Help!! Engine Miss

[Mike Taylor 3601]

Get tdc on each cyl and it will stay,if balancer does'nt have all marks you can listen for air to come out hose as you turn right when it stops will be close sometimes it takes a try or 2
If you leak with rockers on that will show rocker/lifters are problem or not,if have leakage retest without rockers.
Mike Taylor 3601

[Joe Martens]

Ben, do you have a rev limiter? Disconnect it if you do!

[Ben Kallies]

MIke,

Thanks for the tips on leakdown.

Joe,

I've disconnected my 2-step, with no change. Thanks.

-Ben

[monte442]

Are you using a shift light ? I had an Autometer shift light that was acting like a rev limiter.

[Ben Kallies]

Monte,

I've got an Autometer shift light, triggered by an MSD RPM activation switch. I disconnected this as well in the course of testing.

-Ben

[Ben Kallies]

OK, so the leakdown test is done. I checked each cylinder twice with the same results each time. Results are as follows:

cyl 1 12%
cyl 8 10%
cyl 7 11%
cyl 3 7%
cyl 6 5%
cyl 5 12%
cyl 4 11%
cyl 2 8%

It's my impression that these results are good. Thoughts, comments? Is a compression test still necessary, or do these results verify the health of the engine?

Thanks,

-Ben

[Tim Lisson]

Not sure what you are running for rings, but if that was my numbers the engine would be out of the car. Either way, ring seal would not cause the problem you are describing.

Did you warm the engine up a bit before beginning your test?

Tim

[Mike Taylor 3601]

Thats not great but not terrible,10% or less is good naturally the less the better,2-3%is really good. I would remove rockers and intake manifold,headers and hook air straight from air hose full pressure to plug holes and cover port with hand to see if feel pressure leak through valves,if air is coming through intake valve at all engine will not run right compression coming back in intake runner messes with signal to carb.

I have seen engine leakdown good compression test show good,but find valves leaking with air, seal valves and fix problem,may not be problem with your's but I would test it.

If intake valves are leaking enough it could act like your description,compression leaking in runner messes signal to carb.will make miss or can make unable to tune you can change jets and not make any difference I seen one w/valves leaking slightly would die like you shut key off @ 6000 fixed valves back to 8800


Mike Taylor 3601

[MikeMoller]

Originally Posted by Ben Kallies

OK, so the leakdown test is done. I checked each cylinder twice with the same results each time. Results are as follows:

cyl 1 12%
cyl 8 10%
cyl 7 11%
cyl 3 7%
cyl 6 5%
cyl 5 12%
cyl 4 11%
cyl 2 8%

It's my impression that these results are good. Thoughts, comments? Is a compression test still necessary, or do these results verify the health of the engine?

Thanks,

-Ben

Run a compression test anyway. If you have a flatttened cam lobe-particularly intake- the compression may show low on that/those cylinders. Happened to me on a brand new motor.

Mike Moller