Outer Limits 4x4 Board

Pulled the exhaust manifold off my Turbo LPG TB42 the other day to fix a leak between it and the turbo, Anyways found that 2 of the exhaust ports are white.. I know that means lean but why only 2? If the tappets where tight, could it cause this? It does rattle a little when you start it cold, but once warmed up it's pretty quite. Should I adjust them to factory specs, or allow for some valve expansion? Normally I would ask the guys that built this but there closed for holidays. Any ideas? thanks in advance.


heres a pic - http://stashbox.org/1048102/lean_ports.jpg

Definitely check valve lash.... you may want to set them slightly loose, maybe 2 thou more than the book says, to make sure they close properly... the lean out is probably at least partially caused by "log" type manifold design.... also is there any way you can richen up those 2 cylinders individually.... my 2 bobs worth

Thanks for the advice.
I am running a turbo diesel "log" manifold with external waste gate mounted so it was interesting to hear you mention a log type manifold, but.. I took some photos of the ports a few months ago and they were all black..

I can't richen up any ports individually, the set is strait gas with two Gas Research B2 converters and a Gas Research carbi/throttle body mounted on an injected manifold.

I'm thinking now that I will definitely need to measure the clearance on the tappets tomorrow and see if there all the same, before I adjust, if necessary. Hopefully there just tight.. and hopefully it sorts the problem..

is it the middle two cylinders??
ifso ive heard that with the design of the factory intake manifold they lean out the middle two cylinders because they are the first two that cop the forced induction. and they fix this buy makeing a custom intake plannum.

im no guru but thats just what ive been told, but sounds feasible to me.

MEGATROL

I have also heard of the middle most cylinders getting majority of the LPG. I believe this is because the LPG falls from the intake into the manifold and continues falling to the closest ports as lpg is heavier than air. Thus the main reason gas vapor injection for efi vehicles have a massive gain over the old mixer type. I installed vapor injection to my tb45 and was gob smacked at the difference. This system delivers a measured dose into the manifold close to each of the ports.

"I have also heard of the middle most cylinders getting majority of the LPG. I believe this is because the LPG falls from the intake into the manifold and continues falling to the closest ports as lpg is heavier than air. Thus the main reason gas vapor injection for efi vehicles have a massive gain over the old mixer type. I installed vapor injection to my tb45 and was gob smacked at the difference. This system delivers a measured dose into the manifold close to each of the ports."

I doub this because of the velocity and turbulence of the air/gas mixture in the intake manifold. Maybe you are using a bit of oil in the other cylinders, but the rings are still good in the whiter port one? Otherwise, maybe it is better spark plugs and hence combustion?

Thanks for every one's feed back. This motor doesn't use excessive oil and the catch can/intake is clean. I did increase the boost the other day to around 20 PSI and drove around for about 20 km but have since turned the boost back down to 15 after I was told that I need a second gas tank so I can run twin gas lines for the two B2 converters. Maybe they leaned out then... It would be a drag, but I supose I could pull the manifold off again to see if they have darkened up since then.. To me the plugs all look the same.
Yes the motor was built from the ground up for the turbo, (24,000 km ago)

I just did a quick cylinder compression check, Some of the plugs are a bitch to get to with the gas, throttle body and intercooler piping on this thing! I was dreading what I might find on the two suspect cylinders but found that there in spec.

I still need to adjust/check the tappets but haven't yet.. where I live at the moment it is a real pain. Although I just bought a house with garage and will be moving into it in a month. That's when I can really get my hands dirty. I think sometimes that I devalue these apartment's I live in when I'm working on my truck in the visitors car park...

As seen below, pulling the rocker cover off is not as easy as it used to be..