68conv455

I've got a 68 cutlass convertible with a 455. I purchased thorley headers for the cutlass and 455 and just discovered that the passenger side header contacts the fire wall. The header tube just barely touches it. What should I do. I purchased the headers almost 1 year ago so I'm assuming returning them is not viable. The headers also have a nice nickel coating which would be a shame to damage with heat. Should I e-bay them and start over? Help.

64Rocket

Does it touch the firewall or the heater box?
I would make adjustments in the firewall or the box whichever is necessary. Also put some insulating rap around the pipe in that spot.

Gene

J-(Chicago)

That doesn't look too bad. You were fortunate if that is the only problem you had with the fit. My passenger header hit the firewall as well. I just beat the snot of it though. You could always notch out the firewall and weld in a cup.

don71

If it were me, I would try to clearance the firewall. Probably use a long pry bar against the wall with the header as the fulcrum. Use a rag or something to keep from scratching anything thing.

Worst case, remove header, and clearance the firewall with a hammer.

joe_padavano

I vaguely remember a similar problem with a set of Thorley headers on my 68 442 that I built in high school (in the last century...).

88 coupe

Was it a convertible?

Norm

gearhead1218

This calls for a very precise adjustment with a BFH.

joe_padavano

Holiday Coupe. I suspect the problem is production tolerance stackup.

citcapp

Remove header. Use a 9 pound adjustment tool and create a indent in the area required.

Oldsguy

I agree with all the recommendations as any/all of them will work. I pose one question though. Is is possibly caused by worn engine mounts? If so, obviously, that might be a fix. I realize that if the mounts were to wear then more than likely the engine would sit a little lower, not back, but just sharing that idea...

1964f-85

I put headers on my 455, 64 cutlass and had the oposite problem, the headers were hitting the passenger side crossmember, what I found out is that the aftermarket engine mounts are sloppy, with factory exhaust manifolds this doesn't pose a problem. I fixed it by welding the holes on the mounts where they bolt to the block closed and redrilling them to raise the engine up, you may be able to do the same, in the opposite direction to lower the engine away from the floorboards. as long as the oil pan doesnt hit the rossmember you should be fine.
Scott

68conv455

Norm asked if it was a convertible. It is.
Is there a difference at the firewall on the convertible?

I think I'll try to make some fine adjustments to the firewall, and, fine adjustments to the header tube.

Thanks for the advice.

88 coupe

It was that, or ask him if it was a Supreme. Explanation is below.

Header catalogs say there is a difference (in convertibles and Supremes) but no one knows where, or what, it might be.

Header fitment (or misfitment?) can occur with one of two identical cars. Joe_p's "tolerance stack" theory, makes perfect sense to me, especially if space is limited.

Norm

red rocket

Remember that your big block will move under power but the firewall/heater will not. I had to do some banging with my 67 CS convertible 455 but no problems now.

joe_padavano

True, however unless you're drag racing in reverse, the passenger side rotates down.

Jamesbo

Not to high jack this thread, but is this rotation what can cause cracks in the drivers side pillar. I have a friend who bought a real 69 W-30 that came with slicks. [and was drag raced] It has a small crack in drivers side pillar.

joe_padavano

But you did...

Yes. Repeated shocks from launching the car causes the body to torque, resulting in fatigue cracks.

68conv455

Drag race in reverse?

I think you just invented a way to race imports and make it a fair race.

Jamesbo

My sincerst appologies

In the future, I will endeavor to control my inquisitivness.

But thanks for the prompt and accurate [as always] answer