Hot cylinder

hey all. just was curious, whats the exhaust temp supposed to be coming directly outta the head? i used an infared thermometer today and tested my header... cyl 1 and 2 were in the high 200's... like 280-290ish number 3 was low 300's and cyl 4 was like 360 degrees F!! so am i running lean on 4?
i pulled the plugs and one and 2 seem almost rich, 3 a little on the lean side, and 4 kinda lean too. what could be the problem? blocked intake runner?
when i rebuilt my motor, it was all bottom end, i didn't take the carb off the intake manifold, i didn't even take the intake manf off the head!
i'm stumped, and i need it running like you all can imagine. i just need ideas or the magical quick fix!
BTW they are new spark plugs. less than an hour of running on them. prolly a half hour at best.


Thank you

I would suspect the problem is a blocked or partially blocked primary cat,the one just under the exhaust manifold.Unless someone stuck a rag in the intake runner,I have never heard of one being blocked,partially or otherwise.Another possibility is a weak spring on the exhaust valve on number 4which is not allowing it to fully open and get all the hot gases out before it closes.Just a couple of thoughts.BJ

Another issue to look for would be vacuum leaks. I realize you did not remove the intake from the head, but what about the vacuum ports all over the intake. After installing my weber a plug for the vacuum port on runner #3 fell off. Didn't really effect the other cylinders but #3 was basically dead at idle but much better at 2,000 rpm. In your case, it might be worth looking at.

thank you both for the quick replys.
BJ - i'm running open header right now, just getting it running again. no cats or muffler. the weak spring is quite possible.
immortal - i'll check all the vacuum ports. it runs strong and smooth, so i dunno, but i'll definately double check them all. they're all plugged with those little rubber plug things, its possible that one cracked or fell off!
thanks guys!

do you think closing the sparkplug gap might help the problem?
hmm, and how would one tell if a valvespring was weak?

Ya - those damn little red plugs Probably not the best idea. That is what kept popping off. Ended up using vacuum line with a plug in it.

All I can say for the red plugs is..... one little hicup back into the intake and most will go flying

Closing the gap on the plugs is like putting a band-aid on it. If I were you, I would suggest that hoc has the right idea. I suspect it is something of the likes with your valve timing, etc. Your valves cannot be adjusted since its hydro and all, so maybe it is your cam? The lobes could be worn down for the problematic cylinders. Hence why the valves act as they do causing cooler exhaust temps.

That would be my take on it... I'm curious, you say it runs strong and smooth, but yet it does'nt run well? What is your point of asking this question? Is it actually causing a problem?

BTW, I use the yellow port caps. They are like 1/32" smaller than the ports and are a bit of a struggle to get on, but they certainly do a good job staying on!

Check to see what your timing is. What about the spark plug wires? Anything that could lead to an incomplete burn... Your exhaust temp. is suppose to be hot not as cool as 200 or so degrees. Your exhaust manifold or header is supposed to be about 1200 degrees!

If he is running an open header with no cats or muffler,temp would be way down,but I agree 200 F is cool not hot,even 300 sounds cool given the correct water temp on a 2200 is 180 degrees .The best diagnostic on a weak or broken exhaust valve spring is a malfunctioning (carboned up)EGR valve,or a plug that has a badly burned electrode.BJ

Check the temp with some rpm on it maybe 2000 also look at the header tubes are they all the same coming off the head and the same lengh?

If he has a pacesetter header, then from what I was told, they are tuned. But, they run in different paths.

I only say 1200 degrees, because I sprayed on ceramic paint for mine, that was rated for 1200 degrees and it flaked off. May have not been fully cured though..

The fact is, it should be waay hotter. At least 800 I would say because the block gets about that hot.

In the long run, IMO I would say its a good thing to spot this. You could end up with a damaged engine if it is too lean. You need to look your valvetrain assembly over.