Could anyone give me an idea of how much of a gap I need to leave around the manifold as it comes out through the bodywork? I've got a nice neat hole but the exhaust comes within around 10mm of the edge of the GRP. I want to do the final fit of the exhaust today if I can but I'm thinking I might need to trim back a bit further.

I have a 30mm gap around mine with a stainless steel surround. On the road running with air flow it's fine but if I am in the workshop running the engine for anytime the surround distorts slightly and the GRP gets quite hot. Therefore, I would say no 10mm is definately not enough of a gap. Barry

[Edited on 1/5/11 by LBMEFM]

I had 10mm all round and it got a little hot, now Ive got 10mm on bottom and 20mm around the top - works fine now.

Wasn't a problem really, but I left too much of a gap and it failed SVA with the dreaded sharp edge ball, some edging trim cured the problem, the heat off the exhaust kept making it fall off after.

tony

When I built my Indy, I cut a large rectangle out, big enough to pass the whole manifold through should it ever need to come off for any reason. I then made up an Ali filler panel that closed the gap to 10mm around the manifold.

Looked good (IMHO), no problems with heat on the GRP and the couple of times I did remove the manifold were nice and easy.

exhaust wrap should help a bit too.