Manifold Heat Riser question
Thread Starter
Racer
Joined: Jun 2003
Posts: 433
Likes: 0
From: Aspenden Hertfordshire U.K.
Manifold Heat Riser question
Almost finished rebuilding my 350 motor but am unclear as to the correct position for the heat riser restrictor/s on the manifold gasket .
I have fitted later heads (79) to allow for use of unleaded fuel and am running an Edlebrock performer manifold .
Can you please advise as to which side if any the restrictor should be fitted , is it needed with the Edlebrock manifold ?
Also what is the reason for fitting these restrictors what do they do and what are the consequenses of getting it wrong ?
TIA
Mike .
I have fitted later heads (79) to allow for use of unleaded fuel and am running an Edlebrock performer manifold .
Can you please advise as to which side if any the restrictor should be fitted , is it needed with the Edlebrock manifold ?
Also what is the reason for fitting these restrictors what do they do and what are the consequenses of getting it wrong ?
TIA
Mike .
Le Mans Master
Joined: Apr 2004
Posts: 7,106
Likes: 38
From: Newark DE
Mike
are you referring to the plates that close off the crossover passages of the intake?
If so, many people close them off if they remove the heat riser valve from the passenger side exhaust manifold - between the manifold and the exhaust pipe.
The crossover passages allow exhaust from the passenger side cylinders to exit thru the intake and out the drivers side exhaust while the heat riser valve is closed when starting cold.
If you remove the hear riser valve and block off the crossover passages with certail intake manifold gaskets the downside is that it just takes a little bit longer for the car to come off the choke when cold.
FWIW, last year I removed the heat riser valve off my '65 and as per recommendations installed new intake gaskets that closed off the crossover passages. It completely changed the sound of the exhaust thru the sidepipes. Since I only drive the car in the summer I don't see much issue with a prolonged warm-up before the choke kicks off so that's not an issue but the changed exhausr sound is and I don't like it. I just got new intake gaskets to change back to an open crossover.
are you referring to the plates that close off the crossover passages of the intake?
If so, many people close them off if they remove the heat riser valve from the passenger side exhaust manifold - between the manifold and the exhaust pipe.
The crossover passages allow exhaust from the passenger side cylinders to exit thru the intake and out the drivers side exhaust while the heat riser valve is closed when starting cold.
If you remove the hear riser valve and block off the crossover passages with certail intake manifold gaskets the downside is that it just takes a little bit longer for the car to come off the choke when cold.
FWIW, last year I removed the heat riser valve off my '65 and as per recommendations installed new intake gaskets that closed off the crossover passages. It completely changed the sound of the exhaust thru the sidepipes. Since I only drive the car in the summer I don't see much issue with a prolonged warm-up before the choke kicks off so that's not an issue but the changed exhausr sound is and I don't like it. I just got new intake gaskets to change back to an open crossover.
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
Almost finished rebuilding my 350 motor but am unclear as to the correct position for the heat riser restrictor/s on the manifold gasket .
I have fitted later heads (79) to allow for use of unleaded fuel and am running an Edlebrock performer manifold .
Can you please advise as to which side if any the restrictor should be fitted , is it needed with the Edlebrock manifold ?
Also what is the reason for fitting these restrictors what do they do and what are the consequenses of getting it wrong ?
TIA
Mike .
I have fitted later heads (79) to allow for use of unleaded fuel and am running an Edlebrock performer manifold .
Can you please advise as to which side if any the restrictor should be fitted , is it needed with the Edlebrock manifold ?
Also what is the reason for fitting these restrictors what do they do and what are the consequenses of getting it wrong ?
TIA
Mike .
Thread Starter
Racer
Joined: Jun 2003
Posts: 433
Likes: 0
From: Aspenden Hertfordshire U.K.
Thanks for the replies , I am running a 4150/600 Holley with auto electric powered choke set up . So if I have this right I can probably manage without restricting either side , or should I restrict the drivers side to allow more heat to the passenger side which is the side of the choke . I am not too concerned about warm up times as like Barry I only run in decent warm weather ( when we get some in the UK ) .
My thought is to leave them both fully open , what do you think ??
MIke .
My thought is to leave them both fully open , what do you think ??
MIke .
Thread Starter
Racer
Joined: Jun 2003
Posts: 433
Likes: 0
From: Aspenden Hertfordshire U.K.
Thanks to all for your thoughts , I have now fitted the manifold with no restrictors , all I need to do now is get the motor back in the car and get it fired up .
Thanks again
Mike .
Thanks again
Mike .
