Need a RTV type sealant thats Fuel/petrol proof.

[bricol]

With most sealants you need to follow the instructions exactly.

You may know this already but many folk do not.

With most of them you apply the sealant, assemble the joint loosely and tighten the nuts evenly until the sealant starts to ooze out.
Then you leave it for a set length of time, maybe 1 hour before finally tightening the nuts fully.
If you tighten it up fully too soon you squeeze all the sealant out of the joint and it doesn't work properly. There needs to be a thin layer of sealant on the joint faces for it to work.

Although for both the compounds he used, your instructions don't apply.

If sealant squeezes out - you've got too much on. If it squeezes out on the outside, then it has on the inside - and when it falls off and blocks the oil pickup pipe...your big ends start to make loud noises on the M1s going back to uni on a sunday evening...

 

[oldbikedavey]

Might be worth giving the Loctite 510 flange sealant a go.
There's some others in that range, and they seem to be pretty fuel-proof......

 

[addjunkie]

Although for both the compounds he used, your instructions don't apply.

If sealant squeezes out - you've got too much on. If it squeezes out on the outside, then it has on the inside - and when it falls off and blocks the oil pickup pipe...your big ends start to make loud noises on the M1s going back to uni on a sunday evening...

I guess theres a story in that last line.

 

[bricol]

I guess theres a story in that last line.

Aged 19, skint, re-assembled Triumph 1300 engine - applied too thick a layer of hylomar...pulled a lot of it off the oil pick up strainer later. Learnt that lesson well.

 

[Bullet2012]

Stag wellseal!

agreed

 

[Bornfree]

Might be worth giving the Loctite 510 flange sealant a go.
There's some others in that range, and they seem to be pretty fuel-proof......

Loctite 510 and 518 flange sealants are great with metal to metal rigid joints. But I think the OP is using a gasket.

 

[Roger440]

Loctite 510 and 518 flange sealants are great with metal to metal rigid joints. But I think the OP is using a gasket.

Yes, i am. And the joint isnt rigid either, as when the engine gets hot the heads try to "grow" away from each other, so the joint moves every heat cycle.

A crap design, but no different to most V8's of the era. Now, it would be done with a rubber o-ring/seal.

 

[Roger440]

Didnt work. Still leaking

 

[Smallfry]

What is actually leaking though ? Is it an air or coolant leak ? There should only be fuel vapour in the manifold, so I cant see why the sealer would need to be fuel "proof"
If the manifold or head faces have been refaced, the manifold will not line up properly, and will drop deeper into the "vee". If it is not allowed to do so by either locating dowels or the bolts, the manifold will be preventing the gaskets working properly as it is too short between head faces.

Only way round this, will be to elongate any dowel and bolt holes (upward) but there will be a slight or big port mismatch depending how much has bee taken off. OR use two gaskets to make up the difference. Coat all the gaskets with Wellseal, and LET IT DRY for ten minutes before assembling.

Not familiar with the Stag engine, what are the gaskets made of ? I treat all paper type gaskets with Wellseal, and never have problems. The only time I use silicone type stuff is for sumps and covers that do not have gaskets. In which case I use red HTR730 which never leaks if the surfaces are properly cleaned.

https://www.ebay.co.uk/itm/122803643024?_skw=htr730&itmmeta=01KQWZECPJSX0M9T51NBZDG0ZS&hash=item1c97aae290:g:yqYAAOSwgQ9Vzb5E&itmprp=enc%3AAQALAAAA4GfYFPkwiKCW4ZNSs2u11xDE%2BmrC6VCU%2FYnOmzA2Cbrama6n2WuGUoEsBPNTxYOo%2FH8OXKv%2FbHnsrUGw3wEFqBsGjHM5leflrUwGrnq3kYZW%2B3%2Fe%2FhZ0J%2Fmlbvcqxd%2F7MoUfbWyrbz3OMoIhusD7AZS%2Bx8EOtGyCQwM8017Qn9T6HBAFbncgpDJpVDu49cs090GVPWGdYN9ljJIK92NhH%2B7I4fp8BA0lJ%2F9zkjO%2BQ757Dty2YzfYd%2FguABZquY3X6eRcgJ5yOJX%2BtFxjXOiaOs6oZrrbgAvcYD%2BnI3VNXhSY%7Ctkp%3ABk9SR5TMuZ-_Zw

 

[Dozzer]

On some of the engines we used to design LOCTITE 5910 was the preferred sealant. we did use a red Loctite RTV for metal to metal but cannot remember the code.
None of these required a set time before final clamping.

 

[Roger440]

What is actually leaking though ? Is it an air or coolant leak ? There should only be fuel vapour in the manifold, so I cant see why the sealer would need to be fuel "proof"
If the manifold or head faces have been refaced, the manifold will not line up properly, and will drop deeper into the "vee". If it is not allowed to do so by either locating dowels or the bolts, the manifold will be preventing the gaskets working properly as it is too short between head faces.

Only way round this, will be to elongate any dowel and bolt holes (upward) but there will be a slight or big port mismatch depending how much has bee taken off. OR use two gaskets to make up the difference. Coat all the gaskets with Wellseal, and LET IT DRY for ten minutes before assembling.

Not familiar with the Stag engine, what are the gaskets made of ? I treat all paper type gaskets with Wellseal, and never have problems. The only time I use silicone type stuff is for sumps and covers that do not have gaskets. In which case I use red HTR730 which never leaks if the surfaces are properly cleaned.

https://www.ebay.co.uk/itm/122803643024?_skw=htr730&itmmeta=01KQWZECPJSX0M9T51NBZDG0ZS&hash=item1c97aae290:g:yqYAAOSwgQ9Vzb5E&itmprp=enc%3AAQALAAAA4GfYFPkwiKCW4ZNSs2u11xDE%2BmrC6VCU%2FYnOmzA2Cbrama6n2WuGUoEsBPNTxYOo%2FH8OXKv%2FbHnsrUGw3wEFqBsGjHM5leflrUwGrnq3kYZW%2B3%2Fe%2FhZ0J%2Fmlbvcqxd%2F7MoUfbWyrbz3OMoIhusD7AZS%2Bx8EOtGyCQwM8017Qn9T6HBAFbncgpDJpVDu49cs090GVPWGdYN9ljJIK92NhH%2B7I4fp8BA0lJ%2F9zkjO%2BQ757Dty2YzfYd%2FguABZquY3X6eRcgJ5yOJX%2BtFxjXOiaOs6oZrrbgAvcYD%2BnI3VNXhSY%7Ctkp%3ABk9SR5TMuZ-_Zw

Its leaking coolant.

There pairs of ports. Under the rear 2 pairs is a long thin slot which is the coolant gallery. Previous failures have been coolant leaking into the inlet port when not running. Current leak is from coolant slot to valley.

Manifold faces were poor so sorted that. Dry fitting had me at 4/5 thou in the worst place that i could measure.. Theres no location dowels etc. Ive reamed the mounting holes as you can get different thickess gaskets, all of which affect the geometry.

The main issue is previous corrosion around the coolant slots.. Whilst the manifold is prety flat now, the head isnt and has something of a dip in the affected area, no doubt as a result of various attempts to clean up the face.

The right answer is have the heads off and face the head to manifold mating face and use a thicker gasket to recover. Problem is, i already know the r/h head isnt coming off.

The "repair" that was on it when i got it lasted several years and 50k miles, so a good bodge. Sealant turned to jelly from fuel contamination in the end leading to water in the cylinders. My attempts (with RTV) did likewise in pretty sort order. The intake is always wet with fuel. Vapour it certainly isnt! So fuel is running across the floor of the intake port which just destroys the sealant.

Hence changing the sealant. Tried wellseal but that failed straight away when filling with coolant.

One last attempt with hylomar tommorow. After that, its engine out, and full strip because of the stuck head, which means i wont be going on my european jaunt as there not a chance it will be ready in time.

Edited to add, yes, paper gaskets.

 

[Roger440]

On some of the engines we used to design LOCTITE 5910 was the preferred sealant. we did use a red Loctite RTV for metal to metal but cannot remember the code.
None of these required a set time before final clamping.
View attachment 539451

Loctie 5910 doesnt look to be fuel proof. Generally, with loctite products if it is, it says so. Given its a silicone based product, thats not a suprise.

Im assuming you were not sealing any fuel, but oil or coolant?

 

[Dozzer]

Loctie 5910 doesnt look to be fuel proof. Generally, with loctite products if it is, it says so. Given its a silicone based product, thats not a suprise.

Im assuming you were not sealing any fuel, but oil or coolant?

Coolant & oil in some applications. its was mainly diesel engines, but a level of fuel resistance was required. 5923 may be better.

 

[bricol]

I wonder if expanded PTFE tape might help? Form a closed circle/rectangle around each port/passage, crossing the tape over to create a complete seal, instead of the gasket.

Used it to seal access plates in oil filled machines, coolant chamber, and water tanks in industry. Used it instead of a sump gasket on my Lancia, and in the flanged joints of the exhaust system.

It's not cheap though.

https://www.par-direct.co.uk/product-details/EPST/EXPT-10X3

Hylomar isn't going to help if you don't have flat sealing faces - it's not a gap filling sealant.

 

[Turbo]

Its leaking coolant.

There pairs of ports. Under the rear 2 pairs is a long thin slot which is the coolant gallery. Previous failures have been coolant leaking into the inlet port when not running. Current leak is from coolant slot to valley.

Manifold faces were poor so sorted that. Dry fitting had me at 4/5 thou in the worst place that i could measure.. Theres no location dowels etc. Ive reamed the mounting holes as you can get different thickess gaskets, all of which affect the geometry.

The main issue is previous corrosion around the coolant slots.. Whilst the manifold is prety flat now, the head isnt and has something of a dip in the affected area, no doubt as a result of various attempts to clean up the face.

The right answer is have the heads off and face the head to manifold mating face and use a thicker gasket to recover. Problem is, i already know the r/h head isnt coming off.

The "repair" that was on it when i got it lasted several years and 50k miles, so a good bodge. Sealant turned to jelly from fuel contamination in the end leading to water in the cylinders. My attempts (with RTV) did likewise in pretty sort order. The intake is always wet with fuel. Vapour it certainly isnt! So fuel is running across the floor of the intake port which just destroys the sealant.

Hence changing the sealant. Tried wellseal but that failed straight away when filling with coolant.

One last attempt with hylomar tommorow. After that, its engine out, and full strip because of the stuck head, which means i wont be going on my european jaunt as there not a chance it will be ready in time.

Edited to add, yes, paper gaskets.

I don't think any sealant is going to cure your problem on its own. You need a gasket to take up most if the space and support the sealant.

Can you add thicker gaskets on the rear ports to make up for the dip at the coolant ports?

You could use something like jb weld or chemical metal to fill some of the gap. Place a gasket on the manifold so that the jb weld doesn't stick to it apply the jb weld to the head and torque it up.

Leave it overnight to set then take the manifold off and carefully remove any jb weld that has squeezed out and is blocking the ports or coolant gallery.

 

[addjunkie]

Is it possible to skim the bits flat…

 

[Roger440]

I don't think any sealant is going to cure your problem on its own. You need a gasket to take up most if the space and support the sealant.

Can you add thicker gaskets on the rear ports to make up for the dip at the coolant ports?

You could use something like jb weld or chemical metal to fill some of the gap. Place a gasket on the manifold so that the jb weld doesn't stick to it apply the jb weld to the head and torque it up.

Leave it overnight to set then take the manifold off and carefully remove any jb weld that has squeezed out and is blocking the ports or coolant gallery.

I am using gaskets.

I did try the available thicker gaskets, but that made it worse as it means the manifold doesnt seat properly any more.

It might come to jb weld!

 

[Roger440]

Is it possible to skim the bits flat…

Yes, but only by removing the heads. One of which wont be coming off in situ, so its a full engine out and strip. Which i have neither the time or the will to do at the moment.

 

[addjunkie]

Yes, but only by removing the heads. One of which wont be coming off in situ, so its a full engine out and strip. Which i have neither the time or the will to do at the moment.

Ahhhhh, what about something like 2mm soft PTFE gasket sheet and cut your own gasket

 

[Smallfry]

Wellseal does not have much in the way of gap filling capability, but I have cured some seriously corroded thermostat housings with it, so I do think you problem is down to the manifold being a bit too short for the gap between the heads.

Could you "reface" the corroded areas with JB Weld after thorough cleaning, then sand off ?

I did this on a Rover V8 block on the head face. There is a water gallery each end that had a similar problem, I got fed up with it and tried this, and worked a treat. BiL has the engine in a Land Rover and its still fine after five years.

Or as suggested, try making your own gaskets from something thicker.