ZK 351

Ok to start out will explain what i have
351 clevo,
straight LPG
2v closed chambers
wieand single plain intake
vortech V2 supercharger, hitting 8psi of boost @ 4500rpm.

ignition system is laptop programmable megaspark, (based on Megasquirt (do a google search) )
and has not given me any trouble at all since install a few months back.

in last week have put on new leads, colder range plugs with .5 gap, new cap, and rotor... have tried a different coil as well, my coil is mounted on the shock tower so it shouldnt be getting overly hot

now to the problem

about 2 weeks back it started missing and stumbling on off idle acceleration, then once the revs get up it goes pretty well,
progressively got worse, now to the point that you cannot nail it from stand still, it just dont go anywhere and feels as though someone yanked 4 leads off, but if you gradually accelerate with the missing then nail it around 2500-3000rpm it gets up and goes

this only happens after the motor warms up, will run perfect for the first 1 - 2km of first thing in the morning driving. you can bury the foot to the floor though first and 2nd up to 4500rpm from stand still and it will pull clean the whole way...

after that at say the traffic lights at idle it misses on at least 1 cylinder. and takes off like a dog.

now today i did a compression test, did a cold one, didnt feel like burning hands playing with it today, i know i now have to do a hot test
the cold readings i got were
1- 185psi
2- 160psi
3- 180psi
4- 160psi
5- 170psi
6- 175psi
7- 180psi
8- 165psi

AND another thing was the other day on the way to work i had the bonnet up about half way to work to adjust LPG mix a bit and noticed that there was blowby coming out the oil cap like a chimney, i have been checking it every day since then but its not as bad, but you can notice it without taking the cap off

think thats about all

if there is any more info needed, let me know

brenx

lean, ignition module or coil are my guess's. [edit] add head gasket, distributor shaft slop and valve spring pressure.

__________________
XB Fairmont (street car) 11.07@123.02mph.

ZK 351

both ignition modules i am running have a heap of heat sink compound on them, and one is mounted on a 1/2 thick piece of aluminium,.

will a headgasket really get worse after engine warms up?

no slop in distributor shaft, its locked down solid...

valve spring pressure... now would that cause missing?? can you go into a bit more detail with that one?

Cheers

TruBlu351

On a side note, I wouldn't be burying my foot to the floor in the first 1-2km of a cold engine.

Takes me about 7km to warm up full

Being a total gas numby, are gas mixers touchy WRT temp?

__________________
XE Falcon
393 Tremec TKO 9"

ZK 351

yeah but you get that had to test it to rule out the problem occuring when cold .. :)

LTD351V2

same as my work car does, my cause was LPG mixtures bad and timing was retarded too much, have you played with the timing or did it just develope a miss?

ZK 351

havent touched the timing for probably 3 or 4 weeks, but the mixtures on the other hand, yeah been screwing around with them a bit, only a few turns at a time here and there though

brenx

Head gasket- Everything expends once the engine warms. More clearance.

Valvesprings don't retain their pressure forever they do loose pressure. Your's being forced induction could even be blowing the valve open, if soft.

__________________
XB Fairmont (street car) 11.07@123.02mph.

LTD351V2

do you have something to measure them by? often what sounds best isn't if you know what I mean, also the idle mix screw on the 425's the difference between good and bad can be as little as 1/25th of a turn!! thats where the idle miss and poor take-off could be coming from, its too sensitive to just go a bit here or a bit there unless you are super careful and mark where it started out.

ZK 351

IF it was blowing valves open it wouldnt be doing so under light acceleration as well when the bypass is opened