Original 1957-74 heat riser spacer for FI?

[Stuart F.]

Re: Original 1957-74 heat riser spacer for FI?

John;

Just to clear the air of any misunderstanding, from your vast experience and expertise; were their "any" vintage (pre-catalytic Converter)Corvettes of any year (F.I. or Carburated) that used the exhaust pipe connection between left and right bank ehaust pipes, often times referred to as a "cross-over" pipe? My recollection is that they were only used on some dual exhaust equipped passenger cars. For one thing, I think the Corvette chassis did not lend itself well to any extra exhaust plumbing.

The reason I bring this up is that perhaps some of our less experienced members may hear the term "cross-over" pipe from some auto service people who are talking exhaust systems and mis-interpret it as being the engine internal cross-over (head to head thru manifold).

Have a great weekend;

Stu fox

[Mike M.]

Re: Original 1957-74 heat riser spacer for FI?

our 57 210 post , 250 HP 3 speed has the balance tubing between the left and right exhaust header pipes.as does our 57 vettes, a 250 and a 283 HP.Thats the way they were at assembly. mike

[Stuart F.]

Re: Original 1957-74 heat riser spacer for FI?

Mike;

Thanks for clearing that up. I just got the feeling on some of these heat riser related threads with the younger fellows we got to talking apples and oranges. As I had mentioned in one or two threads before, we used to cap off the cross-over pipes as well as block the heat riser passages to get better summer performance, but also to make more noise with our glass pacs. Yaaah!

Stu Fox

[Ian G.]

Re: Original 1957-74 heat riser spacer for FI?

yeah I was a little confused as to the internal intake crossover plumbing vs the exhaust pipe plumbing, but you guys have got me all cleared up.

Also, happily looks like I found myself a NOS FI heat riser spacer based on that part number Joe The word "up" is a little smaller though. In fact, ironically, the one I saw on Corvette Central looks more like the pictures above than the NOS one I bought... course, the word "up" looks slightly different between the two original example pictures posted as well.

[Clem Z.]

Re: Original 1957-74 heat riser spacer for FI?

our 57 210 post , 250 HP 3 speed has the balance tubing between the left and right exhaust header pipes.as does our 57 vettes, a 250 and a 283 HP.Thats the way they were at assembly. mike

that did 2 things it added some HP and it cut down on the exhaust tone. blocking the heat riser crossover in the intake manifold on a dual pipe car will make the exhaust louder as we used to do that on flat head fords using copper pennies in the heat riser crossover in the intake manifold.

[John H.]

Re: Original 1957-74 heat riser spacer for FI?

Some Oldsmobile applications in those days used coil springs between the stud nuts and the pipe flange.

[Clem Z.]

Re: Original 1957-74 heat riser spacer for FI?

Some Oldsmobile applications in those days used coil springs between the stud nuts and the pipe flange.

my 1988 silverado with a 350 V-8 uses springs on this connection

[Joe L.]

Re: Original 1957-74 heat riser spacer for FI?

yeah I was a little confused as to the internal intake crossover plumbing vs the exhaust pipe plumbing, but you guys have got me all cleared up.

Also, happily looks like I found myself a NOS FI heat riser spacer based on that part number Joe The word "up" is a little smaller though. In fact, ironically, the one I saw on Corvette Central looks more like the pictures above than the NOS one I bought... course, the word "up" looks slightly different between the two original example pictures posted as well.

Ian-----


It also needs to be clearly understood that the intake manifold heat cross-over and any exhaust pipe cross-over are two entirely different things and exist for entirely different reasons.

The intake manifold crossover works in conjunction with the heat riser valve to direct exhaust gases through the intake manifold in order to improve cold start fuel atomization and performance. For 1966-72 Corvettes, it's also used for choke operation. The intake cross-over has no "exhaust balancing" function although, incidentally, it might provide some under certain operating conditions. Under its intended purpose, it's function is anything but "exhaust balancing" since the system directs all or most of the right bank exhaust flow to the left side exhaust manifold and exhaust piping.

A cross-over PIPE is located "downstream" of the exhaust manifolds and heat riser valve. It allows exhaust pressure to more-or-less "equilibrate" through the left and right side exhaust pipe system.

By the way, if the intake manifold exhaust cross-over had any significant "exhaust balancing" function, then there would be no need for an exhaust pipe cross-over. However, we know that there were many cars which had BOTH an intake manifold exhaust cross-over as well as an exhaust cross-over pipe.

No C2 or C3 Corvette ever originally used an exhaust cross-over PIPE.