Engine damage

[Adam]

I’ll tell you what I did on the proviso you don’t call me dumbass!! I’ve had enough of that from my mates! Cut a long story short, flat battery, jump start straight to dynastart, polarities wrong way round, engine fired up and ran backwards, bang crash bang, dead! Have removed engine , stripped off heads, left hand side snapped valve, bent Conroe and smashed piston!!!!! Where valve guide goes through head has also been a bit damaged, can I hone this out?? How crucial is this??? I have never stripped an engine before and am enjoying the learning curve!! I think bottom end is fine but want to completely strip down and put new bearings, seals! Any advice on any of the above!! Instead of starting any post with dumbass, maybe just write a capital ‘D’
Cheers, Adam

[heinkeljb]

As per your post above Adam: D!
Ok, next time jump start from the battery terminals. Less chance of getting things wrong. Obviously the best option for the cylinder head would be to get a new valve guide put in and the valve seat cur to match the new valve(s). If you don’t and you use a new valve in a damaged guide, if the guide is bent then it will wear on the valve stem and at the very least you will get very blue smoke from the exhaust as it will burn oil. If it is bad, the blue smoke will be very bad and an MOT failure.
Do you have the repair manual? Although it doesn’t explain things like a Haynes manual, you will need it for the tolerances of things etc. You will also need the parts book to get the part numbers and sizes of the various bearings.

Good luck!

John

[Adam]

Have both manuals!
The chamber in the head where the valve guide inserts is also damaged, as it is a new valve guide won’t slide in because of the burring. I will show my mechanic mate and see what he reckons.

[Adam]

Measured bored to be almost spot on 80mm. Around 79.93-80.04

[AustHaflinger]

"D"

Well in theory if the engine ran backwards there should still have not be any damage - I just checked my spare cam shaft and the back side of the cam lobes is almost the same as the lifting side so the valve gear relative to the position of the piston so there should have been no clash - this is supported by the fact that you can turn the engine backwards by hand with no tightness or clashing.

However you do have the damage so something must have happened.

From what you describe with respect to the valve guide - I assume the piston has hit the valve and pushed it sideways damaging the valve guide - do you have indents in the top of the piston and head from the broken valve? These are not such and issue as long as the basic integrity remains.

You need to take the head to a specialist - they should be able to put an new valve guide in, tig any gouges and recut the the head for the new valve. Note you need the proper valve - these are sodium filled which assists in cooling.

Also check the gap between the pushrod tube and the oil return tube in the head as it can crack between them.

Re - rebuilding the rest of your engine - I have had two major engine failures due to pistons hitting the heads. These resulted in new pistons, barrels, and remanufactured heads - however the conrods were fine.

I am surprised you have damaged conrods - valve/tappet pushrods yes but not conrods.

I have not had to pull the bottom end apart but from what I have read it is a bit daunting so unless there is an indication that main crankshaft bearings or the camshaft is suspect I would think about no pulling the bottom end - I believe the conrods and bigend bearings can be replaced with both cylinder barrels removed, but you need to carefully measure the big end crankshaft journals and obtain bearings that match.

As I indicated at the start, even with the engine firing backwards none of this damage should have happened - so when it is all apart you need to look for evidence - why - pushrods, rockers, cam lobes.

Good luck with it.

Garry

[Adam]

Pushrods damaged, not conrod sorry!!i have just got Polly and flywheel nuts undone, will take to an engine machinist and see what they have to say, cheers.

[heinkeljb]

Valve guides are a "Machine them out" correcting any shape change to the hole at the same time, then heating the head and inserting over size (outside diameter) guides. Recutting the cylinder head valve faces to match the new guide position and lapping valve in. So generally, not something that is done at home. Although I have done replaced a valve guide on a Heinkel head, but the old guide was an easy push out once the head was hot. No damage, just worn hole where the valve goes. If yours has been hit by piston / valve then it really should be dealt with by some one with the correct machines and knowledge.
As Gary says, look for any other reason for things to have gone "Bang":-
Play in the big ends?
Play in the main bearings?
Play in the little ends?
Were the cylinder head nuts loose?
Could the valve clearances have been too tight?
Have the ends of the push rods come loose on the shafts?

I take it at least one valve is now either very bent, or the head has broken off? Replace all the valves and if you are having the heads machined, then get both heads done and save yourself the possibility of having to strip the engine again to deal with the other side at a later date. I will also help to get the compression ratios the same on both sides when you put it back together.

John

[Adam]

Spoke to engine reconditioned who seemed very good. Thoughts are to bore heads to 80.5mm or 81mm. Dale only has 81 atm , only need 80.5, not sure if I should wait or just bore to 81?? Engine guy can sort head where valve guide goes, obviously change both pistons, he seemed to think only replace valve that is damaged????
Split bottom end casing, everything seemed in good order, cleaned and reassembled without too much drama, got all the bearings to line up with locators, quite impressed with myself. I suppose the only downside of going 81mm is there is no more room for re bore?? What are your thoughts on this and also changing all valves????
Cheers

[heinkeljb]

You have me a bit confused now, I think what you are trying to say is that your engine reconditioning place can rebore the barrels to 80.5mm or 81.00mm. Your biggest issue will be to get hold of suitable pistons. If all that you can find are 81.00mm pistons, then obviously you will have to get the barrels bored to suit. Yes, the downside would be that there would not be another rebore available on those barrels.
If you can afford to wait and get 80.50mm pistons, that would be better in the long term, but how long will you have to wait for them to be produced and at what price when they finally get made? Have you tried to find any from the European suppliers?

Personally, I would get both cylinder heads sorted - new guides and valves, that way you know they are good. Obviously, this will cost more money than just fixing the obviously broken valve. At the very least get all four valves seats recut and matched to their relevant valves so you get good compression - You really can't afford to lose too many of the 29 horses that live in a good engine!

John

[AustHaflinger]

Yes I agree with John things seem to be a bit confused.

Firstly why do you need a rebore? Did the damage to the pistons cause damage to a liner? Was the engine already worn out hence the need for a rebore. If the engine was OK prior to this I would have just got a "hone" and refit with new 80mm pistons and new rings - you did say in an earlier post that the barrels checked out OK at 80mm.

I agree with John - get the heads and valves etc fixed first. you will need to see if any gouges in the alloy head need welding up, new valve guides and the lot machined. My view on the valves differ a little from John but all valves need to be carefully checked and if undamaged can be used again - but if any doubt replace - obviously all valves need to be the same size as the opposite cylinder and all valves need to be lapped in again.

If you had piston and valves clash then any of the hit valves also need to be replaced - as mentioned sodium filled exhaust and maybe inlet valves are needed. Also, why did they clash - was it a bent push rod (when you put them back in make sure you put the right ones in against the correct rocker etc. On rockers - there will most like be damage there if the clash was big enough to break valves and wreck pistons.

By all means work out what you are going to do with the bore size - if there is no reason to bore then don't. But your priority is sort the heads and the valve gear or otherwise you are likely to have similar issues in the future.

Garry

[Adam]

Reconditioned said bored were in reasonably good condition, although were quite glazed!!i need some machine work done to sort out damaged valve guide port, and thought might as well get next size up piston and rebore head appropriately so I know in good order!!
I think I will get all new valves and guides, obviously I don’t know much about all this but would prefer try do it properly if I can!!
I seperate bottom end and all seemed fine, a little bit of wear on rockers was all I could see!! Have reassembled now, hopefully I haven’t been too gun ho!!
Found some 80.5mm piston and rings on e bay but want $450 Aussie each, dales 81mm were 116 euro I think, so a bit over $200???
I put in a cheap offer on e bay so see what happens?
I either wait for 80.5 or bore to suit 81??? Not sure?? Thanks for all help

[AustHaflinger]

Ok - I can see where you are coming from but going to a bigger bore just on the basis of a glazed bore - a hone will fix that. For considerable expense you can go up to 82mm but the end increase in performance is bugger all. I run 87mm pistons and barrels and while I do have a bit better performance it is still a slug and in the real world the increase in performance does not warrant the substantial costs.

However if you can get the bits for a good price and it provides you with piece of mind that is all good.

You said the rockers in the bottom wnd were OK but what about the ones in the heads and their bolts?

Also - a couple of times you have mentioned "rebore head" - now I am not sure what you mean by that (I know what I mean by it though). If you are using standard barrels the top fits fine into the groove in the heads and seals up when it is heated (hence no head gasket).

Now on my engine we did have to rebore the head because of the larger diameter cylinder, so the heads would fit over the barrels but this is not needed with what you are proposing.

This thread may be of interest. Ben is in your neck of the woods so maybe PM him and see how he went.
viewtopic.php?f=23&t=3681

Cheers

garry

[Adam]

I may be getting some of my terminology a bit wrong sorry! Haven’t inspected head too closely yet, that will have to wait a few days!! Either way I need 2 new pistons so thought going up to 80.5mm would be the sensible thing to do??

[heinkeljb]

If your barrels are currently 80.00mm and "just a bit glazes" then get them honed, which means they just run a carbarundum set of stones down them which takes of the thinnest layer and removes the glazing. The barrels would then be good to use with 80,00mm pistons and possibly oversize rings. No need for a rebore - EXCEPT if you can't find any 80.00mm pistons!!
Then you will have to go for what ever size pistons you can get.... and obviously get the barrels rebored to suit.

Only if the heads are welded up and the weld either covers or distorts the part of the head that seals on the barrels would you need the head "rebored".

How about posting some pictures of the heads showing the damage as we can make more informed comments about what you could do?
There is a "how to" somewhere on here if you can't work it out. Basically, just next to the "submit" button is "Full Editor" button, click on that, then you can choose a file from your pictures folder or where ever. Then "Add the file" and finally in your post click ""Place in line".

John

[Adam]

My digital vernia reads no more than 80.05, obviously not exact, the reconditioned ran his special tool through them and measured them and said they were worn only a little. Just checking with dale to see if he has 80mm pistons. I am going to replace all valves. Can you put bigger rings in a standard 80mm piston??
Sorry if that is a stupid question??
Will try post photos of the carnage!!

[heinkeljb]

It looks like the piston hit the valve and bent it causing it to seize in the bore of the guide and then as the piston continued up it has forced the guide out of the head. Replacement would be an oversize guide on the part which goes into the head but with a standard size hole for the valve stem. Something your engine reconditioned can do for you.

Question is why did the piston strike the valve? Was the engine running correctly before the flat battery? Could the tappets have been a bit tight?
Can you check the amount of play in the little end in the damaged piston using the same gudgeon pin in the same condos? Then check for play?

A combination of play in the little end allowing the piston to be a little nearer the cylinder head than it should be along with the valve being pushed further into the combustion chamber than it should MIGHT have allowed the two to collide - but that is guess work on my part!

John

[Adam]

I adjusted tappers not really knowing what I was doing, just followed the workshop manual, so may have had them a touch tight??? Engine ran pretty sweet until I ran it backwards!! Everything seems pretty sweet with no play, although will get someone a bit more qualified than me to look at it all!!!

[heinkeljb]

Adam,

Make sure you get the rocker arm involved checked for cracks, straightness as it will have taken a beating when the valve came back up in to the rocker box cover area.

Both the head and the barrel look like it has been leaking oil past the cylinder head seal area. When you took it apart, where the nuts holding the head on tight? I am trying to work out why the piston hit the valve.
Another thing to check - find the push rods and see if any of the ends are loose on the rods. Also check them for straightness as they too will have been loaded very heavily when it went bang!

When the head is checked, make a point of getting the rocker shaft towers checked for cracks as you don’t want them to fail when you put the engine back together!

If I think of any thing more, I’ll post it up.

John

[Adam]

Cheers, yes exhaust push rod bent, will check everything else but all looks pretty good???

[AustHaflinger]

I am trying to work out why the piston hit the valve.

Exactly - and it is not clear at this point of time. I had a valve break in a Subaru and it did not cause any damage to the valve train - the reason the valve broke first - no impact.

The fact that your pushrod bent indicates all was working when the crash happened - can only be the pushrod came of the rocker in the engine or something happened with the rockers up in the head. You have discounted the rockers/camshaft in the engine and that only leaves the head valve gear - so go over this carefully.

Now if it happened in one cylinder - not the other? Points to a mechanical failure somewhere on the damaged side and not the other - before the clash.

I agree with John - there is far too much oil around the cylinder so you need to look at why as well.

garry