Engine failure update

[jono]

Thought I would start a new thread on this one. I am interested to canvass a range of opinion so do chip in please.

The background is that the engine was professionally rebuilt 5 years ago now, first fired up around 2.5 years after and then finally run on the road in the last few weeks. The rebuild was comprehensive - all new bearings, crank ground, dynamic balance, chemically cleaned block over bored to +40, new pistons. QED 360 head job, new valves, seats, verniers etc.

I had an oil leak back in February when I fitted a new pressure sended. I noticed that the cheap mineral oil I had filled the engine with was like mushroom soup. I drained the oil and it was in shocking condition, thick sludge and cream coloured oil. I put some in a glass jar and it remained as drained but a grey layer settled out in the bottom of the jar. I re filled with another cheap mineral oil.

Since then the signs of mayo in the oil have remained and indeed got worse since I started running the car on the road. I have done 80 miles on the engine and after an extended run last weekend I discovered oil in the water as well - light mayo on the filler cap and recuperator bottle and an odour of oil in the water. Lot's of steam on start up as well via exhaust and a constant stream of vapour from the engine breather even when hot.

In conjunction, hot starting was not as clean as it had been - coughing into life and needing some prods of the throttle when previously you could simply turn the key from outside of the car and it would immediately fire and idle when hot. You could 'drive through' that rough running at idle though.

I pulled the head last night, main points of observation were:

1 The centre array of head bolts came off with a good 'crack', wrench set to 100ft/lb
2 Front and rear bolts were not exactly loose but came off very easily with light pressure on the wrench - no crack or sudden release, markedly less torque than the centre array.
3 The head lifted off the block easily - no 'stiction'. No Wellseal or similar present. Copper grease noted on bolts
4 Oil puddled next to cyl 1 where the oil gallery is in the head - this head bolt came out dripping in oil (normal perhaps?)
5 The block surface was clean with no rust or other witness marks. Machining marks evident from block decking when engine built
6 The head surface is visually good, showing machining marks from the head skim when built
7 combustion chambers 2-4 all 'normal' - light dry sooty covering and exhaust valves light brown colour
8 chamber 1 - markedly more oily and more carbon on top of piston than the others
9 No visible signs of cracking or water leakage from cylinders or head (valves not removed from head however)

Gasket - the gasket is a standard copper type stamped 'Made in England'. No signs of damage to fire rings. No other obvious signs of failure except for pronounced delamination between the waterways and head bolt holes between cyl 1 and 2.

Any thoughts guys, I can't see anything obvious but clearly I have a problem?

Will try to post some pics later.

Cheers

Jon

[rgh0]

All the head bolts should need substantial effort to release and based on that alone I would suspect the head gasket was not sealing. Were the head bolts ever re-torqued when the engine was first run in ?

The original copper / steel head gasket can be ( should be?) used plain without any sealant on it. I have not used that style gasket for many years but they used to have a clear vanish of some sort on them.

The head bolts should not have copper anti sieze on them. The should just be clean and be lightly oiled before assembly.

Normally water in the combustion chambers shows up as a very clean head and piston as the steam in the cylinders with the leak removes the carbon deposits. However maybe you problem has not gone long enough for now

My guess without seeing any pictures is that it sounds like you maybe had leakage between the oil passage to the head and water jacket and to No1 cylinder due to the not adequately torqued head gasket. Look very closely at the head gasket for any signs of leakage and post some photos when you have them

cheers
Rohan

[elanman999]

Jon,
Just a thought.
What block are you using? L block or tall block? If using a decked tall block the head bolt holes need a plug tap run down them to clear the thread to the bottom of the hole.
Cheers
John

[robertverhey]

My money's on a cracked head. Suggest a cooling system pressure test (with Stant tester) would have been informative prior to removing head. I would get the head crack tested and then reassemble, do the Stant test and see if there's still a problem

And I wouldn't be driving it with mushroom soup instead of oil......

[jono]

Thanks all, will take some pics tonight and post up.

Robert - mushroom soup was removed and replaced back in February. The engine has only done 80 miles since rebuild so I had not re torqued the bolts. Why do you prefer a cracked head to a failed gasket based on my account?

I pressure tested the water system to 1 bar using a Sykes Pickavant professional tester back in Feb when I first noticed a problem. It held 1 bar for 10 minutes without any movement so I assumed it was okay.

Engine is L block bored +40

Jon

[memini55]

Jon,

I would agree with most of all the post at the moment but mostly with the head bolts not set correctly and water and oil mixing from small seepage between both systems.

The main question is how do you proceed from here, I would take the head for a serious check dependent
on how many head cycles it has been run. I might think it could be warped some now and would want that checked at a minimum. Checking for cracks on aluminum is a little harder to due but a good visual and then if you can find a good shop to inject the water passages with air to pressure test. On reassembly I would make sure you set torque and then run thru a few head cycles and re check once again. You can also do the Stant pressure test as described.
A leak down test on cylinder one could also be good. Never used sealer with copper gaskets and as Rohan said nothing but some lube on head bolts.

Last don't run it much with the combined fluids.

Best of luck
Mark

[jono]

Chaps,

Some pictures added which I hope are self explanatory - some rust just noted on nr 1 fire ring adjacent to delamination.

Another point - which replacement gasket should I get?

Also, my pistons are marked 'BRF +1.016' - does this mean +40 oversize and what pistons are these?

When fitted and compressed should the fire ring edge meet the edge of the bore exactly. overshoot slightly or sit back slightly? The reason I ask is that this gaskets appears to overhang slightly the edge of the bore.

Thanks for comments - keep them coming please

Jon

[memini55]

Jon,

I can answer the firing ring question and since you said the bore was +40 may have been good to take it apart.
When I have bored that far the stock gasket does overhang and I move to a different gasket to keep the fire ring out of the camber as it will torch if in the camber long term. At least that is what my machine shop has told me. I order a Cometic gasket of large bore cambers, I am in the USA so easy since Cometic is located here.

Mark

[512BB]

Jono,

As Mark has mentioned above, the fire ring intruding or overlapping into the combustion chamber is a no no. Not only might it burn, but it is probably the cause of your misfortune, as the head gasket would not and COULD NOT seal properly, as it would not be compressed enough to do so. The fire ring would only be resting on the underside of the head, but the other side of the fire ring would be resting against AIR in the chamber. In other words, NO SEAL.

I believe, what bears this out, is tell tale marks on the copper part of the gasket, between 1 & 2. There appears to be water sepage marks where there should be none. Unfortunately I am not good with puters and do not know how to put on an arrow to show you where I mean.

My observation of the picture you posted of the underside of your cylinder head, is that it is covered in milling marks, and I am sure that should not be. It should be like glass. For milling marks, read scratches or GROOVES. Think about it, what would seal better when pressed against another flat surface, something beautifully polished to a fine grade, or something covered in scratches?

Which leads me to my final point. You asked if you would go with the same gasket again, or one of the fancy composite gaskets. Personally, I would always go with the original copper gasket, as they are very forgiving, and with your head, I do not believe that the surface finish is anywhere near fine enough to use something like a Cometic gasket, where the manufacturer actually states what grade finish is required.

Something else I have just noticed. It appears that the head was skimmed with the small oil core WELSH plug, on the underside of the head next to the oil drain to the block, in place. Not a good idea, as it would have reduced an already thin piece of metal to next to nothing. They should always be removed before skimming and a new one fitted. Replace that Jon before popping the head back on, available from Burton.

The good news though. I think the problem was entirely the gasket, but you might want to get the head pressure tested before reassembling the engine, to check that all is well.

See what Rohan thinks, and hopefully Nick [AVRO] will chime in to.

All the best,

Leslie

[jono]

Thanks guys,

Can anyone tell me about the pistons and whether the reference means a +40 over bore (which is what I was told).

Also, give the surface finish of the head gasket can you tell me which gasket I should obtain and from where? I would like to order one today so that I can re fix the head over the weekend (subject to be satisfied as to flatness of course, however I am hopeful that the head is flat - the engine did not overheat).

Are you out there Rohan?

Cheers

Jon

[Galwaylotus]

my pistons are marked 'BRF +1.016' - does this mean +40 oversize and what pistons are these?

I'm not certain if that's what the marking means but 1.016mm is exactly 0.040 inches ("40 thou"). Seems likely that they're oversized pistons to meet a 0.040" overbore.

[Johnfm]

"Professionally Rebuilt"??

Yet they used the wrong sized gasket?

And machined the head with a plug in place.

Doesn't sound very professional to me.

[AHM]

Also, give the surface finish of the head gasket can you tell me which gasket I should obtain

There was some discussion on here a while ago about the desirability of surface roughness on the head surface, regarding preventing head gasket failure. Someone had phoned-up the gasket manufacturers and asked what the Ra values should be.

Yours does however look a little rough - Difficult to tell with the photo/light - I would use any +40 gasket and a smear of wellseal or equivalent.

John,
Agreed about the Gasket, but machining with the plug in place - I had a discussion with the machine shop who first off insisted on grinding the head "you'll get a better result, and I'm not touching that old thing with an expensive milling tool." second about the plug "We can remove it if you like, but my advice is to leave it in, you are likely to create all sorts of problems with re-sealing it, some people like to replace them with 2p's don't know why - they often fall out"
He was right on both counts!

[rgh0]

I agree the rebuild looks a little amateur to me.

I would replace the welsh plug and get the surface finish of the block and head checked as it looks a little rough in the photos and the machining marks look a little random in pattern, not like you see with a smooth single milling cut done with a single setup that guarantees a flat surface.

I would use a 85mm fire ring bore gasket with a 83.5mm cylinder bore as this ensures no overlap given the tolerances on bore versus bolt location and tolerances in the gasket making.

I still think it looks like just inadequate head bolt torque and gasket compression as no obvious gasket failure. The lighter coloured exhaust valve indicates water getting into that cylinder. I re-torque the head bolts after the first 10 minutes running then again after the first hours when I have bedded in the rings and finally at 500km,s when I change out the running in oil. I would get the head and block pressure tested just to make sure.

cheers
Rohan

[TeeJay]

Jon.
I can confirm that the 1.016 does mean +40 oversize as that what I fitted to my engine. You can just make out the 1.016 by the arrow on the photo.

I had my head re skimmed by the method recommend by Miles Wilkins i.e. to Flycut, a fine cut is essential. The depth of cut controlled down to 0.001 inch."

In my past life I was responsible for an Aircraft Component supply machine shop and I know that a fine fly cut finish will leave a slight witness of machine marks. My understanding is that this finish assists the head gasket to seal. There is a recommended Ra value.

It will be interesting to hear Rohans and Nicks take on this.

Also I can confirm that it is a No No to machine an aluminium head with a metal welch plug fitted, because the dissimilar metals will cause the fly cutter to deflect. That would result in a slightly raised section on the head, so not flat.

Also it is very difficult to see from your photo if the head was machined with the welsh plug fitted, because to me, it appears there is some engine paint over that area. That area does not come into contact with the block, i.e. it's in fresh air. You would have to remove the paint from the plug to check if there is any machine marks. If there is, then you need to take the issues up with your Engine Builder, after further comments about the gasket size question.

Regarding the head gasket, I will also be interested in the comments hopefully from Rohan and Nick.

Edit: - I see that AHM and Rohan have replied while I have tried & failed?? to post photo. Oh, then it appears