347 horsepower estimate

Olivethefet

I will own your nuts! LOL
5 Year Member
May 17, 2018
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Enterprise AL
I know there are tons of threads on here talking about this subject so I'll apologize for this one up front. The car I've been working on the past several months has a 347 in it. I didnt put it together and the guy I bought it from couldn't provide much technical info. I'm in the process of sorting out the suspension and some basic engine issues at the moment. I'm hoping to poll the community with the little info I have just to get an idea of what I have going on now so I can plan a better or improved build in the future.

Current info that I have.
Displacement is 347, can't verify so just gotta go with it.
BBK SSI intake from a few years back.
BBK fuel rail and pressure regulator.
Ford 24# injectors.
Eldelbrock 75mm throttle body.
80mm ford mass air meter.
SVO X302 heads. I dont know if any work has been done to them.
Ford SVO B351 1.60 rockers.
MSD 6AL ignition.
MSD pro bullit distributor. I already had to rebuild the internals.
BBK long tube headers.

I dont know what cam is in it. I have the timing cover off at the moment. If I pull the timing gear off would the info be stamped on the end?

I also dont know what fuel pump is in it.

When I had the car running early this year it ran good but it wasn't what I would call a street beast!

Any educated guesses are welcome. I'm also open to upgrade suggestions. My goal is to make somewhere around 450 at the crank N/A. I figure the intake will go at some point and I know the injectors will need to be upgraded.
 
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Not sure if those heads will support 450 horsepower, but should be somewhere close close to 400 at the crank depending on the cam I would think. The cam is the real factor. I know Trickflow cams have stamps on the end. Custom cams may or may not depending on the grinder. Sure wouldn’t hurt to look since you’re right there. The only negative I heard about that intake is fitment with fuel injectors. Don’t remember hearing many complaints about power delivery if you could get it all sealed up. I could be wrong there though, never went looking for info on it purposely.
 
Without knowing the cam it’s pretty tough to guess hp. Could be anything in there.

Those heads pretty much flow what iron gt40s do. Unless they’re worked over I’d be shocked if it put down north of 275hp to the wheels thru a t5.

Cam should have an engraving on the end of it. Get the numbers and google em.

I’d ditch that bbk intake and get a trickflow or a Systemax also couldn’t hurt to confirm which fuel pump is in it. Dropping the tank will take you 5 mins if you have an extra set of hands.

450 crank hp is about 380 to the tire through a t5. It takes a decent combination of parts to get there.
 
Yeah, I haven't heard anything good about those heads or the intake really. It's just what was on the car when I bought it. I'll pull the timing gear off the cam and see if it has any markings on it. The T5 seems OK at the moment, so I'm not in a big hurry to replace it. Long term I want to put a T56 in it. I'm in the process of replacing all the worn suspension components out with poly bushings. Someone cut on the rear control arms to make room for the exhaust, so I'm going to replace those components with tubular ones. While I have everything out of the way I'm going to drop the tank to replace the fill line and seal. You can smell gas when the tank is full. I'll also go ahead and put in a 255 l/h fuel pump. No reason to do the job twice! Thanks again!
 
My Probe Industries 347 in my 94GT made 444HP / 458TQ at the wheels with a P.M.S. back in 2007.

347 Stroker
AFR 185 Heads
Comp Custom Cam .542 / .562 / 114 Lobe
Scorpion 1.7 Roller Rockers
Holley Systemax Intake with Ported Snout to 75MM
Edelbrock 75MM Throttle Body
Pro-M 80MM Mass Air Meter
30 Pound (Red) Injectors with Kirban Adjustable Fuel Regulator
MAC 1-3/4" Ceramic Long Tube Headers with 3" Collector
MAC 3" Prochamber
MAC 3" Cat Back with 3" Chrome Tailpipes
Full Steeda Suspension

I had those X302 FRRP Aluminum Heads N/A and also with a blower (see below). Probably not the best choice, very small valve 1.94 x 1.58, swirl chambers, castings are meh (very rough), everything just seems small. Compared to the AFR 165's it's night and day, CNC castings. The AFR 185's below on my 347 were gorgeous, didn't want to cover them. That combo is probably in the 325-365 HP range, I"m just guessing though considering you don't know all the key components like the heads, cam, etc.

Stock Vortech Supercharged 302 being pulled, 487HP / 460TQ with FRPP Aluminum X302 Heads, Crower 15511 Crower Cam, Edelbrock RPM Intake, 42 pound injectors, MAC 1-5/8 Long Tubes, 2.5" Prochamber, MAC 2.5" Cat Back.

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94 Mustang Sleeper Supercharged by jpjr501, on Flickr

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Untitled by jpjr501, on Flickr

Tucked wiring harness in the fenders, blocked off a bunch of holes and resprayed the engine bay.

42958766274_f31b16d62a_o.jpg
Untitled by jpjr501, on Flickr

The Stroker arrives at my house.

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Untitled by jpjr501, on Flickr

Installed 347 Stroker

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Untitled by jpjr501, on Flickr

At Idle video clip.


View: https://flic.kr/p/27fnZaz
 
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Awesome looking car! Thanks for all the information. I've got to ask what I'm sure is a noob questions and the answer is obvious, but what do you mean by "at the wheels with a P.M.S. back in 2007."?
 
Awesome looking car! Thanks for all the information. I've got to ask what I'm sure is a noob questions and the answer is obvious, but what do you mean by "at the wheels with a P.M.S. back in 2007."?

Awesome looking car! Thanks for all the information. I've got to ask what I'm sure is a noob questions and the answer is obvious, but what do you mean by "at the wheels with a P.M.S. back in 2007."?

Well when on a dyno it registers the horsepower your making at the wheels. Horsepower ratings on cars are rated at the flywheel so the time it goes through the transmission and driveshaft some of the horsepower is lost. Say your car made 100HP from the factory, most likely it would make 80HP at the wheels, figure 15-20% drivetrain loss.

My car had a PMS which stands for Programmable Management System. Basically it's a box that connects the computer and you can dial in everything...fuel, timing plus monitor all the sensors in the car.
 
Mine have markings on the back of the cam like this.

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You can also degree the cam and measure lift with a dial indicator and duration with the degree wheel. This will at least get you the specs.
 
Thanks for the pic. That's what I was hoping to see when I pulled the timing gear on mine. I just wanted to make sure there wasn't an extra thrust washer or something that also needed to be removed. I just put it all back together last night. I was terrified that something would happen and make the valve train shift and screw everything up! The cam is still in the car with the heads on so its under load. At some point I'll pull the motor and bust it down. It would have been nice to know the specs just for tuning and to give me a solid idea of what to expect out of the car.

I'll go ahead and ask another beginner question. Is there a way to measure any of the specs with the cam installed. Maybe from the rocker side on the heads??

Looking at pics of cam markings on line, it looks like it might be marked on the other end.
 
do you have the intake off? if you do its a simple job of loosening the rockers, removing the pushrods, then you can pull each lifter out of its bore once the spider and wishbones are removed.
Then you carfully remove the cam, use a long bolt that will thread into the cam as a handle and go slow. its not that difficult to do, and if its a roller engine the lifters can go back in anywhere... it does not wear in like a flat tappet.
 
The motor is still in the car. I'm going to pull it at some point just because I want to give it a fresh rebuild and do a HCI that will actually make better power. I'm attaching a pic I took of the car just the other night. The motor is being supported because I'm in the process of dropping the K member to change the oil pan gasket. The ONLY reason I'm doing it this way is because I'm in the middle of redoing all the front suspension and the only things on the K member are the control arms. Everything else is off the car. The gasket on the motor is one with the metal core. Anyway. While I'm in there with the motor loose I'm installing some new poly motor mounts. Thanks for the help!
20181226_212706[1].jpg
 
GT40x heads are significantly better than gt40p's or irons. With a valve job and bowl clean up they can be about almost as good as a set of tw's.
With that said, they are not for a 347 and likely never will be regardless of what is spent on them.

I think a hp rating for you is a crapshoot, it wouldn't be the first time someone was said to have a 347 and just turned out to be a stock shortblock.
And the reality is that people that slap together a bunch of mismatched parts rarely know what they are doing, so the range it could fall in is massive. Could put down 250rwhp or could lay down 325rwhp, the only way you are going to know is driving it to a dyno.
 
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I have to agree with you 100%. Until I break the engine down and actually measure everything I dont really know what I have. Since buying and starting to work on the car back in May I have come across some really shady stuff. The previous owner either doesn't know anything about the build or doesn't want to tell me the truth. Fortunately for me it doesn't matter what it is. I plan to make it what I want eventually anyway.

When I had the car on the road it pulled good and was definitely peppier than the stock car I had back in the day. I'd be confident to say its north of 225 at the wheels, but probably a stretch to say it's over 300.

Thanks for the input and honest opinion!

Good news is a shop close to where I live is putting in a dyno!
 
GT40x heads are significantly better than gt40p's or irons. With a valve job and bowl clean up they can be about almost as good as a set of tw's.
With that said, they are not for a 347 and likely never will be regardless of what is spent on them.

I think a hp rating for you is a crapshoot, it wouldn't be the first time someone was said to have a 347 and just turned out to be a stock shortblock.
And the reality is that people that slap together a bunch of mismatched parts rarely know what they are doing, so the range it could fall in is massive. Could put down 250rwhp or could lay down 325rwhp, the only way you are going to know is driving it to a dyno.

With some work gt40x heads can become respectable. Stock they are hardly better than a set of gt40 irons.

There’s a good thread on speedtalk about stock vs worked gt40x’s. I don't think I’d run them on a 347, but if it’s all you got then you might as well!
 
This is a little off topic, but at least it's a thread I started. I had a shop do some work on my car a few months back and one of the things I asked them to do was replace the leaking transmission tail shaft seal. The car is currently lifted with jack stands in the front to allow me to work on it. I was under it last night and noticed that the cardboard under the transmission is soaked in oil. Before I get mad at the shop, again, I thought I would ask if having the car jacked up like I do is causing the issue. I'll attach a couple of pics. The car has been on stands for about a month now, but only up this high for a few days.
20181229_133428.jpg 20181229_133443.jpg
 
With some work gt40x heads can become respectable. Stock they are hardly better than a set of gt40 irons.

There’s a good thread on speedtalk about stock vs worked gt40x’s. I don't think I’d run them on a 347, but if it’s all you got then you might as well!

I've had gt40y's and x's.
The y's are about as good as the irons, still a bit better.
The x's are plain old better.

My buddy (who has owned a mustang shop for 25 years or so), had a full weight car go 11.80's with a gt40 intake (real), x's with a valve job and a retarded e cam.
Made 316rwhp.
The x's are a bit rough directly out of the box, but it really didn't matter much because he wouldn't install any head that didn't goto the machine shop.
So no matter which head you chose, you needed $200 more for a valve job.
He was tired of inconsistencies in build quality and that went for all brands.
Some heads were modest gains, the x's gain is substantial.
Would I buy them at $1300? hell no, but i'd buy them all day at $500 and sink another $200 into them.
I certainly wouldn't pay to port them either.
If I had a real 93 cobra, I would duplicate that all ford racing parts build.
Over the years I tended to get parts cheap if I had the right amount of cash at the right time.
I ended up with extrude honed twisted wedges on my last pushrod setup.
Gotta love people who buy stuff they can't pay for, since all I had to do was pay the extrude hone bill.

Olive, i'd probably looking into afr 185's or the 190 twisted wedges, if you truly have a properly built 347, but i'd make that decision after you know what you have for sure.
 
Any recommendations on a good out of the box head for a 347 NA setup?

I’ve got a set of twisted wedge 11r 205s on a n/a 347 right now and I like them. You can’t do wrong with afr, trickflow, or even a set of Brodix if you can swing em. I wouldn't hesitate to run a set of victor jr heads either.

I've had gt40y's and x's.
The y's are about as good as the irons, still a bit better.
The x's are plain old better.

My buddy (who has owned a mustang shop for 25 years or so), had a full weight car go 11.80's with a gt40 intake (real), x's with a valve job and a retarded e cam.
Made 316rwhp.
The x's are a bit rough directly out of the box, but it really didn't matter much because he wouldn't install any head that didn't goto the machine shop.
So no matter which head you chose, you needed $200 more for a valve job.
He was tired of inconsistencies in build quality and that went for all brands.
Some heads were modest gains, the x's gain is substantial.
Would I buy them at $1300? hell no, but i'd buy them all day at $500 and sink another $200 into them.
I certainly wouldn't pay to port them either.
If I had a real 93 cobra, I would duplicate that all ford racing parts build.
Over the years I tended to get parts cheap if I had the right amount of cash at the right time.
I ended up with extrude honed twisted wedges on my last pushrod setup.
Gotta love people who buy stuff they can't pay for, since all I had to do was pay the extrude hone bill.

Olive, i'd probably looking into afr 185's or the 190 twisted wedges, if you truly have a properly built 347, but i'd make that decision after you know what you have for sure.

While your buddy made some decent power with his gt40x heads, I wouldn’t recommend someone run them on a bigger cube Windsor. Personally I think there are better options.