Exhaust Manifolds...

I am building a mild street 302 and I really dont want to go the header route. I would like to keep the stock exhaust manifolds but I am wondering how bad this will affect performance. This will be a daily driver but taken to the track on occasion. Does anyone know of any stock exhaust manifolds that will flow better that will be a somewhat direct bolt in swap (other than changing the exhaust pipes) It is a factory 1977, 302, PS, PB, Auto. (will be 4 spd before long). Thanks again.

JP

 

desktop dyno 2000

I used desk top dyno, on my engine I go from 373 hp, 431 ft lbs with large tube headers to 312 hp, 389 ft lbs
for a loss of 61 hp and 42 ft lbs

Desktop dyno isnt perfect but at you get an idea of the change.

 

Wow..

That much of a drop!!! How about on a 1970 351C 4V?? I have been playing with the idea of putting headers on the Eliminator also.

Any suggestions for headers on the 302 with Auto? Best fit preferable.

JP

 

In my opinion you have just as much room, if not more, when it comes to changing spark plugs with headers. I have dealt with headers ever since I got my car and then I put plugs in a 77' with exhaust manifolds and the header car was easier.
The bad thing with headers is making sure you have everything away from them, but I would have headers over the stock stuff anyday.
IMO.

 

351C V4

A quick check with desktop dyno showed about 70 hp gain going to long tube headers over stock exhaust.

 

If you have floor shift, the Heddmon shorties would be the a better choice at about $110 over stock irons.

 

If you still have the column shift, headers will be a problem.

One of the Ford mags built a 347 stroker motor for a 64 Fairlane and put the usual goodies in like cam and aluminum heads. They ran it through K manifolds, which are very similar to 351w manifolds, and they also flow better than the 302 standard manifolds. Whne they switched to headers, they gained over 100 rear wheel horsepower.

Unfortunately, even the K manifolds won't fit.

 

Stock exhaust manifolds work just fine on a daily-driver and do not radiate nearly as much destructive heat under the hood as headers do. The power advantage of headers really only comes into effect over 3000 RPM...

While it's a fact that headers will always out-flow manifolds, it really depends on how radically your engine is built as to whether they're worth the expense and hassle...

 

The engine will have a holley 600, 4bbl intake, decent cam (not sure which yet, recommendations taken), flat top pistons, minor head work, roller rockers and gasket matching, windage tray, better ignition system, electric fan, 3.00 gears, auto (for now). It sounds like headers on this might be worth it.

JP

 

Hooker 6901s are said to fit perfectly. Theyre long tube headers, not shortys

-Todd

 

Depending on how much time you have on your hands and how much you like grinding you could port out the manifolds and improve the performance, but headers are always the best performance choice!!

 

What compression ratio will it have , do you plan to put screwin studs and guide plates? Do you want a mechanical or hydraulic cam and what do you have for a torque converter ?

Richard:confused:

 

Ok...lets see. It will be about 9.4 on compression. Hydraulic cam, yes, screw in studs and guide plates. Probably the stock torque converter for now. Only going to run about 6000 rpms...maybe more depending on if I am loosing!

JP

 

Do you really gain much porting exhaust manifolds? Although I guess any would help.

 

If you plan on racing at the track on weekends then I would recommend a 2800+ torque converter . The camshaft would be a Lunati SP Hydraulic series #638-30613 dual patern to help the exhaust side , 280/290 duration 523/555 lift with RPM range 2600/6800 . This is a package that would work quite well of course you would need a valvespring upgrade for this lift .
This is only a sugestion to think about , anyone have any other package?

Richard