Packard Forum Index » V-8 (1955-56)

All,

Is the heat riser found on the driver's side of the v-8 exhaust an absolute necessity? What are the pro's and con's of having or not having one?

I believe it's purpose is to increase cold driveability and hasten the warmup and help gas vaporization when really cold and also so choke releases a bit quicker when coming up to temp.

Many have been found blocked open either on purpose or thru rust and deterioration and except for a few minutes in really cold places, doubt if missed that much. If stuck closed on the other hand, on older engines overheating and exhaust valve damage could result.

The heat passages through the intake can also be blocked closed by carbon. Especially important on dual exhaust systems where the "flapper" in the exhaust manifold still works and shuts off the flow, like it's supposed to. Exhaust gases that were meant to pass through the ports in the intake from the blocked side to the open manifold have nowhere to go. Makes the car run kinda funny.

The automatic choke will eventually pull off without the heat riser, from either warming coolant or electrically generated heatl, depending on the type. Cold driveability will suffer, as well as mileage, during warmup, as intake mixtures hit the cold manifold and the fuel condenses. These gadgets are there for a reason.

I removed the heat riser from my Carib about 13 years ago when I had a new exhaust system installed. I do occasionally use the car in late Fall, during the Winter, and early Spring and w/o it, the car is balky for perhaps the first 2-3 minutes of operation, after which it's fine. I regret leaving it off and will reinstall at some point.

The exhaust pipe curves forward and a rather tite bend around the PS slave. Deleteing the heat riser will cause the ex pipe to set VERY close to the PS slave unless somekind of spacer is used for which a gutted heat riser would work well as a spacer.

I just made the exhaust pipe correspondingly longer to compensate for the absence of the heat riser, thus maintaining the clearance to the PS cylinder.

Hi Kevin:

The heat riser is an absolute should have especially on the V-8 because it helps reduce sludging via leaner mixture.

If your car has dual exhaust stuff a rag in one tail pipe during warm up.

Heat Risers in some form or another were being used all the way back to pre-1910.

With the straight eight the units can be arduous to fix but definitely make the cars run better.

Hope this helps, and remember the rag trick.

"If your car has dual exhaust stuff a rag in one tail pipe during warm up."

Tim, I love it! But how long do you wait to take it out, and do you let it run in the driveway or stop somewhere along the road?

tie a string to the rag and the other end to a gate post or something. When u drive off it'll pull itself out.