Switch to rpm air-gap?

[Ed's 1970]

Hello everyone,
Now that I have driven my corvette around for the last few weeks, I have a better idea of what it's all about. This car is pretty fast for a small block, it revs like no tomorrow, pulls like a mofo up top but it does not have much low end torque.
I found out it has a solid lifter cam (maybe the original LT-1) and 492 camel hump heads. It has sidepipes. On top it has an old edelbrock torquer manifold with a newer 5160 holley.
Would switching to a edelbrock rpm air-gap, hotter carb (like a 650 DP), and possibly roller rockers make any difference? I have a L-88 hood so I think hood clearance is okay. I really don't know much about the torquer manifold, it looks alright.
Thanks,
Ed

 

[GerryLP]

Hello everyone,
Now that I have driven my corvette around for the last few weeks, I have a better idea of what it's all about. This car is pretty fast for a small block, it revs like no tomorrow, pulls like a mofo up top but it does not have much low end torque.
I found out it has a solid lifter cam (maybe the original LT-1) and 492 camel hump heads. It has sidepipes. On top it has an old edelbrock torquer manifold with a newer 5160 holley.
Would switching to a edelbrock rpm air-gap, hotter carb (like a 650 DP), and possibly roller rockers make any difference? I have a L-88 hood so I think hood clearance is okay. I really don't know much about the torquer manifold, it looks alright.
Thanks,
Ed

First, find out if it is the original engine and if it is an LT-1. Then, if it is original and an LT-1, then perhaps there is some other problem (engine health, tuning). The LT-1 is one serious kick-butt engine, Nevertheless, the LT-1 had a 3310-Styled Holley carb in it with a Holley -36 intake.

If NOT original or LT-1, then perhaps you're not very far from making it run just right, but I doubt that the changes you mentioned will do very much good. The roller cam requires modifying your old engine to accommodate the roller lifters (I believe that the valleys have to be shaved down).

GerryLP:cool

 

[Ed's 1970]

I know it is not the original LT-1 motor, that is for sure and I wish it was. But thru some research I have done, the LT-1 motor ran the 492 camel hump head castings. The heads I have are similar, but the code on the heads indicates these were obtained over the counter from gm. Also, the cylinder block is a CE block, not the original. After pulling the valve covers, it became apparent to me that this engine has a solid (mechanical) camshaft in it by how loose the rocker arms are. If it was a hydraulic, there would be virtually no play in the valvetrain. I think it is a pretty mild camshaft though, it does have a slight lope, but idles very good. Perhaps the lack of low-end torque is due to the large diameter headers (1 7/8") and sidepipes.

 

[Crimson Thunder]

I had the same problem when i bought my car.The previous owner installed a Weiand single plane intake and an Edelbrock 600 carb.(I guess to go with the 300+ duration cam he used that dropped a valve in the numbers matching block)I switched to a Performer intake(hood clearance) and a 670 Holley Street Avenger and it made a HUGE difference in driveabilty.

 

[Hib Halverson]

If the car has an L88 hood, ie: a power bulge with a rearward facing intake on top of a standard big-block hood, then an Edelbrock Performer RPM will fit under it.

That's a great manifold choice provided the engine has the right heads and camshaft.

You mention that you've determined that the camshaft has mechanical lifters based on the valves being "loose". They need to not only be loose but have clearance. In some cases, you can have a hyd. cam with zero lash yet, when the lifters are on the base circle, you can still move the rockers a bit.

When you lift the intake to change it, you'll be able to determine if they are mechanical or hyd. by looking at them.

 

[Ed's 1970]

What I meant to say is not only loose, but plenty of clearance. I have a 94 Z28 with a hydraulic roller cam and the roller rockers on that motor have some play, but not nearly like the ones on the corvette motor. At first, I became alarmed and thought they were way too loose, but after thinking about it, I realized the cam is solid, not hydraulic.

I'll probably just get the rpm air-gap on it for now and see what happens.
Eventually, I want to build a nice 383 out of this motor (since I am pretty sure the block has 4-bolt mains and a forged crank) with some nice heads and possibly a roller cam. Looking for approx. 500 horse and 500 tq.

 

[bradfordsvettes]

check your axle ratio and make sure it meets the expectations of the engine .you sure do not want a 2:73 axle ratio and expect any low end grunt :ugh . just my 2 cents Steve

 

[Ed's 1970]

check your axle ratio and make sure it meets the expectations of the engine .you sure do not want a 2:73 axle ratio and expect any low end grunt :ugh . just my 2 cents Steve

Very good point. The code on the rear axle is: 1 CAC(or maybe CAO) 12 70W
Does anyone know what this means.

 

[keith6469]

If it does say CAO, it is a Posi 3.70:1 ratio

 

[Evolution1980]

Perhaps the lack of low-end torque is due to the large diameter headers (1 7/8") and sidepipes.

1 7/8" ??? :W Your primary tubes are almost 2" in diameter?!? I'm far from being a engineer, but that's probably way too much breathing room for a mild small block. Yes, that could definitely cause a loss in low-end torque, along with the side pipes. Great for upper-end HP though...