80 series rough idel

[MAD80]

ok here is another thread that starts with,,, i know this has done before but here goes,
i got a duel fuel 80 series cruiser, i drove my car on petrol for about 20 km's, runs rough on pet and am booked in to get the injectors cleaned, any way i filled up the gas tank went back to gas, it drove fin for bout 10km then stated to idel rough, progressivly got worse over the next 10km, and stated missing slightly but seemed to beok round 2k rpm under mimnimal load, i changed the leads there and then knowing i had 1 diky cable that i repaired few months ago,, after checking old to new cables they where not to bad, no backfiring so asume its not ignition prob
going to do a compressing check on weekend, i am thinking possibly burnt valve, maybe big valve clearances, i have a upper head lub system. also heard that possible hole in inlet pipe between airflow and throttle body could be calprute but pritty sure thats all ok. any ideas will be appreciated
cheers

[Toyo80]

Could be the valves in some form. Have a go at cleaning your throttle body also.

[Ice]

check the big rubber intake pipe

probally is split somewhere in the ribbed section where its hard to see

very common on 1fzfe motors

[mike_nofx]

We did a compression test on MAD80's engine.

Cylinders 1-4 are around 190psi. cylinders 5-6 are around 50psi.
Also the engine makes a different sound when cranking with the gauge on 5 or 6.

We are guessing its a head gasket. Anything else that could be causing this problem, or worth checking?

Mike

[mike_nofx]

For reference, head gasket was blown between 5 & 6 cylinders.

Also, the head gasket looked like it was either a shit make, or not fitted correctly. There were sections where the gasket protruded into the top of the bore, and on the opposite side, you could see about 2-3mm of gap. Like the gasket hole didnt line up 100% with the bore hole.

Have been told it may be a pre-ignition issue. Any opinions on this?

(MAD80 has been known to have premature issues himself...)

[dow50r]

Head gaskets on the 4.5 is common, usually water leaking in, but between cylinders will do it.... did u notice the head bolts to be loose? buy good quality aftermarket head gasket and new head bolts and you should be ok.
Andrew

[MAD80]

nar the head blots were prity tight, the head gasket was slightly distorted may have been a cheap gasket or even possibly overtightend. head is getting checked out skimed and valve clearance redone, ill let you know how it goes.

[tiler0172]

make shore you replace head bolts as they are a stretch bolt and should only be used 1 time then tossed
they are only 60 - 80 dollars for a set