Jowett 7hp Cylinder head tips

[MartinRaine]

Hi i still can not get the cylinder head gasket to seal it has leaked water into the bore but only on the right hand cylinder. I Have replaced and sealed all the cylinder head studs and had the cylinder head skimmed.To test for water leaks I have made a rubber gasket and made a plate to resemble a cylinder head but cut out in the middle so i can see in , i have filed the radiator back up and opened the inlet valve to check the water and inlet manifold for leaks. After 7 days there is no water leaks??. So i need some tips on fitting the gasket. ie Do i anneal the head gasket it is from jcs, what do i coat the gasket in, what pressure to tighten the head nuts, or do i put sum sort of radiator sealant in. have any one had similar issues. Thanks Martin

[Tony Fearn]

Hello Martin,

Make sure both faces are clean without any old gasket goo etc on them.

I use blue Hylomar on both sides of the gasket.

I always use new cylinder head nuts (from JCS), as re-using the old ones didn't seem to work in the past, as they splay out at the bottom and, when tightening, sometimes strip. The new studs you've used, together with new CH nuts is the best option.

Tighten the nuts as per the sequence in the instruction book until tight, I don't know if there is datum for torque setting.

Roy Braddock, our late lamented Jowett guru, told me that it was wise to add radiator sealant after every enginge rebuild, and this is what I have done.

Run the engine until it's hot and tighten up the CH nuts. You'll probably get a bit more of a turn on them.

Other than that, perhaps George can fill in the blanks.

Tony.

[Leo Bolter]

I have used this product when re-using head gaskets (in this case, on the same head/block that the gasket came off). It was recommended by a "stock car" engine specialist.
It may be useful for your water weep situation, but it sounds to me as if you really need to have the cylinder face checked out, studs removed and re-faced if necessary.

[ian Howell]

I had exactly this problem a few years back. I had checked the heads on a surface plate and checked the cylinders for leaks in a similar way to Martin. I cleaned the cylinder tops VERY carfully, aware of possible stripping threads raising 'collars' around the studs.

Finally I took Tony's advice and all seems (so far!) to be OK. The reason is a mystery to me, but Hey! it works.

[george garside]

I concur with Tony's suggestions .Iwould add that if you have had the induction pipe off & have a leak ( slight weep even) on the induction pipe to pot gasket it is just possible that water is passing from the cooling part of the pipe into the induction part and thence into the cylinder if the inlet valve is open., saame goes for a porous induction pipe .On the recomendation of Roy Bradock I always used two gaskets per side on the induction pipe along with a gasket sealant. I like that Tonys idea of using a rad sealent to take care of such a leek so that would be worth trying first. I always had some in the radiator in the hope that if any small leek developed anywhere in the cooling system it would already be there to do its stuff!

george

[MartinRaine]

Hi i have been on with the problem today i pressure tested the head again and it is OK, the head was surface ground so that is OK, i have had another pressure test on the inlet manifold and this is OK, the barrel surface is OK. So i started to look at the gasket and found a old JCS gasket of about 30 years ago, i checked it against the new ones from JCS and found it is about 4mm difference ie the new one is 4mm wider at its narrowest point so it is sticking onto the bore further off the edge of the barrel this not allowing the gasket to seal on its rolled over inner edge. It looks like the new gaskets they are getting made are no good for my barrel i will speak to them tomorrow, This to me is the problem, has any one else had the same problem with gaskets been to large?? thanks Martin. Ps i hope this makes sense

[Tony Fearn]

That's worth knowing Martin, let's hear the outcome.

On the recommendation of Roy Braddock, I always used two gaskets per side on the induction pipe along with a gasket sealant.

There's another tip regarding fitting of the induction pipe that also came from Roy Braddock, and I've mentioned this in several and various posts, (see:- 'Water in the Bores' by Alan Bartlett Sat June 30 2007 in the pre-war section) but it won't harm mentioning it again. The older induction pipes become a bit brittle and weakened, on the inside near to the flanges, due to electrolytic action between the aluminium manifold and the cast iron cylinder.

(Second-hand ones that Roy fettled, before he sold them on, had had the insides of the water channel, around the flange thoroughly cleaned and wire-brushed, and then filled with plastic metal to approximate the original profile.)

But of course they were still weak at this point, so he suggested (and perhaps this is in an original Jowett Cars publication as well) that the cylinder flange nuts should be loosened slightly, before the manifold nuts were tightened, to allow a little leeway at the manifold flange. Of course when subsequently the cylinder flange nuts had been re-tightened, the tappets would need checking.

Tony

[george garside]

not sure that its of any relevence but the bradford bore is exactly 4mm greater than that of the 7 (both standard size) - but ? if you inadvertntly had a bradford gasket it would work the outher way i.e. it the hole in the gasket for the cylinder bore would not reach the edge of the bore??!

[ian Howell]

I raised just this point with Bill Lock at Wakefield. I queried it because to my mind the copper protruding into the cylinder space would provide a 'hot spot' that might cause 'pinking'. He assured me that the gaskets he was providing for the post 1930 (i.e. removable head) cylinders were exactly to the original pattern.

The plot thickens.

[george garside]

Tony's suggestion re loosening cyl basse nuts etc was I think in factory publication of 1946 "hints for the mechanic". Unfortunately I have lost /mislaid my copy but, as far as I remember, It was particularly recommended that if fitting a new induction pipe and/or a new pot the induction pipe nuts were tightened before tightening the cyl base nuts. i.e. it was not necessary to slacken the cyl base nuts when removing & replacing the same induction pipe without having disturbed the pots. I took it to alo mean that if the pot(s) were removed for any purpose the induction pipe should always be bolted up before the pots & if fitting a new/different induction pipe the pots should be loosened as Tony has stated.

george

[MartinRaine]

Hi thanks for the info, dose any one have Bill Locks telephone number as if he can supply the same as the original ones then i will get some off him. Thanks Martin. Ps i am still looking for a stainless steel starting handle hole cover that fits into the radiator.

[Forumadmin]

If you find the hints , how about putting them in the Gallery......?

[george garside]

not sure whether I still have it but will continue looking. Meanwhile if anybody else has a copy?

george

[k. rogers]

I used to have occasional problems with the head gaskets on my Weasel, presumably only a slow leak into one bore or the other, resulting in the car only starting on one cylinder if left for more than a fortnight until clearing itself after a few seconds. I remember thinking how tight these gaskets were over the studs when removed (incorrect geometry?) to the extent that they were unusable by the time I manipulated them off! However, this all changed when I found a set of original Payen gaskets at Beaulieu which seemed to solve the problem. I reckon the ill-fitting gaskets were distorting when tightened causing the leak.

[AlanBartlett]

How about the soaking technique of soaking the gasket in soapy water to soften up the inside and then fitting and tightening, ive used this one a few times, can't remember who said about it though perhaps a topic on here or at a lunch?