carbster09

Guys,

Gofast is rebuilding my LS 5 and making into a 489

The engine has never really run "cool"; then again its a BBC and I was living in Texas

I presently have a Stewart Stage III pump fitted with a DeWitts radiatior. I want to back to a stock or nearly stock pump and work from there. Some have said that the Stewart pump flowed too much, not allowing the water engough retention time in the radiatior. I don't know that I actually believe this

I checked out Doc rebuild and they have two part number for '71 454. They are not sure which is correct GM 3992077 or GM 386100.

Can anyone tell me which pump is correct and / or give me some advice?

Thanks

Carbster09

HamadUP

I'm using a Stewart Stage II pump (which is about 30% more flow than the stock) and I have a Dewitt's aluminum radiator with dual spals which has again a 30% more capacity, so I think that return the balance to the system. I have no over heating issues so far (esp. when I installed a Sanden 508 compressor with the smaller parallel flow condenser) .. last summer I noticed that the maximum temp with a moderate stop and go traffic with A/C on was 210*F, which is not bad for a 110*F ambient temps.

volition

The biggest challenge facing the C3's cooling system is a relative lack of airflow across the radiator surface. No amount of cooling components can overcome this.

It's easily overlooked and should always be your first diagnosis point when tracking down cooling issues in C3's.

There needs to be a complete seal from the radiator to the support core. There also needs to be a complete seal from the core support to the hood. Last but not least there are also rubber flaps that seal the air gaps in the frame reals.

Moving farther back, the A-Arms ahve another piece of rubber to further seal airflow in the engine bay.

Cooling begins when the front spoiler (often missing) forces air up across the radiator surface which must then flow through the radiator and out the side vents on your fenders.

Any air leaks that allow air to go around your radiator rapidly diminishes the effectiveness of any cooling upgrades you may perform.

A correctly sealed radiator , despite what many will tell you, is crucial even to cooling when idling or doing city driving. Without the proper seals, you fan will end up recirculating hot engine bay air across the radiator due to the underhood air flow.


I apologize if it seems like a large rant but when it comes to cooling I see many people chasing the problem the wrong way. In these cars proper airflow should always be adressed first because of it's unusual design. The biggest upgrade you can make for your new engine is to seal every little gap in front of that radiator to maximise it's heat dissipation.


As for the pump itself the stock pumps are more than adequate even for mild big block applications. Water flow is rarely the problem except in cases of cavitation. More important is heat dissapation.

As for the two part numbers, I beleive they both describe the same part. On many items there are 2 GM part numbers, one that was used when the car was made and a "2nd generation" part number for later retail versions of the same product. I don't beleive GM makes either product anymore so just use the numbers for cross-reference.

carbster09

agree with the above "rant" as you say. Ihave addressed all of the issues; seals etc.

The two part numbers are different and carry different prices. I think one might be an LS 6 unit?

carbster09

volition

I think it may be a difference in shaft diameter

volition

edit: see below

volition

Ok here's a rough breakdown

Up to Jan 1970 Production date used 3992077

Up to August 1970 used 3856284

The rest of the 71 and 72's use 386100

CCrane65

Not quite Volition.

According to the NCRS 1970-1972 Corvette Technical Information Manual & Judging Guide,

"...1970 and 1971 up to at least s/n 1400 used water pump casting number 3940960. However, 1970 Corvettes as early as s/n 2077 used casting number 3992077. There is clearly some overlap of 454 casting numbers in 1970 and 1971. For 1972 the casting number was also 3992077 with a possibility of the 386100 being used."

cc

Eddie & the Cruisers

Corvette America says

Their no. 40860 for 70-74 Dated Rebuild BB Large Shaft #077, and 70 Late or

Their no. 40859 for 68-70 Dated Rebuild BB Small Shaft #284, and 70 Early

Evidently you need the large shaft for your 71.
since it is for the 70 late thru 74.

Also - not dated rebuilds

Their no. 44656 for 68-70 427/454 - Replacement and

Their no. 44657 for 71-74 454 - Replacement


For whatever its worth.

volition

It's definitley a difference of shaft diameter. Some have 3/4 some have 5/8. I guess it's really going to depend on if you plan to use a stock fan or not which one to choose.

71 Green 454

Yes, when I bought my '71 LS5 in 1975, the original owner had replaced the water pump. With the engine running, the pulley appeared to be going up and down. I thought it was an illusion but it drove me nuts.
I removed the fan and sure enough, a 3/4" fan/pulley on a 5/8" shaft water pump.
Replaced with 3/4" shaft water pump.....problem solved.

530planeman

Hi
saw your post about '71 LS 5 water pump .I am putting together an 71 Ls 5 for my Vette and trying to come up with correct pulley and belt set up .My car has power steering only .Does your engine have power steering ?Do you happen to know pulley #s ?ANY ENGINE PICTURE WOULD BE GREAT .
Thanks
Wes

71 Green 454

Yes, mine has power steering. You should be able to find a picture of a BB with PS and no AC. I don't have the pulley numbers, but without AC you would only need a 2 groove pulley on the water pump, or a 3 groove for future AC, a 2 groove pulley on the PS pump, a deep groove pulley on the alternator, and an idler pulley for the crank to water pump belt.

1st belt is short, crank to water pump, slack taken up by idler pulley pushing in.
2nd belt is crank to water pump to power steering pump.
3rd belt is power steering to alternator.