tri-y, long tubes or manifolds?

Hi guys, i would like your advice on what headers to use for my car.
I've recently completed restoration on a '67 fastback with a-code 289. I rebuild the engine with 4.020" hyper pistons, ported the heads and installed hardened valve seats, added roller tip rockers and a 204/214@.050" cam.
Performance has been very underwhelming so far. I guess this mostly has to do with the 4300 autolite carb, which is a b*tch to tune (like everybody warned me), and the stock single exhaust.
As the fastback will be a councours driven car, I'm stuck with the 4300 carb, which I might have rebuild by Pony Carbs.
I plan on replacing the exhaust with a stock style dual exhaust system, either 2"or 2.25". I'm still not sure on wether or not to use headers (which will be the only deviation from stock I'll allow myself) and what type.
I had my hart set on ceramic coated tri-y headers from thorley (www.thorleyheaders.com) as I feel I will need all the torque I can get, but they are $490.99 from Summit. I could spring for the chromed ones (329,95), but I could get ceramic coated Hedman 4 in 1's for less. What to do? What kind of difference in performance will I see between headers and the stock manifolds anyway?

TIA

I read something once (think it was in the tech section of this web site) that the typical replacement pistons being peddled for 289 / 302's results in a half-point compression drop due to a slightly lower top of piston height. You have to check the TDC of the piston to make sure it's not sitting too low below the block deck surface.
http://66.96.130.106/members/archive...r/index2.shtml

Also, underwhelming performance comes from underwhelming camshafts. Not sure where that camshaft falls in the 'performance' profile...? Lift numbers?

But, even so I'd still recommend the dual exhaust and tri-y headers. You will be able to feel the difference. I'd probably try to shop the headers in person first so I could look at the quality & collector design near the last collector. Some of the brands are not very good down there regardless of nickel or ceramic plated. I'd probably stick with 2" for your engine, but 2-1/4 would probably help the top-end.

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'67 Mustang fastback / 5.0 EFI / AOD / TCP r&p

<font size=-1>[ This Message was edited by: kewolfe on 10/5/03 2:06am ]</font>

<font size=-1>[ This Message was edited by: kewolfe on 10/5/03 2:12am ]</font>

Hi kewolfe,

Thanks for your reply. It sounds like 2" pipes and quality tri y's would be fine for my application.

The piston height was identical to the original pistons, altough we lost a bit of compression because the much larger valve reliefs.

The cam is from Clevite, but it is the same as the Edelbrock Performer cam and the Summit SUM-3600 cam for instance. It has .448/.472 valve lift, and a 112 degree lobe seperation.
It's a very mild cam, so I wasn't expecting miracles, but the car is performing noticably worse then the propane run c-code 289 in my '66 hardtop which is completely stock except for a pair of cheap tri-y's and 2" dual exhausts.
The car will be used for cruising 90% of the time, so it will spend most of it's life between 1500-3000rpm. I don't plan on running the engine beyond 5500rpm at all, so the cam seemed like a good choice, just like dual exhausts and a pair of tri-y's.

I just got Bob Mannels book 'Mustang &amp; Ford Small
Block V8'in the mail today. He lists 4 Ford technical service bulletins on the 4300 carb, all about reducing bogging, stalling and hesitation on acceleration. I'll take a look next week to see if any of these adjustments were made to my carb.

Cam should be fine for what you're shooting for. Tri-y's make good torque, a little small tubed for higher rpm help, so that'll work, too. Make sure you use an H-pipe, again, for torque down low. Get the headers installed, re-tune the carb and you'll be very suprised at the result.[img]/phpBB/images/smiles/icon_tup.gif[/img]
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