318 vs 340 exhaust manifolds
- Thread starter steveh
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C130 Chief
Mechanical Genius
If you are talking about 68-71 340 manifolds, the yes. But unless you have a set laying around, a set of garden variety headers would be cheaper.
MRL Performance
Well-Known Member
Short answer, No. Even headers with a MILD 318 wont gain you that much.
Johnny Dart
Well-Known Member
Absolutely 340 manifolds will be an improvement over the 318 logs. Team them up with a nice 2.50" dual exhaust and free flowing mufflers,and you will feel a nice improvement.
The drawback,they can be pricey. 340 manifolds or headers would be an improvement over your 318 logs. I say,go for it.
The drawback,they can be pricey. 340 manifolds or headers would be an improvement over your 318 logs. I say,go for it.
Though this is a mild 360, you can expect similar gains percentage wise.
http://www.moparmusclemagazine.com/..._0307_mopar_crate_engine_exhaust/viewall.html
http://www.moparmusclemagazine.com/..._0307_mopar_crate_engine_exhaust/viewall.html
unorthodoxneon
Member
Nice Article find. Been search past couple days for something like this.
1968FormulaS340
Well-Known Member
The gains would be so small that you would feel like you just pissed away $400-$500.
Thx all, I've pissed more than my share of money away over the years. Will probably just stay with what I got for now.
RRR,
The dyno chart was a keeper. Nice comparison, really shows what a difference money can by when it comes to the tti set up
thx again
steve
RRR,
The dyno chart was a keeper. Nice comparison, really shows what a difference money can by when it comes to the tti set up
thx again
steve
67Dart273
Well-Known Member
Took me a bit to figure this out.....................(how to post the photo that is)
What would be more interesting would be to see some more comparisons.............
at 350, 400, 450 hp, , eh?
http://www.moparmusclemagazine.com/...307_mopar_crate_engine_exhaust/photo_17.html#
What would be more interesting would be to see some more comparisons.............
at 350, 400, 450 hp, , eh?
http://www.moparmusclemagazine.com/...307_mopar_crate_engine_exhaust/photo_17.html#
unorthodoxneon
Member
In the article they said once the HP goes up you will want Headers. For normal street builds exhaust manifold aren't the weak spot yet as this points out. 10HP at the crank is very minimal I feel
Treblig
Well-Known Member
This article must be old because I didn't see them try the 98 -02 Magnum truck manifolds. The magnum manifolds came with 2 1/4" exit hole. The hole at the head exhaust port is gigantic. When I tried to port my 302 casting heads to match the magnum manifolds it was impossible, the hole in the manifold was just too big. The motors that these manifolds came on in 98-2002 put out 250 HP and that was restrictive catalytic converters and smog ports. I wonder how much horse power they could handle. I have a passenger magnum manifold on my "69 Barracuda (fit like a glove), they only cost $60 on ebay. I scrounged statewide craigslist and found a 340 driver's side for $150.
The gasket in "blue" is 318, the full length gasket is 360. The 360 almost swallows the 318 gasket, maybe 20 or 25 percent more flow???!!!
Seeing is believing,,,see pics
Treblig
The gasket in "blue" is 318, the full length gasket is 360. The 360 almost swallows the 318 gasket, maybe 20 or 25 percent more flow???!!!
Seeing is believing,,,see pics
Treblig
Here's another with a slightly hotter engine. Too bad you can't install two early 340 right side manifolds.
http://www.moparts.org/Tech/Archive/exhaust/9.html
http://www.moparts.org/Tech/Archive/exhaust/9.html
Treblig
Well-Known Member
Crackedback, that is some excellent info. I'm building a 390 (318 stroker) and was wondering how my current exhaust (340 and magnum manifolds) would do. I hope to make 350 horses at least, I'm building a torque monster (nothing over 5800 RPM) so I guess I don't need super flow headers anyway.
To make things even more interesting, the manifolds I have on my 318 are 2 1/4" exit hole (I think the 340 is a little bigger) which is larger than the ones in the test you posted. So that makes things even better. After I saw this thread (just out of curiosity) I went outside and used a piece of .030" safety wire to fashion the shape of the entrance to the mag manifolds. Then I found a large washer that perfectly fit the wire. It came out just a hair under 1 5/8". I believe that is the standard diameter (1 5/8") for small block headers. now I haven't ported my heads 360 (596 castings) yet but I know for a fact I can get them well beyond 1 5/8" and blend the manifolds as well.
Who needs "stinking" expensive headers when your building a torque monster street machine??????
Treblig
To make things even more interesting, the manifolds I have on my 318 are 2 1/4" exit hole (I think the 340 is a little bigger) which is larger than the ones in the test you posted. So that makes things even better. After I saw this thread (just out of curiosity) I went outside and used a piece of .030" safety wire to fashion the shape of the entrance to the mag manifolds. Then I found a large washer that perfectly fit the wire. It came out just a hair under 1 5/8". I believe that is the standard diameter (1 5/8") for small block headers. now I haven't ported my heads 360 (596 castings) yet but I know for a fact I can get them well beyond 1 5/8" and blend the manifolds as well.
Who needs "stinking" expensive headers when your building a torque monster street machine??????
Treblig
67Dart273
Well-Known Member
As usual, LOL cracked finds the good stuff. THANKS man
Too bad they didn't use a 3" collector on the headers or have everything stub on cast iron to a 2.5" tube. May have moved things a little. I'd bet that the tti headers would have worked really well on that engine.
Funny that the 2 pass side early 340 manifolds kicked the snot out of the original matched set. The drivers side exhaust manifolds are turrrrrrible! LOL There's not that much difference in cast iron IMO, to justify spending the money on early 340 manifolds. For the difference, I can buy a 75hp juice unit and kill the 340 manifold runner.
For the OP, run what you got and save some money would be my approach, unless you want to boast about having 340 manifolds...
Funny that the 2 pass side early 340 manifolds kicked the snot out of the original matched set. The drivers side exhaust manifolds are turrrrrrible! LOL There's not that much difference in cast iron IMO, to justify spending the money on early 340 manifolds. For the difference, I can buy a 75hp juice unit and kill the 340 manifold runner.
For the OP, run what you got and save some money would be my approach, unless you want to boast about having 340 manifolds...
67Dart273
Well-Known Member
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