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lean condition on #2,3 and 4
#1
We checked intake manifold gasket replaced it--had a bad egr replace it, got good spark,good compression,injectors are good,fuel pressure good. pulled heads replaced gasket. It acts like there is one hell of a vacuum leak
This is in my 92 Mark-347 stroker engine. We were hitting it pretty hard with a 175 shot when the trouble began..Any ideas???
Ive fallen and i cant get up
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#2
have you checked the compression? could be bent valves.
If you're gonna build it, make it fast!



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#3
Compression was 150 per cylinder-however we did a leak down test last night and the jugs in question indicated 15% leak down-the "good" side indicated 5%-what the hell that means ?? Short block I guess
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#4
(12-31-1969, 08:01 PM) link Wrote:Compression was 150 per cylinder-however we did a leak down test last night and the jugs in question indicated 15% leak down-the "good" side indicated 5%-what the hell that means ?? Short block I guess

Do the compression and leak down test again with some oil squirted in the cylinders. That will tell you if its rings or a valve sealing problem.

Have you done a fuel pressure drop test on the injectors? That will help to determine if the injectors are partially plugged.

IF you have access to an EVAP smoke machine, smoke the intake system and crankcase for leakage. You could have a vacuum leak inside the engine where its not visible.

If you run catalytic converters, check them for restrictions.
ASE Master Tech with 15 years experience


Daily Driver: 1994 GMC Sonoma, Extended Cab, 2WD, with the 4.3 V6 Vortec.
Future plans/projects: Finishing that darn 64 Malibu SS
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#5
No cat converters , don't have acess to smoke machine but we did squirt ether into the oil fill spout on the valve cover and it sort of smoothed out which made us recheck the lower intake--no vac leaks there. We had some spare injectors and tried them--no change. We pulled the engine and so far haven't seen any cracks, piston rings looked good. We had the heads checked and they were good. The damned thing is a mistery. Good compression-good spark- injectors are fireing-no vac leaks that we can detect and still the sucker misses on the passenger side bank. We converted it years ago to mass air-- maybe wireing or computer related. Big race comeing up next month and I sure wanted to run the linc but doesn't look good at this time----boo-hoo.
Ive fallen and i cant get up
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#6
so any updates?
1991 black special edition typhoon intake and y303 heads crane cam, turbo coupe swaybar with addco rear bar. Kyb's all the way around. cold air intake offroad Hpipe and flowmaster with stainless tips. 3:73 gears with mac diff cover. thanks to lscSS and old school , and mike J for making my se dreams come true:cheers: 1990 Red Special edition now my backup funcar . silver one gone to new home so now the FUN begins:naughty:
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