"New" GT-40P heads purchased, what now?

You guys can stop trying to convince me to back off (the ones that are trying). Like I said, I could put these on today and drive off with significant increases in performance. What I have purchased is what I want to consider a "project in themselves". I take pride in saying "I bought stock GT40Ps, did my own mild porting and polishing job, milled .025" off the bottom, found headers that allow spark plug clearance, and now I have .5 more compression and XX more horsepower!"

Look Ma! I did it myself.

Anyone can buy a set of Edelbrock RPMs with the kit and have 325 HP. But there is no fun, heartbreak, broken fingers, and cut knuckles involved with that. Then all you have is an engine comparable to a later model Mustang GT.

This is my Maverick, and I am going to build it.

For all the encouragers out there, thanks for all the guidance. I agree that I do not know ALL the things I need to know. If I did, I would not be typing on this website every day. What I don't know, I gather and learn from the knowledge of ALL OF YOU GUYS!

 

Busted knuckles

Well, I can do that changing the oil filter, so I could certainly do it putting any kind of head on. Go Scott, I'm expecting closer to 400hp(crank) out of a 289 with my P's. I've said it before, but it's been done to a 302 with original 289 heads with less flow and less compression than I'll have.

 

The replies are starting to get into other things.
My point is he will not benifit from those heads with all the chnages that need to be done for an old stock block setup, period.
I have all the flow data also on most all the various heads so there is no snow blowing here.
He certinaly free to do whatever he wants -foolish or not.

 

Ok

I'll agree a bit, the heads need a lot of other stuff to make them REALLY useful. Which is true of any head. Since he's looking to the future, not necessarily doing it all now, heads, especially ported, and headers will do some good and he can add the other stuff whenever, Afr 185's would be the same story, but a lot more money, and probably would not work all that well without all the other stuff added immediately. If he just wanted to slap a set of heads on and get 20 more hp and be done then ANY older head with a decent(small) sized chamber, ported, would work, after he paid for the hardened seats that is, which he doesn't have to do with the P's.

 

If I slap these heads on my current engine, what hp gains would I get, with and without headers?

I recognize that without headers, these are likely not much better than stock heads, but just out of curiosity.

Has anyone done this to verify how much the headers free things up?

 

It's very hard to give an estimate on power increase.
In the end it is all guessing and bench dyno session.
No two folks will agree on anything, and fact is they are probably all wrong.

All I will say is it's a fact that the best thing you can do for your engine is headers.
Don't even consider running manifolds now, or with your P heads...
Headers are good for HP, TQ, and fuel economy.
No matter what you do, put headers.

Good luck
Dave

 

Yeah.

Don't even think without headers.

 

Scoop, you keep on keepin' on man. I like your attitude.

 

Thanks for all the encouragement guys. I am on e-bay right now looking for headers.

I think I will stick with the cheaper Hooker 6901s, even with the plug issues. I did some research, and the long tubes are looking more promising than the tri-Ys. I may have to run a U-turn to hook up my side pipes for a while, but when the pipes rust away, I will swap over to Flowmasters (TL-you win ).

I just cannot justify putting that much pipe under my car, zig-zagging around to get to the sidepipes. Unless things look different when the Headers are installed.

Anyone have some 6901s they want to sell?