Big block Chevy cooling

[DLinson]

I finally drove my Nova for the first time to a local cruise but I am a little concerned with the temps.

I have a 427 Mark IV block with GM performane aluminum heads, Accel fuel injection, and it's using an Edelbrock reverse flow tall water pump. I'm running a 180 degree thermostat.

The autometer mechanical temp gage is reading the temperature from the middle of the passanger cylinder head. The fuel injection temperature sender is reading the temp from the water passage next to the thermostat. The problem is the two temps don't agree. When the fuel injection is reading 185 degrees, the mechanical gage is reading about 230.

The radiator is not overflowing but I did just change the oil and there was about 3 quarts of coolant in the oil pan. I went ahead and changed the intake gaskets, I was thinking it was leaking into the lifter valley. I don't think I have a problem with the head gaskets. There is no oil in the radiator, it is not pressurizing the coolant system and there is no coolant coming out of the exhaust.

What do you guys think? Two of my friends are running about the same set up but their engines never get above 190 and they are sampling the coolant temp from the cylinder head as well. The only difference is they are running standard rotation water pumps.

I had the car idling in the driveway and the temp climbed pretty quick and got up to 230. The EFI only read 185. I think it would have kept rising if I wouldn't have shut it off. I am runnign out of ideas on how to fix it.

Thanks,
Dennis

[derekf]

Are you able to swap the locations of the sensors? Some sensors may just report differently.

However, coolant in the pan is A Bad Thing. Have you run enough to see if the coolant is still making its way down there?

[John McIntire]

My guess would be that the mechanical guage plumbed into the side of your cylinder head is reading much higher because of its location. It is near the exhaust and the temperature is much higher over there.
I agree with derek, you should first isolate how coolant is getting down into your pan. That is definitely not a good thing.
And also try swapping sensor locations. Maybe the one for your guage is no good? or maybe thr guage is out of whack?
Good Luck!

[TonyHuntimer]

Hey Dennis,

It's possible the coolant in the pan came from some leaky head bolts or head studs...the ones located under the valve covers. If they are not leaking anymore, than they have sealed themselves. I've seen this on fresh Big blocks before. I had a leaky stud (outside the valve cover luckily) on mine for the first hour or so of running, but it sealed itself...luckily. 2600 miles later and still not leaking a drop. My engine builder told me to keep an eye on it and if it didn't seal itself I'd have to reseal the studs. He had seen this before on other engines. He said I should have used better thread sealer on the bolts.

Where are your sensors? What does a turkey thermometer in the radiator cap outlet say? Do you have a bypass hose? Did you drill a small hole in the thermostat for trapped air bubbles under the thermostat?

Tony Huntimer
RaceHome.com

[MrQuick]

I agree, double check the head studs/bolts. I must be a large enough leak to not build excessive pressure as indicated by no boil over. Glad to see you didn't flatten your cam. Roller?

I never liked using mech gauges in the head areas due to radiant heat from the exhaust. I like intake manifold ports.

[MarkM66]

I had a 396 once that the building didn't seal the head bolts. Wasted that engine before I new it, less then 500 miles. Definitally don't drive it anymore until you know that problem is fixed. You might even want to do an oil analysis just to make sure. As even a little leak is a very bad thing.

[kamaroman68]

Do you have a serpentine belt setup on your engine? Just curious as to why you would be using a reverse rotation water pump? Chris

[DLinson]

I haven't tried swapping the sensor locations yet, that will be an undertaking. The EFI sensor wiring harness is bundled in with a few other harnesses and is set up to go only to thier current locations.

I am not running a bypass hose but neither are my two friends and they are not having the cooling problems. I haven't tried drilling a hole in the thermostat. I'll try that when I drain the system.

Before I changed the intake gasket, there were puddles of coolant on top of the cylinder heads under the valve covers. After changing the intake and running the engine up to temp, there were only traces of coolant. I'm wondering if they are reminants of coolant in the passages that didn't not drain out when changing the oil.

I used Loctite brand thread sealant on the head bolts when I had to remove one of the heads for a different problem I inflicted on myself. The engine builder used sealant on the head bolts when he assembled it. I have a stud girdle on the rocker studs and the I have to remover the front master cylinder in order toget off oneof the vavle covers. Looks like checking the head bolts is going to be a chore.

Is it okay to remove one head bolt at a time, reseal, and reinstall? I know that the outer head bolts are not leaking so I'm hoping not to have to remove all of the head bolts or replacing the head gaskets.

The 3 mile round trip to the cruise was the longest drive I've taken so far and the highest the temps have ever gotten.

I am running a serpentine belt system that I designed myself. The pulley sizes are the same as the old V-belt system.

I have an e-mail in to Edelbrock's tech department, it's their heads and water pump. Hopefully they'll answer a few questions I had for them.

I'll try some of these suggestions. Any more?

[TonyHuntimer]

Dennis,

The pictures show your heads to be GM Performance. You said they are Edelbrock.

Not sure about the replacing one bolt at a time. You would be better to ask a builder that question. I'd bet he would say it's okay but when you're done you would have to retorque the whole head in the correct pattern. But don't take my word for it.

Bummer about the master cylinder. With my masters and DSE wiper motor in tact I can take my cylinder heads off with all the STUDS in the block. I was pleasantly suprised when I found out. It makes servicing a much easier chore. Although I'm envious. I wished I had aluminum heads the whole time I was replacing my head gaskets.

You should look into installing water transfer hoses from the back of the intake manifold to the front...you know...hoses that run from the ports over cylinders 7 and 8 to the front of the intake. These hoses evacuate trapped air bubbles that form in the back of the heads and create hot spots on 7 and 8 combustion chambers.

Tony Huntimer
RaceHome.com

[DLinson]

The heads are GM performance heads but they are rebadged Edelbrock RPM oval port heads. Edelbrock makes all of the GM big block aluminum heads. The only difference is the GM use a 2.25 intake valve instead of the 2.19.

Do you have a picture of a setup with the two hoses from the #7 and 8 coolant ports? I wandered about that but have never seen it done. What size hose would be appropriate? I'd guess about a #4 an would be enough to releave air.

I am running a pressure test on the coolant system right now. I have had it under about 18 psi of pressure for about 3 hours now and don't see any seapage around the head bolts so I'm thinking it's not the head bolts leaking. I'm going to let it sit under pressure over night to see if the coolant level drops. If it does, I guess I'll have to pull the intake off an check it again. I still need to take the thermostat housing off to drill a hole in the thermostat. The housing has a leak in it anyway.

The cam is a roller and I checked it out when I had the intake off and it looked good.

Thanks,
Dennis

[parsonsj]

Hey Dennis,
I've got no ideas for you, but congratulations on taking the car for a drive. Way cool!

Sorry about the engine situation. At least replacement is a bolt-in deal now. No more parts to make. Good luck, and keep us posted.

jp

[DLinson]

Thanks John.

I did end up remaking a water pump pulley. I made the first one about 86% the size of the crank pulley and it apparently Edelbrock recommends 70% the size of the crank pulley. I don't know if this will help with the discrepancy between the two temperature gages but it's worth a shot. Too bad the Vintage Air front-runner wasn't around when I designed my pulleys and accessories mounts.

I ended up getting the 2-bolt main block from my friend. I had it magnifluxed and pressure checked and it's good to go. It's already been decked so it only needs to be bored .070 over so they can install all of the components into this new block. Lucky for me I didn't drive it too much with that coolant in the oil. The cam, lifters, crank, and pistons all survived.

Hopefully I'll get the engine back in a few weeks so I can paint it and put it back in the car.

While the engine is out, I'm repainting the frame rails and roll cage tubes in the engine compartment. They had bunch of chips and scratches. This time I'll try to be more careful installing the engine.

How's yours coming along? Did you get it done for Columbus? I haven't seen any postings so I assumed it wasn't there.


Later,
Dennis

[parsonsj]

Did you get it done for Columbus?

Alas, no. I killed myself this spring to make that happen, but I spent all the time on getting the engine running. I finally have a running car, and I'm almost done wiring (once the final set of bulbs get here). A setback here, a lost weekend there, a move to Florida, and it's nearly September. I was hoping to get to Pigeon Forge with the car ... but that's pretty much out too.

I need to get my mill and welders up and running down here in Florida so I can finish up the last few things.

jp

[J2speedandcustom]

That sucks! I hope you get the car done for KC GG's. I really want to see it.