71 LT1 Holley CARB Base plate Tabs Cracked/Broken

[Paul C.]

Pulled the holley #3989021 carb off my 1971 LT1 because of vacuum leak. Found that 2 tabs on the base plate had been poorly welded and the 3rd was only expoxed on--fell off when I removed the carb. I know they changed the baseplate in 1971 because of this problem. My carb is a Sept 1970 although the car was built in Jan. 1971. What happens point wise if I put the newer base on OR can you get these tabs welded back on so they look good? Any suggestions appreciated.

[Paul C.]

Re: 71 LT1 Holley CARB Base plate Tabs Cracked/Broken

Pulled the holley #3989021 carb off my 1971 LT1 because of vacuum leak. Found that 2 tabs on the base plate had been poorly welded and the 3rd was only expoxed on--fell off when I removed the carb. I know they changed the baseplate in 1971 because of this problem. My carb is a Sept 1970 although the car was built in Jan. 1971. What happens point wise if I put the newer base on OR can you get these tabs welded back on so they look good? Any suggestions appreciated.

Question: I found out that holley carbs were very prone to having the tabs break if you overtightened the nuts attaching it to the intake manifold. Sometime during the middle of 1971 Model Year Holley changed the base plate to thicker flanges/tabs due to this problem. Therefore the same holley carb with the same number might have the old style (4 thin tabs), an intermediate style where one side is thin and the other side was thicker; and then the later style where all 4 tabs where beefed up to prevent them from cracking/breaking when torqued down. The timing for the transition was from September 1970 to March 1971--approximate. Is the baseplate even judged during NCRS judging? If not I am going to replace my thin tabs base with the thick tab base to prevent another occurrence of cracking. Any thoughts?

[Daniel S.]

Re: 71 LT1 Holley CARB Base plate Tabs Cracked/Broken

Yes base plates can be changed. I would reach out to Eric Jackson @ Vintage Muscle Car Parts. Tell him I sent you. Good dude. sales@vintagemusclecarparts.com

[Paul C.]

Re: 71 LT1 Holley CARB Base plate Tabs Cracked/Broken

Eric has my Holley carb right now. Trying to figure out if they judge the base plates or where I can find a thin tab one. So far he and I can't find one.

[James G.]

Re: 71 LT1 Holley CARB Base plate Tabs Cracked/Broken

I am not going to say all do not check, however when I mentioned it to a judge recently at a meet I received a perplexed look.

I have found junk LT1 carbs on ebay for 250 - 300 with correct base plates in the recent past.

[Paul C.]

Re: 71 LT1 Holley CARB Base plate Tabs Cracked/Broken

The early Holley carbs all had thin tabs; then in about March 1971 they went to thin on one side and thick on the other; and then later all tabs were thick. You find lots with the thick base plates and thin/thick base plates, but hard to find any with the thin ones because so many were broken by overtightening and incorrectly listed torque specs. The cheapest I found was $600 because people are also looking for the correct numbered metering blocks and the correct date code. The days of buying correct Holley carbs are probably over. A restored LT-1 carb goes on ebay from $1495-$1695. I found one but will keep the rest of the correct dated parts in case my carb needs additional maintenance work in the future. Thanks Wallifishrmn

[James G.]

Re: 71 LT1 Holley CARB Base plate Tabs Cracked/Broken

I have seen an early 72 with the old style base plate... so who knows.
One of the things I typically check for since dealing with 67-70 4150's -- my car was last day 71 I was not sure about the weak foot or the bulbous foot, my carb is original 2nd week june - but I suspect the base plate was changed as there is a note in the car maintenance records about a warped baseplate - which it currently does not have.