Low Exhaust Temps

kevink · Posted: Sat Oct 04, 2008 4:28 am Post subject: Low Exhaust Temps

Hey guys,
I recently rebuilt the 327 SB in my 69' El Camino and just got it back in and running. The rebuilt was just to replace the main and rod bearings and put in new rings. The heads were resurfaced but the block was not and did not need to be honed either. I did not make any performance upgrades or even replace any other parts (The engine was already recently built up before I acquired the car. An unnoticed oil leak forced the rebuild after ruining the bearings).

After I got the engine back in the car, running, and the timing set, I noticed that the temperatures of the header pipes were unusual. I used an inferred thermometer to take the temperature of each header pipe with the engine at normal temperature. On the passenger side header all the pipes were between 375-415 degrees F, which seems normal to me although I don't know what exhaust temp is usually like. On the driver side header though, the #1 cylinder only read around 110 degrees, the #3 cylinder around 130-140, the #5 around 230 degrees, and the #7 cylinder around 330-340 degrees.

I'm not sure what could cause this problem or what it really even means but I'm guessing that with exhaust as low as 100 degrees I must be losing a big chunk of performance. I have triple checked the timing and also reset the valve lash for both heads and had no change. Does any one have any ideas about what could be causing this problem or how to fix it? One person suggested that the hydraulic flat-tappet lifters may be shot and need replacing. Could this be the Cause?

Thanks for any help,
Kevin

464elky · Posted: Sat Oct 04, 2008 8:42 am Post subject:

Do a compression check to start. Check for vacuum leaks.
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Snaggle To0th · Posted: Sat Oct 04, 2008 10:05 pm Post subject:

your having miss fires or low compression in those cylinders, run a leak down check and compression check.
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old_coot · Posted: Mon Oct 06, 2008 10:57 am Post subject:

Need a little more info actually, do you have a single plane or dual plane intake----off the top of my head It appears you have more than one problem. It appears number 7 is near normal the others on that side appear to not be firing and those temperatures are probably due to conduction (notice how the temperatures get cooler as you go toward the front of the engine) from the number seven rather than firing at all---could that side of the engine be flooding to the point its not able to fire????
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Snaggle To0th · Posted: Tue Oct 07, 2008 12:01 am Post subject:

i could see a rich condition on those cylinders but its kinda odd that the rear cylinder is running a good temp. I think its something related to combustion or even a simple spark plug issue. It would make sense if its a single plane manifold 7 being the furthest one but it doesnt make sense due to the right bank is running fine. Has to be related to an internal issue or ignition related. Another check he could do would be to check the valve clearances on thsoe cylinders and adjust them if they are out of adjustment. THe engine was apart so those valves could be slightly loose or too tight having more lift cause it to suck in more air/fuel and it being to much. DUNNO thats my 2 cents and what I'd check!
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texaselky · Posted: Tue Oct 07, 2008 7:05 am Post subject:

I had the same symptoms when I put a new 350 in my El, I adjusted the valves and they all evened out. I guess the guy who built the engine (me)didn't set them properly from the start.
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old_coot · Posted: Tue Oct 07, 2008 9:00 am Post subject:

I agree it could be the valves being too tight---loose would just make them rattle but the engine would run ok---and if they were adjusted in a static state without running the pump and turning the engine over that would account for it but it could still be flooding---once a plug is flooded it can take several minute of running even after the flooding condition is fixed to clear the plugs-----I suspect he is not driving the car in this state so if the left front corner of the car is lower than the rest the excess fuel would run to that corner and flood it first----just need to check the carb and make sure the float hasn't stuck while the engine was being redone, and check that the rockers haven't been tightened too far, then look at bad plugs and wires , rotor button being busted and distributor cap being broken--lots of things can do it---right now we are just guessing.............Dan
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Snaggle To0th · Posted: Wed Oct 08, 2008 7:24 pm Post subject:

very true...hard to diagnose engine problems over a phone or internet.
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