Just picked up a used 305 (yes 305) for my ride from an 89 Camaro TBI. It has a roller cam, likely the "peanut cam". I want to use a non computer HEI from a 1980 truck. Can I use the older distributor and its gear on the newer motor or do I need to change the distributor gear ? Thanks.

 

The stock gear will be fine. The factory roller cams aren't as hard as the aftermarket billet roller cams we've heard about all these years.

FWIW, the factory says to use a "melonized" gear with their factory roller crate engines. Same thing they used on production roller cam engines. I may be wrong, but I believe the distributor shaft is the same non-roller vs. roller, so your stock gear should go on the older distributor. I've also been told they started using the melonized gears before the roller cams became the norm.

 

I forgot to mention that I did not get a distributor of any kind with this engine, so I don't have one to swap on it. Will the older gear from the 1980 be OK ???

 

I measured my stock 89 TPI distributor shaft and it was .427.

I am running a comp billet steel roller cam now and needed to switch to a bronze gear, as comp was out of the cast/melonized gears when my cam was made.

The older distributor gears are either .491 or .500.

 

Yes, you can. No gear change needed on the distributor.

Aftermarket (billet or otherwise) roller cams are a different animal.

 

As far as dizzy shaft diameters go, I think the stock GM HEI diz uses the .491 shaft. BUT... The external coil computer controlled HEI used the smaller .427 shaft. The .500 shaft is used by aftermarket MSD dizzys only, AFAIK. I have no idea the shaft size of the other brand aftermarket examples, but I'd guess they'd be the GM .491 size.

GM used the "melonized" gear on their roller motors. Aftermarket companies provide bronze gears for use with rollers, but I hear the bronze wears out fast. MSD makes a plastic gear that is supposedly OK with rollers, and doesn't wear nearly as bad as bronze, but it's only available in their .500 shaft size.

Argh, I think I might need to replace my dizzy, the shaft has a bit of wobble.

 

The other problem is that nobody offers the poly/composite gear in a .427 size, it's either the .491 or .500.

I am stuck with a bronze gear for now. There was someone on camaroz28.com making a shim to insert into the .500 gear to fit on the .427 shaft, but they have stopped for some reason.

I guess I could swap over to a coil-in-cap distributor and use the poly gear, but I'll see how much wear the bronze gear will give me first.

 

So I am good to go - right ???

 

Yes, you can. No gear change needed on the distributor.

Aftermarket (billet or otherwise) roller cams are a different animal.

 

Does a GM roller cam require a different fuel pump push rod?

 

I just went through this same deal with the gear size issue. Crane Cams sells a gear made out of aluminum/bronze in a .427 shaft size. This will work better then the bronze but not as good as the polymer. I mistakenly bought the .491 polymer gear and now its useless. $110 OUCH. The crane cams gear was only $40.

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