When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hi guys,
Me and Dad bought a C3 1976 l48 auto back in late 2017.
This past summer we had the radiator rebuilt. Yet still overheating. Going to buy a radiator from Dewitts. But here comes my struggle. Due to radiator and radiator supports being different from early to late models I need to figure this out to get the c3 back on the road. We live in Portugal, Europe and there are no corvette mechanics here.
Is it an early model or late model Vette?
Vin is IZ37L6S435352
Trim tag J19
152 trim
13 pain
The last 5 digits are the number of the car in production order. Your car was number 35,352 off of the assembly line. There were 46,558 1976 Vettes. Production ran from August 1975 to August 1976, but the number of cars made per month varies. Looks like yours was made in May 1976:
1 - Chevy
Z - Corvette
37 - 2 door coupe
L - 350 ci engine
6 - last digit of production year (1976)
S - Built in St. Louis
4xxxxx - production number (I'm not sure why there is a 4 prefacing the actual production number)
Okay...radiator STILL overheating. You MUST go back to the fundamentals of cooling systems.
1. SEAL all the surrounds on the existing radiator....around the rad, on top of the rad, between the fan shroud and the radiator....if air is getting AROUND the rad. but not through the CORE...you're going to have problems.
2. Attend to the fan....is the fan clutch operating correctly...if not just get a big-block fan clutch that comes on early, temperature-wise.
3. Make sure there are no vacuum leaks in the vacuum system and manifold...this will cause a lean condition and contribute to overheating.
4. Take out the thermostat and put it in a pan of water with a thermometer...slowly bring up the temp....is it opening at the correct number. Throw a 180° F unit in there if it's suspect.
5. Make sure the anti freeze is at least 50/50%....not just water.
6. Make sure the water pump is functioning and the lower radiator hose has the spring in it and in good condition.
Do not blame the radiator quite yet....L-48's tend NOT to overheat....so it could be a combination of cheap things to fix.
First - Welcome to the Forum. Lot of great people here to help you. Second - welcome to the 76 Club. I too have a 76 and have run into the same issue that you are going through with the radiator/radiator hoses. I have teh following in my notes and it should direct you to the right parts.How to Tell Early 76 from Late 76 - Radiator/radiator hoses
Early 76 upper radiator outlet pipe points to the RIGHT
Late 76 upper radiator outlet points straight to the REAR.
Let me add the your VIN number cannot really tell you early from late as far as the parts changes through a production year. Early/late really only applies to before or after the mid production change was made. With the radiator, mine is early - prior to the mid production change. The "Early/Late" tag will be vary by the specific part.
Hope this helps a bit.
Last edited by Go Vette Go; Nov 7, 2019 at 02:32 PM.
There's two easy ways to identify if you have the first or second design radiator.
First, check the radiator's bottom outlet. On the first design radiator, the lower outlet is a couple inches above the bottom of the radiator, and above the lower fitting for the cooling line on automatic transmission radiators. The lower outlet is all the way at the bottom of the radiator's tank, on the second design radiator.
The second way is to look at your core support and fan shroud. On the first design, the support has a threaded stud on each of the two lower saddles, that the bottom of the shroud goes onto to attach it to the support. On the second design, the bottom of the shroud just slips into a slot in the bottom of the support.
I just had to get a radiator support for a local customer of mine, who has a 76 Corvette. His car was also built around May, and had the first design radiator, support and shroud.
I do agree with L-46man though, before replacing the radiator, make sure the problem lies with the radiator, and not elsewhere. Besides the things he mentioned in his post, also make sure your timing is set correctly.
But are you sure the car is over-heading? Have you tested the sender to make sure? It could be a replacement sending unit not sending the correct ohms to the dash unit.... There is a fix for this that's way cheaper than buying a radiator and/or support.
First of all thank you for all the help and responses.
I'm pretty sure it's overheating due to clear evidence of water coming out of the radiator. As you'll see in the photos. Water pump was replaced last summer.
Still bit confused after seeing photos, tomorrow I'm going to see the car, as it's in the shop rn, to figured the radiator model.
Un-engineered electric fans are the devil... Whomever installed those did a ****-poor job. .With a FAN SHROUD and regular fan the ENTIRE FACE of the RAD is is pulling air through. What I see is 50% coverage.
I wish people would stop using electric fans as a BAND-AID....for NOT understanding Thermodynamics..
AT the VERY LEAST the fans should be 'PLENUM-ED' across the entire face of the radiator. So Air is drawn across ALL the fins...every dang one of them.
What is the PSI of the rad. Cap...should be 15psi and IT SHOULD BE WORKING!
Un-engineered electric fans are the devil... Whomever installed those did a ****-poor job. .With a FAN SHROUD and regular fan the ENTIRE FACE of the RAD is is pulling air through. What I see is 50% coverage.
I wish people would stop using electric fans as a BAND-AID....for NOT understanding Thermodynamics..
AT the VERY LEAST the fans should be 'PLENUM-ED' across the entire face of the radiator. So Air is drawn across ALL the fins...every dang one of them.
What is the PSI of the rad. Cap...should be 15psi and IT SHOULD BE WORKING!
I do not see ONE SHRED of sealing foam.
Doomed to fail....
It's was done by the previous owner... As yes its badly done, you can tell by the poor wiring..
If I buy a dewitts kit with electric fan, is there need for Radiator Support Seals and hood to air damn seals?
Early rad, the upper outlet is curved like yours the late comes straight out.
Yes I went to shop today. And confirmed its curved on the upper outlet.
Correct me if I'm wrong, but it only matters because of the radiator support and hoses. You can easily convert to 66LATE if you buy late radiator, support and hoses?
Unknown if Early or Late Model 1976
