Petter Head Gasket Problem

[Lakesailor]

Anyone had a problem like this?
I am helping someone rebuild his Petter AC1W in a Snapdragon yacht.
After asking me advice about non-starting I suggested it sounded like his engine needed a re-bore. He stripped it and took the head and barrel to a local guy I know. He pronounced it all-but dead. However he refurbished the head, and suggested he had the barrel re-bored, Which was done to +0.030" by a specialist firm in Lancaster who supplied the new piston.
He bought the gasket set from ebay from a Petter specialist. They are genuine gaskets.
It's a bit complex fitting as you have to measure the squish gap (bump clearance) in above the piston and adjust it by use of shims beneath the cylinder barrel.
So we fitted the new piston and put the shim on the crankcase then the barrel onto the piston. Assembling the head with new gasket we used soldering wire to compress into the squish area and then removed the head to measure the solder's finished thickness.
This led us to remove the shim, before reassembling the head and connecting everything up.
The engine started and ran well, but water pissed out of the block/head joint.

We took the head off and the firing ring (the metal bit around the bore, which is supposed to compress, was not very compressed and still 0.010" above the gasket material. This meant the gasket material was not sealing the water passages.

The head nuts are only supposed to be tightened to 20 lbs/ft, which we did with a torque wrench. We decided to clean up and lubricate the stud threads and face up the washers and nuts so that nothing was distorting the torque figure. I called a friend who is very good motor engineer who suggested maybe going up to 24 or 25 lb/ft.

We re-assembled it and started the engine. Nothing had changed. A jet of water peeing out. Stripped it again and the firing ring had not compressed any further (0.055" as opposed to the original gasket which measured 0.039") There have been different thickness gaskets over the years but they have presumably matched the firing ring thickness to the surround material.

My friend then called the engineers who supplied the gasket set and the guy he spoke to said that he had an engine in the workshop with the same problem and we had solved the issue by finding this. He told us who he got the gaskets from (Lister Petter) and their phone number. They weren't particularly interested. "We sell half a dozen a week and no-one has reported problems".
Hmm. Well now 2 people have. Obviously a rogue set of gaskets.

Anyone had similar problems?

New gasket

Old Gasket

Cylinder top

 

[rotrax]

Been caught out with one like this before-air cooled, just compression escaping.

It transpired that the head/cylinder studs were threaded a turn or so short-putting good spring washers on top of the flat washers fixed that one,

The torque wrench was measuring the nuts going tight on the end of the thread-there was little clamping action.

Worth a check.......................

 

[Lakesailor]

Ah No. We cleaned up the stud thread and wound nuts right down as far as possible, which is lower than the head top.

See the length of stud above the head

 

[doug748]

I used to have a twin and seem to remember there were two gaskets available.

This may or may not be relevant to your problem but the name Goetz (or something similar) rings a bell. Googleize it.

 

[Lakesailor]

Yep. One gasket was 0.030" thick and the other was 0.060" thick.
You measure the bump clearance between piston and head with the head torqued down. Your aim is for the clearance to be in the range 0.022" to 0.026". To achieve this you can remove or add the shim under the cylinder block. If you need you could machine the top of the block. The shim we have measures 0.029".
The problem is that the firing ring is compressing to 0.050" but the gasket material is thinner, so doesn't get clamped.

 

[mtb]

yes mate
twice I had the same fault after buying head gaskets from a firm in York.
even though I tightened to 24lb and had refaced the heads and used gasket sealant around every ring on the gasket within two hours of test running a gasket blew
I then brought gaskets from uxbridge boat center plus other parts

No problem job done, I had in the mean time brought a yanmar 2qm 15 and fitted that in the boat but still have the petter twin and other parts sat in my shed just incase

I believe the material used to make the faulty gaskets is poor quality more like paper than halite material just because they say it's original I'd not take their word for it.
I also think because of the poor quality the gaskets are prone to compress after heating even when you re torque the head bolts it wont help

cheers
mick

 

[toad]

I had this problem many years ago and I seem to remember that the base of the barrel was out of true. When you bolted the head down you only had full clamping force on one side.

 

[Lakesailor]

The problem on this engine is that apart from being nearly impossible to start latterly, it didn't leak any water. It's only since fitting the new head gasket that the water leaks are occurring.
The old gasket sealed not only the three passages which pass into the head, but also the two passages which do not go through. The new gasket has a leak like a little boy peeing from the water passage on the starboard side of the cylinder barrel but also seeps water from the two "blanked off" passages. Undoubtedly the firing ring has not compressed enough to allow the grey material to be clamped by the two surfaces.
It's as though the firing ring is from the 0.060" gaskets but the sealing material is from the 0.030" gaskets.

As mtb suggests there are some rogue gaskets about. It may not be the supplier's fault, but some dubious quality from the manufacturing chain. It now depends how the suppliers deal with the problems.

The owner bought the gasket set from a reputable engine dealer in Devon. It seemed from the telephone call that they had an engine in the workshop with exactly the same problem.

It's a shame the old gasket is a bit knackered or I would have been tempted to put it back on.

 

[vyv_cox]

A possibility may be that the material of the firing ring has changed, perhaps thicker or stronger? If the clearance is correct can you make your own gasket to fit outside the firing ring to seal the water leakage? Something of a bodge but from here I cannot think of a reason why not.

 

[Lakesailor]

I think you may be right in that it may be possible to do that. I do have some sheets of gasket paper in two thicknesses, so that is something we could explore.
It's wrong though. If someone makes a gasket that can't perform the task then the suppliers should pick up on this and find a new source. I have no doubt that for such small production runs they are getting them knocked up in China at a few pence per unit.

 

[vyv_cox]

Another bodge suggestion! The head tightening torque seems remarkably low and it surprises me that the nuts do not back off. Presumably the head is lightly built and that's the maximum it will take. Could you pre-compress the firing ring to a thickness similar to the old one? A substitute solid cylinder head would no doubt be best but maybe some plate pieces in a vice might do it?

 

[Bilgediver]

Maybe these old gaskets perform correctly ??


http://www.stationaryengineparts.com/Petter-AC1W-head-gasket.html

 

[Lakesailor]

I've bookmarked that page. It may be the answer. We are getting a new cylinder base shim as the thicker gasket requires it. I've spoken to a guy at Bryco who deal with these engines quite a bit. He thinks it may be a rogue batch of gaskets.

With regard to pre-compressing the ring. I've been to see my engineer friend who suggested we put it in his press to do just that. The only problem is that the firing ring will then be ultra solid and refitting to the engine may not produce a seal.
The torque figures are low. They have been revised to 21 lbs/ft. But they are only 5/16ths studs and very long, plus they are screwed into an alloy casting so overloading them isn't going to be undertaken lightly.We have tried 25lbs/ft but it made no difference.

 

[twohats]

I have had a similar problem with this engine. The clearance between the valve and piston is small and after having the head machined the two were touching. The engine ran but apparently this caused enough vibration to cause water leaks. Needed the valve seats relieving to restore proper clearance.

Similar example here https://www.youtube.com/watch?v=9aZJ5EMVZ9E

Also, check the bump clearance with two pieces of wire on opposite sides of the piston, to avoid canting the piston and ending up with less clearance than you expected.

 

[Lakesailor]

Ahead of you there You also have to slightly offset one bit of solder wire to engage with the head face properly.
The bump clearance we measured was more than the range specified, But the firing ring hasn't compressed enough, even though we torqued down to 25 lbs/ft (this isn't as rash as it seems as the rocker pillar nut is specified to 24lbs/ft and it is the same stud and nut as the other 4 which are specified to 20 lbs/ft (which had then been revised to 21 lbs/ft by the manufacturers).

I spoke to Bryco in Leeds and he assured me that Sleeman and Hawken in Devon (who supplied the gaskets) are a reputable company. He feels, like us, that these are a rogue batch of gaskets.

The owner has now ordered one from Uxbridge Marine on the recommendation of mtb, who has had similar problems. Not a criticism of S&H, but in the hope that Uxbridge have a stash of gaskets which are to spec.