Exhaust and intake choice for my new engine build

[LarsD]

Looking for opinions on what I should do. I am having a 347 being built by Fordstrokers.com and I should have it sometime in the June/July time frame. There are a couple of things I need to decide on and I am looking for outside opinions. It is going to be an N/A setup with around 10:1 compression, stock block, and Trick Flow 170 heads.

The parts in question is my GT40 intake, and whether or not to go with long tubes. The car has Hooker shorties on it right now, I was planning on going with BBK longtubes. However, I was driving my Cobra all over town last Friday and it's longtubes seem to scrape everywhere. I already have this problem on my Dodge, and it is really annoying. I don't drive the Dodge and Cobra very often, so it isn't as big a deal on them. I am thinking utility over anything else.

The 91 gets driven a lot, has A/C, heat, PS, everything. It is a DD, not a race car. Next up is the GT40 Tube intake that I have. I know most of you are thinking, "why put such a restrictive intake on a 347"? Couple of reasons. One, I scored it off of Ebay for a decent price. It is new, the PO bought it, stuck it on a shelf, sold his car, and it sat for 6 years. Other then being a little dirty it is perfect. Two, I look at it as a period piece. You don't see them very often, and it is my favorite intake to look at for the 5.0 Lastly, I'm blowing the %^#$* out of my budget, and not having to sell this intake and buy a new one is appealing, though not the primary motivating factor. I originally bought this intake with the intent of putting on my stock short block (this was before I found it was hosed).

Anyhow, so there it is, flame away!

 

[Adams91LX]

Don't sell the Tubular GT40... give it to me?

Honestly... that is a super cool piece... I'd hold on to it, for now at least... I'd run it and slowly save some cash for a new intake that would better suit the rest of the engine build.

 

[Rick 91GT]

With the proper cam it will run very well with what I will call a restrictive intake for a stroker.

Made 360/380rwhp/tq on a mustang dyno with a 10.5:1 333ci, stock afr 185, stock.cobra intake, my own custom cam...car is a blast to drive. On a nice cooldown pull with good air it made 380/404.

Keep the shorties...much less trouble in a street car.

 

[1bad67sbf]

that should be a fun car with power and all the DD goods to go with it.
do long tubes have height issues on all foxes or does the suspension setup have alot to do with it?

 

[LarsD]

Honestly I think I can get away with the GT40 intake since it is a street car that will likely never see the high side of 5K rpms. I always wanted one, and you just don't see them that often anymore. I was considering having Tmoss port the lower, not sure if it will make enough difference to justify the cost though.

 

[LarsD]

Next question is, should I got with a 70mm TB/spacer or a 75MM TB and EGR spacer.

With the proper cam it will run very well with what I will call a restrictive intake for a stroker.

Made 360/380rwhp/tq on a mustang dyno with a 10.5:1 333ci, stock afr 185, stock.cobra intake, my own custom cam...car is a blast to drive. On a nice cooldown pull with good air it made 380/404.

Keep the shorties...much less trouble in a street car.

If I can see 360 at the wheels through my TKO600 out of this motor I'll be pretty happy.

 

[Rick 91GT]

I like the 75mm if you need to buy one but youll need to open the intake up...

 

[LarsD]

I like the 75mm if you need to buy one but youll need to open the intake up...

All I have is the stocker for now. I had an Accufab on my last build and I liked it a lot, since AM carries them in 70mm and 75mm that's what I need to decide on.

 

[smokin joe]

GT40 tubular intakes are still advertised in DFW for 350 to 400 so I would say keep it. As far as the throttle body I would go with the 70mm IMO.

 

[NIKwoaC]

Don't beat yourself up on TB selection, it's just an air valve. All it does at WOT is get out of the air's way. Like Rick said, the 75mm is the better choice, but you'll have to grind on the intake a little to get the opening to match the TB size.

FWIW, there are street driven NA 302s out there running 90mm TBs. Read about a couple of those and you'll start to wonder why you're considering a 70mm for a 347!

 

[LarsD]

Well, I'm thinking the 70MM would probably be better for my usage (95% street), but when I decide I want more I'd hate to have to rebuy the TB/spacer, so maybe I should go with the 75MM. I keep remembering stuff I meant to put in the original post. Should I get 30lb injectors? I already have a set of 24's and a ProM Maf that is cal'd for 24's, but I think they might be a little small.

 

[NIKwoaC]

Well, I'm thinking the 70MM would probably be better for my usage (95% street), but when I decide I want more I'd hate to have to rebuy the TB/spacer, so maybe I should go with the 75MM. I keep remembering stuff I meant to put int he original post. You guys think I should get 30lb injectors? I already have a set of 24's and a ProM Maf that is cal'd for 24's, but I think they might be a little small.

See, you're over thinking it. The 70mm will have no better street manners than the 75. I run a 70 on my 302, hell, I ran that 70mm TB on my 302 back when it was bone stock. I've never had any issues on the street. Do a 75 and don't look back. Hell, I'd tell you to go even bigger, but you'll probably run into problems trying to hog out the intake to match. Consider that the 2011 5.0 has an 80mm TB. Does it have any problems on the street at low RPM?

And yea, the 24s are probably going to be on the small side. Realistically, depending on the cam, that engine will make high 300s or maybe even low 400s HP at the crank. 24lb injectors on stock fuel pressure are starting to struggle once you get into low/mid 300s at the crank.

Check out this injector calculator:

Injector Size Calculator

 

[LarsD]

See, you're over thinking it. The 70mm will have no better street manners than the 75. I run a 70 on my 302, hell, I ran that 70mm TB on my 302 back when it was bone stock. I've never had any issues on the street. Do a 75 and don't look back. Hell, I'd tell you to go even bigger, but you'll probably run into problems trying to hog out the intake to match. Consider that the 2011 5.0 has an 80mm TB. Does it have any problems on the street at low RPM?

And yea, the 24s are probably going to be on the small side. Realistically, depending on the cam, that engine will make high 300s or maybe even low 400s HP at the crank. 24lb injectors on stock fuel pressure are starting to struggle once you get into low/mid 300s at the crank.

Check out this injector calculator:

Injector Size Calculator

K I'll just do the 75MM then. I figured the 24's would be too small. I am shooting for at least 400hp at the flywheel. Thanks for the calculator!

 

[Cobra912]

I'd stay with the GT40 and get some 1 3/4 " shorties

 

[Cobra912]

I like this calculator: (go to bottom of page)

RC Fuel Injection

I would not use 24's! I ran 30's without a tune, but i'd go with 42's for room to grow especially if ya boost it or juice it later. IMO

 

[LarsD]

I like this calculator: (go to bottom of page)

RC Fuel Injection

I would not use 24's! I ran 30's without a tune, but i'd go with 42's for room to grow especially if ya boost it or juice it later. IMO

Nah, no spray, and since it is a stock block I won't risk the boost. If I want more I can S/C my Cobra or build a monster motor for my Dodge. Anybody know where I can get some cheap 30's?

 

[NIKwoaC]

Nah, no spray, and since it is a stock block I won't risk the boost. If I want more I can S/C my Cobra or build a monster motor for my Dodge. Anybody know where I can get some cheap 30's?

I grabbed a rebuilt set on ebay for $150. Seller was "precisionfuelinjectors". I have not ran them yet, obviously, but that seller was very professional, the injectors were clean and nicely packaged, and came with test flow data at no extra cost.

 

[LarsD]

I grabbed a rebuilt set on ebay for $150. Seller was "precisionfuelinjectors". I have not ran them yet, obviously, but that seller was very professional, the injectors were clean and nicely packaged, and came with test flow data at no extra cost.

Cool, I'll check them out. Thanks!