71 LS5 carb

[Roberto L.]

Hello friends, a BB owner here in my country needs info about his carburetor (car is 71 LS5 with manual trans). Asuming he has the original carb (no confirmation yet), I need to know which is especific rebuild kit for this carb (7041205). Owner is rather serious about factory specs. Any help would be appreciated.

Roberto, NCRS #30019, RMC

[Joe L.]

Re: 71 LS5 carb

Roberto-----

The Rochester major rebuild kit for the GM #7041205 carburetor was GM #7036813. The minor rebuild kit was GM #7039171. Both are long since discontinued. However, even if you could find one(old minor rebuild kits are not that hard to find; major rebuild kits are tough to find) I don't know if I'd use it. Very likely, many of the gaskets will have dried out and partially deteriorated. For a rebuild kit which will service this carburetor perfectly, I'd look to a Filko Automotive Parts dealer. Filko manufactures excellent carburetor and ignition parts.

[Chuck S.]

Re: 71 LS5 carb

Roberto,

The part number you posted is correct for a '71 LS5 with four-speed manual transmission.

To determine if it is the "original" carburetor, check the production date code and compare it with car's build date. There is a vertical boss on the left side rear of the carburetor main body where the Rochester part number and a four digit julian date is stamped. In the julian format, the first three digits will be the DAY OF THE YEAR produced, e. g. "001"=January 1, "032"=February 1, etc. The fourth digit is the last digit of the production year, which in this case could be "0"(for an early car) or "1". The carburetor date code should PRECEDE the car's build date; sometimes by as much as several months. This doesn't prove it is the original carburetor, but it is strong circumstantial evidence. If it is not the original carburetor, someone would need to go to the trouble to get the correct part number with a reasonable date code for the car; only a knowledgeable Corvette enthusiast would go to the trouble.

The car's build date is on a stainless steel plate riveted to the left door hinge column; in the upper right corner of the text should be an alpha-numeric code like "A30" where "A" is the month (A=August, B=September, etc.) and "30" is the day of the month the car was built.

Chuck Sangerhausen

[Jack H.]

Re: 71 LS5 carb

Hygrade also makes a minor rebuild kit that works well. We get 'em here by calling NAPA or other local parts houses. Have to remember to supplement the basic rebuild kit with a float and airhorn gasket as these are NOT included in the core kit.

By '70, the Q-Jet float was Nitryl coated foam replacing the earlier soldered brass ball style float. Nitryl works great but seems prone to fatigue (skin cracks allowing gas to waterlog the foam core) over time especially if the car is stored for long periods, without periodic exercise, and the fuel bowl drys up....

Joe has posted in the past, Filko still supplies brass floats. But, guys I've talked to prefer the Nitryl devices despite their inherent propensity to waterlog -- why?

Local carb guys say you can forestall Nitryl fatigue problems by simply running the engine briefly to keep the fuel bowl full, AND, when this float starts to waterlog the symptoms are obvious if you know and watch (rich running engine). Plus, 'death' of the Nitryl float is long/slow, vs. brass float that dies instantly and these days being out in the middle of nowhere, carb parts may not be that easy to pick up.... They also say (old wive's tale?) that Holley who continues to use brass seems to wear better due to shape/placement of float and design of bowl vs. Q-Jet.

[motorman]

Re: 71 LS5 carb

the brass float has a different density than the stock Q jet float so the dry setting will be off from the stock specs. holley now uses a plastic float in most of its non racing carbs.the float setting for these floats are different than the brass. do not use the stock Q jet float if you use octane boosters because they attack the float coating, also the inside coating of the float bowl.

[Roberto L.]

Thanks to all (no message)