I'm installing a 2.5" exhaust system on my 68 Cutlass. Right now I have the entire system slip-fit together, not clamped tightly yet. I tried to keep it up as high as possible and have about 1/4" between the top of the pipes and the exhaust crossmember. At the tailpipes, I have about 1/2" between the pipe and the shocks.

Are these enough clearances at both locations to account for normal movement? If not, how much should I shoot for?

Also, are there any references for trumpet tip placement relative to the bumper? How much past the cutouts should the edge of the trumpet be?

Thanks.

 

The crossmember clearance might be too close depending on how much engine rocking the mounts allow. Only way to know for sure is to drive it and see what happens.

 

I’m not sure what system you went with but I’m in the middle of installing FlowMaster pipes with Magnaflow mufflers and Hedman headers with ball flanges. I have over an inch between the over-axle pipes to the shocks. I hung everything loose for fitting but I could not keep it aligned how I wanted so I pulled the H-pipe and mufflers back out today. I set them perfectly aligned side to side and front to rear with the H-pipe and welded them solid. Now everything stays in place and provides a solid section to mount the over axle pipes and tail pipes. I’m still waiting on a ball flanged offset pipe for the left header as it sets higher and to the left of the transmission support opening. My right side pipe that crosses the transmission support is 1/4” to 3/8” clearance.

 

another area to look at is the rear tires not sure what size you are running make sure you have enough clearance when the car is down on the ground if possible

 

Here is the correct trumpet measurement. 2.5" off the face, not the lip.
The gap is about...well I can get a finger in between the two. I don't have gorilla-sized meat hooks.
Obviously this is a 68-69. So don't take it to the bank for 70. The Assembly manual should reference it.