stock manifold down

[johnbeck]

I'm close to getting my 302 together. I recently viewed the April 2020 Westtech Performance Group video of a dyno test of a stock 5.0. The initial finding stated a stock upgrade with shortie headers is "worth almost nothing". Swapping out shortie to long headers went from 252hp to 261hp - nine hp.(less than 4percent). Torque went from 306 to 321ft.lbs. -15ft.lbs.(an increase of just under 5percent). The bottom line is I don't think I want to trade off access to the drive train for that gain. What I'd like is finding the best performing exhaust from the manifolds back, probably 2 into 1, exiting behind the passenger's rear wheel. I heard Magnaflow has a Hush model muffler- any reviews? What size exhaust pipes? Thanks I know by not using headers after stepping up to aluminum heads and a mild performance cam seems foolish to many but I don't think the performance difference will be that significant in my daily driving at 1500 to 3500 rpm. Your thoughts and suggestions are greatly appreciated.

 

[Timmy390]

Long tube headers build a ton of power in the mid to high RPM range.

Shorty headers perform best in the idle to mid-RPM range.

Tim

 

[jckkys]

I agree headers are a waste of time and money. The added heat in the engine compartment, fire wall, and floor erase the tiny advantage in full throttle power. Any grownup knows full throttle high RPM operation is seen only a small percentage of driving a non race vehicle.

 

[Timmy390]

I agree headers are a waste of time and money

But all the cool kids have them.....and Cherry Bombs......;D

Tim

 

[Broncobowsher]

I've taken headers off and got a set of fresh repop 289 K-code manifolds and put them on a 351W. Spent a few hours port matching them to the aluminum Trickflow heads. Maybe you would see a change on a dyno? But you can't tell the difference on the street. That was what was on it when I sold it.

 

[SHX669]

I agree that on a stock motor headers aren't worth the issues they cause.
Only as added interesting info - lol - in the late 1960s Ford added HP parts to 289/302s in stages and dynoed the results as they went. These were car motors of that era so there could be a difference in compression and etc . vs later EB motors also Ford was testing for Horsepower as in drag racing . They installed the parts in order of horsepower gains and ease of installation
600cfm carb and aluminum intake - 31 horsepower gain
Hyd version of 289 HP cam - another 40 HP
Long tube Headers - added 15 hp to the above combo
Next step was a head change in those days the were 351w heads - added another 32 HP
Then they put GT 40 valves in those heads and gained 7 more HP
Next step was replace hyd cam with a solid lifter cam - 19 HP over the hyd version.
So for CAR motors in the mid 1960s they determined in order - intake and carb - cam shaft - headers ( after intake and cam change)

 

[SteveL]

Never checked my hp or torque specs but I know going from stock manifolds to long tube headers my mileage improved with my 351w. My dad's place is 200 miles round trip. With the stock manifolds I would have to stop for gas on my way home. With the headers I could do the trip and have some to spare.

 

[johnbeck]

I have the 600cfm edelbrock carb. and aluminum manifold, AFR 165 heads and just installed the 289hp hydraulic cam. I worked hard and was thrifty. I'm think of trying stock manifolds and if that doesn't work throw them away and go long headers. Any guidance for what size exhaust pipe from manifold to muffler to exhaust pipe behind pass. rear wheel? Thanks

 

[jckkys]

The best guidance I can provide is to save the OE exhaust manifolds for sale to a restorer. I would also remind you that full throttle is a tiny percentage of driving. All the listed "improvements" are for racing. I also have the little Ford performance manual that came out in the mid 60s. I was a kid then, who only cared about HP. The '66 Bronco Roadsters changed that.

 

[DirtDonk]

I would just go with the common 2.25 inch tubing for the first section John. Then probably 2.5" from the muffler out to the back.
This is assuming either a Y-pipe junction ahead of the muffler, or a 2-into-1 muffler.

The reason I say 2.5 out is that it's not overkill and your other mods all support the larger tubing. You do not need 3" however I would not think.
You've got heads, cam and carburetor, so you don't want to go too small on the already low volume exhaust segment of your engine. Even with stock exhaust manifolds I see no reason to totally choke off the exhaust.
And this way you're ready for headers should you ever decide to go that way after all.

And speaking of upgrading, with what you've done already, and I think we talked about this in another thread recently, I would certainly think that the HP289 exhaust manifolds would be your best compromise between performance, and all the other things that make stock manifolds so desirable.
Look up Broncobowsher's thread on the subject and see if it meets with your needs/hopes.

Paul

 

[johnbeck]

Thanks Paul. I have to choose manifold or headers soon. If I go long headers there's a number of those to review. Performance(MY only reason to consider them), quality, ease of installation, access to other components, sound- good or bad. Thanks again.