Ok, here's the deal.

One of my friends is about to rebuild the 305 on his Camaro(I know, He SHOULD get a 350, but he won't listen), the engine is a LB9 out of a 1991 Z28 so it is Speed Density controlled.

What we're trying to find out is if a cam swap is both worth it and doable, is the stock PROM compatible with a mild cam, say at least the l98 cam?

I have an LT1 cam laying around and am wondering if he could use it.

What are your experiences with camming Speed Density LB9s?

Can you use the PROM from a Manual LB9 car with the l98 cam on an Automatic?


Any suggestions?(Besides getting a 350, I tried HARD talking him into it but he won't listen).

Thanks for any input.

 

was the 305 out of the 91 z28 a stick or automatic ? the 305 automatics had the weak cam and the sticks usually got the l98 cam so you might already have the l98 cam ..

 

Yes, it is worth it. ECM's work via threshold. Cam's don't add as much power as one would assume to drastically effect ECM control (O2 correction). So long as you are maintaining the correct injector size that the current bin is burned for, it is only a matter of increasing fuel pressure to bring your BLM's back to the targeted area, which happens to be the 128 value. Cams introduce more air, ECM's balance air and fuel by maintaining its' programmed stoich target. By adding a larger cam you are introducing more air into the engine, and the ECM, by default, will run leaner, despite trying to correct for it. By raising fuel pressure, this will allow the ECM to be able to correctly maintain that programmed stoich target again because you are now supplementing more fuel with that added air being provided by the new cam. That is all it is. Stock 19-lb injectors are good for 300 horsepower at 100% duty cycle, and to be honest, I don't see his 305 making that much from just an LT1 cam swap, and your spark table is fine staying the way it is because the heads aren't being touched. Install the cam, raise your fuel pressure to accommodate, and have fun...

 

It came from an Automatic car.

Im pretty sure it has the peanut cam since his manual lb9 z28 pulls MUCH stronger than this engine.

Basically all he wants is for the Auto LB9 to fell the same or better than the manual car without messing with custom tunes, is this even possible?

I read another post where someone mentioned installing a manual lb9 PROM on his auto car and noticing no ill effects save for the missing lock up control. Anyone else done something similar?

 

Great, actually I think he does have access to an AFPR.

 

ALL Speed Density 305s had the same cam. The lesser HP cars had the crappy LG4/L03 exhaust manifolds, Y-pipe and single cat where the G92 cars had dual cats from the L98. The L98 single cat system was also used on some LB9s and works much better than the L03 garbage.

A F/Y-car LT1 cam won't make much difference over a L98 cam. B-car cam is what came in a Vortec truck and it is a joke.

 

Sweet! Then all he needs is to rebuild the engine and install his headers and new exhaust.

Thanks for the replies!