1968 Overheating

**Robert S.** · August 1, 2006, 05:58 PM

Re: 1968 Overheating

Seems to me you have done everything correct thus far. Except as you said "replaced the radiator (the car sat for 32 years so I thought it could plugged)" I would bet there is a far amount of gunk/rust built-up in the engine water-jackets too from sitting so long. Did you reverse flush the the system as well? That might loosen up some of the stuff in the engine, just hope it doesn't block other passages.

Do you have the correct fan, shroud and especially the radiator seals?

One other option for you to try is a high volume water pump. Check JEGS or Summit for what is available for your car.

**Rolly Carlson** · August 1, 2006, 08:04 PM

Re: 1968 Overheating

Thanks for the response. The engine was totally rebuilt at the time of restore, so it should be free from all gunk. Only around 500 miles on it. Yes, I do have all the orginal equipment and will put what I can back on. But, I'm afraid It's going to take some aftermarket 'stuff' to fix it. I'll look in Jegs.

**Wayne P.** · August 1, 2006, 09:42 PM

Re: 1968 Overheating

Don't forget to make sure the timing and advance are correct.

**Mark #28455** · August 1, 2006, 10:28 PM

Don't buy non-stock stuff yet

I own several BB cars and they ALL run totally stock cooling systems - and work OK. That includes my 489 cu in L89.

You have to remember that the oval port engines were totally streetable and were factory designed for reliable day to day use. You are missing something!

Is the fuel/air mixture correct? Is there a vacuum leak? Is the exhaust heat riser valve opening? Is the ignition advance working? Is the timing correct - both initial and total? Is the vacuum advance working and attached to manifold, not ported vacuum? Has the engine been "hot rodded" or is it stock? Are all the radiator/fan shroud seals intact? Is the fan shroud intact? Is the spoiler under the nose of the car intact? Etc.

Once you find the glitch, it will work fine.

Mark

**Clem Z.** · August 2, 2006, 08:31 AM

was not there a call back on 68s to cut open

the front of the car for more air,was that done?.

**Terry F.** · August 2, 2006, 08:42 AM

Re: 1968 Overheating

Rolly,
It is possible that the engine has a head gasket leak. Compression that pushes past the head gasket and into the water jacket will make it look like it is over heating. You can watch for air bubble in the radiator when the engine is running and warmed up. I would take the radiator cap off when cool and run it untill it gets hot. Watch the water/antifreeze in the tank for continuous bubbles. You will need to make sure it is fairly full so you can see the bubbles. Just a possibility depending on the condition of the deck surface and type of head gaskets used. Seen it before. Terry

**Michael H.** · August 2, 2006, 08:45 AM

Re: was not there a call back on 68s to cut open

Clem,

I remember the TSB that GM sent on the over heating problem and the modification that you mentioned. I don't know much about C3 but seems I remember some early C3's originally had no holes in the lower front panel? The TSB included templets used to cut the rectangular shaped holes.

**Terry F.** · August 2, 2006, 08:47 AM

Yes, early cars were recalled to have the

front valence panel cut open to improve air flow. Not sure if it was an actual recall or not. I also read that the front end would get light at high speeds and this would help that a bit also?? I have the templates for the cut-outs that were issued back then in a dealer tech bulletin. Take care, Terry

**Terry F.** · August 2, 2006, 08:50 AM

Re: 1968 Overheating

Rolly,
Does your car have its original lift brackets still in place? If so, any chance you could send pictures of them or tell me what part numbers and marking are on them? Thanks, Terry

**Terry F.** · August 2, 2006, 08:53 AM

Re: 1968 Overheating

The problem with a seeping head gasket is that it may not leak untill the engine is fully warmed up. So, it can be a pain to catch. Thereb have been a lot of suggestions made that are good. Each system needs to be in place. I have an original 390hp. If you need a picture of something, let me know. Terry

**Michael H.** · August 2, 2006, 09:20 AM

Re: 1968 Overheating

Rolly,

I may be completely wrong on this but I seem to remember the first engine lift brackets coming in on the new 69 models? Could it be that big block had these in 68 but not small block? My new 68 Z28 Camaro definitely did not have the lift brackets when delivered. In fact, I vividly remember scrounging a set for my 68 from a replaced complete warranty engine assembly from a new 69.

**Jack H.** · August 2, 2006, 09:25 AM

Before you go too far...

DEFINE 'overheat'. If it's not popping the rad cap and spewing coolant while you're driving, you may NOT have a case of bona fide overheating. Many simply see the cockpit temp gauge reading higher than they believe to be safe and then declare their car is 'overheating'...

There are MANY prior threads in the archives that address the inaccuracy of the temp guage with suggestions on how to approach the issue. Basically, you start by getting a 'second opinion' of the actual temperature of the engine coolant (use an external IR thermometer, duct tape wrap a meat thermometer onto the upper rad hose, Etc.) and compare that to the reading shown on the temp gauge.

Lots of folks have 'chased their tails' believing the dash guage was accurate when it wasn't!

**Terry F.** · August 2, 2006, 09:26 AM

Re: 1968 Overheating

For the most part I believe the engines had the lift brackets on them. It is possible that some dealers removed them when the car arrived as part of the dealer prep. I have pictures of several 68 corvettes with them but the pictures don't shoe the details like part number and symbols and small holes. The forward bracket on some big blocks had a small hole drilled through it. Looked like a throttle spring might have attached there?? Terry

**Michael H.** · August 2, 2006, 09:42 AM

Re: 1968 Overheating

I suppose it's possible that the brackets may have been a mid 68 addition and early cars had no brackets? (my new 68 was a December 67 build) Also, could it be that big block started using these before small block?

The brackets would have had nothing to do with new car delivery, or "prep", so if they were installed at Flint/Tonawanda, they remained on the car.

1968 Overheating

1968 Overheating

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