So I have a 351W in my 84 F250 that has a stroke kit on its way. I have a guy that owes me a favor and is willing to cut me a deal on port and polishing my heads. This truck is going to get a super charger later and such. the truck is going to be a mean rice killer and will still see some dirt. What intake and exhaust size would be good. What specs should I make these heads?

 

what heads are you starting with? remember when supercharging a motor you need to keep compression low

 

The stock 84 351W heads. I just want these heads to make this stroked engine scream. Ill worry about change when I get the money for the supercharger.

 

What CI are you going to? Your probably going to need some 2.02/1.60's especially if you are getting some port work done, concentrate on the exhaust ports if you plan on supercharging, the intakes are not as important in that case.

 

Im going to stroke to a 393 with a final 11:1 compression if the stock heads can take it. Ill buy new heads and pistons when I get the money for the charger.

 

with that comp you can forget about SC that motor. and a change to do so would be costly because you would have to change pistons, heads etc... but if you got that kinda flow its all good.
if you shoot for more in the 9.5 range you could run that on pump gas much better and that could still run a sc on mild boost with no changes. 11.1 is high man and will give you some power but the stroker will already produce some great numbers with out that high of compression. its just not necessary

 

Oh, I know a guy taht runs his mustang in competitions and he was willing to give em soem pistons. I kinda forgot about the gas thing. So Ill just get the normal 9:1. I just want to get this truck to kill. Its not oging to see alot of high way miles just my DD around town and such and to kill ricers. Thats what this engine is going to be doing. Im building this truck to roll up destroy some ricers egos and go home.

 

You won't make big power with stock heads, ported or not.

Look into some better heads. Maybe some world products heads and have those ported.

Your compression depends on what psi you're going to run with the s/c. If around 6-8psi than 9-9.5:1 would be ok. If running 9-15psi I'd look more down towards 8-8.5:1.

 

Im poor right now and the port job is free. So its a no brainer on getting them done to play with till I get the money for some good heads.

 

Well...

The problem is that 393 cubic inches needs a lot of air. I assume you're running a carb.

How good is your free port job?

Those stock 84 heads are probably the worst head or very close to the worst head ever put on these engines. They are probably a low compression emissions head.

Find out what heads are on it (stamped on it)...if they happen to be E7TEs than you can make those flow alright with a good port job but they still stink.

To be perfectly honest, all ford heads on these engines don't flow worth of crap and arn't worth squat. You can get stock heads to flow enough for a warmed up 302, but when you're talking 393 ci or in some cases up to 427ci, it's just simply not enough air.

You don't want 393ci that's going to put out the same power as a 302.

Typically, in this situation...I would advise that the person just simply hold off on the engine build until they can afford good heads for it. You typically just open a can of worms when you try and mess around with putting XYZ on it and trying to switch it later on...ends up in lost money.

Does the porter have access to a flow bench? It would be pretty important to check the before/after flow #s.

The E7TEs are pretty close to the best stock heads and they flow about 165 on the intake and 114 on the exhaust (at .500 lift).

For compairson, the smaller head that most people put on a 393 runs about 265 on the intake and 185 on the exhaust (.500 lift).

Racers looking for all out performance, non-street use, would run 300-330ish on the intake and 230-240 on the exhaust.

This is basically how much air the head can flow - if you can't get good enough flow numbers out of whatever head you're going to use - you won't make power out of it.

According to desktop dyno, running an E7TE powerhead and appropriate cam/intake, it tends to run out of steam after 3800-4000 rpm. It's basically choking the engine to where it can't breathe and make power.

RPM HP TQ
2000 165 433
2500 208 436
3000 250 437
3500 292 438
4000 327 429
4500 351 410
5000 358 376
5500 342 327
6000 306 267

Those were the #'s on it...notice how the tq drops right off after about 3800 rpm, but the hp goes to about 5000 rpm. That stinks, that means that your pretty much going in different directions. It makes nice low end tq, but the hp isn't low with it...so as you get up to 4000+ rpm, the tq drops off and you start loosing power despite the higher hp figures. Now if the HP figures were lower (maybe in this case the rest of the components could of been picked for a better powerband) and in the same range as the tq it wouldn't be that bad but you're still only using 3000 rpm or so...you won't make power over 4000. (this is N/A).

The powerhead is basically a ported E7TE, using 1.9/1.6 valves vs the stock 1.78/1.48 valves. It will do about 215 on the intake and 175 on the exhaust.

The combustion chamber cc's on the E7TEs is around 125 or so, the heads I refered to run about 185-225cc's. My heads are 175cc's.

If you were to use a small head on it, you'd need a cam, intake, and exhaust to match it. Then, if you went and wanted to swap heads to something big, you'd need to revamp the entire thing and do everything all over again in order for it to work right. You can't just simply swap to a big head later on.

I've been through this before...I've tried to do a similar thing...I started off with a 187hp 393.

If your porter guy has access to a machine shop, find out if you can have a 400M crank ground down to fit the 351 block - if you can do it for cheap it's a great way to save $200+ on the crank. You can run basic 351 rods and 302 pistons too. The shortblock can be done for pretty cheap money when you put into perspective what's being done.

You can run a supercharger, but those are expensive. Do your homework. They run about 2500-3500 - and the one you'd want for your truck is about 3300 (kb twin screw). A set of AFR185s is $1300.

I think I'm going to run AFR185s for heads, a trick flow intake, and custom exhaust. Might go custom cam unless I can find a good off the shelf cam for it.

The AFRs flow about 260/180 for int/exh - the trick flow intake runs about 300 per cylinder and is capable of 500+hp. This combo would run at around 480-500hp and around 500 tq (ballpark). Now that is a ricer killer.

 

and do it all on pump gas

listen to justin, he has been battling this for awhile now

 

I say skip the supercharger.

Other opinions vary, but I don't feel that putting a supercharger on an engine that doesn't run real strong N/A is a waste.

Like putting a supercharger on a stock 351...nawwww....only real reason to do that would be if the engine is already in great shape and you're looking for a quick/easy power. Unfortunately, most of us don't have a nearly fresh 351 to work with and they're being rebuilt anyway. So...in that case...you'd be better off building an N/A motor vs a stock (or near stock) rebuilt engine and supercharger combo.

A well done 393 N/A would beat the pants off a supercharged normal 351, or probably even a s/c'd 393 with a low flowing h/c/i choice.

I'd be willing to bet you could do better N/A in your situation than with a supercharger.

Unless of coarse you can get a supercharger for a steal. That 3000 bucks can buy a lot of performance parts.

 

The guy that will do my heads owns a machine shop. I fixed his network when it went down he offered to pay I told him just let me get some mahcine work doena dn he said anything so Ive asked and he will do an engine for me. The stroke kit has arrived its in my floor in my room as we speak (yes my room Im only 17). Ill hold off on the head work till I can get the heads that would do my job. Ive been looking at cams and he said he would get a custom one done for me just gotta get the numbers. Ive got a 750 carb waiting with a trickflow intake and custom bent headers. But thanks so much for the info Ill keep this around till D day and Ill probably post again when it gets time.