Engine damage

[Adam]

So there we have it!!! I was making it drive backwards by continually powering up dynastart, and let’s just say that’s what stuffed the motor!! Sorry if I confused everyone and thanks for everyone’s help.

[AustHaflinger]

I stand by my assertion that the engine being rotated backwards by any means did not cause the failure - if it had been running for a while then Jim's point about the top end not being lubricated would come into play but just on the starter i doubt it would.

And I think the problem would have cropped up even if turning in the correct direction.

Maybe due to lack of use or whatever, the valve has stuck or the spring broke and the valve did not retract under spring pressure.

However all that does not matter now. You are in the rebuild stage and need to look forward - in that process, as you are doing, replace dodgy bits with new, satisfy yourself old parts are still OK, use correct engine assembly lube on the parts that require it - and given your comments on the valve guides you will need to ensure the they are machined/drilled to correct cold tolerances to ensure they do not stick again and cause the same problems you have just been through.

Good luck with it.

Garry

[Adam]

I’m back!!!!
My engine is back from machinist! New 80.5mm pistons, one new head from dale that was for 90mm pistons machined back to 80.5mm. New valves, new rocker shafts, near new everything. When machining heads just skimmed valve guides, suggested to put a copper head gasket in as a almost consumable part. He seemed to know what he was talking about, and I have no idea, any thoughts?
Super thin, maybe 10 thou?? Just to protect surfaces a little. Also insisted on re torquing head bolts after initial start up and again after 100 kms.
Any other tips be gladly appreciated!
I’m all good installing engine, mainly rebuilding engine not so sure. Thoroughly clean piston barrels and then engine oil them for assembly, bottom end already together after pulling apart and cleaning.

[heinkeljb]

Glad you have gotten all your parts back and can now start putting things together. I am not sure I understand the suggestion of putting a copper gasket in as all that will do is reduce the compression ratio and another point of possible leakage. Unless it is actually required to make sure the valves do not touch the piston, I would not put one in. Plus you would have to do the same on both cylinders.
Did you get the valve guides checked - reamed straight?

Checking the heads are torqued down several times after a rebuild is a good idea in any case.

John

[Adam]

Valve guides have all been replaced and reamed, heads look great. I think because he didn’t want to machine any further due to possibly putting hole in pushrod tube?
I think the idea was a malleable gasket that could mould a tiny bit over small lip?
Jeweller cousin has been able to make gasket.

[AustHaflinger]

As you will be aware the standard head has a small grove in it where the top of the barrel fits in and as the lot heats up the faces seal on each other with expansion - hence no gasket is needed.

I am not sure why a copper head gasket is needed - with it fitted, as the cylinder heats up it will try to push the head up and with the copper gasket there restricting it, the long studs that hold the barrel and heads in place could be over stressed.

Unless faces have been machined to account for the thickness of the copper gasket then I would not use one - unless I could be other wise convinced it is safe to use.

I have haflinger heads on VW barrels and do not use any special sealing.

Garry

[Adam]

Thanks for all the input. I will relay this all back to machinist and try get a clear reason for him suggesting the gasket. Thanks again. I think his concern was his machining got so close to pushrod tubes he maybe couldn’t get the facing he wanted?? I will try take a photo of the heads for you!
Spent quite a few dollars on all this so hopefully get it right!!!

[Adam]

Hopefully you can see the machining has just broken through to the push rod tubes! And there is no step in that head for the barrel. Is this a concern do you think??

[AustHaflinger]

Sorry not following this - you have 80.5mm pistons - why did the heads have to be machined to fit the barrels?

I have 87mm pistons and my heads did have to be machined to fit the larger barrels and mine were not machined as much as yours. When the heads are machined that far out what you can get are cracks in the heads where the tubes are.

See an old head of mine with the read arrow pointing to a crack and my heads were not machined as far as yours are so that the metal from the tubes shows.

Also you can see I still have the intent around the outer inside of the head for the top of the cylinder liner to fit in.

Garry

[Adam]

I got a replacement head from dale that was 90mm I think so had to be machined to fit the 80.5mm piston liner or barrel or whatever you call it???
All of this a bit over my head unfortunately!!
I just want to put engine back in and go driving!!
Boo hoo hoo!

[AustHaflinger]

If you needed to reduce the internal diameter of the head then I would have expected your mech to machine up a ring to be pressfit in to reduce the diameter. So not sure why he is actually machining the head.

His approach is different to what would normally be expected but thelogic may have been lost in the communication process.

I suggest you just do what he has proposed and if it all works great, but if it doesn't then you have some recourse back to your mechanic. With your heads as they are, I would be weary of cracks developing where the tubes are as happened in my pic.

Good luck

Garry

[heinkeljb]

I am now totally confused by the logic being used. Piston / barrel is 80.5mm. Head apparently already machined to take 90mm piston / barrel. That's 9.5mm BIGGER that the piston / barrel going to be used.
Now unless the thickness of the wall of barrel going to be used is actually bigger that 90mm then there would be no need to do any machining on the head except to tidy the various faces up from damage. The top of the barrel should be machined DOWN to the appropriate size to fit in the head.
If the barrel going to be used was smaller in diameter than the machined 90mm head, then either as suggested by Gary a ring would be machined to fit the head and the barrel OR the head would be welded to build the missing material back and then re-machined to the correct size for the barrel being used.

I think a long conversation with the machinist to work out the details and getting a written guarantee that they will redo things if they don't work will be needed.

I take it you have at least one head that is the original size and shape they can use as a template to match the 90mm head to?

John

[Adam]

Ok, very sorry, the head I got was a 70mm head from dale, not 90mm!!
Now you can understand me jumping dynastart wrong way round! Obviously then had to be machined out to 80.5mm, and just skimming push rod tube. The gasket being a suggestion or recommendation to try and preserve the head from any wear from barrel as I understand it!
I see the original head has the lip on the face whereas the machined one he didn’t want to take any further as already broke into pushrod tube. I don’t understand enough to know if this was a fault in his machining or not. He has been very helpful and worked on lots of air cooled engines and seems to know his stuff???

[heinkeljb]

Ah! It makes sense now.... Sounds like you got an Invacar head (500cc). Now that the head has been machined, I wonder what his tolerances are. Putting a copper gasket it suggests there is slightly too much clearance, but that could be what is needed to take up the expansion of the barrel. Unless you have been told how thick the copper gasket should be, you run the risk of putting something in that is too thick and best scenario would be that it just leaks. Worst would be that it splits the head. I think you need to ask a few more questions on how thick the gasket should be.
Personally, I would be on the look out for a proper Haflinger head. I know you could probably get one from one of the European suppliers, but it would be expensive and shipping would make it more so. A request on one of the Haflinger facebook groups might result in one at a reasonable cost.

John

[Adam]

Thought I would let you all know that engine is back together, refitted into the haf and purring like a kitten!!!
Have re torqued head bolts after first getting engine to temp, will then redo after around 100 kms. No sign of any oil leaks as yet, so pretty exciting!!!! Now to try get it registerered, which leads me to my new topic!
Thanks everyone for all your help and advice.

[AustHaflinger]

Thats great to hear - well done

Garry

[heinkeljb]

Really glad to hear you have gotten the engine rebuilt and running. I hope you can now jump through the required hoops to get it “on the road”!

They are great fun off road , not so much on tarmac due to their slow speed against modern traffic. Having said that, I have driven mine to Holland and back several times, just going slowly. Admittedly, Europe is more built up and you are never really far from some sort of help if you need it.
Was supposed to happen this year, but should now happen next year, round trip to the Dutch Treffen will be in the region of 1000 /1200 miles round trip over five days.

John