Ported X head 340 header size?

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midnight340

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Hey All, just a question that some of you might have an opinion on. (there are some opinions here if I recall.) :D

My 340 is pretty well sorted at this point, tuning etc. I have a true 9:1 motor, Lunati solid .526/.546 lift cam, port-matched LD340, big Thermoquad, etc. Cope built 518 OD with 4.10's.
My heads were ported/polished and really worked over by Bob Mullen way back in the day. (apparently he designed the W-2 heads?) I've been running 1-5/8" mid length headers that I made from some long tube ones years ago. My question is about what size primaries you guys might suggest. (I expect some differing opinions, but that's fine.)

Since I can't do advanced math to figure port area, I took some used header gaskets and carefully formed some wire to the port outlines, then rebent the wire into a circle and it came out at exactly 1-7/8" I.D. I'm thinking that's a lot to try to run into 1-5/8" (...even though I did do some port-matching so there's no sharp edge dam, but it's more of a rounded transition.)

Fitment not an issue as I may make my own, or am game to modify some existing ones. Street/strip use. Ideas???
 
I have always run 1 7/8" and they let the motor rev nice, 7600 and still pulling.
 
If your using factory heads 1 7/8 for a 202 208 valve 340. 1 3/4 for a 188 valve 340-360 or a small cam 202. 1 5/8 for a 318-273.
 
My attitude has always bee run as big of a primary tube as will fit. Period.
 
If you don’t already have it get the motor trend app. $5 a month Lots of mopar content.

engine masters has been testing headers lately on a 450hp sbc.

My vote would be 1 3/4 or 1 7/8. With a 18 inch extension. A mute point with full exhaust. Either one would suffice
 
Hey All, just a question that some of you might have an opinion on. (there are some opinions here if I recall.) :D

My 340 is pretty well sorted at this point, tuning etc. I have a true 9:1 motor, Lunati solid .526/.546 lift cam, port-matched LD340, big Thermoquad, etc. Cope built 518 OD with 4.10's.
My heads were ported/polished and really worked over by Bob Mullen way back in the day. (apparently he designed the W-2 heads?) I've been running 1-5/8" mid length headers that I made from some long tube ones years ago. My question is about what size primaries you guys might suggest. (I expect some differing opinions, but that's fine.)

Since I can't do advanced math to figure port area, I took some used header gaskets and carefully formed some wire to the port outlines, then rebent the wire into a circle and it came out at exactly 1-7/8" I.D. I'm thinking that's a lot to try to run into 1-5/8" (...even though I did do some port-matching so there's no sharp edge dam, but it's more of a rounded transition.)

Fitment not an issue as I may make my own, or am game to modify some existing ones. Street/strip use. Ideas???
What heads do you have?????

Standard port heads for your Street/Strip engine, 1-3/4
Standard (fully ported) or W2 head for your Strip/Street engine - 1-7/8.

Note the wording in the bold....
 
If your using factory heads 1 7/8 for a 202 208 valve 340. 1 3/4 for a 188 valve 340-360 or a small cam 202. 1 5/8 for a 318-273.
I like this though on a more conservative engine, I move the pipe size down on on the valve size. This should be a chart for the heavy hitter like street car builds.
 
Then I’ll assume this is a bit of a beasty or an engine.
What’s your cam duration @050?

Maybe milder than you are thinking? ... duration at .050" is 235/243, it pulls pretty good 2200 up. Solid with EDM lifters. Fun cam with good pull and a nice sound. I'm only running a 2500 stall from PTC. I do wish I would have had the heads flow tested the last time I had them off.
Just a feeling, but I think the motor would like to breathe better. I have yet to open the intake for the TQ (adapter for now) and think the headers are too small for what it wants. No way to know without trying it.
 
Maybe milder than you are thinking? ... duration at .050" is 235/243, it pulls pretty good 2200 up. Solid with EDM lifters. Fun cam with good pull and a nice sound. I'm only running a 2500 stall from PTC. I do wish I would have had the heads flow tested the last time I had them off.
Just a feeling, but I think the motor would like to breathe better. I have yet to open the intake for the TQ (adapter for now) and think the headers are too small for what it wants. No way to know without trying it.

That would be correct. I myself would do a 1-3/4.
I asked because of the 9.0-1 compression ratio.
I have a smaller (Hyd. roller) cam in the wife’s 360 @11.6-1 and TF heads W/1.6 rockers. Love the small cam high flow head combo.

I used to have a LD-340 with the MP mods. Opened up for a TQ and a milled down divider. I ran it with the big TQ. Sold it here a while back. It was very good with the mods and a high lift cam.

(Note, I’m a nut case that would try everything because I can... for no other reason because I can and don’t mind tinkering with what others call good or perfect.
Why? .... No, why not! Because I might find something!
More Power! ROTFLMAO!)
 
Hey All, just a question that some of you might have an opinion on. (there are some opinions here if I recall.) :D

My 340 is pretty well sorted at this point, tuning etc. I have a true 9:1 motor, Lunati solid .526/.546 lift cam, port-matched LD340, big Thermoquad, etc. Cope built 518 OD with 4.10's.
My heads were ported/polished and really worked over by Bob Mullen way back in the day. (apparently he designed the W-2 heads?) I've been running 1-5/8" mid length headers that I made from some long tube ones years ago. My question is about what size primaries you guys might suggest. (I expect some differing opinions, but that's fine.)

Since I can't do advanced math to figure port area, I took some used header gaskets and carefully formed some wire to the port outlines, then rebent the wire into a circle and it came out at exactly 1-7/8" I.D. I'm thinking that's a lot to try to run into 1-5/8" (...even though I did do some port-matching so there's no sharp edge dam, but it's more of a rounded transition.)

Fitment not an issue as I may make my own, or am game to modify some existing ones. Street/strip use. Ideas???
340s like to rev. Use the 17/8 headers specially if your heads were ported by Mullins!
 
340s like to rev. Use the 17/8 headers specially if your heads were ported by Mullins!
Yes, these heads are beautiful. Thanks for one more vote for the 1-7/8”s. I’ve always felt a little guilty about not really using them more fully. The next time they are off I’m getting them to a flow bench to see what they really do.
Years ago when I first had the seats touched up, the machinist said, “Man, somebody really broke the bank on these heads!!”
(long story about how I came to have them. ...And this block, which has the cross-over oiling, and other work, done by Larry Atherton’s shop.) Piece of history!
 
1 5/8 circle area = 2.07 sq in
x 4 = 8.28 sq. in. (One side)
3 in circle = 7.08 sq. in ( one collector)
1 5/8 headers already have more volume than the collectors and your still going to
squash it in to 2 1/2" exhaust pipes on the street.
...but if your racing it would be different through open headers, and who knows what
happens when the exhaust hits atmospheric air pressure after 35 inches?
 
Thanks! I do see that the 1-5/8” flow enough. What always bothered me is the idea that exhaust flow out of a port with equivalent area to 1-7/8” is hitting the smaller header right off the exhaust port. That airflow “dam” off the port has to cause some turbulence that can’t be very helpful to flow.
When I built/modified these mid-length headers out of a full length set, I did try to radius the transition in the flange a bit, but still... :)
 
Yes, these heads are beautiful. Thanks for one more vote for the 1-7/8”s. I’ve always felt a little guilty about not really using them more fully. The next time they are off I’m getting them to a flow bench to see what they really do.
Years ago when I first had the seats touched up, the machinist said, “Man, somebody really broke the bank on these heads!!”
(long story about how I came to have them. ...And this block, which has the cross-over oiling, and other work, done by Larry Atherton’s shop.) Piece of history!
340s like to rev. Use the 17/8 headers specially if your heads were ported by Mullins!
I’ll put my 340s up against any stroker combo any day of the week!
 
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