'66 Big Block Heat Riser Position w/ Images

[Joe L.]

Re: '66 Big Block Heat Riser Position Question w/ Images

All-------


There were actually 3 different heat riser valves used on Corvettes over the 1965-74 period. The first, used for 1965 and, possibly, early 1966 was GM #3767651. The second, used for the rest of 1966 and, possibly, early 1967 was GM #3886071. The third, used for 1967-74 is GM #3887034. Unfortunately, how these valves differed I do not know. But, I'm sure they differed in some way.

[Dereck S.]

Re: '66 Big Block Heat Riser Position Question w/ Images

Attached are a few pics of one of the original versions of the 3887034 BB heat risers. One of them is the functioning original from my September built 67 big block along with two NOS valves of the same configuration. It's tough to find the NOS early valves. There are clear characteristics associated with this version versus the later versions. Most differences are on the body around the pressed-in pin area which has a thick section. I can post more pics if someone needs more details.

[Joe L.]

Re: '66 Big Block Heat Riser Position Question w/ Images

Attached are a few pics of one of the original versions of the 3887034 BB heat risers. One of them is the functioning original from my September built 67 big block along with two NOS valves of the same configuration. It's tough to find the NOS early valves. There are clear characteristics associated with this version versus the later versions. Most differences are on the body around the pressed-in pin area which has a thick section. I can post more pics if someone needs more details.

Dereck-------


The GM #3887034, while used in PRODUCTION only for big blocks, was also SERVICE for 1962-65 small blocks with 2-1/2" outlet manifolds.

1965 L-78 used heat riser valve GM #3767651, the same valve used for 1962-65 small blocks with 2-1/2" outlet manifolds. Early 1966 big blocks may also have used heat riser GM #3767651 or heat riser GM #3886071. I do not know how either of these heat riser valves differ from the 3887034 but I'm sure they differed in some way. I've never even seen a known example of the 3886071.

The GM #3887034 was also used for all 1967-74 big blocks except 1969. 1969 big blocks, all of which were equipped with 2-1/2" outlet manifolds but 2" exhaust piping, used a unique heat riser valve of GM #3969903. This valve had the counterweight on the opposite side compared to the 3887034.

[Dereck S.]

Re: '66 Big Block Heat Riser Position Question w/ Images

Thanks Joe
Great information. Back in the early 80's I bought up many early NOS BB risers. I always thought they didn't last long and needed to be replaced. I remember them rattling on cars or sticking open/closed when I was younger. I know guys replace their risers with a spacer. My 3x2 engine runs better with the riser even though I only run my car in the summer. I felt the riser improved atomization of the fuel and eliminated rough idle and improved the warm up transition. It was noticeable going from a spacer to the riser. Once at operating temp I couldn't tell the difference. Just my opinion. If you run a riser you need to ensure the intake manifold ports aren't blocked by a gasket. Here are some very clear pics of another early NOS 3887034. I use pics from posts all the time. Pics are immensely valuable. It's time I started contributing by adding pics for others.
Dereck

[Joe L.]

Re: '66 Big Block Heat Riser Position Question w/ Images

Thanks Joe
Great information. Back in the early 80's I bought up many early NOS BB risers. I always thought they didn't last long and needed to be replaced. I remember them rattling on cars or sticking open/closed when I was younger. I know guys replace their risers with a spacer. My 3x2 engine runs better with the riser even though I only run my car in the summer. I felt the riser improved atomization of the fuel and eliminated rough idle and improved the warm up transition. It was noticeable going from a spacer to the riser. Once at operating temp I couldn't tell the difference. Just my opinion. If you run a riser you need to ensure the intake manifold ports aren't blocked by a gasket. Here are some very clear pics of another early NOS 3887034. I use pics from posts all the time. Pics are immensely valuable. It's time I started contributing by adding pics for others.
Dereck

Dereck------


I wonder what part number is under the hand written label on the box? That hand-written label is not something that GM placed there.

[Dereck S.]

Re: '66 Big Block Heat Riser Position Question w/ Images

Here's how I installed my riser on my September built 427/400 car. If you observe the weight during idling it barely moves off it's closed position. It's not until you rev the engine when it starts to open.