I have rebuilt a 292 L6 Chevy and it ran and sounded fine. I used Leo Santucci's book for all of the specs and tips. It is bone stock and not in a "hot rod" at all. The owner has it for a highway cruiser. After cam break in and then breaking it in on the road, it later developed a hellacious squeal and running hot, especially on the highway. I thought the rebuilt water pump was going bad, so I replaced that and when it still was squealing/whining, decided to check the rocker arm adjustments. Backing off a half turn fixed the squealing. Two weeks later, same overheating problems are evident. I'm at a loss because I was very careful assembling this engine. Everything was bone stock, I replaced bearings, seals, rings, gaskets. I had the engine blasted at the machine shop and hardened valve seats installed. I cleaned everything again as I put it together. The radiator looks good, no gunk coming out when drained. Oil doesn't look burned. New thermostat and hoses, everything seems to be working perfectly. Anyone have an idea? The truck is over an hour from my shop so I want some info. before I head down there to check it out again.
The engine is a 1970 in a Suburban. Stock radiator, shroud and mechanical fan. Actually, I don't know if the fan is stock because it's a flex fan. The engine was running before I rebuilt it, just poorly, and leaking all over everywhere.
" I seem to be fine driving around town but on the freeway, it overheats within 10 miles, especially if are driving 60 mph or higher." This is the quote from my customer about the engine. Could it be a timing issue?
What gear do you have in the Rear? Must be a 4 Spd. Tranny. Have you run a Compression Test? Lose the Flex fan, and get a old one off of Clutch Fan. How much room do you have between Fan 7 Radiator ?
I agree about the clutch fan, but it's what the customer had. I'll have to talk with him again. It is a TH 350 Auto trans that seems to work great. I did the filter and the front and rear seals in that while I had it out, but it didn't have any other issues so I didn't mess with it. I'm not sure about the rearend gears at all. I think maybe 3.73. Compression test not done. It's a fresh rebuild, perhaps 500 miles total after break-in.
The client says there is no pinging that he's noticed but says that it seems to be straining at highway speeds. Too much advance? Lean condition at speed? Could either of these or both cause overheating?
No ping would to me equal retarted timing or dist advance frozen/not working properly. Lean also causes overheating but with that you usually get some ping. Are you getting oil to the rockers ,no oil on the top will cause noises. Lack of power on the hiway also points to a retarded timing issue. Squeal ? possiable vacumm leak ,that also could cause lean-hot issues.
Cool around own and overheating on the highway makes me think the radiator is either not flowing (clogged) or going thru to fast (not probable). Hard for you to figure an hour away. Good luck
Have a 292 in a 65 C60 pull a trailer with it. It would get warm then puke of coolant wher you slowed down. Changed out cap no more puking and it runs alittle cooler. Did you pre cook the t-sat to make sure it is working ? I test everyone before i install.
I did test the thermostat. I don't think it's radiator related. Timing seems to be it. Retarded at speed would make it feel like it's straining, right? I put in a pertronix module but the weights being stuck makes sense. Timing good at lower revs. No good up high. Thanks for all suggestions. I will be going to mess with it soon.
Special thanks to JohnEvans. The issue seemed to be timing, and when I got down there with my fancy new adjustable timing gun, sure enough the engine was severely retarded. About 24* total timing. However, with the new gun, I could watch the centrifugal advance kick in and it was all in at 3000. So, that solved that issue. Got it timed correctly and then test drove it and tweaked it a few times. The A/C unit really puts a stress on it, but I think I even worked around that. I also put an aftermarket temp. gauge with numbers on it and it matched up with the in dash gauge going up and down, so that's reading correctly. I could see the gauge react as the thermostat opened up, so that was good. Now though, white smoke is coming out of the tail pipe. Damn it! I had been at this guys house for four hours and had family coming to the airport so I had to leave. I am guessing a freaking head gasket leak, and I think it's on the number four cylinder because that spark plug looked really crusty. All the others were good. Couldn't do a leakdown test, but the compression tests read 142-145 on all cylinders. I guess I'll have to get it back to the shop and replace the head gasket before the engine is further damaged. I couldn't see any bubbles in the coolant, nor oil, just the white smoke from the tailpipe which produces a good puff when you rev it up. Again, thanks for all the help guys, everything to check was a help and I'll keep on trying. I'll update when this is resolved.
Pull the head and have it checked for cracks. Also look at the valve stems in the ports looking for a lot of carbon build up =usually a bad guide/s. Crusty plug usually= guide issue sometimes rings. With that good of compression I would suspect a guide/s if no crack found.
Thanks again for all the help guys. I got this thing to the shop and it drove fine, good power, until forty minutes of driving or so and then the temp. gauge started to creep up to about 200, and then it would "bobble" in jerky little motions. I stopped to get a coke and let it rest and it made it the last 35 minutes to the shop just fine, but still with temps around 200. Once I got it in the shop, engine still warm, I pulled the plugs and did a leakdown test. All of them even, all showing about 17 to 19 % leakdown. Leakdown was through the oil fill hole in the valve cover, indicating rings, right? Nothing going through carb or exhaust, no bubbles in radiator. I'm attaching a couple of pictures of the plugs. They don't look bad to me, but maybe some valve guide seepage? I put the new o ring type in. Should I redo that and put some umbrella type in? Thanks in advance for any input.
The Jalopy Journal
