Hey guys any suggestions on this problem i have sure would be appreciated. New 502 modified was set up on a dyno 540 hp. Ran super for 15 hrs. I went out yesterday to try out some different props and at about 3500 rpm and above the engine would miss. Came back to the shop pulled plugs, 7 of the plugs are showing a bit rich(due to the fact the engine was dyno"d at sea level and we r at about 2500 ft) but # 6 is WHITE . Did a compression test 175 lbs on all cylinders. Replaced plugs, retorqued intake manifold, bolts were not loose, lake tested , It still craps out at anything over 3500. Engine idles and runs great till about 3200-3500 then misses. Please help and thanks


syringa

Correction on my previous post it's # 5 not 6 . (not that it woould make a difference) ??? I quess i have to get more sleep!!

i would hook a timing light to #5 to eliminate the easy stuff first like a bad wire, cracked cap, moisture etc. if it fires then pull a valve cover, get a base line measurement off of #3 cylinder rocker arm lift @ int. and exh. with a dial indicator and then check #5 and compare the two. if they are identical, your possibly leaking coolant into the cylinder from a head gasket, intake gasket, or a cracked head regardless of compression.
good luck, hope it's something simple
Fran

IS IT CARBURATED OR FUEL INJECTED?CARB YOU MAY HAVE A PROBLEM WITH HEAD GASKET OR CYLINDER HEAD LIKE INDICATED PRIOR//INJECTED-MAY HAVE A BAD INJECTOR..LEANING OUT--GOOD LUCK

The motor is carb not efi. Just got back home, I think i'll do a leak down test and find out how much work I have in store for myself.. Thks for the replies

Syringa