exhaust / inlet gaskets & sealant

[Dave Mann]

I recently rebuilt an engine without manifolds which the owner fitted after the engine was in the car. It didn't want to start, and when it did there was a distinct whistling noise telling me there was an air leak, one of the intake joints could be wiggled about. Removed the inlet manifold, faced it up and refitted it and the engine started straight off.

[Greig Smith]

I had a little blow-by from the manifold I built for the supercharged car and as the flange plate was rather thin I was reluctant to consider skimming it.

Instead I bolted it up tightly to the thick steel plate I use as a manifold building jig and heated it up red-hot with a very large propane torch, when it was all glowing red, I thumped the back of the manifold plate a few times with a large hammer between all the bolts. The shock waves then caused the flange to pull up tight and the #1 pipe now has a tiny ripple in it where the 'warp' on the plate ended up. End result was 100% true without the need to remove any metal off the plate.

The propane torch is a USA weed burner and they are used for applying Torch-On waterproofing products as well. I run it off a 19KG cylinder

Aye
Greig

[Colin Reed]

HI OLIVER,
If you look at Greigs Photos you will see that the Inlet pipes are welded to the base flange along with the Exhaust pipes,
this is a good move as it Eliminates having two gaskets on the intake less chance of an air leak 

Colin
NZ

[Howard Wright]

Hi Oliver

I used a standard A7 gasket behind the plate and two heat resistant gaskets, cut from a sheet, behind the intake manifolds.  I didn’t use sealant but needed to tighten the manifold studs several times to get to a leak free situation.

It is especially difficult with the bunch of banana exhaust as the central stud is missing so you have to rely on the remaining ones. As mentioned your manifold plate looks very thin so don’t go wild with getting it flat.  Greig’s method looks really good.

Here is a pic of my set up. If you look closely you can see signs of exhaust leaks on the aluminium head. These have now healed after tightening up.

Cheers

Howard

[mopetta]

Thanks for the feedback. The main issue I have is thin backplate of my exhaust. I have a new backplate from the chrished supplieres
but it does not fit well to the pipes of my exhaust.

[Greig Smith]

Being concerned about the extra pressure of the blower, I opted to make the central pair of pipes separate with just enough space down the middle to get an Allen head bolt / Cap screw which has been machined down on the sides. In addition I heated up #2&3 exhaust pipes and gently pressed a shallow dent in each one so that my very skinny Allen head bolt will just fit between them. I have a long Allen key with a ball end to tighten it up. All the bolts are dipped in Stag steam pipe jointing compound which has proved to be rather effective at sealing the threads and stopping things falling off.

Yes I know I should have made 1-4 & 2-3, but I didn't and the bonnet has been cut and there's no going back.... it's force fed, so hopefully I'm not loosing too many Shetland ponies.

This picture shows the offset motor as well as the blower drive, a Yamaha 650cc shaft drive which my incredibly talented Engineering friend Steven made. The coupling at the blower end is flanged & bolted together with 4 shoulder bolts with a 1mm tolerance taken up by small O rings so in theory I have a 1mm expansion allowance on the blower drive.

I made up a blunt square with a tapered end out of scrap steel which I hammered into the red hot ends of the mandrel bends to make them the same shape as the holes in the manifold plate - you can see the ends have a square just where they are tack welded to the flange. I did the same with the intake feed pipes from the blower, but made those rectangular to match the plate. Having square sides helps with clearance for the Allen head manifold bolts. The pipes required careful trimming to get the angle of the bends to suit the tapered location of the offset motor, in the block Jig picture you can see the line of the 'body' on the steel plate below the block as well as a cardboard template next to it. Dad had a few manifold flanges lazer cut from a gasket in case I made a hash of something, but in the end, I only used the one.

It was a fun project and very rewarding to build & drive

Aye
Greig

[spannerman]

When I biult my engine I had block top and
Inlet and exhaust ports skimmed as well.
Never use any sealer on head or manifold
And never had any problems

[Greig Smith]

Thanks for the feedback. The main issue I have is thin backplate of my exhaust. I have a new backplate from the cherished suppliers
but it does not fit well to the pipes of my exhaust.

Another option you have is to weld the new backing plate or flange plate directly to the existing one, so to 'create' one thick plate. If you bolt the whole lot to either a head or a thick manifold building plate like mine you should be able to TIG weld the 2 flanges together. Once you have done this you can carefully TIG weld the inside of the ports together and then grind & file everything smooth in the ports and you can grind to match the block ports. Thinking back on our build, the job lot of aspirant Ulsteroid bits came with a flange that didn't match up to the block, so we made our own ones off a block which matched up perfectly. I probably have a spare & can get them cut here, I can post you one, but we're half a world away from Yonder Isle, so it would probably pay you to make a paper template of what you want & have a local Lazer-Cut / Water Jet Cut place make you another flange - PM me if you want to chat further re the flanges

I use Wurth high heat exhaust assembly paste for sealing the exhaust gaskets and then STAG jointing paste for sealing the threads on the manifold bolts - in my case I use Allen head screws to hold my manifold onto the block. Dip to get a good thick layer over most of the thread & then bolt into place so the excess fills the space around the bolt shank in the manifold plate.

Aye
Greig

[JonE]

Seeing Howard's picture, if there a good way of creating a telltale for where the leak occurs? I have sensed exhaust coming into the car at times, but wonder whether it is due to misalignment of the exhaust pipe joint (from bad fitting part) rather than the manifold itself. No visual signs like the aluminium allows in H's pic.

[Howard Wright]

Hi Jon

Although the leaks became visible as black marks on the aluminium head.  I found that a quick spray of WD40 along the joint pin pointed exactly where the leak was coming from.  It bubbles nicely  .

Cheers

Howard