Cylinder Head Studs

[JackFitz]

Hi, I've stripped my engine down (again) in the hope of curing some leaks from mistakes I made during the rebuild 6 months ago.

Some of you may have seen my article in the January 2021 issue of the Sprint magazine, anyway...

I reused the existing studs, pad washers and nuts previously. The plan this time is to replace them but I've just found out the cost and the studs don't seem to want to budge.

I've been given conflicting advice on the studs, some people are saying they stretch and should be replaced, some are saying they do not stretch and can be re-used. Would anyone be able to settle this for me?

I'm also struggling to find a source for the pad washers, does anyone know where to get these?

Thanks!

[Bogsye]

I misplaced a pad washer when I was rebuilding mine. I struggled for a suitable replacement, and ended up going to a local engine shop and raked through their scrap bits. I found a suitable thick washer that had the correct inner dia, but was a bit too large on it's outer diameter, so I turned it down on the lathe. I think my particular example came off the bottom end of a diesel Vauxhall.

[Jhonno]

JackFitz said:

Hi, I've stripped my engine down (again) in the hope of curing some leaks from mistakes I made during the rebuild 6 months ago.

Some of you may have seen my article in the January 2021 issue of the Sprint magazine, anyway...

I reused the existing studs, pad washers and nuts previously. The plan this time is to replace them but I've just found out the cost and the studs don't seem to want to budge.

I've been given conflicting advice on the studs, some people are saying they stretch and should be replaced, some are saying they do not stretch and can be re-used. Would anyone be able to settle this for me?

I'm also struggling to find a source for the pad washers, does anyone know where to get these?

Thanks!

They don't have to be replaced, check their condition though.

Pad washers... I misplaced one, but spoke nicely to an engine builder who sent me one. Couldn't find them otherwise.

[a1rak]

One of the weakest points on an AJP is the head fixing and location. The heads lift and the gasket pressure and location is reduced under hard use, hence so many guys with head gasket issues. With the amount of work it takes remove and strip the engine to reuse 20 year old head bolts might be a saving not worth risking. I’d replace them. You could always get a local machine shop to make the washers. Obviously this is only my opinion

[ukkid35]

I have struggled to get the heads to seal in the past

However the last time I did the job it has been very successful

Resurface the washers if new are not available

Make sure the stud threads are clean by chasing them as required

Make sure they are properly lubricated

Torque to spec, leave overnight, check and torque as required, leave overnight, check and torque as required

We don't have the luxury of being able to run the engine to temp and then rechecking, because of the timing cover hidden stud

I you ignore the hidden stud and torque the others after heat cycling that risks twisting the head

Please take all the above as merely my opinion, I am definitely not an expert, but I have spent a lot of money on AJP8 head gaskets

[spitfire4v8]

I put engines into a heat chamber .. it's grander than it sounds .. basically get a massive cardboard box and put it over the engine, then put a fan heater inside the box .. you will be surprised how flipping hot the recirculated heated air gets, the engine gets almost too hot to touch! Let it get thoroughly warmed through for say a couple of hours, then let it cool overnight. Re-check the head nuts. If you have the time you could do a few heating/cooling cycles before re-checking the head nuts. I've never had a composite head gasket issue on either the ajp8 or the sp6 doing this. Not that I have built many of them mind, but of my tiny sample of builds there's a 100 percent success rate

[TwinKam]

Genius! I will be remembering this.
Tell me Jools, were you involved with Barnes Wallis in designing the Stratosphere Chamber at Brooklands?
Btw, if you've not seen it, it's well worth a visit, great (big) bit of kit. The fan heater didn't exist then, but serried ranks of gas bottles with their synchronised valves stand proudly alongside, like sentries.
Rik

[JackFitz]

ukkid35 said:

Resurface the washers if new are not available

Make sure the stud threads are clean by chasing them as required

Make sure they are properly lubricated

Torque to spec, leave overnight, check and torque as required, leave overnight, check and torque as required

This is pretty much what I did last time, other than leaving overnight twice and checking the torque again. I'll give that a go this time. It's good to know that I don't necessarily need to replace the studs. Thank you

spitfire4v8 said:

I put engines into a heat chamber .. it's grander than it sounds .. basically get a massive cardboard box and put it over the engine, then put a fan heater inside the box .. you will be surprised how flipping hot the recirculated heated air gets, the engine gets almost too hot to touch! Let it get thoroughly warmed through for say a couple of hours, then let it cool overnight. Re-check the head nuts. If you have the time you could do a few heating/cooling cycles before re-checking the head nuts. I've never had a composite head gasket issue on either the ajp8 or the sp6 doing this. Not that I have built many of them mind, but of my tiny sample of builds there's a 100 percent success rate

That's a great idea! Although, knowing my luck I'd end up setting the box on fire somehow...

I'm currently torqueing up the head nuts using an offset ring spanner with a hex-key socket on the end with the torque wrench at a 90° angle. The 2 sets of spanners I have bought do have a bit of flex in them though and I'm worried this is affecting the torque reading, could anyone recommend a set that won't flex?

[TwinKam]

Jack, you have a pm (email).
Rik