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Water leak - Austin Nippy - 18-03-2025
Hello everyone,
I don't know if anyone has any ideas for this one please. I've finally managed to get the "real" Nippy engine inserted into the Nippy. Full of anticiaption, I began filling it up with water with a view to trying to see if it would start. Sadly, water is pouring out of the exhaust manifold studs, mainly appearing to come from the second one back.
I've attempted to re-thread both the stud and the hole (both 5/16 BSF) and initially tried sealing around it with Stag jointing compound without success. I've repeated this using some thick black silicone "goo" which says will seal anything - still the water pours out within seconds of putting the water in.
The second stud back is the most likely culprit and doesn't really go in tight - it feels like it's tightening up with my fingers but then, using a pair of nuts to lock against each other, it becomes "soft" in the hole as soon as a short spanner is applied holding the shaft as close as possible to the stud.
Is it possible to make the hole bigger - say 3/8ths or will this cause more damage?
Is a helicoil the answer to keep at 5/16th? Is it possible to drill this too deep and do something later regretted?
Can the hole be filled with "plastic metal" to allow the stud to tighten properly?
Is there some sort of magic sealant that will stop the water leak in its tracks?
Unfortunately, I have very little time during the week or at weekends to spend messing about with this and have the car entered for some different events beginning with the Sevens to the Sea in a few weeks' time so need to find a way which is effective but also requires very little time, equipment or expertise which I appreciate is probably nigh on impossible.
I look forward to hearing of any suitable suggestions as to how to fix this or, alternatively, who can fix this please. I live just off junction 31 of the M1 for location. Obviously the car is not driveable and I have no access to trailers etc so it's stuck where it is at home.
Best wishes,
Nick
RE: Water leak - Steve Jones - 18-03-2025
A Helicoil is the answer, Nick, with the stud sealed with a couple of turns of PTFE tape for belt and braces. Drilling out for the Helicoil tap should cause no problems. Are you sure the thread is 5/16" BSF? Originally it would have been 1/4" BSF and if all the studs are 5/16" then it should be possible to Helicoil them all back to 1/4" although if the manifolds holes have been opened out to 5/16" you'd be better off leaving everything at that size.
Steve
RE: Water leak - Austin Nippy - 18-03-2025
Hi Steve,
Thanks for the reply.
The studs are a variety of 5/16 at both ends and 1/4 going into the block which are stepped studs in reverse - the 1/4's go into the block but they're all 5/16th on the outside (the bit going through the manifold) - which is how it was when I bought it last year.
I suspected the helicoil was probably the best way to go but am pleased that you've confirmed this for me. The most likely culprit is the second stud back which is a double ended 5/16th one. I'm tempted to leave the other studs as they seem OK at the moment as they are - firm in the holes and apparently water tight...
So it looks like getting the manifold off again; re-drilling the hole with the bit in the helicoil set; re-tapping the new hole and then screwing in the helicoil unless I'm mistaken. Hopefully, all will progress smoothly from here on in once I can find some time to get it done.
Best wishes,
Nick
RE: Water leak - wild_willy - 19-03-2025
Hi Nick
I am currently having similar issues with head studs on a sports block. Some of the stud holes were helicoiled at 5/16 BSF and 2 of the helicoils pulled up and out of the block. Because the stud holes are adjacent to the bores (a bit like the centre manifold hole) I was not keen on going up to 3/8 instead I decided that a M10 1.25 thread might tap a half decent thread in the damaged hole (recommended hole size is 8.8mm) allowing the use a stepped M10 to 5/16 BSF stud. A 5/16 BSF repair tap is about 9.3mm so with a damaged thread this leaves about a 9mm hole for the M10 1.25 tap. There was no need to drill the block to tap these holes as there wasn't much thread left.
I think my problem was due to corrosion around the original threads which didn't allow a sufficient depth of thread to be tapped to hold the helicoil. Using Loctite 577 hi temp thread sealer to try to keep the water at bay.
Was very frustrating finding this issue after trying to torque the head down failing at 10 ft/lbs.
Wishing you all the very best with your repairs.
Bruce
RE: Water leak - Colin Cooke - 19-03-2025
Hi Nick,
Note that water can work its way up threads, including helicoil external thread, so probably good to use loctite on the helicoil and stud, in this application.
One thing to consider, when you come to tightening the exhaust manifold nuts - if you have any concerns with the thread quality, leaking exhaust gasses is better than leaking water. Sevens to the Sea sounds too good to miss.
Good luck,
Colin
RE: Water leak - Chris KC - 19-03-2025
I like to do this job with the head off as you can then see the ends of the studs (or any inserts) protruding into the waterways and limit the extent to which they do so. A helicoil or stepped stud is a good repair, but both depend on a sound thread in the block for success. Both will leak if not sealed, Loctite 577 would be my choice too. Drilling & tapping square and on centre is important otherwise you'll be fighting to assemble your manifold over wonky studs.
Is this a sports chromidium block we're talking about? They are few and far between - if it were mine I'd go the extra mile to make a good sound repair, and bring the studs back to correct size while doing so.
RE: Water leak - andrew34ruby - 19-03-2025
(18-03-2025, 07:59 PM)Steve Jones Wrote: A Helicoil is the answer, Nick, with the stud sealed with a couple of turns of PTFE tape for belt and braces. Drilling out for the Helicoil tap should cause no problems. Are you sure the thread is 5/16" BSF? Originally it would have been 1/4" BSF and if all the studs are 5/16" then it should be possible to Helicoil them all back to 1/4" although if the manifolds holes have been opened out to 5/16" you'd be better off leaving everything at that size.
Steve
Nick, don't forget the PTFE tape as mentioned by Steve.
If you are not familiar with this tape, have a look here https://www.youtube.com/watch?v=6PR0zTU_v30
RE: Water leak - Robert Leigh - 19-03-2025
I am a believer in stainless steel studs for the exhaust manifold. If the manifold holes are all oversize I would find another manifold; there should be plenty around. I always loctite a helicoil into place, and if there is water behind the stud I loctite the stud as well. It's probably best to use high strength loctite for the helicoil and lower strength for the stud, so that the stud can be removed without disturbing the helicoil.
RE: Water leak - dickie65 - 19-03-2025
If its a Nippy manifold they are not common at all there was one on ebay recently though.
I have a chromidium block which has had all the bad threads repaired as well as the valve seats by laser welding which was marginly cheaper than buying a brand new block.
I have used gasket goo under manifold washers to slow leaks down in the past.
RE: Water leak - Austin Nippy - 20-03-2025
Good evening everyone and many thanks for your helpful replies and advice regarding my water leak (the one on the Nippy at least!).
The engine I bought last year has a 1 1/2 inch crank in the proper ribbed casing. It doesn't obviously have the Chromidium block (no triangle markings etc). It does have a Paul Bonewell cam fitted and a Supalloy head which came with it. The manifold is the correct Nippy one albeit with a downdraft SU carburettor. It was apparently running well in this guise a few months before I found it for sale and managed to snap it up.
My intention was (is) to fit it as bought to see how it goes and then, possibly, try it with the genuine, original Nippy head and Downdraft Zenith carburettor I have on my other engine to see what happens, should the mood take me.
The other engine is currently not running after giving sterling service since 1997 and covering a lot of miles so swapping them back over isn't an option at the moment. I will eventually have it rebuilt (hopefully making it finally free of significant oil leaks which has so far proved beyoned everyone who has tried to make it reasonably oil tight) so that I'll have a good spare in stock for the future.
I think I'm going down the Helicoil route first as this sounds like the most obvious solution (complete with sealer and PTFE tape) as this won't necessitate changing any of the studs which all look pretty new and I also have a 5/16BSF helicoil kit in stock. I trust that this all does the job...
The biggest challenge will be finding sufficient time, prior to the excellent Sevens to the Sea event, to try to repair this due to pressures of work and other non-A7 related commitments at weekends. I'll let you know how I get on with it once I've had a go.
Best wishes,
Nick