What’s the difference between the 1970 high performance 340 and 1973 high performance 340 manifolds besides the casting numbers?
High performance manifold differences
- Thread starter 70scatpack
- Start date
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Inertia
Well-Known Member
The early ones have a flat pipe flange using a gskt. The later ones have a bell/ball flange, no gskt reqd.
Thanks,port and flange end diameters are the correct?
Good question
pishta
I know I'm right....
Good catch, I didnt know that.
Partially correct. Early manifolds had gaskets on both sides as stated. Later performance manifolds from 1971-74 used a gasket on the left side as the early manifolds and a ball joint connection/floating flange connection on the right side requiring no gasket. The right manifold (626 casting) was also used on 1971-74 b and e body applications with 340/360 engines.
ir3333
Well-Known Member
they are shaped completely different although the drivers' side are similar.
Isn't there a difference in outlet size as well? I need to look it up here in a bit.
Treblig
Well-Known Member
From all the 340 manifolds that I've had (I've had over 100) every one had a 2 1/4" outlet EXCEPT in the 70s (71 and up I think) passenger's side had a 1 7/8" outlet. The 60s 340 driver's side had a different design that made it rise a little higher over the plugs and it also hugged the block a little more. The 60s 340 driver also DID NOT have the extra ribbing like in the 70s. The 70s 340 driver's side didn't rise as high and also moved away from the engine block (just a little). That's why (if you have manual steering) you can use the 60s driver's side 340 manifold on the early As.
On the left is a 70s 340 drivers' manifold, you can see the ribs on the far left. you can also see how the 60s 340 (on the right) rises higher:
Here you can see the 70s 340 (ribs) and how it is designed so that it's further away from the block compared to the 60s 340 (left).
The ribs are very obvious on the 70s 340:
Yes, I've had a few..........
treblig
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All those manifolds made me dizzy!
Treblig
Well-Known Member
They are a thing of beauty!!
I have decided to go with the hp manifolds and scrap the flattened Hooker headers. Do I need to install the heat shields and do they need gaskets on both sides or just one side?
I've been running the old hipo manifolds on a variety of small blocks in a variety of 1967-76 A-bodies for decades and have never used a factory heat shield on any of them. I gave up on headers on my street cars for the same reason - poor performance after damage.
another tip: if you care about looks, use the POR brush on exhaust paint. If a bit peels or gets damaged from oil or brake fluid, you just touch it up with a small brush, start the engine to melt the paint and the brush strokes disappear and it all looks fresh again, without any masking or manifold removal!
another tip: if you care about looks, use the POR brush on exhaust paint. If a bit peels or gets damaged from oil or brake fluid, you just touch it up with a small brush, start the engine to melt the paint and the brush strokes disappear and it all looks fresh again, without any masking or manifold removal!
Thanks for paint tip,but I am having the manifolds ceramic coated in cast iron gray before I install them in about 2 weeks and also decided not to use the heat shields.
What type of mufflers do NOT give you that deep drone tone? I did install the HP manifolds would like change out the mufflers.
Deep drone tone inside the car?
Best I found are the Dyno Max turbo muffler.
However, there’s more to sound control than the muffler alone.
A Helmhertz (?) pipe addition helps.
Pressure wave cancellation boxes after the header, before the H or X pipe help.
Moving the muffler rearwards to the bumper instead of under the rear seat helps.
Longer mufflers help a lot.
Best I found are the Dyno Max turbo muffler.
However, there’s more to sound control than the muffler alone.
A Helmhertz (?) pipe addition helps.
Pressure wave cancellation boxes after the header, before the H or X pipe help.
Moving the muffler rearwards to the bumper instead of under the rear seat helps.
Longer mufflers help a lot.
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