Running hot issue, BBc

[F-BIRD'88]

12.5:1 cr. Pinging... You may have popped a head gasket from detonation... I hope you did not dyno it on pump gas or intend to run it on pump gas with 12.5:1 cr...

The head gasket acted like a fuse. May have saved you a set of pistons. 12.5:1 cr is too much for pump gas.
Yup it will overheat.

[Old School]

Back in my younger days I have a very similar engine to yours. Like you I had too much compression for the fuel I had. I raised a head gasket and lightly torched the head and block between the cylinders. The detonation also hammered on the piston tops and closed the ring land up on some pistons and cracked others.

After I lowered the compression, decked both the block and head all my heating problems went away.

If you can run fuel to handle the compression a high compression engine will run just as cool, if not cooler than a lower compression. I would rather have lower compression and be able to run the correct timing instead of trying to band aid high compression with lower timing. The lower timing will add to the heat.

Hope you didn't hurt parts but a milling the block and head for flatness would be my first thought. Checking the pistons and ring lands to see if collapsed or raised at the valve notch should be done. I would just pull the engine and trans, send the trans to the builder and satisfy myself that the engine was ok.

If you are planning to run pump gas with a cast iron head and closed chamber in a bbc with a dome piston the most I have been able to get away with and run the correct timing curve is 10 to 1 max. That is on 93 octane out of any pump, some pumps don't seem to have the octane others do.

[af2]

Come on Guys It HELD PRESSURE FOR TWELVE HOURS. What that tells me is the water pump in reverse or the radiator not big enough or the T-STAT is not correct Or the lower hose is collapsing as in no spring in it. I realize he has a re-stricter but how much?

[arlancam509]

Come on Guys It HELD PRESSURE FOR TWELVE HOURS. What that tells me is the water pump in reverse or the radiator not big enough or the T-STAT is not correct Or the lower hose is collapsing as in no spring in it. I realize he has a re-stricter but how much?

yeah, it is pretty funny how complicated some of us like to make it. haha. it held pressure for 12 hours, how can anything be wrong in that situation? sounds like the head gaskets are perfect!

i was breaking in a cam once about 20 years ago and it was late and i was tired and it was dark and i noticed the header tubes starting to change color. wait a second, are they ... no way ... can't be... it has only been running for 3 minutes!!! the headers are glowing! what the fuh-hell?!?! haha.

after an hour of checking EVERYTHING, i found the bottom radiator hose collapsing. no spring. woohoo.

[67 Nova]

So, fired it up, and the pump is running and moving water well??? Was about 2 inches down at idle, rav'ved it a bit, water went down and flowed in well. So WATERPUMP is running correct. Figure now that water is getting to boiling point and contaminates are foaming once water boils. Still no reason why it's running so hot though. Going to do 50/50 coolant and water plus a 180 t stat and see where it is. That is once the trans is fixed and car is back to me. Didn't do compression check as new compression tester had damaged threads and wouldn't screw in. So will look at that this coming week at trans shop.

Thanks for the help.

[F-BIRD'88]

As wisely posted, check the lower rad hose for a internal spring to stop it from collapsing when hot.

Engine spark timing curve.
If 12.5:1 and reduced wot timing is desired for pump gas then a very different, specific diz timing curve setup will be needed. A stock like curvevwill not work and may well result in overheating while driving around.
12.5:1 is a big mistake (anything street driven)

[67 Nova]

I know 12.5 is pushing it. I know there are alum headed deals with 12 to one and they seem to be ok. I have another pump gas motor in my other car. More strip then street, but is a streetcar. it's a noticeably more than this one but alum heads and block. I dyno'ed with 65/35 mix of 94 and 118 fuel and it made 785. Bit of a let down but other issues with that.

Anyway, I'm more concerned with the engine getting warm/hot while sitting, but when moving at 30-40 MPH it's not getting any cooler then when sitting still? Will check the hose, but this was a streetcar last summer with the 502. Do think it got this hot so can't see it being the hose? BUT you never know.

[F-BIRD'88]

Pushing it is a understatement. Nobody is running true 12.5:1 on a carbed street motor aluminum heads or not on pump gas.

You spent all this money on the motor and noq inevable detonation is going to kill it on the street.
Engines do not self heal. It will be a old huffer in no time...
Then where are you at.

Hot running and hot idl;ng, retarded timing (to avoid detonation) crutch... Poor thru air flow.. Rad, shrouding, front chin spoiler... Water flow issues. All add up.
Keeping a bbc cool in a Chevy II chassis is hard enough.
The excessive CR is going to be your down fall..
Its just not practical. Those who claim this and that are liers.
Getting the tming curve right will help..
I have been where you are...

Yes that lower rad hose is CRITICAL...

With 502 cid you do not need nor want 12.5:1 cr to make 700+ hp. This was a big mistake.
All you are going to do is tear up the $$$$ motor...
High compression ratio needs high octane gasoline.

[Newold1]

Shoot a pic and post of the engine bay especially the area between the engine and radiator.

What type of fan and shroud are you running and are you using undersize crankshaft pulleys?

How do you know your compression ratio is actually 12.5 to 1?

Measure your cranking compression-two benefits, 1. find leaks and 2. help calculate dynamic compression and fuel octane issues. No guessing!

What timing values are you running and how were they verified?

[Schurkey]

Parallel-flow head gaskets installed on a series-flow block? Dramatically restricts coolant flow from the block into the head--so it looks like the water pump isn't pumping enough.

[67 Nova]

Car is out at trani shop. Will get some pictures.

The car was a running 502 with Edelbrock Pro Flow EFI and no other gauge when I bought it. I bought it rolling BUT got rad, water pump, pulleys headers etc.

Cooling consist of:
Rad is 2 core alum, Merch serpentine pulley and lower alt kit (only 3 pulleys, crank WP and alt at this time) FULL alum shroud with NYLON fan (not sure on diameter or #of blades off hand), and no thermostat just a reducer with about 1/2 hole it it (mabe bigger not sure).

Motor:
Calculated 12.5 to 1 using this calculator:
4.280 bore, 3.76 stroke, 4.37 HG dia. .039 comp height of gasket, 105 cc'ed chamber, piston 43.1 volume and piston down .021 in block.
http://www.csgnetwork.com/compcalc.html

Block is .030 BBc "289" block. Head gaskets are Fel Pro 17046 I believe. Heads are GM ported Gm "215" ovals, Holley Strip dom intake with reducer no T stat.

Motor only got about 180 on dyno made 629Hp at 6900 and 588 at 5100 on Klotz 100 octane fuel.

[F-BIRD'88]

Change to a 120cc open chamber head will drop cr to 10.6:1 for street pump gas.

[GRTfast]

What timing curve are you running? Vacuum advance?

If the timing is too retarded at idle and during cruising, it will dump a ton of heat into the exhaust port and make the car run hot.

[F-BIRD'88]

What timing curve are you running? Vacuum advance?

If the timing is too retarded at idle and during cruising, it will dump a ton of heat into the exhaust port and make the car run hot.

Heats up the exhaust port and the cylinder walls also.

[F-BIRD'88]

Never substitute a thermostat for a restrictor on any street driven car.