super chevy

The cam I'm looking at has a lobe centerline of 109, while I think the stock cam in my '93 5.7 truck has a lobe centerline of 112? If I were to install this cam, what effect will this have on my ECM function?
Thanks, SC

steve8586iroc

Possibly a low vacuum at idle. This would cause the ecm to richen up the A/F ratio at idle. The closer the centerline the more overlap in the cam, the more overlap = less vacuum at idle. Anytime the map sensor see a lower vacuum signal it makes the ecm think the engine is under a load, even at idle. Hope this helps.

Steve

Brent

iTrader: (1)

Are you sure you don't mean lobe separation? Centerline usually refers to the intake lobe. Lobe separation is only part of the story. The other half is overlap. If you have short intake and exhuast durations, 194/210 for example you can run a shorter lobe seperation without having any overlap. The stock L03 runs a 109 separation. Comp Cams has some good reading about this on their site.

Edit: got my terms confused.

steve8586iroc

Looks like I got ahead of myself, with the info Super Chevy gave you really can't say what type of cam he has or is talking about.
My bad

Steve

super chevy

I don't know what the LSA is. The cam is the factory 350 RamJet/HT383 hrdraulic roller cam. Only specs given for it in the GM Performance Parts catalog are: 196/206 @ .050 , 431/451 , and lobe centerline of 109.
I thought this cam might give me a little more low to mid range torque for my truck - but I'm worried about compatibilty with my Ed Wright Stage 1 chip.
SC

DM91RS

Read some of Astro's posts. I think that he runs that cam in a van. He's burning his own chips but I don't think that cam would be a problem. The stock POS LO3 cam is 109 as Brent has said.

Is your engine set up to use roller cams?

super chevy

It's a roller block, but has factory flat lifters. I can get the cam and roller lifters for $100. What else will I need to make the roller conversion? SC

evil t/a

The lifter "links" that keep them from spining , the retainer that bolts into the lifter valler , cam thrust plate , roller cam timing chain , shortter pushrods and if you valvesprings are stock I would suggest changing those as well because roller lifter are ALOT heavier than flat tappets and valve float becomes a problem with them. Comp cam selld everything you need in one package , its about 70 bucks.