redvetracr

what is the pound rating on a factory cap? 11lbs doesn`t sound like enough and if memory serves each pound is worth an additional 3*

doorgunner

I think it's 13 lbs......but my radiator is so thin that I can dent the top of it with my little finger....I was using 11 lbs to keep from ballooning or blowing it up because of the overheating problem...

Also.....the top radiator hose gets so hard that you can even squeeze it at operating temperature.

68/70Vette

Here we go again..

When I did a restomod on my 68, I installed a new ZZ4 and a Be Cool BB aluminum radiator. The ZZ4 is a SB. I had adequate cooling capacity with the BB radiator. When I wetted the cooling system, I only added 100% ethylene glycol...green stuff. There is no water at all in the cooling system. The advantage of pure glycol is that it doesn't boil below ~350 degrees F. Because of the boiling temp, a 100% ethylene glycol cooling system will NOT pressurize at normal engine operating temperatures. In my first test drive around the block after my engine install, I didn't even have band clamps on some of the radiator hoses....just pushed on the hoses and with no pressure in the cooling system this would not cause leaking.

I have 100% ethylene glycol coolant in my daily drivers..95 Cadillac Seville..and a 97 Ford Thunderbird. I drove the Thunderbird for about a year with a slight leak in the coolant system, since the coolant system never pressurized, I only lost about a quart of ethylene every week.

OK..next concern...ethylene glycol is a little less efficient of a coolant than water. I did notice the Tbird ran slightly hotter with pure ethylene. (The caddy doesn't have a water temp gauge.) However for radiative heat transfer, heat transfer is a function of the 4th power of the difference between incoming air temp and radiator temp. This means, for example, that at 4% increase in engine temperature will result in a 20% increase in radiator efficiency. I don't think that it is possible to overheat an engine with 100% ethylene glycol....that 4th power factor just dumps tremendous amount of heat.

When I removed the original engine from the 68 about 6 years ago, it had not had water in the cooling system since about 1972. There was no rust in the engine coolant passages...they were covered with a white coating of silicates from the anti-freeze.

All WWII fighter planes with liquid cooled engines used 100% ethylene glycol...no water

Just my experience, FYI. I know you can't use pure ethylene glycol in temps below 0 since the ethylene takes on the consistency of honey........the engine starter will have problems turning over the water pump.

doorgunner

68/70Vette..............thanks for the info.

doorgunner

Slight improvement concerning overheating after 1 hour of driving at 70 mph......................

Timing is set to 14*

Distributor is plugged into Manifold vacuum

13 lb. radiator cap

New engine cooling fan drawing ambient air is installed

Idling for 30 minutes plus----NO overheating/stays at 180/electric fans turn on and off correctly

Top radiator hose still gets very stiff/unsqueezable after 180*thermostat opens....

it seems to be getting just enough coolant through the radiator to maintain 180* while idling and driving 45 mph or less

BUT....the good news is the inside cabin-firewall/cabin floorboard/tunnel temperature is only 10 degrees ABOVE AMBIENT AIR temperature even with engine temp. at 210* with one hour of highway/60-70mph driving!

REELAV8R

180* is good. Wouldn't want it any colder. What were the ambient temps on these test runs?

briankeery

I think the addition of a good four core, or dare I say it a Dewitts, might allow you eliminate a lot of this plumbing and go back to a more stock look cooling system. Especially with your summer climate buddy, you might be able to put this issue to rest. Maybe Santa will bring you a new rad.

Raphiki

Stupid question - are you sure your thermostat is not in upside down? I've seen this before with the pressure buildup in the top hose,

doorgunner

Yep......180* is great.....but 60mph on highways----the temp creeps up to 220* plus....which is the problem for me........



Very true....but that conglomeration of ducting has allowed me to get the floorboard/tunnel temps down to 4* above 95*F ambient temperature in August...I think Santa will e-mail your DeWitt post to my adult children tonight......


So.....here are the faccccccccccts:

'34 truck SBC/' 350 flat-top pistons A/T A/C.........radiator top hose can be squeezed even at operating temp with thermostat OPEN.

'06 Escalade 6 liter stock A/T A/C .......radiator top hose can be squeezed even at operating temp with thermostat open.

'68 Corvette/'70 SBC350 stock A/T .....radiator top hose CANNOT be squeezed at operating temp with thermostat open.

HMMMMMMMMMMMMMMMMMMMMMM?????

Bad Bird

Yes, this is correct for radiative heat transfer. However, the majority of heat dumped by a bar and fin radiator is by convection. These radiators are not radiative heat sinks.

doorgunner

I'm on meds.......I hope I DO have the thermo upside down........the "bulb" goes DOWN.....right????

(anyone?)

briankeery

Well, in case you need Santa's address, just let me know. He is Canadian after all...........

doorgunner

That would explain why you have one of his helpers in your Avatar pic!

76CSRvette

The spring thingy goes into the intake manifold

76CSRvette

Pic

doorgunner

RATS! I installed it correctly....(the meds had me second-guessing myself)......

now I'm stuck with either a bad radiator or an engine head problem....I think I'll remove the spark plugs (again)to check the cylinders for coolant-----passenger's side first.

The13Bats

Door,
I still think you have an old, less than perfect radiator,
My 66 when it got to that point was on a trip from Orlando to jax to visit dad, the whole time we putzed with the car, and driving home was fine just so long as I didn't push it past about 35-40 mph, you could creep up the speed and actually see where it started making the temp creep up, but to me over 200 is hot especially at a good highway speed,

After I installed a new stock radiator ( stock 327 ) the thing always stayed about 180-190
I was only running a junkyard Fiero electric fan from the 6 gt fiero,

I don't believe this to be your problem but I recall reading or being told the story of a fellow ( perhaps Tom Dewitt told me this I can't recall for sure )
Anyway his engine was tight, hard to turn over, it ran okay but overheated because of the extra friction and work needed to turn it.

wish you were closer I would give you the radiator out my 69 it did keep both the 383 and 454 cool the 454 better than the 383 go figure, it would tell you this is or is not a radiator issue.

Solid LT1

First thing...you would be better served by posting your question in the C3 tech/performance section. You said your timing is 8deg BTDC....this is a little retarded, good for emissions but bad for power. I would bump the initial timing to 12-14 degrees BTDC and see what happens. You are sure the cooling system is full? I fill my Vettes without the thermostat housing on, making sure system is topped off at intake flange. Then I install thermostat and gasket/housing leaving the top radiator hose off the radiator connection, then fill the radiator, last the top hose and quickly connect it onto the radiator, yes you will lose some fluid but system should be 90% full at this point. Sounds like you were already partially down the right path as hooking vacuum advance can onto intake manifold would advance timing at idle. you can advance initial timing until you run into detonation problems or hard starting due to excessive initial advance.

doorgunner

Bats---it's true.....the current radiator must have been for the 327 engine---it's 7" SHORTER than a "standard radiator"!

Anyhow.....I pressurized the system to 20 lbs. just to be sure/spark plugs removed to eliminate cylinder pressure/let the car sit for 3 hours/then cranked over the engine to see if any coolant blew out of spark plug holes.

Results:

The pressure dropped to 18 pounds and stayed at 18 until I removed the test pump.

NO coolant blew out of the spark plug holes after 3 hours


I removed the radiator from the car and test-rigged a water hose to fill it/positioned the radiator so that the outlet was the highest point and I filled it through the inlet.

Results: The 40 p.s.i water pressure struggled to force the water up and out....apparently somebody put some type of radiator leak stop in it before I bought the car causing the tubes to be restricted...

that would explain why the new pump causes the upper radiator hose to be so stiff----the pump is having trouble forcing the coolant through the radiator.

SO......the head gaskets ore O.K.........and the new pump is standard rotation per water spraying out of the disconnected upper hose with the engine thermostat opened


(Being a rookie is bad.....being a rookie on meds is worse )

Brack c

DG , glad its not the heads / head gaskets ...that's what I was worried about .