Heat Riser

[Richard G.]

Is the heat riser on a 67 435 inter-changeable through-out 68-69?

[Mike M.]

Re: Heat Riser

yes if the 68 and 69 are big blocks. btw, the current service replacement riser's configuration differs from that of originals. mike

[Joe L.]

Re: Heat Riser

Rich------

The 1967 big block heat riser is the same as that used for 1968 big blocks AND for 1970 through 1974 big blocks. It's still available under the original part number of GM #3887034, although as Mike says, the configuration varies slightly from the original piece.

The 1969 big block heat riser is unique to that application. That's because ALL 1969 Corvettes, including big blocks (even L-88s), were ORIGINALLY equipped with a 2" exhaust system. So, the heat rise for this application was special. It is GM #3969903 and, believe it or not, it's still available from GM, too. It also varies a little from the original in configuration, though.

[Warren F.]

Re: Heat Riser

Joe:

Are the '69 427 exhaust manifold flange portion end smaller than '68 or '70,'71 & '72. Or is just the heat riser just smaller for mating to the exhaust pipe flanges.

I learn something new here everyday!

[Joe L.]

Re: Heat Riser

Warren-----

The 1969 big block exhaust manifolds are the same as other years. ALL big block manifolds use a 2-1/2" outlet. For 1969, the forward exhaust pipes had a 2-1/2" flange which was thereafter swaged down to the 2" size. The heat riser valve was a 2-1/2" valve but it was configured differently. I really don't know why this was necessary, but that's what was done. I need to study the 2 different valves (I have both) to see if I can figure it out. It's 12:20 AM now, though, and I'm not going to dig those valves out now to look at them.

[Warren F.]

Joe, thanks for the explanation! *NM*

[Richard G.]

Re: Heat Riser

Joe

Thanks, I'm interested to hear your answer this evening. I'm going to compare mine off my 69 to my neighbors 67 over the weekend. Although mines on the car so it might be hard to tell

Rich