I have a '53 belair with a '59 235. It has split headers, gl***packs and pertronix. Supposedly it was rebuilt 2 years ago. It runs strong and idles steady. The thing I noticed the other day while holding my palms at the exhaust tips is that the left hand exhaust pulses while the right hand is smooth. Also, the left side seems cooler than the right. When I had my brother bring the idle up to 1500 - 2000 RPM and then let off quick, the left side was hotter during deceleration while the right side was cooler, and then returned instantly to what I decribed before. During the rev, no black spots or soot flew onto my hands, only clear vapor, and it didnt smell rich. I did a compression check and a spark check. Plugs looked a bit sooty but not too bad. Compression findings were: #1=125, #2=133, #3=133, #4=110, #5=130, #6=130. Stock stats for the 235 say 130 or better is great. I would think #4 would be the problem with the pulsating exhaust note on the left side, except that #4 goes into the header that is directed to the right side, which purrs. My question to the 235 owners with split manifolds: Does one side have a pulsating note, like puff-puff-puff-puff. and the other side puuurrrs? I cant understand what would make this happen. Maybe a collapsed or broken valve spring on 1, 2 or 3? Thanks for any tips
I have the same kind of compression numbers in my 261. #2 is 110, the rest are 130-135. Still runs strong. Smokes a tiny bit on hard acceleration and I get some oil fouling on the #2 plug occasionally. Exhaust should be kind of the same. Different length pipes from side to side could affect it if one were a lot longer. Or one pipe considerably straighter (less back pressure) that the other. I'd be curious to know what a check on the valves reveals. Check everything (lol ) and let us know what you find out.
If you have a split manifold you may get pulsating if it is not a full bock. If you have two carbs you could also get that.
it prolly just has something to do with the firing order. i dont think a spring is broken or something. honestly if its running good i wouldnt worry about it to much but thats just me.
A Six with the manifold split in half has even firing impulses out each pipe. If one pulses more than the other, it's not firing right. 110 comp will still fire, try a new plug in each cylinder, A handy diagnostic tool is an infrared thermometer, point it at the exhaust manifold by each port, the temp will show the one that's missing.
Stovebolts often have random misses at idle. Usually it's caused by a worn valve guide. Unless it really freaks you out, just ignore it!
This is what I was thinking. If OP's down cylinder is due to rings, the plug may be getting fouled by oil and need changing. Monster, did you do a second compression test after squirting oil in each cylinder? What were the numbers?
1-5-3-6-2-4 leftside rightside 1-3-2 5-6-4 I have my pipes split wide in the back and they always seem to pulse 'uneven'.
Could be a leaking exhaust valve. You can take an old spark plug, remove the ceramic center and thread it for an air compressor fitting. With both valves closed, pump compressed air into each cylinder. You can easily hear if the valves are leaking at the intake or exhaust. At the same time check the head gasket and rings, while you're at it. Remove the thermostat and look for bubbles and listen at the road draft tube.
I think about all split manifolds on 235's are split 2 cyl. and 4 cyl. its hard to split the exaust 3 and 3 when the center 3 and 4 cyl are out the same port
Sorry Spidercoupe, that's not right. 1 is alone, 2-3 and 4-5 are siamesed, and 6 is alone. All the intakes are paired. Road runner...a standard 1/4" pipe thread air hose fitting will thread in to a 14MM plug hole. Put some goo on it so you don't have to tighten it too much, and it will work for a leakdown test.
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