340 exhaust manifold questions

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H22A4

H22A4

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I was out cruising in the Scamp yesterday and while stopped at a light, the guy beside me asked if was interested in any A body parts. Always wanting to know what's out there I asked him what he had.... turns out he's got some early ('68 to '70) 340 exhaust manifolds (not cracked) that he's willing to sell. I know that I'll need to check the casting numbers before pulling the trigger on them but am wondering if it's worth going the next step based on my engine and plans. The guy is asking $275 for the manifolds.

I've got a mild 318 (1974) that will be getting a new exhaust system shortly so this would be an ideal time to change manifolds if the price is right (not just for the manifolds but also the extra work/costs required for the exhaust system).

If I decide to buy the manifolds, what are all the issues I might run into into when doing the install?

Would it be worth spending ~$275 for the manifolds given the potential extra work required fitting them on my block, etc for the minimal power gains I'd get?
 
H22A4 said:
I was out cruising in the Scamp yesterday and while stopped at a light, the guy beside me asked if was interested in any A body parts. Always wanting to know what's out there I asked him what he had.... turns out he's got some early ('68 to '70) 340 exhaust manifolds (not cracked) that he's willing to sell. I know that I'll need to check the casting numbers before pulling the trigger on them but am wondering if it's worth going the next step based on my engine and plans. The guy is asking $275 for the manifolds.

I've got a mild 318 (1974) that will be getting a new exhaust system shortly so this would be an ideal time to change manifolds if the price is right (not just for the manifolds but also the extra work/costs required for the exhaust system).

If I decide to buy the manifolds, what are all the issues I might run into into when doing the install?

Would it be worth spending ~$275 for the manifolds given the potential extra work required fitting them on my block, etc for the minimal power gains I'd get?
Click to expand...

Check the casting numbers, the 68-70 last three numbers are 553 for the drivers and 549 for the passenger side. 275.00 is a fair price.
 
Mine says 548 on the passenger manifold. Is it the same as a 549?

IMG_0757.jpg


IMG_0758.jpg


If they're decent, $250 is an awesome price. I paid $450 for mine.

You'd need a 90* oil filter adapter (unless your car came with one like my 318), and a hardware kit which seems to run from $50 $65.00.

I don't know what they are worth for power, but mine look like they'd be a ton better than the stock 318 manifolds.

Steve
 
As long as they are straight, for $275.00 you will be stealling them.

As far as the 318,put them on. They work really well on a 318. Nice 2.50" dual exhaust,h-pipe,your favorite mufflers.

Also if you want to upgrade to a 340 or a 360, your exhaust will be done.

Been there done that.

Pic of a 318 I had with 340 manifolds.

Picture 498.jpg
 
Seems like a very good price. I have seen rusty sets at swap meets for $400. Is it really necessary to use the 90 degree filter adapter on the 318's? I plan on doing the hp manifold mod sometime down the road but sure hope I don't need the adapter to make it work.
 
7duster4 said:
Seems like a very good price. I have seen rusty sets at swap meets for $400. Is it really necessary to use the 90 degree filter adapter on the 318's? I plan on doing the hp manifold mod sometime down the road but sure hope I don't need the adapter to make it work.
Click to expand...

It depends on which year you get for the passenger side. The swept back units like I have (pictured above) require the 90* adapter. The later ones have a "center dump" manifold that doesn't require the adapter. The swept back units supposedly have better performance.

I've read the article listed above, and its very interesting. However, I think the results would change dramatically (especially regarding the headers) if they didn't use the stock Durango camshaft. In cars, most people are going to want to make peak power higher than 4500 RPM.
 
I agree with what you said completely, LX Guy, but as the rpms increase, I think the differential between cast iron manifolds and headers will increase.

Moving more air through the same pipes ( at higher RPM's) would favor the individual pipes of a set of headers, I would think.
 
I am sure as the RPMs increase the headers go on to claim a huge advantage. I'm betting the hp manifolds will widen the gap on the 318s as the rpms increase also.
 
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