Does anyone have the original carb specs for a LT-1? My '69 was rebuilt by the PO to resemble a LT-1 and is fitted with a Holley carb. I have the 11:1 compression pistons and a cam that has a higher lift and longer duration than the original LT-1 motors along with the correct intake manifold and long headers. It would help me to know the original jet sizes, accelerator pump nozzle sizes and power valve ratings. At least this way I would have someplace to start with my new Holley 650.



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'69 350/350 conv.

If you can get someone to give you the numbers off of their Holley carb on an original LT-1 motor. Holley can tell you the factory spec.s for that carb. The numbers you need are stamped on the front of the choke/air horn. You may can contact Holley any way, and get the information with out knowing the numbers.
Good Luck,

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sstanford '76 L48

Thanks for the idea. I have the original '70 Z28 carb that came with the intake and I'm almost positive that it is the same 780cfm carb the LT-1's used. I'd tear this one down to see what's in it but someone has already rebuilt it.



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'69 350/350 conv.

A '70 LT-1 used a Holley R4555A and application number of 3972121. That's for a 370 HP LT-1. The Camaro LT-1 was rated a bit less horsepower I believe, but not much.

That carb number should allow you to find the appropriate jet sizes, etc. There's your starting point since you have a different cam.

Actually thats incorrect. The 0-4555 was for 1970 Z-28 with the 350 360HP engine mated to an automatic trans. The OE number you gave is correct. 780 CFM was its rating.

There were two part numbers for the 1971 LT1 Corvette.

0-4800-1/0-4800, O.E. 3989022, Fitment 1971 z-28/Corvette with the 350 LT1 with an automatic Trans.

0-4801-1/0-4801, O.E. 3989021, Fitment same as above, but for Manual Transmissions.

Both were rated at 780 CFM

Part number for a complete rebuild kit is 37-1539
Poor Mans Rebuild kit P/N 37-1544

Specs for the 0-4800/0-4800-1 and the 04801/0-4801-1
Primary jet 70
Secondary Jet 76
Primary and secondary Power Valves 85
Primary Discharge Noszle .025
Vacuum Secondary Spring Color Yellow

If you can find these two books you can find any information you need to know about holley carbs.

P/N 36-168 Holley Carburetor Numerical Listing Guide.
This is invaluable for swap meet hunting.

P/N 36-51-7 Holley Illustrated parts and Specs Book.
This is great because it shows how they go togethere and the part numbers for each component that goes in each carb. Incase your looking for a missing part to a carb.

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Thanks for the clarification...I stand corrected. I was using information in the Corvette Black Book. I would think the Holley book would be the definitive source. I'm sure most will agree on that.

Where else can you find 2 guys debating carburetor numbers and build specs for 34 year old cars!!!

God I love this place.

Thanks guys!!!



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'69 350/350 conv.

On my 72LT-1 carb# R-6239A, 3999263, 780cfm,63f 73r jets, 65pr.,85sec.,p.v. taken from 72 ser.manual and holley book

The Holley Carb listing book shows a 6239A to fe for a 72 pass 350 engine Z-28 with Standard Trans which was later replaced with the 6239-1. GM did not change the MGF part no of 3999263. Although according to this book the 6239-1 was designated for the LT-1 not the 6239. Not sure what that means. Although your carb should have had 68 jets in the primary according to Holley's book. Could be a typo.

Who says were debating, just trying to get the right information out into the open.

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Right on After Shark, I have the 6239-1 model. The car ran good to about 4000 and then I got a hi speed miss.Looked at the plugs and they looked a little lean, Took the carb apart had 68's and 73's,bumped the rear to 75's,no difference.The miss went away when I replaced the point dist. with a Davis Performance Distributor HEI.

The sad thing is here that I will be returning to 9mpg.

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'69 350/350 conv.