I race a 91 Camaro in SCCA American Sedan. I recently bought a used, professionally built 305 race engine (recently freshened) - Which I installed my self - my first engine swap. It ran fine in my first race, but this past weekend I spent the whole time chasing odd over-heating problems.

In practice, after about 4 hot laps, my water temp was up to 230 and oil temp was over 270. This seemed too hot, but not necessarily terribly so. Later, in the race, again after only 4 or 5 hot laps, my oil went past 300 and water remained around 230 or so. The engine-builder was at the track, but he didn't have any major theories other than to "try the usual things"...

I tried several things: retarded the timing from 38 to 35; increased jet sizes from 64/74 to 66/76 (although the plugs looked fine); increased my water restrictor from 5/8 to 1". I also replaced the radiator cap with a 22-24 lb cap. (I have a Griffin aluminum race radiator but it had the stock Camaro cap - I replaced it when I noticed that simply squeezing the top radiator hose forced water into the catch tank).

This seemed to help a little…in the next practice session I pushed hard for 6 labs and water was at 190 and oil at 250. Still not great, but improvement...

However, later in the race, again after just 4 laps, water quickly went to 230 and oil was just over 270. A bit later, water was approaching 250 and oil was still just over 270 - so I backed out and limped for a few laps to cool things down. Although oil cooled to 260, water remained just over 230…then suddenly climbed back to 250…I pulled onto pit road and then watched the water temp gauge spin all the way around!!

I went to my paddock and popped the hood…I then heard a faint "pop" and the water temp immediately dropped to 140…

I also found that the radiator is way down (about half-empty), but nothing pumped into the catch can...it obviously went somewhere - out through a broken head gasket - or worse??

I'm guessing that I blew a head gasket?? And that the rapid temp climb was steam hitting the water temp sender??

Can you give me any hints as to what may have caused this behavior in the first place and what my possible damage might be at this stage?

It strikes me that over the first part of the weekend, oil temps were running proportionally higher than corresponding water temps. If my issue was a cooling problem, I'd have expected water temps to have run higher than they did. Then, towards the end, water temps skyrocketed, but I'm thinking this was a mis-read caused by steam in the system. …so I'm puzzled as to what my root cause was in the first place.


(And I have a new air deflector below the radiator...blocked off around the sides of the radiator, etc...over-heating was not a problem in my first race on this engine - or on the previous stock engine...just this time...)

 

What kind of fan setup are you running?

I would assume your not using an electric fan setup as your an all out road course racer?? If thats the case, you may need to fab a custom fan shroud if possible.

I've had to troubleshoot cooling issues on dirt race cars and the first thing I looked to everytime, and was the remedy more than half the time was an inadequate fan shroud.

If your running electric fans you should check the relays, or you should really consider a fan switch. (But I'm sure you know all this so I guess I'm wasting my time heh) Are you sure your water pump is functioning properly? I know from experience, sometimes installing a motor, filling the block & radiator you can trap a large amount of air and have intermittent overheating problems. Pop the radiator cap off with the car cold and let her run until water starts to bubble up (keep an eye on the temp guage so you don't fry her in the process).

Also, if your running anti-freeze..that's a :nono: and I'd suggest you try straight water, with water wetter & some anti-rust agents.

If all this does nothing...then it's time to start worrying about a head gasket.

 

I'm running a dual electric fan with a manual switch in the cockpit which I had on the entire time. I also verified that is working and is pulling in the right direction.

I also did run it while looking into the radiator filler and could see water cascading down as it circulated...so I'm pretty sure the water pump is working properly...I could also feel heat in the lower radiator exit host...

But I am wondering if I had either air in the block, or possibly blocked passages?

 

Oh yes, I forgot to add...I'm running distilled water and Water Wetter...

 

Hm, have you tried flushing your radiator and watching how well the water flows out?

It could be a number is stupid and ridiculous things ya know?

So your fans are operating correctly & your using straight water with water wetter... Flush the radiator and see how that goes, water wetter is only a couple bucks so I'm sure that won't hurt your wallet much.

Did you say you were actually losing water? If you really lost half a radiator full of water....and it didn't go anywhere out on the track... Check your oil, if it happens to look like freshly mixed chocolate milk then I'll save you the pain and cry for you, while you go buy some head gaskets.

 

Thanks, I'll check that next...

Yes, a lot of water is gone from the radiator, so it definately went somewhere, but as far as I can tell, it never gushed out...

But, right after I pulled off track, I saw what looked like steam around the passenger side headers/heads...so, I'm thinking it was steaming out thru some sort of crack or gasket leak there??

A head gasket doesn't sound catastrophic, or horribly expensive...Do you think that's all it is? Or, could it be something more serious (meaning $$$)??

Would a gasket going bad have explained the early signs I was seeing? (water temps running slightly high, but not dramatically so - and oil temp running hotter than it should proportional to the water temp)

At this stage, what do you think the get-well plan is? Pull the heads and replace the gaskets?

And, did a bad gasket cause the over-heating, or did over-heating damage the gasket? If the root cause was over-heating, then I still don't know what went bad between my first outing and this weekend...

Is there a special procedure to fill the water that I didn't follow? (I filled it, ran it briefly, filled it some more, etc...) Is there a better way to make sure there are no air pockets in the block or elsewhere?

 

I'm sure you did everything you needed to do correctly.

As far as the gasket blowing and causing overheating or vice versa..that's a tough one to decide. My bet would be the gasket was crap and once alittle heat got to it, it just broke.

It's not a catastrophic problem, don't worry. Just take your time repairing, if you plan on doing it yourself. It just takes a bit of time to remove the head.

If your motor had seen 260-270 or higher for a period of time then I'd say the block is probably toast but you said you backed off and let it cool right away.

 

What steps should I take to check the health of the block or any other parts that heat could have damaged? Do I need to go the full route and pull the engine and get it magnafluxed?

Or, do I just would it be obvious?

(Thanks for all the help by the way!)

 

Some other guys may be able to help with this better than me. I was heavily involved with a racing operation, and there was a time we experienced blown head gaskets & overheating problems with our 30,000 dollar engines.

We would tear down the top end of the motor down, and we would turn the motor and inspect every cylinder wall as closely as possible.

But here is what you should consider:

The price it will cost to tear the entire block down (if you don't want to do it yourself as it requires a lot of part stamping and organizing), having it magnifluxed, then inspecting the entire rotating assembly and putting it all back together.

Then you have to factor in a worst case scenerio, a cracked cylinder wall...If the block has been bored before, how much it was bored, is the crack so deep it can't be bored out. Stupid crap like that...

IMO, If you don't want to do all the labor work on tearing it down to a bare block and then rebuilding it, or you can't or don't have the knowledge and you must pay someone... I would suggest pulling the heads, visually inspect each cylinder wall to the best you can. If all looks acceptable, go ahead and replace those head gaskets and go racing.

If she blows up, it'll cost about the same for another rebuilt & healthy 305 motor, maybe less than it would to go the extra step to make sure your current setup is 100% (considering you don't do any of the work yourself).

*edit* I forgot to mention, that we only lost 1 motor out of 4 that overheated and blew every gasket imaginable with a very detailed visual inspection. The one motor that did blow up, the 427 block had already been bored 60 over and well, can't do much more than hone & sleeve it. Sleeving cylinder walls really sucks. Speaking from experience I'd ONLY sleeve in a worst case scenerio, I.E. racing for points in the top 10, championship...something like that. The sleeve jobs we have done in the past 4 years normally last the weekend of abuse with 700hp big blocks.

You should really, no matter what the circumstance, whenever purchasing a motor, even if it's from a builder, for a racing application you should really tear the top end down and replace the head gaskets, intake gasket, stupid stuff like that. Our racing program was purchasing $30,000 dollar big block Enders Racing motors, with the unblemished record these guys have, every motor we received from them we still tore it down before the initial drop in. Ya never know...

 

I may not have a blown head gasket after all...

I did a compression test and all cylinders cam in between 140 and 150 PSI...wouldn't that indicate no blown gasket??

However, my plugs are looking like they ahve a slight gray or white color (all except #2). But, could this just have been caused by running hot for a while??

After the over-heating episode, my radiator was nearly empty, with nothing in the catch tank...so it all exited somewhere...if not thru the head gasket, then where??

I guess my next move is just refill it with water and run it standing still and look for leaks?

 

hey jus to throw an idea at ya.. did you make sure when you filled it up that the thermostat opened and it sucked all the water into the motor? Sometimes i would fill the radiator up, and it would run for like 15-20 minutes and then the stat would open and suck down 60% of the water and then i would have to fill it up again. I'm sure you did that, but you never know.

I have a constant overheating problem. Seems like no matter what i do, it still ends up gettin too hot. I changed the waterpump, thermostat, radiator, all the hoses, and it still gets hot on me. This weekend im going to flush the whole system and put some wetter in it. Hopefully this will help, cause i hate not being able to use my ac.

good luck..

 

Fill the radiator and put some in the overflow bottle, Get one of the Stant lever caps (for relieving pressure from the rad before opening) Put the cap on the radiator and leave the lever up. Start the car and let it warm up while watching the overflow bottle inlet for air bubbles, if it keeps belching air bubbles into the overflow, its time to tear the heads off and start inspecting heads/block/gaskets.

 

That sucks you haven't figured out whats going on!

Since your racing, I would suggest tearing the top-end down anyways and looking it over. You don't wanna lose a motor in a race. That could be REALLY bad...could kiss a wall or some nice ugly tires.