The heads are of! Valves knackerd!

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V8 Vouge

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Pulled the heads over the weekend due to the coolent system pressurising and no compression or very low compression in the left hand bank.
Once the heads were of I thought it looked like the head gasket was leaking as there is residue around the gasket. A second opinion reckons that's just oil that has run out of the heads when I removed them. The fire rings all look good.
So, I poored some petrol onto the valves with the heads turned up side down. They are all leaking especially the two cylinders that had no compression.
That explains one problem, can anyone explain to me how this could be the problem with gasses entering the coolent system please?
 
carefully check the liners and get the valves reground or replaced and head skim and crack tested
 
valves wont have anything to do with gasses in coolant and id be surprised if any would hold petrol after a year or two running
 
Check that all the liners are flush with the top of the block. If any are low block is knackered. Did you find any clean piston crowns? Look for minute track marks between cylinders and water jacket.
 
Liners are all level. Will have a closer look at it when I get home. Dropping the heads of this afternoon for pressure checkin.
Thanks for the in put!
 
Quick update, dropped the heads of today. Spent a bit of time there with the engineer. Valves deffinatelty not sealing. Valve seats worn! Only on the left hand block? When he looked at my head gaskets straight away he thinks the gasket has not been compressed enough to make the cyclinders gas tight.
The heads were rebuilt about 20k ago, he surgests that the locating dowls that allow the cylinder head to sit in the correct position are too long after the head was priviouly skimmed thus not allowing the heads to make a tight seal against the block.
Anyone with any thoughts on this?
 
V8 Vouge said:
Quick update, dropped the heads of today. Spent a bit of time there with the engineer. Valves deffinatelty not sealing. Valve seats worn! Only on the left hand block? When he looked at my head gaskets straight away he thinks the gasket has not been compressed enough to make the cyclinders gas tight.
The heads were rebuilt about 20k ago, he surgests that the locating dowls that allow the cylinder head to sit in the correct position are too long after the head was priviouly skimmed thus not allowing the heads to make a tight seal against the block.
Anyone with any thoughts on this?
Click to expand...
Remind me - was your engine on LPG??

If it was - was there a Flash Lube (or similar) system fitted??

My 3.9 Classic didn't have one fitted....but my current 4.4 L322 does - apparently what this does is dribble a tiny amount of oil into the induction system, and helps to get the valves, stems and seats lubed as Gas is dry and this can ruin the vavle seats....

Flashlube Valve Saver Fluid: Flashlube fuel additives Synthetic lubricants for the automotive industry
 
V8 Vouge said:
Quick update, dropped the heads of today. Spent a bit of time there with the engineer. Valves deffinatelty not sealing. Valve seats worn! Only on the left hand block? When he looked at my head gaskets straight away he thinks the gasket has not been compressed enough to make the cyclinders gas tight.
The heads were rebuilt about 20k ago, he surgests that the locating dowls that allow the cylinder head to sit in the correct position are too long after the head was priviouly skimmed thus not allowing the heads to make a tight seal against the block.
Anyone with any thoughts on this?
Click to expand...

Told you so. Anyway how much did you have off the heads? Dowels should take up a normal skim easily but i suppose it is possible. If you had a lot taken off it is possible you are running at high compression with wrong timing set up. That would burn the valves. LPG needs a lot of advance or it will still be burning when exhaust valves open. Think about some composition gaskets to lower compression ratio. You would have to measure combustion chamber volume to work out compression ratio you presently have.
 
You should be able to check the dowls length vs the depth of the holes in the head/block! Check them.

Another note! my liners had not dropped, they where leaking though. Have you got photos of gaskets and block, agree staining would show.
 
Saint.V8 said:
Remind me - was your engine on LPG??

If it was - was there a Flash Lube (or similar) system fitted??

My 3.9 Classic didn't have one fitted....but my current 4.4 L322 does - apparently what this does is dribble a tiny amount of oil into the induction system, and helps to get the valves, stems and seats lubed as Gas is dry and this can ruin the vavle seats....

Flashlube Valve Saver Fluid: Flashlube fuel additives Synthetic lubricants for the automotive industry
Click to expand...

No one has ever told me before to use any lube before! I had the LPG system installed new, I would have thought they would tell me to use this. They said I should never have any problems with it.
Well it's killed the valve seats in the left hand c/h. Right hand one don't look to bad.
 
jamesmartin said:
non gas tight gasket would have obvious staining
Click to expand...

I did notice some coolent staining on the left hand side of the block when I was removing the heads.
Will measure up the dowls and check them tomorrow when I drop of the new exhaust valves.
 
Look at the simple things first. The stretch bolts could have worked loose or faulty.
They do take some welly to tighten and may of not been done properly when rebuilt.
mine loosened up the first time i did my heads, so made sure i went a good 10 deg more to make sure they wouldnt move the second time.
You dont need flash lube . Mines done 90k on gas (2000 thor)and heads and compression ok.
Who ever did the job 30k ago on yours didnt do a good job.
I had a slight crack in one liner at the very top. I used irontight and no longer seeps coolant in that cylinder.

many things can make your engine overheat and its not fair to shout liners, bin it , doom and more doom.
Well done for getting the heads off , just take your time putting heads back on and do a work sheet and tick off each bolt when youve tightened them, as the phone always goes or your mind wanders on the dreaded turning of the key for the first time, and you loose which bolt you did last. You will need a 400-600mm bar to tighten back up.
just run on the liquid gold for a while when its done to take the lpg out the equation if anythings a miss. I have magnacor leads on mine which is a must for lpg. So whilst its all off and you dont have a chunky set of quality leads change them, as a poor spark dont help matters.
 
sorry forgot to tell you about push rods. If you didnt mark the order they cam off then you will have to reset the hydraulic lifters. If the valves not been seating properly then could be a problem with the lifters on those cylinders. faulty lifter would keep valve open and burn seat, so sorry something else to think about before putting back together.
 
Willos mate stretch bolts don't work loose. However they can be incorrectly fitted specially if you use a composition gasket. Many make the mistake of when doing the initial torquing of going over them only once. With the bolt threads lightly oiled the initial torquing should be done twice, then after allowing gasket to settle a third time before any angle tightening is done. If the bolts are not lubricated the initial torque setting will be too low. If the torquing is not repeated as described the initial start point for angle tightening will not be achieved on some of the bolts, leaving them with less tension applied than the rest. As for the lifters. They should be put back in the same place they came from as should the pushrods. Lifters tend to expand when removed, so compress them gently in a vice to retract them before refitting.
 
Last edited:
If the bolts are soft they will not stretch , just get longer. You presume the bolt has been heat treated in the appropriate manner. I agree with everything else when tightening up.
 
Willos said:
If the bolts are soft they will not stretch , just get longer. You presume the bolt has been heat treated in the appropriate manner. I agree with everything else when tightening up.
Click to expand...

Well yes, if you have a set of putty bolts you are on a loser from the start. Stretch bolts came about because Aluminium expands at a different rate than steel. With the old Alloy heads fitted on studs the Alloy over time was worn away as it expanded against the head stud washers. Meaning the heads had to be torqued on service. Stretch bolts actually stretch and contract as the Alloy heats and cools to prevent this wear.
 
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