Overheating question
- Thread starter DOMINIC
- Start date
Maybe someone with a 409-409 could let their engine idle and see how long it will run before overheating. That would give a baseline on what is acceptable.
Hillary Clinton
Phil if you have a blown head gasket the product of combustion would place hydrocarbons in the coolant.
That wasn't a bit necessary Mike!!!!!!!!!!!!!!
Phil,As MRHP said it stands for hydrocarbons.In this case,it'a more accuate to call it unburned hydrocarbons because it's unburned hydrocarbons [basicly and exhaust gas leak] caused by the warpage/poor sealing gaskets.Before we had the more modern air/fuel meters for tunning,we often used the CO [carbon monoxide],and HC [unburned hydrocarbon] readings to make the car perform better,get better mileage[unburned hydrocarbons are after all unburned MONEY going out the tailpipe]Hope that helps.
Thanks Ray. I'm familiar with the concept just not the initials!!
DOMINIC
Active Member
Sorry again. I thought i posted this hrs ago.
Thermometer, raytec and independent guage. All the same. A baseline would be good but before this began the car would overheat within a few miles on a mild day. Any motor in this setup should idle for quite awhile without exceeding 220. I have done this with every motor I build. Great for breaking in cams, adjusting valves and carbs, timing and especially verifying no oil leaks before install. I like to run at least 5gals of fuel through a motor before I pull it off. I think compression is to high for street use idling. The 104 octane made a difference of 10 extra minutes in idle time. Im gonna get after it again on Monday. It makes sense lowering the combustion temp. with 104. And yep,, this engine should run out of gas before it overheats. Little frustrated, Dom
Thermometer, raytec and independent guage. All the same. A baseline would be good but before this began the car would overheat within a few miles on a mild day. Any motor in this setup should idle for quite awhile without exceeding 220. I have done this with every motor I build. Great for breaking in cams, adjusting valves and carbs, timing and especially verifying no oil leaks before install. I like to run at least 5gals of fuel through a motor before I pull it off. I think compression is to high for street use idling. The 104 octane made a difference of 10 extra minutes in idle time. Im gonna get after it again on Monday. It makes sense lowering the combustion temp. with 104. And yep,, this engine should run out of gas before it overheats. Little frustrated, Dom
Dominic, did you say you ran a cylinder leakage test? I agree that 150 lbs compression is very low, which means the obvious. If there was warpage between the block and heads could be that a couple of thousandths might not have cleaned it up especially if the number pad is still legible.
Now, a real left field overheating problem I had.....I have a 340 HP 62 Vette. When we rebuilt it a couple of years ago it overheated almost immediately. Bottom line without dragging everyone through the agony of hearing the entire story, we found "slag" inside the water jacket of the block that had come loose, looked like a coat hanger stuffed inside the block. I really doubt the slag pieces are your problem, but I would recheck the amount the block/heads were decked.
Good Luck.
Now, a real left field overheating problem I had.....I have a 340 HP 62 Vette. When we rebuilt it a couple of years ago it overheated almost immediately. Bottom line without dragging everyone through the agony of hearing the entire story, we found "slag" inside the water jacket of the block that had come loose, looked like a coat hanger stuffed inside the block. I really doubt the slag pieces are your problem, but I would recheck the amount the block/heads were decked.
Good Luck.
triple check timing, make sure it aint running to lean, do you have a fan in front of rad to siumlate road driving, or just trying to get a sitting there ,no overheat condition? my motor is 13.5 to 1, and will sit there all day with a stock rad, stock shroud, and a fan clutch setup, 160 stat, wont go over 200. . Ive found myself in similar situations, K.I.S.S. we`ll figure it out
I also remember reading about block pressure ( water pump pressure) to be checked. I don't remember all the perticulars, but it is a good diagnostic tool to see if the waterpump is flowing enough gpm to properly cool the motor. I would also try an aftermarket hi performance pump if you believe your radiator, airflow, cam timing, initial timing, are correct. I believe compression has little to no effect on your heat problem. Can you get the specs on the cam, and where it was degreed in at. I can't help but think 150 cranking compression is too low for this motor. My 12.0 motor cools decent. Yours should too.
DOMINIC
Active Member
13.5 to 1 wow. What octane do you use? How big is the bore?Has anyone taken temps at original exhaust manifold exists while running?
I like your questions about radiator/hose height. That is often overlooked but I am perfect there. leak down was done. 2% to 4%. Im locked up tight there. Compression is upper 150's as I look at my notes but it is what it is. Leak down is good.
You all gave me some things to revisit. Yes Tom,, I live by the K.I.S.S. method. Keep It Simple Stupid !!!!!
I like your questions about radiator/hose height. That is often overlooked but I am perfect there. leak down was done. 2% to 4%. Im locked up tight there. Compression is upper 150's as I look at my notes but it is what it is. Leak down is good.
You all gave me some things to revisit. Yes Tom,, I live by the K.I.S.S. method. Keep It Simple Stupid !!!!!
What about water pump by pass hose? I plugged mine to force all coolant through the radiator. only left a small weep hole. I also read some where that those hi performance water
pumps can push water too fast through the radiator, not giving it enough time to do it's job. (just thinking here.)
pumps can push water too fast through the radiator, not giving it enough time to do it's job. (just thinking here.)
The car I bought from my buddy in 1988 always had overheating problems when he had the car. Found the problem was the radiator was from a 6 banger. Wrong inlet/outlet placement. FYI..............
What's different about the 6cyl radiator?? I was planning on recoreing the radiator in the parts car I just bought and using it in front of my new engine..
Bad impeller or impeller to back cover clearance. Will cause it to cavitate. Try a different water pump. Sometimes there is casting metal inside the block where the water pump bolts up. hard to see. Adds a big restriction. Make sure the lower radiator hose has a spring in it, hose likes to suck closed. Mine can idle all day in the summer at 210, drop to 160 when I start moving.
Too small Ricky. Get an appropriate size for your new engine. I consider a 4-core radiator an absolute necessity for any 409. You can't get a wide enough core with the 6-cylinder side brackets.