Header and side pipe clearance?

[Aussie Mike]

I'm building the headers and side pipes at the moment. I'm curious as to what people have found is acceptable clearance between the primaries and the sides of the foot boxes? The closest the pipes get to the foot boxes so far is about 1-1/2". The foot boxes are fiberglass, not aluminium and will be painted the body colour. They headers will be Jet Hot coated to reduce the heat. Will the paint survive or will I need some heatshields? The resin used in the body is vinyl ester rather than poly ester and has a higher heat deflection temp. Vinyl ester deflects at 105 degres C where as poly ester resin deflects at 74 degrees C. The paint will be catalysed 2 pack but I'm not sure how it copes with the heat.

I'm also curious as to how much clearance I should have between the body of the sidepipe and the paintwork. The side pipes will be Jet Hot coated as well.

Cheers

[Michael C Henry]

I bought an older car and had to replace the exhaust,completely. The footboxes were allready clad in heatsheilds. They were made in two peices each tunnel side and front. Thin alluminum and foil clad rigid insulation . Voids under the alluminum to run hoses and wiring. Couldn't emagine not having those sheilds. The headers as made by EM have large square flanges connecting headers to collectors. I had to alter the front sheilds and remove insulation in a small area on each front sheild.
The mufflers are 1" away from the body.I have covered each muffler with perferated SS sheild from Finish Line. I'v been burned before. Long periods of running in place , the pipes get hot ,paint at exit turn will try to change color slightly and the grass dies underneath the oilpan ,collectors, and muffelers.
Anything that needs to be done to the ceramic coated parts like welding will have to be glass beaded first . Welding ceramic is like welding dirt. then recoated.Plan it all out before coating. I incorporated Burns SS V-flanges and clamps. Bacicaly I have three different pairs of mufflers . Quiet muffelers ,LoBacks and a straight set of empty pipes, and the turn outs clamp on to the what ever pair I'm running.If a local cop decides in his opinion that my exhaust is too loud , can do something without cutting and welding and sending my parts out to be coated.

[Aussie Mike]

Thanks Michael,

One thing I didn't mention, the side pipes I'm building are my own design and are re packable. They also have cat converters inside them. We have some strict emissions laws down here and big fines for offenders. I'm building the sidepipes so I can slip off the outer body and repack them or change the baffles completely.

1 inch from the body sounds good. I thought I'd have to have them further away. An inch of clearance means I'll be able to tuck them well in and out of the way.

I'm machining up square flanges from 10mm plate for the side pipes to bolt to as well. It seems like the best way to me as I figure there is a better chance of them staying sealed this way.

Cheers

[Bob Putnam]

Mike,

Don't forget that cats generate their own heat! I would be pretty liberal with the distance to the glass/paint. You might even consider an intermediate heat shield over the pipe, possibly with insulation in between.

[Aussie Mike]

I agree Bob,

The cat is physically inside the body of the side pipe. The tube used for the main muffler body is 4.5" and there is a small airgap between the outside of the cat and the inside of the muffler body. I'm hoping this will reduce some of the radiated heat. I think I'll play it safe and space the whole pipe a bit further from the paintwork too.

Cheers

[JOHNNYCOBRA]

I've taken a somewhat differenat route.

I laid 1/8 inch cork on the footbox surfaces and topped the surfaces with aluminum sheet .050

The cork will insulate the fiberglass and hold the heat down
in the drivers side box area.

I got the idea from aerospace applications where I work

The sheets of cork come with an adhesive backing and I made templets for the footbax which were used for the cork and aluminum.

I finished the aluminum edges with aluminum angle I formed
on my handy dandy home brake.

It looks really good and should cut down on the heat transfer

Johnny

[Aussie Mike]

I'd like to avoid heat shields if I can since a clean, painted engine bay looks good in my opinion. Especially since it's the nice gelcoat side of the footboxes that's visable in the engine bay.

The cork and aluminium sounds like a good idea since it would be quite rigid and strong. I had been thinking about fiberglass cloth behind aluminium or even just an airgap between the aluminium heatshield and the foot box.

Here's a couple of pics of the home made headers. It's hard to see in the pics but there is at least an inch between the headers and the foot box at their closest point.

I tried to run the header pipes low down to increase the amount of air they get from under the car. Hopefully if there is a lot of heat it will only build up when moving slow or stationary.




Cheers

[SCOBRAC]

Doh. You put the steering column on the wrong side.

[Aussie Mike]

Nope, It's on the Right side

Cheers