340 Chrysler Street Header Questions

[exhausted]

I draw the port shape in CAD and let the computer figure the area.
The port shapes are rather irregular so slop is involved to some extent. I try and draw on the smaller side of things. The ID area of a 18ga 1.625" tube is unfortunately pretty accurate.

[stealth]

Looks like a good time to fit a rack and pinion into project. Just think of the room you would make for headers...

[Mattax]

I draw the port shape in CAD and let the computer figure the area.
The port shapes are rather irregular so slop is involved to some extent. I try and draw on the smaller side of things. The ID area of a 18ga 1.625" tube is unfortunately pretty accurate.

I wasn't doubting that, or imply that counting squares was particularly accurate!
Really just pointing out that an untouched casting might have significantly smaller area if not blueprinted. Depending on the rest of the combo matching the port to a gasket might or might not be desireable. I'd assume your customer will be winding the motor fairly high and very concerned about top end power.

[exhausted]

I draw the port shape in CAD and let the computer figure the area.
The port shapes are rather irregular so slop is involved to some extent. I try and draw on the smaller side of things. The ID area of a 18ga 1.625" tube is unfortunately pretty accurate.

I wasn't doubting that, or imply that counting squares was particularly accurate!
Really just pointing out that an untouched casting might have significantly smaller area if not blueprinted. Depending on the rest of the combo matching the port to a gasket might or might not be desireable. I'd assume your customer will be winding the motor fairly high and very concerned about top end power.

Nope, hydraulic cammed NHRA stocker. I have no idea what the casting I was sent is so who knows. I think I posted before that this was the first 340 I've ever done, (that I can remember), no I'm sure. I do not want to get into the engine builders head about different heads and all. The area I look at at the flange is what I am dealing with. If it was up to me or say my car (or cars) I would have each flange made for each cylinder head.

The main thing here is that the closer to the cylinder your dealing with things, every little hit the flow and velocity takes costs power you will not be able to mine out of the exhaust system no matter what you do. All the way to the point where the engine is numb to whatever you do to the header. It starts at the valve. If the port area curve is bad, you can only fix so much with the rest of the system. The good/sad part of this is very few folks want to deal with it or try to understand.

[Mattax]

Homestretch now.

[groberts101]

nice work! now I'm starting to feel even more claustrophobic for building a custom set for my Comet GT.

what did the merge's choke ID end up at for your combo? looks to be near 2.25"?

[Mattax]

We went with Calvin's suggestion, 2". The exit is 2.5" OD
An H will go about 20" from the end of the secondaries (about 1.5" in from chokes). The cones are 5" long.
I say about because the l & r are not exactly the same.

The inner fenders on the small fords make me feel claustrophobic! But then you'll have some more room where the t-bars on the Chryslers.
Really exited about seeing how it all works when we fire it up. Unfortunately work is starting up so I don't know how much tuning time I'll have, plus there was a clanging in the engine that has to be figured out. it went away with an oil change but I want to investigate. I'm trying to get a spare engine and heads ready..

- Matt

[exhausted]

Looks nice. Lots of work. I am in the middle of 68 Barracuda 340 but it is a 4into1.
I will post some pics soon. While I am happy with how they have come out, they are much more compromised than say a 67-9 Camaro header. The torsion bars being the biggest offenders, followed by the oil filter and the HUGE steering box...

[Mattax]

Is he willing to make some changes?
The manual steering box is smaller and lighter. 3 ratios are available, 24:1, 20:1 (for nascar), 16:1 (best for slaloms but hardest to turn at low speed).
Flaming river also offers a iron/steel version - I think its a little smaller.
Borgeson is making a version that requires some tinkering to make it all join together.

[exhausted]

Well this already has the standard box. It is not in the way as much as is is in a Hemi car but
it does add a bit of length to get over it...

[groberts101]

Those smaller chokes and 4-2-1 design should really wake that little motor right the hell up! I'm also thinking that your fuel curve will change quite a bit too.

I wanted to go with something similar myself but with such limited clearance as you rightfully pointed out above(2 inches narrower than even the earliest Mustangs) I don't think I'll even get close to that design once I start mocking it all up. My 342" SBF heads exhaust ports(RHS heads with stuffed floors/high port conversion) have been designed to match a 1.5" primary before stepping up to 1.625". And my current thinking is that because of that improved velocity maintenance I doubt that my chokes will need to be that small. Was even thinking that it may end up just being a conventional merge without a choke but I'll surely be picking some smarter brains once I get closer to that point of final collector design.

[exhausted]

So, 68 Plymouth 340 4into1 header.
The torsion bar is sort of a pain but it came out just fine.

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[wyrmrider]

again- look real nice
many builders of SBM and AMC use too big a tube off the heads due to the dog legs

[Mattax]

That is nice! And its fun to compare. I can see why the oil filter was a bit in the way. The rest is similar in terms of space constraints.
We briefly looked at changing the oil filter to remote arrangement but it didn't buy any useful space for us.

AMC doglegs - What's the thinking behind that? Is it about keeping low rpm velocity high along the roof, or something about the head design?

[exhausted]

That is nice! And its fun to compare. I can see why the oil filter was a bit in the way. The rest is similar in terms of space constraints.
We briefly looked at changing the oil filter to remote arrangement but it didn't buy any useful space for us.

AMC doglegs - What's the thinking behind that? Is it about keeping low rpm velocity high along the roof, or something about the head design?

AMC Doglegs?