ive got a miss i think in #1 and #2 cylinders most noticeable at idle and cruizeing if i put it to the floor it seems to run fine but thats the only time ive replaced coil ,distributer, wires,plugs,cap,rotor done a compression test resealed the intake checked grounds i dunno what it could be im running an lt1 intake 2nd year for it no probs from it last year holley tb cc305 cam afr 195cc heads any ideas? thanks guys

 

If you're sure it's only 1 or 2 cylinders,
you have to narrow your search on the
items independent among cylinders:

injectors clogged

sounds like you've touched on the others
(plugs/wires/etc)

Try doing a leak-down compression test
to double check the valves.

Oil leaking into the intake (gaskets or
PCV) will cause a miss

Have you ever had the motor into valve-
float? Did you upgrade the AFR springs
to handle the cc305 and >5500rpms?

If all else fails, put the car on a chassis
dyno with a WB-O2 and see what the
AFR looks like when it's missing..

mike

 

Very possible it is the EGR block off plates. The EGR is piped in from the back and is tunneled to the front of the manifold. This EGR passage then opens to two orifices right behind the TB. Any leakage at idle would go right to the front two cylinders.

A friend converted an LT1 manifold and he tapped and plugged the two openings. I can't remember the exact reason though.

Another possibility are the IAC passages. On the LT1 intake the IAC is piped to a small opening in each runner. This gives a good even distribution. If you have changed from the original TB the IAC may not be plumbed correctly.

Check the PCV also. Anything that can produce an uneven distribution within the manifold is suspect.

RBob.

 

Perhaps the LT1 intake isn't sealing the 1 & 2 intake ports in the head and it is breathing oil. You say you resealed it, did you check for evidence of pulling oil when you had it off. I'd also expect something like that to be worse with a closed / part throttle because vacuum is highest there.

Something like ignition would generally do the opposite. Considering how many people have taken a crankcase of coolant over an LT1 swap, a big port head not sealing wouldn't surprise me at all.