340 Chrysler Street Header Questions

General engine tech -- Drag Racing to Circle Track

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Amilcar
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Re: 340 Chrysler Street Header Questions

Post by Amilcar »

That's impressive work of both of you... =D> =D> =D>
Calvin, is it needed to remove the torsion bar on passenger side to install the header?
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Re: 340 Chrysler Street Header Questions

Post by wyrmrider »

The heads were also changed in 1970. 1966-1969 heads have rectangular exhaust ports. 1970 and later heads have a “dog leg” or “pork chop” shaped exhaust port.
The larger port increased exhaust flow by around 50%, making AMC heads the best flowing production heads available.
For this reason the Chrysler “Magnum” V8 head was based on the AMC design.
The new ports also required new exhaust manifolds.
http://gremlinx.com/amc-myths/
IMHO the BBBuick heads were also very good
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Re: 340 Chrysler Street Header Questions

Post by Mattax »

Calvin, Wymrider mentioned them {edit:} and posted a bit more above. The funny AMC exhaust ports.
AMC360-on-sled-2015-4-6.jpg
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Re: 340 Chrysler Street Header Questions

Post by exhausted »

Amilcar wrote:That's impressive work of both of you... =D> =D> =D>
Calvin, is it needed to remove the torsion bar on passenger side to install the header?
No, the two center tubes on the same flange are inside of the Torsion bar. The end cylinders are individual tubes.
The Driver side center tubes have a slip section just past the steering shaft.
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Re: 340 Chrysler Street Header Questions

Post by exhausted »

Mattax wrote:Calvin, Wymrider mentioned them {edit:} and posted a bit more above. The funny AMC exhaust ports.
AMC360-on-sled-2015-4-6.jpg
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I see. :( may hae high flow but low velocity.
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Re: 340 Chrysler Street Header Questions

Post by Mattax »

Sorry I hadn't posted pictures of the finished exhaust when we got done.

H- Pipe is about 20" from the choke, based on pipemax and space availability.
MVC-501F.JPG
MVC-498F.JPG
Magnaflow 4x9 oval, 18" L worked out in terms of fit, flow, noise reduction.
Reproduction of stock tailpipes for a '67 with 383 cid v-8.
2016-6-18-Exhaust-2-r.jpg
IMG_1303-r.jpg
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Re: 340 Chrysler Street Header Questions

Post by exhausted »

Hey, looks very nicely done.
How does it run?
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Re: 340 Chrysler Street Header Questions

Post by cjperformance »

Good work, and hey looking at the colored pipes, do you run a dual plane intake and does the 2nd and 4th pipe from the front run off of the same intake plane, AND does the color on the other side pipes correspond to the color pattern on the pipes in the pic? May need some jetting adjustments, check the spark plugs, and as exhausted asked,, how does it run now ?

(Edited for typos as usual!)
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Re: 340 Chrysler Street Header Questions

Post by Mattax »

Seat of the pants its running great. Only retuning so far has been idle mixture screws! Got in one autocross and I'm using the car all the time now and really enjoy driving it. Stuck in standstill traffic is still a bit brutal, but not particulaly worse than it was with manifolds, maybe better. Maybe better because it sounds and feels like the headers are helping with reversion even if they make the engine bay a little hotter. After one autocross, I reset the suspension height more for rally conditions (due to the roads I'm travelling this summer& fall) and again its been great - feels like I finally have the car I wanted.

Engine is eating oil but otherwise running fine, however the radiator has a leaky center tube or two which has been kept under control with 'stop leak'. Until that is dealt with, no track time.

The tube color pattern is very interesting. I haven't had a chance to pull the spark plugs - hopefully this weekend or upcoming week. There were a couple of weeks with the WBO2 but thelogger went flakey due to wiring, and haven't had a chance since to reinstall.

Darkest coloration is on numbers 3, 7 and 6,8.
Dual plane intake, LD340. Upper plenum is driver side and supplies 1,7, 4,6
IMG_1302-r.jpg
MVC-660F.JPG
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Re: 340 Chrysler Street Header Questions

Post by wyrmrider »

On the AMC we ended up welding extensively, taking two heads to make one etc
Mopar question
What's the best spread bore manifold for the small port LA heads 318 with 318 non 360 heads
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Re: 340 Chrysler Street Heade... now 318 intake Q

Post by Mattax »

wyrmrider wrote:What's the best spread bore manifold for the small port LA heads 318 with 318 non 360 heads
Don't know first hand, but my go to references would be:
For drag racing, the Direct Connection recommendations which you probably have.
Also Paul Cesarine used to post a bunch of info from his days of testing on FABO
for example: Getting the Intake on Intake Manifolds, mostly 340/360 but some 318
and 273 Mopar Intakes 'General Information'
For vintage road racing, I know one person doing well with an LD4B, but hasn't tried a lot of combos. I'm not sure how well the LD4B will accept a spreadbore; ;the LD340 can be and was done for drag racing, although there's not much room for error). I'd like to see how the Holley Street Dominator (later renamed Contender IIRC) compares against the dual planes over a wide rpm range. It does accept a spreadbore, and even with fat spacer allows plenty of hood clearence for a decent air cleaner assembly height.
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Re: 340 Chrysler Street Header Questions

Post by wyrmrider »

Thanks
Mattax
stock 318 one owner 69 C body Polara Coupe, Auto trans cruz control to carb
current 2 bbl is worn out
time to hit some swap meets
I have scads of TQs, some AVS
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Re: 340 Chrysler Street Header Questions

Post by Mattax »

Wyrmrider. Factory 4bbl 318 cast iron might serve well for that purpose, no?

Randy, I met Brian through a turbo Dodge guy that happens to have the same name as one of Calvin's customers. Started a conversation and he sent me some pictures of Brian's work and that was enough to convince me to talk with him. I am glad he agreed to take it on. I wish I had back to back data but with the radiator weeping and my work schedule its not going on any sort of track or dyno for at least a couple of months.

Next time back, I hope to have a chance to install a fresh set of plugs. All of these have been on the car for quite a while, except one which may be slightly fresher. One disappointment was that one all the wire attachment nubs were loose. I recall this set came out of the box tight enough they didn't seem like they needed to be tightened like the old days. (champion RN9Y C)
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Re: 340 Chrysler Street Header Questions

Post by wyrmrider »

If I remember correctly the factory 318 4bbl - at least in the later years came with the larger port 360 type heads
the links provided previously show some manifolds for the smaller port 318 heads
turns out these heads are going to need guides
and I have several 360 heads with guides and seats but the compression would suck
so maybe some magnum heads or a complete magnum take out is the answer
in cold weather or at high altitude the 2bbl is a bitch
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Re: 340 Chrysler Street Header Questions

Post by Mattax »

exhausted wrote: Fri Sep 02, 2016 11:17 pm How does it run?
To add some data to my earlier answer.
In the quarter mile, went from 14.3 98 mph (before) to 13.3 103.8 mph (after)
I know there's at least another .1 in ET between better driving and tuning.
The air was pretty good - subjective evaluation there but cars were breaking out of their dial in.
Unfortunately 1 or 2 passes per night is not much fun or good use of time.

Differences between before and after.
340 manifolds to headers (subject of this thread)
3" X-pipe about 40" back to H pipe at 20"from merge. (also covered in this thread)
Accurate mufflers 2.25-2.5" to Magnaflow 2.5" mufflers. Same tailpipes. (project begun to improve the muffler to tailpipe connection)
Plus Tuning steps,
a. rework of the timing advance,
b. On carb lower and reduce the secondary idle feed restriction
c. Also reduce the secondary HSAB.

What I can do to improve:
Better driving.
Work/test shift points.
Restrict primary PVCR
Experiment with faster secondary opening.

However I spend most of the recreational time with car autocrossing, so it may be a while to get back to the strip.
Image Image
.2 off the 60' is probably mostly timing changes. Going down the track I have to think its a combination of everything.
All season radials - nothing sticky other than what the racers have left on the concrete.
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