Exhaust manifold gasket - use sealant or not?

[Graham C]

Hello

I think I am having problems sealing a new exhaust manifold gasket, which may be giving me air leakage into the carbs - allowing air into the cylinder. At the weekend tested the gasket seal with starter spray and had increase in revs, tighten up the nuts more but still having back firing when slowing down.

Carbs have be refurbished recently so these are good.

I have never used sealant on these gaskets before hence my question.

Would people recommend using a sealant and if so which type - red hematite sealant?

Car is GT6, standard set up.

Graham

 

[NonMember]

I've never used sealant on manifold gaskets. I wouldn't trust it with the temperatures.
What mark of GT6? The Mk1 clamping mechanism is rubbish and gives lots of grief, although usually in the form of permature gasket failure rather than straight out leaks. The Mk2/3 manifolds are generally pretty good if assembled correctly but access to some of the nuts is awkward. How's the condition of your inlet manifold?

[68vitesse]

Have a Mk1 Vitesse manifold shows some gaps with a straight edge, repro gaskets thinner than original have been suggested to use two and retighten after first run then check torque at intervals.

Regards

Paul

[Graham C]

Hello

MK3 GT6, yes and some of the nuts are hard to get to.

Non Member - I was was concerned about the temp and the sealant, but sealants have improved and changed since I needed to use them last, so I was interested in other people approaches to this task.

Paul -Two gaskets would work and checking against a straight edge would be a good idea.

Graham

 

 

[Pete Lewis]

sealer on manifolds is not a good idea the manifolds pant and move about on their fixings/clampings 

any sealer will be worked out and then your in worse state than you started 

flat clean dry is the optimum 

if its mk1 then some anti seize on the bolts to  aid  tightening , mk2 is more straight fwd.  just studs and bolts  with dumbell clamps 

do make sure the studs have a die nut run down to clear the threads as you may have tight nuts but not clamping the manifold 

Pete

[Nigel Clark]

The Mk3 manifolds should seal more easily than Mk1. As has been said, check the faces of the inlet manifold is flat (unlikely a cast iron original exhaust manifold or the cylinder head will be distorted). I use a Payen JA510 gasket with Wellseal on my Mk3 and  - crossed fingers - haven't had a problem.

Nigel