1969 427 exhaust manifold part questions

[Keith C.]

I have a '69 427/390hp car. Number matching car. It is a side pipe car. Previous owner took off stock manifolds and put on long tube headers to the side pipes. But they saved the correct factory manifolds thank goodness. I am putting the stock 2.5 inch manifolds back on. 1 - Did my car have a heat risers on each manifold from the factory? Did it have one riser and if so which side? Or did it have none? 2- Did my car have exhaust manifold pipe spacers instead of heat risers? Can someone help me with what my car should have had on it from the factory. Thanks in advance. Keith - 60935

[Scott P.]

Re: 1969 427 exhaust manifold part questions

Keith, Mostly my possible help can come in the form of buying the sidepipe headers from you. Can you send me a pic, if you still have them.
Thanks Scott Fogaley@sbcglobal.net

[Keith C.]

Re: 1969 427 exhaust manifold part questions

Scott, thanks for the offer but I am keeping them for another project. Keith

Still looking to the forum for some assistance with the original questions.

[Leif A.]

Re: 1969 427 exhaust manifold part questions

Keith,
Welcome to the TDB. Your car originally came with a 2 1/2" heat riser valve and gasket on the right hand side. The left hand side had a 2 1/2" donut alignment sleeve. Hope this answers your question.

[Bill B.]

Re: 1969 427 exhaust manifold part questions

While I'm a 1970 model owner, according to my various sources, the '70 used a heat riser valve on the passenger side of the manifold. The exhaust manifold studs were longer on that side to accommodate the thickness of the riser valve. I suspect the 1969 models were identical/similar.

The purpose of the heat riser was to "persuade" the hot exhaust gas to the intake manifold where it would "warm-up" the intake plenum as well as cause the divorced thermostatic choke spring to react and start opening the choke plate on the 4-bbl carb during a cold start. As the engine "warmed up" to stable temp, the heat riser would be open and not force divert the hot exhaust gas to the intake.

I'm sure the '69 experienced folks will chime in and confirm or add more detail about this.

[Stephen L.]

Re: 1969 427 exhaust manifold part questions

Leif's description fits my 427/390 exactly. Additionally, mine is also a sidepipe car. 1967..........

[Keith C.]

Re: 1969 427 exhaust manifold part questions

Bill, Leif and Stephen,
Thanks so much for your help. With your help I think I can now get it back together to factory specs. Take care.

Keith

[Joe L.]

Re: 1969 427 exhaust manifold part questions

While I'm a 1970 model owner, according to my various sources, the '70 used a heat riser valve on the passenger side of the manifold. The exhaust manifold studs were longer on that side to accommodate the thickness of the riser valve. I suspect the 1969 models were identical/similar.

The purpose of the heat riser was to "persuade" the hot exhaust gas to the intake manifold where it would "warm-up" the intake plenum as well as cause the divorced thermostatic choke spring to react and start opening the choke plate on the 4-bbl carb during a cold start. As the engine "warmed up" to stable temp, the heat riser would be open and not force divert the hot exhaust gas to the intake.

I'm sure the '69 experienced folks will chime in and confirm or add more detail about this.

Bill------


1970 BB used the same right side exhaust manifold as 1969. However, the left side manifold was different. All 1965-74 BB used 2-1/2" outlet manifolds. All used 2-1/2" exhaust systems EXCEPT 1969 which were 2" for all engines.

[Bill B.]

Re: 1969 427 exhaust manifold part questions

Thanks Joe.

Interesting that all 1969 BB used 2" pipes. Would be interesting to understand what prompted Chev Eng'g to do that? Deproliferation initiative? Supply chain availability?