175hp LM1 overheating

Time to fix the engine.
- Quite browned coolant (level ok, no leak), dirty and a little bit oily - Engine oil at recommended level 10W40 synthetic (leak 1quart every 2 months at the main seal but will get fixed new oil pan gasket and main seal) - Radiator blades are clean, - Fan rotating ok, and factory fitted to the radiator. - Overheating was not an issue until this summer (got it to vapor lock because of coolant boiling in the following conditions: 1979 Camaro Berlinetta 1.6 metric tons + 4 passengers 250 Kg [total 1.85 t] 2 US ton, 15km (9.32miles) ramp up at average 4%, 32°C outside temp 90°F, larger tires than factory (255/60R15 rear, 235,60R14 front) with factory 3/23 rear transmission. These where hard conditions for an old engine but it should not have gone to the point of boiling the coolant. (Hopefully I didn't engage the air conditioning compressor because it need upgrade and refill)
From web searching, these may reveal a possible exhaust gas leak into the coolant because of cracked head gaskets (coolant color change and overheat). Do you agree with that diagnosis?
I'll have to wait until September, for a mechanic to look at it but, would like to order replacement parts now, because of significant lag in delivery to Europe.
If head gaskets need to be replaced, what kind is suitable for a 30yo stock unmodified GM factory LM1 who went over the 5 digit km counter at least once)?
There are many kinds of head gaskets listed with different thicknesses, materials rated applicable for this 1979 chevy 350cid V8 (AKA LM1).
Are these gaskets ok?
Reply to
Lea Gris
In article ,
Possible I'd flush the system out with clean water and check the thermostat first. See what happens. Is the Rad cap ok? Belts not slipping? Maybe change the stat anyway. I've had one that appeared to work in my LT1 but changing it cured some weird symptoms.
Not sure what thickness gasket your motor should have but those are probably fine. Ask summit what they'd reccomend. You'd also need the inlet manifold gaskets as well.
Reply to
Terminal Crazy
Perhaps. But the first thing is to completely clean and fix the cooling system.
Four passengers and 32 degrees uphill can be quite a load. Perhaps more than an unmaintained cooling system can handle.
I don't know standard factory tire fitment for Camaros; I imagine something like FR70-14. Tires may be a bit oversize but not terribly so. Should not make any difference.
Not really. It is much more of a problem with heads/blocks with different materials, specifically aluminum (heads) and cast iron (blocks). Aluminum expands more than cast iron, so gasket is sheared (a small amount) every time engine warms up and cools down.
First thing is to clean cooling system and change coolant. When was the last time it was changed? Must be ten years or more! I have never seen rusty, oily coolant and I have been lazy about cooling system maintenance myself.
I suspect that the radiator may be a bit plugged, which will cause overheating under heavy load. A bad head gasket will cause overheating and bubbles in the radiator and coolant tank even in normal operation.
Are you losing any coolant, or is the level in the tank staying at the same place?
If you are losing coolant, and can not find a leak anywhere, then maybe you have a gasket problem after all.
If you are not losing coolant, then I would NOT start with an engine overhaul, but with a cooling system overhaul.
--remove all the old "coolant"; it's bad already --flush out the engine block and heater core --have a good radiator shop look at your radiator; a bad radiator will cause overheating as you describe; you may need a new radiator, and I would recommend that if the existing radiator is original and looking corroded --replace all hoses (this will likely require a special order but shipping will not be TOO bad I hope) --if your fan is a clutch design (spins freely, has a big aluminum disk in centre) make sure it is working properly; although bad fan usually causes overheating in slow driving or stopping, a bad fan does not make much difference in faster driving --do you have a temperature gauge, or just a "HOT" light? you should have a gauge to really understand what is happening at your engine --maybe the thermostat needs replacement; I would go with the factory recommendation which is probably 195F or 91C
My old 1979 Firebird went 425,000 km. We had to remove one head to fix a broken exhaust manifold stud; otherwise the engine was never apart. Okay, that was a Pontiac 301 engine, but I would figure a Chev 350 will last a long time too. Honestly, if you are going to start pulling the heads off to replace the gaskets, why not take the engine out and do a full rebuild? Chev 350 parts are cheap (in North America) and should not be impossible to find in Europe. Maybe a US or NATO base is close by you?
Reply to
Ed Treijs
Coolant was purged completely when the lower water hose splat disemboweled last year. I replaced both upper and lower hose with proper factory design repros with proper turn around the AC compressor (for upper).
Today I went with it in a a ride on the A75 highway to Millau. The temp gauge did not reach the red zone but stayed near between 200 and 220°F after the first 40Km. Quite hot but the highway here has long ramps and turns between Millau (famous bridge) and Marvejols. Reference operating temperature should be between 180 and 190.
No noticeable coolant loss.
Yes, it turned reddish quite fast in like 6 months. Accounting this is a hobby collector car and not my daily commuter. It runs like 500Km/month.
The current radiator was replaced by a new one like 6 year ago and the last owner did not use the car that much as he spent most of the 8 years he owned it filling legal requests and forms, and paying insane amount for dynos (required by legal registration), brake metering, and master cylinder side clear transparent canister to get oil level visible (required by registration), to have it registered legally in France as a collector :) So he drove the car like 2 and half a year. Finally after spending significant insane amount on legal nightmare and too little on real restoration parts, and beside it ended right, he sold it to me :)
Already done (see above)
I'll have the mech. check the fan clutch pulley, good idea!
Just a gauge with lower mark at 180, upper middle range between 200-220 and the red zone between 220-240 upper mark of the gauge..
The 1979 Chevrolet service manual tells the normal operational temperature is between 180°F and 190°F and the water thermostat should open at 180°F.
I bought a full engine rebuilt kit for 200$ with all new gaskets, pistons, piston rings, all shafts bearings at the size required for an unmodified 1979 chevy small block.
Luckily there is a good mechanic nearby with the tools and knowledge to do the engine rebuild. The car will go to his garage tomorrow for an overall look and evaluation. The rebuilt itself and all the new parts I bought will be done during October.
Reply to
Lea Gris
On mine, it was oil coming from the transmission that get in the radiator. This cause exactly the same symptoms as you.
How is the oil in the engine? If it look clean, maybe you got the same problem as me.
Reply to
Pascal Boivin
My Camaro is at the mechanic shop. The oil pan has a crack to be soldered fixed. Radiator and coolant circulation will be checked purged fixed. The work's going on it. I'll keep you tuned.
Reply to
Lea Gris
Me wrote :
Hello !
Here are news about the restoration job going on my 79 Camaro Berlinetta:
The oil pan crack was soldered. Crank bearings where checked and are in a perfectly good shape and so left unchanged. The radiator is being rebuild with new threads because there where too much oxidation and rusts clogs. I expect it to be done at the end of this week Oil pan and valve covers repainted and remounted with new gaskets. New 4in1 exhaust headers and true dual lines are being mounted in place of the rusted and over-patched originals. Will be filled with 10W40 Motule 300V oil. New 15"x7" ARE Tork Thrust II polished aluminum wheel will be mounted next week (waiting for proper P215/65HR15 tires, can't find White Side or Raised White Letters here).
Reply to
Lea Gris
Good work keeping an old Chevy going in Europe! When you say the oil pan was soldered, I hope you mean welded (electric arc) or brazed with brass or bronze, and not soldered with lead/tin solder.
Here in the states there are 2 kinds of soldering, soft and hard. soft solder uses lead/tin or the newer lead free solders. Hard soldering is also called brazing and uses a brass or bronze rod for filler.
Did your mechanic pull the cylinder heads off?
How do they look? any signs of a blown head gasket?
Thank You, Randy
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Reply to
I got my car back last week and went with it for 300km total on roads.
The oil pan was indeed welded (thanks for the help).
The radiator capacity was reduced to half due to rust accumulation. That was the main cause for overheating.
The cylinder heads where not taken apart. The mechanic had a test for the coolant to detect CO2 leak and it was ok. The gaskets don't leak.
Wheels where finally fitted Cooper Cobra RWL tires.
Carburetor was nicely adjusted as well as CO output minimized.
Got race quality oil (Motule 300V).
The new exhaust sound great, a bit like those of motorbike because there is no H or X tubing.
There are still adjustments and fitting issues with the new exhaust exits. It beat at the leaf springs and inside the lower rear quarter panels. I hope some adjustments will sort out the issues. I choosed a premium kit but would had better choosed a more factory-like configuration.
The new exhaust have mufflers under the floor pans and it slightly reduce clearance passenger side. I would had better choosed one big combined dual in dual out muffler at the right place behind up the rear axle transmission, as it was factory designed that way.
You may enjoy new shots here:
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Or watch a short video of the new exhaust sound here:
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sound only here:
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Reply to
Lea Gris

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