Page 2 of 3

Re: Exhaust gasket.

PostPosted: Mon Aug 30, 2010 10:24 pm
by twincamman
you're going to pull the head to replace a gasket and heilacoil the thing for 30 MINUTE JOB?????? think may be the next valve job may be the time to put the inserts in ????? you know what a giraffe is ???? its horse put together by a committee ----ed

Re: Exhaust gasket.

PostPosted: Mon Aug 30, 2010 10:30 pm
by robertverhey
Just getting back to the original question, I may be missing something, but is there a good reason for only replacing the blown gasket? It doesn't take long to whip all 8 bolts off and replace the lot, does it? And a new set of four gaskets is only a fiver......

Re: Exhaust gasket.

PostPosted: Mon Aug 30, 2010 11:23 pm
by garyeanderson
This discussion sounds like that age-old adage that "if it ain't broke now, it will be soon"! Fix what needs to be fixed when it breaks and just drive the bloody thing...

Gary

P.s. = I often wonder how many Elan's were all but totaled because someone was going to "fix" that oil leak that left a spot on the garage floor the size of a coffee can lid? It Sat for 25 years and now it parts or a total restoration!

P.p.s. - just add oil :D

Re: Exhaust gasket.

PostPosted: Tue Aug 31, 2010 3:16 am
by rgh0
While studs are certainly the tehnically pure solution, I have been using socket headed cap screws into the heads on my elan and plus 2 for 30 plus years for maintenance convenience with good success. The Elan has the exhaust on and off regularly with changes to exhaust, heads and engines, the road Plus 2 much less so and probably only had the exhaust off 3 or 4 times over 30 years. While thread stripping is a potential problem in practice I have only had to helicoil a couple of the threads in the race heads that I have used over this time and none in the plus 2. If you strip a thread they are easy enough to helicoil in situ so I have not bothered with preventitive helicoiling.

A few preventative measures to avoid stripping threads in the head

1. Clean the head threads and cap screws and use a good quality antisieze such as loctiite nickel antisieze paste.
2. Ensure you engage the threads properly and that they can be tightened up with finger pressure. If they are tight when first started and require effort to screw in something is wrong and stop before you strip the thread.
3. Learn what final torque does not strip the thread but seals the gasket and dont overtighten. I do it by feel and its about 5 to 7 ft lbs but if not confident use a torque wrench to determine a value you are comfortable with.

Where the joint arrangement requires high clamping loads such as a head gasket I would certainly not try replacing the head studs you typically find in an alloy block with bolts. However with the low bolt loads required in the exhaust join you can get away with it OK I believe ( or at least I have)

regards
Rohan

Re: Exhaust gasket.

PostPosted: Tue Aug 31, 2010 6:38 am
by JJDraper
I have replaced the exhaust gaskets in situ. It was a 30min job, even with studs, although IIRC I jacked up the engine (piece of wood and scissor jack) and disconnected the engine mount on the exhaust side to give a little extra 'wiggle' room.

I considered Studs, but for the extra hassle decided against it. Interestingly, I changed the bolts on the thermostat housing for studs because the threads were marginal - a PO had fitted bolts that were too short and stripped the top half inch. Studs make use of the remaining good thread and no further problems.

Jeremy

Re: Exhaust gasket.

PostPosted: Tue Aug 31, 2010 7:54 am
by alexblack13
Aye its not a difficult job, and I certainly would not helicoil the studholes for the fun of it. If it were required well that's another story. Being able to remove the manifold easier is a plus though and so is the bit extra torque available which might help keep the exhaust gaskets a bit longer.. :wink:

Good discussion though guys. Very interesting reading all the different views...

Cheers.

Alex...

Re: Exhaust gasket.

PostPosted: Wed Sep 01, 2010 5:17 pm
by richboyd
The exhaust flange gaskets are Volkswagen items. The same gasket was used for all of the original air-cooled VW engines (40HP through 1600), so they are easy to get and cheap. A perfect fit for Twin Cam headers (with non-modified ports).

Try VW part number 111-251-261B.

Re: Exhaust gasket.

PostPosted: Tue Jan 29, 2019 11:37 am
by elansprint71
Could someone confirm the thread required for the cap screws, is it 5/16" UNF?

Would there be an advantage in fitting Stainless screws?

Thanks.

Re: Exhaust gasket.

PostPosted: Tue Jan 29, 2019 12:00 pm
by nmauduit
elansprint71 wrote:Could someone confirm the thread required for the cap screws, is it 5/16" UNF?
Would there be an advantage in fitting Stainless screws?


the original studs would be UNC in the alloy head and UNF to secure the exhaust - so if you just replace the studs with cap screws you'll have to go with UNC (if you use inserts like Timesert etc you should be able to convert into UNF cap screws).

I'm not sure of a clear advantage to use stainless (of the appropriate grade, some are more brittle), it's not really humid there - but I use a smidge of copper grease.

Re: Exhaust gasket.

PostPosted: Tue Jan 29, 2019 12:06 pm
by billwill
Talking of exhaust studs, what is the logic behind using brass nuts on those studs?

Re: Exhaust gasket.

PostPosted: Tue Jan 29, 2019 12:30 pm
by nmauduit
billwill wrote:Talking of exhaust studs, what is the logic behind using brass nuts on those studs?


brass (contains copper and zinc) would not weld onto the stud like a hot steel nut may tend to do over time, it is less strong (which can be compensated by taller nuts to increase the number of threads) but is behaves like a lubricant. I still use a smidge of copper grease with these...

Re: Exhaust gasket.

PostPosted: Wed Jan 30, 2019 7:08 pm
by Bigbaldybloke
Like Rohan, I?ve had 5/16 unc cap screws securing my exhaust manifold for over 30 years, no problems, just get ones the right length. They don?t get undone that often, are well lubricated with anti seize compound and not over tightened - use the Allen wrench with the long section in the bolt somyou only have the short piece for leverage and it?ll be fine. If you do strip one, as already mentioned it possible to helicoil it with the head insitu.

Re: Exhaust gasket.

PostPosted: Wed Jan 30, 2019 7:23 pm
by elansprint71
Thanks for the replies chaps. :D

Re: Exhaust gasket.

PostPosted: Wed Jan 30, 2019 8:46 pm
by Barney
bcmc33 wrote:So I guess I should Helicoil the plug holes too!!!!!!


Reminds me on my original head, #1 plug had stripped and the previous owner had bodged a metal electrical conduit piece set into the head. The centre was threaded to accept the plug.
Basically one of these cut down
super-helicoil.jpg
super-helicoil.jpg (10.48 KiB) Viewed 177 times

Blew it out of the head one day after spirited use and caused minor cracking to bonnet where it impacted.

Re: Exhaust gasket.

PostPosted: Thu Jan 31, 2019 6:16 am
by 2cams70
I wouldn't use a Helicoil to repair a spark plug hole. There's much better inserts such as "Time Serts" or "Lock-N-Stitch" types available for this repair.