273 manifolds

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L8RG8R

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Hi all
I have a stock 360 in my 65 dart with 273 ex manifolds how much hp can these manifolds flow at what point will they have to go?
 
They really screw the flow up because the ports are larger than the manifolds and this makes turbulance and impedes the flow of the exhaust at a critical point. There is a way to use 340 manifolds . A few guys I know changed the coupling on the steering colume to the box with a Jorgensens? swivel and got the clearance they needed to use the 340 manifolds. The 68 348 A body manifolds are the ones to use . Otherwise get the sawsall out and put in headers
 
so headers or 68 340 manifolds and those are it for the exhast options well if I got to cut up my inner fender wells I might as well go big block oh well more cubes is better and to much cubes is great
 
I've been running the stock 273 exhaust mainfolds on my warmed over 360 for about 15 years now, and although they're obviously not the best flowing system around, they should be just fine on a stock 360. Mine is a 66 Valiant so, same weight etc, as yours, and I've blown away many an unsuspecting off-brand street hero with just my old 273 manifolds and a 2 1/4" dual exhaust system. :) Sure beats cutting up my inner fenders.
 
The best flowing factory small block manifolds are the 92/93 magnum engine manifolds. The outlets will interfere on some vehicles so you need to check. Another option are block hugger headers, not as effective as long tube headers but not cutting of the car to install.
 
Dave, I'm not sure if either the magnum manifolds or the block hugger headers will actually fit on the pre-67 Darts/Valiants. I've read a lot about how they should fit, but haven't actually seen pictures of, or heard of anyone that's actually gotten them to work. This time around I'm going to try and build a set of headers of some type for my application because I hope to get my 360 to the 400 flywheel HP level, and by that point, the 273 manifolds will obviously be a major restriction and HP limiter. Not exactly what I'll be looking for after building a good street engine. :)
 
Sid, Don't know if I kept them but I had a set of magnum manifolds from a 5.2. If you want them, pay the shipping and there yours. I will look this weekend to see if I tossed them in the "don't want but somebody might" pile. These aren't the good 92/93 ones (they are from a 99 engine) but at least you can figure out if they will work.

The shipping shouldn't be two bad, I sent a pair of heads 1/2 way across the country for $50 so I would expect <$20. If you want to figure the cost I live in zip 02359 and FEDEX Ground seems always be cheaper than UPS.
 
Dave, sorry it took so long to get back to you - honey doo list weekend setting up new furniture. :) I have a buddy who has a scrap yard just a few miles from me and he says he has some of those manifolds that I can use to do a mock-up when I get everything back together again. I really appreciate the offer, but I'll pass in case someone else can use them.
 
Hey dgc333 and L8rG8r I saw a guy at the fall fling in LA a month ago and he had a 340 6-pack with 92 magnum exhaust manifolds in a 65 Barracuda. Beautiful car. I hope to see him again this spring. I did not ask him about the driver's side and the fitment issues (universal joint or whatever). I know the passengers side is no biggy and the maifolds dump more towards the rear = better flow. The port sizes are much better on the 92/93. This guy said he got really good flow from these manifolds. I guess the objective is not to cut the fenders. I want to avoid this too on my 66 Valiant 340. Next option is Doug's headers $$$$ 1000.00 bucks. TTI still has not worked out the early a-bodies yet. Darn.
 
spitfires are around if ya look hard enuff... no cutting shorites, I'm runnin about 400 hp thru them now with no problems. (12.80 @108) with 3.23's
 
One guy I talked to that used Durango/Dakota stock manifolds had to shim his engine mount.

Actually, here's his email....

98-02 Durango/Dakota (approximate dates, I am not exactly sure) 318/360 exhaust manifolds will fit. They are higher flow than the original 273's (which I liken to pooping through a cocktail straw) or the 340 types. The benefits are a balanced flow between the manifolds. The stock 273 drivers side manifold is highly restrictive due to several harsh curves and the compressed area where it goes around the starter. 2 1/4 to 2 1/2 inch collectors will bolt right up.

The only mods necessary are of course new down pipes, different length mounting bolts and possibly you might have to shim the motor mounts as much as 1/4" to safely clear the steering box. Mine cleared no problem. Power steering will not work though. Some people have had to dimple about an inch at the point where the firewall transitions to the floorboards on the passenger side to allow the down pipe to clear without heat transfer problems. I simply spliced in a pipe with a 30 degree curve off of a donor car.
I have a 4 speed manual so clearance was tight in the torque shaft (z-bar) area, so I routed the pipe OVER and down past the starter . Otherwise I would have had to oval the pipe to pass between the block and starter...... which would have restricted the flow.
These manifolds are plentiful on Ebay. I paid $35 for my pair.

Clearance, although tight is no where as tight as it appears here. The steering box clears by at least 3/8 an inch at the tightest point. (Below the center ports). The manifold does not touch the steering shaft, even though it looks like it. I also ground a little off the steering U joint just to be safe. Oh, three on the tree will not work either.

Spitfires are problematic and the new versions don't fit right, if you can even find them. One guy I talked with had them and they were leaking at some of the welds. I'm going with the 340 manifolds, although they are really expensive, I've got one half and got a lead on the other half for a decent price. See my other post in another topic about this. This guy here ->http://www.ultrajosh.com/resources/ has done the 340 thing, click on exhaust in his left menu. Or go here ->http://www.ultrajosh.com/myshop.htm to see photos.

340 HP Manifolds
 
HP.jpg
 
Hey 65s, thanks for the info and photo. That's the most detailed description I've heard yet from someone who has actually done this swap. Definitely worth a few horses over the stock 273 manifolds. :)
 
It's not that hard to make the 340 manifolds fit! I did attempt a set of Magnum manifolds on my car, that wasn't happening! :drinkers:
 
65s said:
I'm going with the 340 manifolds, although they are really expensive, I've got one half and got a lead on the other half for a decent price. See my other post in another topic about this. This guy here ->http://www.ultrajosh.com/resources/ has done the 340 thing, click on exhaust in his left menu. Or go here ->http://www.ultrajosh.com/myshop.htm to see photos.

340 HP Manifolds
Click to expand...


Please note, my post above is talking about two different sets of 340 manifolds. The Durango/Dakota manifolds are what I started talking about first when I quoted an aquaintence. I don't really know anything about them. The second ones I'm talking about are shown in the photo, they're the High Performance 340 ones that cost a lot, they're the ones I have and I'm planning on using, just like UltraJosh in the links provided.
 
I used a set ov 1969 Dart 340 manifolds, and machined the flange(Manifold to head surface) at a 7* angle, to tuck them closer to tha block...If U use power steering, U will have to grind steering box and the manifold at the pipe flange....if U use std steering, U good to go!!....I had a 380HP 360 then, but now have a warmed up 318...Heres a pic wit P/B booster and P/S!!

66wagon3.jpg
 
Hmm,the performance gains for the 340 manifolds
don't seem so great,for the money I see them sell for.:(

16 hp increase using the TTI headers,I wonder how much the
"new 63-66 early a-body" headers will be worth.... Hmm.
{Also :( How much will they cost too.}


http://moparmusclemagazine.com/techarticles/155_0307_exhaust/

Exhaust Blowout on a Mopar 300hp Crate
Running the numbers on a mild 360

For our baseline test, we fitted the 360 with the lowest of exhaust low, a set of stock small-passage 318 iron exhaust manifolds. Bolted to the manifolds was a set of 21/4-inch head pipe extensions 24 inches long. So equipped, the 360 put out a respect- able 311 hp at 4,600 rpm and 403 lb-ft of torque.

We moved up a notch from the early 318 iron manifolds to late 360 iron log-style manifolds. The 360 manifolds are nothing to look at, but the internal passages and outlet are significantly larger than those of the 318 pieces. Power was up a little, moving to 314 hp and 407.1 lb-ft
'

Our final test of factory iron was a set of rare and expensive early 340 high-performance manifolds. With the 340 exhaust, the 360 inched up to 315 hp and 409.1 lb-ft of torque, which represented very little gain on this engine.

The layout of TTI's headers is unique, with none of the low-hanging tubes of the other designs and ample clearance for the plug wires up top. Past experience has shown they have excellent chassis fit. Power output with the tti's was the best of all the systems we tested, clearing 327 hp and producing a healthy 425.5 lb-ft of torque.
 
You forgot to mention that the engine is only rated at 300 HP to start with so I don't think this motor is powerful enough to really exploit the benefits of any kind of header or 340 manifold.

Even with tube headers they only got 322 hp,(and the headers didn't fit properly) and with Hooker headers 319 hp, then with TTI headers they got 327 hp. Finally with Super Competition racing headers they only got 319 hp. I mean, except for the 340 manifolds, all the headers require cutting up your car, so unless you want to cut up your car (not for me thanks) the 340's are not a bad choice. But I can see what you're saying, you might as well stick with the 318 manifolds, if you're using their 300 hp motor. What if you've got a more powerful motor like a 400 hp motor?

How much better are the 318 manifolds vs. let's say my old '65 273 manifolds?
 
65s said:
You forgot to mention that the engine is only rated at 300 HP to start with so I don't think this motor is powerful enough to really exploit the benefits of any kind of header or 340 manifold.

Even with tube headers they only got 322 hp,(and the headers didn't fit properly) and with Hooker headers 319 hp, then with TTI headers they got 327 hp. Finally with Super Competition racing headers they only got 319 hp. I mean, except for the 340 manifolds, all the headers require cutting up your car, so unless you want to cut up your car (not for me thanks) the 340's are not a bad choice. But I can see what you're saying, you might as well stick with the 318 manifolds, if you're using their 300 hp motor. What if you've got a more powerful motor like a 400 hp motor?

How much better are the 318 manifolds vs. let's say my old '65 273 manifolds?
Click to expand...

Good question Neil,
I would quesstimate 5-8 hp for our 273 64-66 manifolds,with dual exhaust.

I would like to see them redo that test,with the 273 manifolds,and with
a "340" or so cam.

I do know if you put the 340 in your car,you will make more power with
the AVS,than an AFB LOL,so the carb you bought will come in handy.

I quess my one point was,is 15 hp worth $500+ ??
I would bet that if you use stock type mufflers,that they will be more of a restriction,than the stock manifolds,so at least use "turbo" mufflers.

I know my Valiant woke up,when i took the car to Midas,and had the
duals added with Dynomax,Super Turbo mufflers,it is a 2 1/4" system.

Merry Christmas to all!!
 
i used '73 ish manifolds from a 318 in a duster. i just port matched the manifolds to the 360 port size and it made a difference coming from 273 manifolds. you'll need to change the head pipes but they are cheap, avaliable and they fit. they should be fine for that power range.
 
Has anyone seen a dyno test on the new TTI early abody headers?

That would be a cool test, 273 early manifolds,
vs the new TTI headers,
especially, if they also tested the "Spitfires" too. :)
 
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