I've seen quite a few people with sheetmetal intake manifolds that have them crack often. I realize it costs a lot to have one welded absolutely perfect, as well as having it sent off to be stress-revieved.

I was wondering what you guys would think about just using the 'ITB Method' where you just use 4 couplers to attach the plenum to the main runners? Get some very stiff silicone couplers, good clamps, then cut your runners & clamp them down. This would reduce almost all of any stress from thermal expansion, as well as keep your plenum cooler.

You could also tune the runners, adding in a small section of runner-sized pipe to elongate the runners. Add it when you're on the street (better mid-range), then remove & shorten for the track (top-end).

 

i have run my HP Racing IM for 2 years with no problems...

I dont think your coupler method would work out too badly as long as you braced it so it didnt wiggle (and eventually split the couplers.) It seems like you've put some thought into this

 

This was actually done years back by Magnus. Had one on my DSM about 5 years ago, worked alright.

 

I was thinking the way to 'brace' it to keep it stiff would be to put a stainless sheeth around it, then put the clamps over that. Zero ballooning, zero flex, and stainless bling to boot.

I was thinking this would be good for the DIY'd manifolds, or at least the cheaper manifolds from ebay or such. It would allow the DIY'er to make one much easier with a stock flange, since you wouldn't have to worry about the problems welding to cast metal.

 

ive personally never had problems with plenum's blowing apart or runners cracking... (i have seen some pics of the GE/STR manifolds or "style manifolds" with the endcap of the plenum completly off. )

on our Golden Eagle manifold, the fuel rail mounts werent welded all the way around, so that started to crack, but we fixed it before it fell all the way off ( the car was shooting fuel from the rail being loose)