73 454 intake numbers

[Jim Tipton]

Hello,
I have been a Corvette admirer for the past 39yrs,6mos. I will be turning 40 in December and have bought my real corvette. On Mothers day weekend this year my wife (Mother of two) finally let me buy a Corvette_(1973 LS4 454 numbers matching engine and Trans).

I have found however the Intake and Carburator are incorrect and I am trying to locate correct ones. For the intake I have found that I currently have casting #3955287 and "Paul Herd's" book "Corvette Parts Interchange Manual" lists that I need casting #336788 or replacement cast iron casting #353015, (ALSO DOES THIS MEAN THE CORRERCT ONE IS ALUMINUM?).

I have located and recieved an intake with casting #353015 from a nice man through the internet. My dilema is that from "Paul Herd's" book it appears this is not the correct casting number, but is a usable replacement. (oddly enough, the one currently on my car is a correct replacementfor the man who sent me casting # 353015, for his 1970 Chevelle.) So, for me to have a correct intake should I continue to look for a casting #336788 with a date code that is correct, or use the casting #353015 with the date code that does fit with the build dates I've found for my car.

Sorry this is so wordy but after collecting only matchbox corvettes for 39 years I've been in heaven since Mother's Day weekend.

[Jack H.]

Re: 73 454 intake numbers

First, I'd suggest you plunk down the $30 and buy a 1973-74 NCRS Technical Information Manual & Judging Guide for 'baby' (available at the 'store' -- this web site). It'll tell you the lion's share of specifics judges look for when judging factory authenticity. A LOT of the fun in this sport/hobby comes from gaining the knowledge of this/that on your car!

Back to the intake... The LS5 in '73 shipped with a cast iron intake, casting no. 353015. Plus, they were dated. So, to go back to factory stock appearance, you'd want a 353015 intake with a casting date 0-6 months before your car's build date AND prior to the engine's assy date as indicated on the stamp pad.

My hunch is the car's original carb got 'tuckered out' and prior owners siezed the opportunity to fix things by replacing the carb AND swapping the CI intake for a lighter, 'prettier', cast aluminum intake. If your car has automatic, it won't be that difficult to find a correct 7043200 QJet to use for restoration. But, if you've got a 4-Spd, locating a 7043201 QJet is going to be a bigger chore.

One of my fellow chapter members looked for a '201 for his '73 LS5 for about 5-years without sucess until last year when I just happened to stumble on one, in pieces, at a swap meet for $35.... So, a lot here is a tradeoff of personal time vs. $$$ in tracking down the correct original parts for restoration and some find it fun and challenging NOT to dash off to the catalog houses for turn-key solution(s) vs. 'blowing' personal time to look here/there and eventually find the real McCoy item at bargain prices!

[John H.]

Re: 73 454 intake numbers

Jim -

The correct intake for your car is casting #353015 (cast iron); suggest you put the Herd book on the shelf and purchase the 1973-74 NCRS Technical Information Manual & Judging Guide, available from the on-line store (button at the top of the page), which will describe in great detail the correct original configuration of your car. Enjoy your Corvette!

[Joe L.]

Re: 73 454 intake numbers

Jim-----

The GM #3955287 is the 70-71 LS-5 big block manifold. As John and Jack have mentioned, the correct manifold for your car is the GM CASTING #353015. Actually, as far as configuration and material goes, the 3955287 and 353015 are very similar manifolds. Both are low rise, cast iron big block manifolds with oval ports and Q-Jet (spread bore) flange. However, there is one significant difference between the two: the 353015 has provisions for EGR and the 3955287 does not. Corvette engines began using EGR beginning with the 1973 model year, so intake manifolds had to be revised to accomodate.

I expect that the reason that your car has the 3955287 manifold currently is that someone wanted to "rid" the car of EGR and all "vestiges" of its once-presence. Sometimes, state emissions control inspectors don't "take well" to a blocked off EGR fitting on the intake manifold. They should be able to confirm whether the car is supposed to have EGR, or not, independent of that observation, but it doesn't always happen.

So, if you acquire and re-install a GM #353015 manifold, that will lead to the necessity to acquire and re-install the EGR system if correctness is your goal.

[Jim Tipton]

Re: 73 454 intake numbers

Thanks for the help. I will spend the $30.00 for the manual.

The 353015 that I have aquired does have a date casting within a month so it should work out great. Also the car is an original 4 speed M-21 with the optional 3.55 ratio so I will be in search of the 7043201 QJet if I can find one. My plan is to keep the car a driver while aquiring all the right parts over time, changing some as I go. The when my 2yr old boy is bigger we can restore it together.

I am a little confused as you refer to the 1973 454 as an LS5 but everything I see calls it an LS4?

[Jim Tipton]

Re: 73 454 intake numbers

Thanks I appreciate the help and advise, I will get the manual.

[Jim Tipton]

Re: 73 454 intake numbers

Thanks for the help. I see now that the 353015 must be the correct manifold, and yes you are correct it will reqiure an EGR Valve. Any idea where I can get one?

[Jim Tipton]

Re: 73 454 intake numbers additional

Joe, Jack, or John,

You all recommended the manual and I will get me one. One question though....the "paul Herd" manual (to be shelved) mentions a part number for the 1973 LS4 454 to include casting # 336788, until I get my new manual can any of you advise me why he lists this as the part number for this application? wuth the #353015 cast under Note(s)?

[Joe L.]

Re: 73 454 intake numbers

Jim-----

1973 and 1974 Corvette big blocks were designated LS-4. They primarily differed from the earlier LS-5 engines by virtue of a different camshaft. There were some other differences, of course, but the camshaft was the main one.

[Joe L.]

Re: 73 454 intake numbers additional

Jim-----

I think that Paul Herd got his numbers wrong. There was a GM CASTING #336789 manifold, but there was no 336788 (although an "8" and a "9" are easily confused when reading casting numbers). The GM CASTING #336789 manifold was used for 1974 Corvettes and other Chevrolet models with LS-4 engines. It is very similar to the 353015 and could easily be used as a functional replacement. It would not be generally considered "correct", though, for a 1973. I would not absolutely rule out the possibility that the 336789 was used on some 1973 Corvettes; it's completely interchangeable on a functional basis. However, IF it was ever originally installed on a 1973, it was certainly "not typical of factory production".

[Joe L.]

Re: 73 454 intake numbers

Jim----

The original valve was GM #7047066. It was discontinued in March, 1986. A GM #17051867 can be used as a functional replacement, but it was discontinued in May, 1984 (yes, 2 years before the original valve was discontinued).

You may be able to find an NOS valve on eBay or at a swap meet. Such a piece might bring big $$$, though. A used valve is another alternative; these valves usually have the part number stamped on the steel cover section of the valve. However, you always need to be leery of used EGR valves. EGR valve usually fail in one of two ways:

1) the internal actuating diaphragm fails. In this case, the valve is "dead". I know of no way to repair the diaphragm since the valve is of crimped construction and "non-repairable". The high heat that these valves are exposed to contributes to diaphragm failure, even though the valves are designed to "isolate" the "hot section" from the diaphragm chamber;

2) the valve plunger sticks at the orifice due carbonization. Many valves are scrapped due to this problem, but it can be easily cleaned with a Dremel Tool and restored to operation. If the valve sticks in the closed position, usually no operational problem is encountered (except at functional emissions inspection check time), so it just stays that way. If the valve sticks in any open position, the engine wil run badly. This is usually what prompts valve replacement.

You also have the option of obtaining a non-functional used valve for "appearance" purposes. If you ensure that the valve is "permanently closed", even a valve with a defective diaphragm can be used. It will appear correct and only your state emissions control inspector will know the difference.

[Jim Tipton]

Re: 73 454 intake numbers

Joe,
Thanks again, I ordered the catalog from the site today and signed for a two year NCRS Membership. I've copied down the numbers you gave for the valve and will begin looking to find one. I already have the Manifold on a straight up trade with someone for the manifold on my car curently so I'm halfway there minus the carb as yet.