Manifold Query

[Tee]

Hu guys, changed my exhaust manifold gasket twice now and still it manages to find a leak after a few days, I've skimmed both surfaces and tightened everything nice and tight.

I know some bolts and studs are not recommended to be re-used so just wanted to ask if you reckon it worth me getting all new bolts/studs or should that not make much difference?

 

[zpuppy]

cyl head bolts and such should never be reused, not 2 sure on exhaust manifold would have thought so unless they are obviously stretched or warped. What I think is happening is the manifold plate is warped slightly,,check with a known straight metal straight edge, same way you would check a cyl head. I know you've stated you have skimmed it, but unless it's clamped and done on a mill the warpage will still be there. Hope this helps !

 

[vpulsar]

Do they make a multi layer exhaust gasket for the Z ?, On my pulsar I used to get a few problems like this until I fitted a metal multi layer gasket, It never leaked again after.



Rob

 

[Tee]

That may be the problem puppy, it was at the back of my mind but hoping it's not the case because of cost! I hve roughly checked but will check more accurately tomorrow.. Pulsar that's exactly what I need but can't get one, I've even made enquiries about custom gaskets but no-one does them.

 

[Tee]

Btw has anyone doubled gaskets?

 

[Rob Gaskin]

Btw has anyone doubled gaskets?

Yes and it lasted a few hours!

I use a thick gasket from Mr F (beige in colour - he will know the one) but these are no longer available for the 240 head so I have to use a 280 one and put holes in it. The intake holes are not too clever either (bit close to the edge of the manifold) - but it's the best one I've tried.

I'm sure changing the studs won't help with your leaking problem.

 

[Nigel Brook]

Got a Payen multi layer gasket DC 386 for my 280.
Rob: Can't understand why the holes are any different 240 to 280 unless you've got much bigger inlets ?
Incidentally those "cardboard" single layer gaskets are next to useless.
Just found another one, made in Japan marketed by Stone part no 14036-N3500. Must have got it from the US.I think the problem with these multi-layer ones is that they contain the dreaded asbestos.

 

[Rob Gaskin]

Rob: Can't understand why the holes are any different 240 to 280 unless you've got much bigger inlets ?
Incidentally those "cardboard" single layer gaskets are next to useless.

I could describe my extra-special home cast cylinder head but I would have to shoot you afterwards.

Nigel, Mr F would know more about which model my gasket was for but it was an injection 280ZX with the injector cut-outs in the port face. The cut-outs are only just covered by the manifold.

I can assure you I did have to cut holes for some manifold studs into the gasket. I placed the old gasket on top of the new one and spraypainted over the gasket to produce a 'stencil' so I knew where to cut the holes.

This gasket is perhaps the cardboard one you think are useless - from experience over the years it works just fine for me . The layered ones I've used separate and blow after a while.

Tee I realise now that you have a 280 so you may not have to modify the gasket - not sure if Mr F has any in stock now though.

 

[Tee]

I've actually had 2 gaskets off Mr F and problem has persisted, to be honest they line up pretty good, but not exactly, gasket holes are slightly too big

 

[zbloke]

Incidentally those "cardboard" single layer gaskets are next to useless

Do you mean the compressed fibre manifold gaskets Nigel?

 

[Tee]

New bolts and studs ordered, I'm going to find a machinist in Leicester tomorrow who can mill my manifold in case there's any warp, and then re-fit.

In all honesty any gasket should do the trick as long as everything is true, maybe some gaskets last longer but there definitely shouldn't be any leaking unless there's a bigger fault.

 

[Rob Gaskin]

New bolts and studs ordered, I'm going to find a machinist in Leicester tomorrow who can mill my manifold in case there's any warp, and then re-fit.

In all honesty any gasket should do the trick as long as everything is true, maybe some gaskets last longer but there definitely shouldn't be any leaking unless there's a bigger fault.

You're right, but I do think things change a bit when everything heats up. Don't overtighten those manifold studs . Are you based in Leicester then, I don't know the 'around' area?

 

[Tee]

lol yep I'm in Leicester Rob, unfortunately might I add, bloody terrible place!

It's a fine balance between making sure the bolts aren't too loose but not too tight, here's to hoping I get it right

 

[AndyMinto]

Tee,

to be honest they line up pretty good, but not exactly, gasket holes are slightly too big

This is the problem as I have found in the past. The gases can start on an outward journey into this gap and put pressure onto the gasket. It also creates a week point. I believe Mr F has some performance gaskets.

Mine could be a bit worse due to the back pressure created when the gases hit the turbo.

Hope this helps

 

[Ian Patmore]

Tee,
I can't quite gather if this has been checked in what you have written.... is the manifold face of the cylinder head checked to be flat and true?
To add, have you made sure the large thick washers that hold the exhaust and inlet manifold are touching properly, so there is even clamping force?
Tighten the bolts to the factory spec, it is a low figure (something like 8lbs- off the top of my head) and does not take much to over-tighten when using just a wrench.
Some people have found a better seal by covering the cylinder head and gasket surface lightly with spray on copper or something like Copper seal.
Tighten your bolts in a sequence, so a good clamping/tightening regime is in place. Don't just tighten one bolt at a time to spec and move along to the next. Start with to hand tight for all bolts/nuts, a little bit more and gradually work your way to OEM spec.

You maybe doing some of this anyay, but just in-case you are not...

 

[Tee]

Andy that's whats happened to my new gasket, having had virtually 4 miles use the leakages have caused the gasket to slightly wither.

Thanks for advice Ian - yes the head is true, Is the copper spray a replacement to sealant? and will take extra care when tightening nuts and bolts, stupid question but what tool do you need to check the torque settings are correct?

I took the manifold to get milled today and it seems their expert eye picked up a couple of areas which may be prone to leaks, so tomorrow hopefully we'll be set to fit everything.

 

[Nigel Brook]

I could describe my extra-special home cast cylinder head but I would have to shoot you afterwards.

Nigel, Mr F would know more about which model my gasket was for but it was an injection 280ZX with the injector cut-outs in the port face. The cut-outs are only just covered by the manifold.

I can assure you I did have to cut holes for some manifold studs into the gasket. I placed the old gasket on top of the new one and spraypainted over the gasket to produce a 'stencil' so I knew where to cut the holes.

This gasket is perhaps the cardboard one you think are useless - from experience over the years it works just fine for me . The layered ones I've used separate and blow after a while.

Tee I realise now that you have a 280 so you may not have to modify the gasket - not sure if Mr F has any in stock now though.

Rob: I thought you meant the port holes in the gasket had to be altered. BTW, is'nt your head a Kevin Irons one like mine ?

 

[Rob Gaskin]

Rob: I thought you meant the port holes in the gasket had to be altered. BTW, is'nt your head a Kevin Irons one like mine ?

To be honest I don't know the history of it. Kevin has worked on it when he built my engine but it had been worked on before that. However the previous owner was very friendly with Kevin so

Perhaps it's one of those very common Spike heads that every Z has

 

[Nigel Brook]

Do you mean the compressed fibre manifold gaskets Nigel?

I was going to put up a picture of the one I meant but I seem to have thrown it away.

 

[Ian Patmore]

Tee,
Tighten with a torque wrench. You may find some big torque wrenches start at 10lbs, but go up to 100lbs+ (as mine did). I had to buy another torque wrench that started at Zero.

The copper spray/grease is your sealant, I would not be tempted to use anything else

Good luck