Coolant/unburnt fuel leaking from head gasket

[Charles73]

I think if I find no cracks, I'll check the bolts weren't bottoming out. I plan to replace the bolts, maybe with stud/nut setup.

studs are a bit pricey but well worth the expense imho... there would be dies one can use to enhance small cracks, but the bottoming or poor clamping of some bolts (were they new? of the thin waist type? with suitable washer where appropriate? risk of something partially filling one of the bores?...) sounds like a promising and optimistic lead... good luck !

I reused the existing bolts. The TC specialist who overhauled the head advised that they were fine to use again. Regardless off what I discover once I investigate further, I think I'll replace them for peace of mind, if nothing else.

Thanks

[Charles73]

I see that the block has been faced. Do you know how much material was removed? Is there still a step up from the front cover to the block?

Edit: a 25 thou step is about right.

I'm not certain on the amount of material removed, but there is a step up from the front cover. I'll measure this later. Thanks

[Charles73]

Okay, so after a good clean up and close inspection I'm fairly certain that the block and head are crack free...hurrah!

Again, no signs of head gasket failure either. But the Ajusa gasket leaves alot of the underside stuck to the block face when removed, and the top/head side remains more or less clean. So could the coolant be passing over the top side of the gasket and not leave any visual indications?

Or, as suggested in previous comments, maybe the bolts were bottoming out after the head and block being faced, thus preventing the gasket compressing properly?

I really would like to be certain as to what the problem is before I go ahead an reassemble. Any other suggestions?

I'll attach photos of the block from immediately after removing the head, but due to any remaining fluids dripping out on removal, it was quite messy....


Thanks

Charles

[Charles73]

Quite alot of carbon build up on the pistons, I put this down to it running rich until recent tuning. Seems to be even on all cylinder though.

[RichardHawkins]

I used ARP studs supplied by Burton. My head bolts were a mixture of types,and obviously stretched. To my horror I could not get all the studs to pass through the head and align with the block. I had to take the head off and enlarge some of the holes before the studs could be used.

Hope this helps,

Richard Hawkins

[Charles73]

I used ARP studs supplied by Burton. My head bolts were a mixture of types,and obviously stretched. To my horror I could not get all the studs to pass through the head and align with the block. I had to take the head off and enlarge some of the holes before the studs could be used.

Hope this helps,

Richard Hawkins

Thanks for the info Richard.

I ordered a set of ARP studs this morning, along with a new gasket of course. The existing studs seem to be in good order and all of the same type, but I want to rule them out as the cause of the leak. Hopefully the new studs align nicely. Did you fit the studs into the block before fitting the head, or visa versa?

[nmauduit]

it does seem that a bit of corrosion was starting developping around cyl#3 (you'll be able to see for sure when the block has been fully cleaned up), indicating coolant/water seeping and sitting under the head gasket... you may want to use a good straight ruler with a back light to check across the block (and the head) for any sign of being machined concave (e.g. too much tool feed speed making the machine flex and digging a bit more in the middle).
When reassembling, make sure all the head bolts/stud holes are clean (with compressed air).
Then in such a situation, even though not recommended by Ajusa, I would install the next gasket with some wellseal in hope to cope a little longer with minute coolant infiltration (caution: it'll make the next cleaning more time consuming)...
good luck !

[Charles73]

it does seem that a bit of corrosion was starting developping around cyl#3 (you'll be able to see for sure when the block has been fully cleaned up), indicating coolant/water seeping and sitting under the head gasket... you may want to use a good straight ruler with a back light to check across the block (and the head) for any sign of being machined concave (e.g. too much tool feed speed making the machine flex and digging a bit more in the middle).
When reassembling, make sure all the head bolts/stud holes are clean (with compressed air).
Then in such a situation, even though not recommended by Ajusa, I would install the next gasket with some wellseal in hope to cope a little longer with minute coolant infiltration (caution: it'll make the next cleaning more time consuming)...
good luck !

Thanks for your thoughts.

I'll check the block face later once I've cleaned it up. I did check it after the reface before assembly and didn't notice anything. My gut feeling is the problem is related to the bolts not properly compressing the gasket, even though I did my best to ensure they were clean l, along with the holes.

Cheers

[alanr]

You seem to be concentrating a lot on the state of the block and I do agree with nmauduit that there seems to be some corrosion showing around cyl3 which is slightly suspicious.
However, if it were me I would be more concerned about the state of the Cylinder head ( no photos?)and I would personally want it pressure and crack tested. Remember it was manufactured in a time when cylinder head alloy material composition was not as good as it is in todays cars!
I would want it to be checked for any internal porosity and fully crack tested by a reputable company and also the face checked again for flatness.

Just my thoughts

Alan

[Charles73]

You seem to be concentrating a lot on the state of the block and I do agree with nmauduit that there seems to be some corrosion showing around cyl3 which is slightly suspicious.
However, if it were me I would be more concerned about the state of the Cylinder head ( no photos?)and I would personally want it pressure and crack tested. Remember it was manufactured in a time when cylinder head alloy material composition was not as good as it is in todays cars!
I would want it to be checked for any internal porosity and fully crack tested by a reputable company and also the face checked again for flatness.

Just my thoughts

Alan

Yes you're right. I've just cleaned up both the head and block face and gone over them with a rule and a light and both seem flat.

So I either go ahead and get the head tested, or put the leak down to the bolts/gasket and refit (maybe with some wellseal) and hope that solves it.

Here's photos of the head anyway

[RichardHawkins]

Charles,

With respect to fitting the studs, I can’t really remember. I think I used two studs to align the adjusa gasket , lowered the head and found that I could not get all the studs in. Much faffing about, and decided I had to either buy bolts, or open up some of the stud holes in the head, which was what I did, not all holes needed to be enlarged.

There has been an interesting recent discussion between Rohan and 2 Cams 70 about the merits of studs, bolts, and how to tighten.

Hope this helps,

Richard Hawkins

[rgh0]

i would also hardness test the head

vheers
Rohan

just out of hospital and into rehab after a does of covid and complications. unfortunately missed my races last weekend due to it

[Mazzini]

i would also hardness test the head

vheers
Rohan

just out of hospital and into rehab after a does of covid and complications. unfortunately missed my races last weekend due to it

Sorry to hear that. I wish you a full and speedy recovery.

[TBG]

Rohan get well soon - this forum needs you!! D

[2cams70]

I too wish Rohan well.

A couple of points:

1. Did you ask your engine builder what compression ratio he machined your pistons to achieve? It's obvious from the pictures that pistons intended for racing application have been used. The valve pockets are huge and so is the intruder. Whilst it will work it's certainly not ideal for an engine running road spec. cams and valves. Unecessary lumps and bumps on the piston don't make for efficient combustion. It's best to run pistons using valve pockets no larger than what's actually needed. If your compression ratio is too high this will stress the head gasket.
2. Yes I reckon the ARP bolts are better than the ARP studs for road application and may even be better for race application. See previous discussion on the topic. If the ARP studs were a similar thickness to the ARP bolts and also the original bolts they would be better. As is they are much thicker and less elastic than the original bolts unless you torque them to achieve a clamping load higher than what the block and head were originally designed to cope with.