Helicoil for the Rear Timing Cover

[David Morris]

Hi, I am asking for advice on behalf of Vic Francis, who I believe is a member but doesn't have internet access.

He is busy saving another Javelin and needs to overcome a stripped bolt hole in the engine block that takes one of the two securing bolts that hold the rear timing cover down onto the top face of the block. You know the two bolts, they often strip through overtightening some time in the past 60 years by a previous owner trying to cure the oil leaks that are all too likely to occur here! Not one of Gerald Palmer's best days in the office!

Anyway, the bolt hole nearest to the distributor has stripped it's thread on Vic's engine and he intends to cure this with a helicoil thread insert. A common solution here.

His question is how deep can he make the blind hole for the helicoil before he causes another problem? I hope someone can advise?

Any help would be much appreciated

Many thanks,

David

[Forumadmin]

You could have a look at the engineering drawings in the tech library, but you do need to be a member. I have done this but cannot remember the depth. Searching JT and its library and archive might help but you need to have member privileges. You should gave those David.

[David Morris]

Hi Keith,

Thanks for your email. I think Vic was a returning member last year, but not sure if he has renewed? However, he hasn't a link to the internet and anyway he is severly dyslexic. I am sure you would agree that, as one of the most friendly clubs, we wouldn't wish to be restrictive with our help and advice, to all Jowett owners.

Obviously, we need to be protective with access to the Club archives and especially spares, but it must surely be in the sprit of the Club's long-standing helpful ethos to offer the hand of friendship to other Jowett owners, inside the club or on the fringes? I am sure you would agree?

All the best,

David

[Forumadmin]

David you can pass on info you glean from the resources. I even allow access to non members who are acting on behalf of a member but only to JT and not member services. So yes it is all part of keeping Jowetts on the road.

[David Morris]

Hi Keith,

Thanks for the info. Actually, Vic has had the Helicoil fitted successfully, but he is still experiencing a severe oil leak from the infamous rear timing cover gasket. He used a new regular gasket and a smear of Green Hilomar, but it still leaked. He also checked the fit and cleanliness of the two aluminium surfaces before tightening down. Also, he was careful to tighten the two vertical bolts before hand-tightening the five bolts coming in to the housing from the front cover. So, he took care but was still beaten! As we probably all have, at some time! I remember driving up to the Rally in Crieff, leaking oil all the way from that horrible gasket!

I will try to help him by making up an aluminium version of the gasket and we will use three Vitron 'O' rings. We will try again! No wonder the EU is short of oil!

All the best,

David

[Keith Clements]

Worth checking exactly where the oil is coming from, by cleaning and sprinkling with chalk dust or flour.
Sometimes the casting cracks around the oil pressure feed union. Also the filter seal.
Remember only tighten the 5 front nuts to 10 lb ft and do that after tightening down the two top bolts otherwise the housing does not sit properly.

[David Morris]

Hi All,

I suspect that, during engine assembly at Jowett's, they had a policy of what we would call ' select for best fit' for the Rear Timing Case Cover?

I have seen so many variations in the casting for the cover. Jowett's played about with the thickness of the boss for the oil pressure take-off port, as well as other minor changes in the casting, all without changing the part number, which would be a drawing office crime in my days! The oil holes in the casting, both on the Rear Timing Cover and the block, also varied in position and size.

With the passage of time, the original components for an engine will have inevitably been swapped and replaced, so what might have been a good fit in the factory, has been lost.

This makes the selection of the gasket difficult, especially if the age of the composition gasket means it might have shrunk. In my experience, just slapping a standard gasket on and hoping it all lines up, will probably result in catastrophic oil leakage. You need to make paper pencil-rubbing templates for both the cover and the oil holes in the block, to check for gasket alignment. This is even more critical if you are going down the 'O' ring gasket solution. If the oil holes don't align with the holes in the aluminium gasket, the 'O' rings are likely to be unsupported at some point on their outer edges and will fail, sliding down one of the oilways.

In my view, the Rear Timing Cover was the worst component on the engine, design wise. I have often dreamt of a conversion to a remote position for the oil filter. This could then be fitted somewhere within the engine bay, with three flexible oil pipe connections, tapped into the existing oil ways on the top of the block. One for the main feed up from the pump, and two outputs down to the oil manifolds running along the top of the block. All the oil ways are there, you would just need to tap into the existing holes and provide flexible pipes.

Not only would this solve the likelihood for oil leaks from the gasket, but you could mount the oil filter with its bottom facing downwards, preventing it draining when the engine is turned off, increasing the life of the bearings.

Dream over, but I wonder how many Javelins and Jupiter's have dry engine tops? I remember an International Rally at the Anderton Canal Lift, where there must have been 100 or so Javelins and Jupiter's parked in the sloping car park, and almost all of them had oil streaks under their engines, shining with glossy colours in the rain!

All the best, and stay safe,

David