As some people know, a certain individual was making up billet oil pump drive spuds for these engines. An old thread discussing these parts was shut down 2-3 years ago, because the maker wasn't a forum sponsor.

I don't want to start any trouble, so I won't mention this person's name (He has closed his business, I assume, a victim of the slow economy), but I communicated with him on another website, about obtaining one of these billet parts, as I have a Camaro with an LT-1, as well as my Corvette.

This person tells me that he no longer has any of these parts on hand, but if he can get 5-6 people together that want one, he can get another batch made. Without causing any trouble, is there any way to see if there is a need for these parts?

 

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bump...

 

The one I bought was too large to fit into the block and the hole for the shaft that holds the gear was too small. He did refund my money, but acted like I should have just spent more on machining to make it work.

 

I heard there were some issues with one of the early batches, and it was corrected later on. With respect to the OD of the drive itself, I'm wondering if there are variances in the blocks, as they come from GM, or GM simply makes the OE plastic pieces on the small side, and hopes for the best...

 

I bought one from Herron Performance a few years ago...a very nice piece...but the problem then was an unavailability of a new gear (which necessitated reuse of my existing gear). Outwardly the external dimensions of the gear are the same as any other small block (or big block) distributor drive gear...and it would have been a simple swap except.....drum roll please....gm decided to use a small diameter shaft.

all other chevy distributor drive gears are made to fit on either a 0.491 inch or 0.500 inch shaft (depending on distributor manufacturer) while an LT stub shaft ("upper oil pump drive unit" in gm speak) uses a 0.427 inch diameter shaft.

I've seen posts where a stock chevy distributor drive gear was sleeved to reduce its inside diameter from 0.491 inch to 0.427 inch, and this is certainly an option.

However there does appear to be at least two other options (not including bronze "race only / replace often" gears):

AC Delco 19052845; MOST application listings for this gear only include it's use on late model EFI style distributors, BUT Summit specifically lists this for Gen II (LT based) engines....so this should be THE ONE; and it is melonized which means it is the factory recommended style gear (required on all crate engines) to match up with the factory camshaft gear; and ,

Lunati Everwear Distributor Gear 89032 for a 0.427 inch shaft and advertised to "eliminate any issues of compatibility or wear" .

Please note that the above info is only what I gleened from an extensive internet search and while I believe it to be accurate, as they say, "your results may vary". Good luck.

 

I doubt GM just rolled the dice and hoped for the best with thousands and thousands of engines. The spot it fits in the block is machined, so its not just a casting with a wide tolerance. Never had an issue using a distributor from one SBC to another or an aftermarket replacement fitting a block, so I'd have to say it was the piece I bought. The recommended fix was to sand the housing down. I put the brand new oil pump drive I had bought back together and have not worried about it since.

 

I understand where you're coming from. I'm kind of looking at from the point of the GM plastic part being durable over the long haul. My Camaro is going on 18 years of age. Not a lot of miles, and it's stored during the winter, but it's a lot of heat cycling that the "upper oil pump drive unit" has endured, and I'd hate to see it fail, and take out the engine in my otherwise good running, but depreciating in value, car.

 

^ bump...

 

I need a couple complete drop in units. Fixing an LT1 now that lunched its oil pump drive and tore up the engine.