulled the motor out of my 91, I'll keep an eye out when I'm disassembling.
Thanks,
S-D