[WildStang88]

Ok, engine building gurus. I'm planning on building a 408. I'd like to use AFR heads if possible, question that I'd like to know is would the GT40 lower intake bolt up to these heads? I have a gut feeling they will not, which means I'm going to have to replan my build. Any input on this is greatly appreciated.

[ryanw]

the 351 gt40 intake should bolt right up. but id go with a better flowing intake if your going to spend money on afr heads. what size afr heads were you planing on going with ?

[WildStang88]

Airflow Research (AFR) 1387 - AFR 185cc SBF Street/Strip Outlaw Heads - Overview - SummitRacing.com

I also looked at the 205cc heads, but the cc volume is 58. Trying to keep that compression low for the supercharger

[GreenMustang00]

Originally Posted by ryanw the 351 gt40 intake should bolt right up. but id go with a better flowing intake if your going to spend money on afr heads. what size afr heads were you planing on going with ?

Could port the gt40 lower intake out if you want to cut cost a little. Should be a mean build though

[ryanw]

im not sure what the CC is on a stock 351 head. But on a 302 the compression would go up with a 58cc head. Stock 302 head is 61cc

[WildStang88]

Originally Posted by GreenMustang00 Could port the gt40 lower intake out if you want to cut cost a little. Should be a mean build though

Oh, yes it will be

Originally Posted by ryanw im not sure what the CC is on a stock 351 head. But on a 302 the compression would go up with a 58cc head. Stock 302 head is 61cc

Thats why I'm trying to stay away from the 50's. If my calculations are correct, say I did use heads that were rated at 61cc, bored .030 over, my compression would be just under 10:1 (9.94:1 to be exact), using reverse dome Probes -22.0cc and with 72cc.... somewhere around the 9.0x:1 mark?

[ryanw]

okay, im not good a figuring out all the compression stuff. but ya id say around 9 to1 maybe 9.5 to1 if your going to run boost

[MustangMatt96GT]

Your Building the engine right?

Why not use the bigger heads (your going to need atleast a 205 if not a 225 IMO), and buy different or custom pistons? The price of custom pistons is normally the same as normal or withing 100 bucks. But with that said, you prolly don't need to go that route, because of below.

I have been running numbers for a windsor build lately, and your compression ratio numbers are off... with a 4.030 bore, deck height of .005", 61 cc head, 22 cc dish piston, .040 gasket compressed height, and bore of 4.050", you would be at 9.17:1.


With a 58 cc head everything else equal you are at 9.47:1 Static Compression ratio.

[WildStang88]

Originally Posted by MustangMatt96GT Your Building the engine right? Why not use the bigger heads (your going to need atleast a 205 if not a 225 IMO), and buy different or custom pistons? The price of custom pistons is normally the same as normal or withing 100 bucks. But with that said, you prolly don't need to go that route, because of below. I have been running numbers for a windsor build lately, and your compression ratio numbers are off... with a 4.030 bore, deck height of .005", 61 cc head, 22 cc dish piston, .040 gasket compressed height, and bore of 4.050", you would be at 9.17:1. With a 58 cc head everything else equal you are at 9.47:1 Static Compression ratio.

Ya I'll be building the engine, reason why I wasn't thinking of going with 225's is because I thought it would be too much therefore loss in horsepower, but then again going too small can have that same effect. Just curious why you think I should go with different pistons? You talking about just a different brand name or going with dish, flat top vs reverse dome's? I had a general idea where my compression would be, I just didnt add all the other stuff.

[MustangMatt96GT]

What is the ultimate goal of this car?

[WildStang88]

Street / Strip leaning more towards Strip 35/65% 450-500 to the rear wheels might be a bit much or goal of 425-475

[Mustang Boy]

Have you thought of using E85 as your fuel? That would allow you to run a higher compression ratio.

[MustangMatt96GT]

Originally Posted by Mustang Boy Have you thought of using E85 as your fuel? That would allow you to run a higher compression ratio.

He doesnt need to and its a restriction where you can drive... Thats what I ran my motor on before it decided to want a new power plant.

Originally Posted by WildStang88 Street / Strip leaning more towards Strip 35/65% 450-500 to the rear wheels might be a bit much or goal of 425-475

450 will be cake with the right cam and heads. With forced induction, you want a large CFM and velocity head coming in and as big as an exhaust port as you can. So the headers getting it out will play a role too, 1 7/8s primarys to 3 inch collectors and 3 inch all the way through will make the most power, be about perfect.

The AFR head is a nice inline head, but I am a trick flow man personally. The AFR will make good power though. I would do the 225s if I were you with that many cubic inches and a blower. If it was all motor you could get away with 205s.

The piston wont really matter who you go with, but I am a fan of Diamond and JE pistons. I also have used Probe pistons without issue in a 500 horse small block.

What block are you going to use? If you are using a stock 351 block, you are restricted to about 650-700 horse anyway and no need to spend a whole bunch on a bulletproof rotating assembly.

A DSS stroker kit would be fine for you, or a Ford Strokers setup. And im sure they give you the option of what size dish piston you want, but i would be in the -22 to -18 range. 9.2:1-9.3:1 would be about optimal, and if it doesn't make the power you want put a little more boost to it. Your only going to need 6-8 psi if the engine is built correctly to make 450-500 hp.

Boost is just a measure of the resistance or the (ineffiency of your parts). So more boost doesnt always make more power. But You will have a very nice setup, with a large head and the right cam.

The cam will be a big key factor to making good power. You don't want a whole lot of overlap with a boosted motor, but I have never built a Kenne Bell setup, just centri setups and nitrous setups, so Im not sure how much else would be relevent to the KB as in lift and durations and ramp rates.

You are going to have a TORQUE monster though, Big stroke, and then a KB on top, will make a crap ton of torque.



My new motor is getting a 9.7:1 compression ratio on E85 as a street car. Its getting a dart block, big bore, eagle crank, scat H beams, custom Diamond pistons, Trick Flow 240 High Ports, and a custom cam setup from me... On 20-23 psi I should be able to crack the 900 range pretty easy in my street car!

[WildStang88]

Originally Posted by MustangMatt96GT He doesnt need to and its a restriction where you can drive... Thats what I ran my motor on before it decided to want a new power plant. 450 will be cake with the right cam and heads. With forced induction, you want a large CFM and velocity head coming in and as big as an exhaust port as you can. So the headers getting it out will play a role too, 1 7/8s primarys to 3 inch collectors and 3 inch all the way through will make the most power, be about perfect. The AFR head is a nice inline head, but I am a trick flow man personally. The AFR will make good power though. I would do the 225s if I were you with that many cubic inches and a blower. If it was all motor you could get away with 205s. The piston wont really matter who you go with, but I am a fan of Diamond and JE pistons. I also have used Probe pistons without issue in a 500 horse small block. What block are you going to use? If you are using a stock 351 block, you are restricted to about 650-700 horse anyway and no need to spend a whole bunch on a bulletproof rotating assembly. A DSS stroker kit would be fine for you, or a Ford Strokers setup. And im sure they give you the option of what size dish piston you want, but i would be in the -22 to -18 range. 9.2:1-9.3:1 would be about optimal, and if it doesn't make the power you want put a little more boost to it. Your only going to need 6-8 psi if the engine is built correctly to make 450-500 hp. Boost is just a measure of the resistance or the (ineffiency of your parts). So more boost doesnt always make more power. But You will have a very nice setup, with a large head and the right cam. The cam will be a big key factor to making good power. You don't want a whole lot of overlap with a boosted motor, but I have never built a Kenne Bell setup, just centri setups and nitrous setups, so Im not sure how much else would be relevent to the KB as in lift and durations and ramp rates. You are going to have a TORQUE monster though, Big stroke, and then a KB on top, will make a crap ton of torque.

Well I'm glad I posted this, otherwise I would be going too small and you seem to know what your talking about. A buddy of mine and I are gonna be searching the junkyards soon for a seasoned block hoping to find a F4TE and take it straight to the machine shop. I pretty much knew that the horsepower range was gonna be what you listed for the block, even though I might not need a bulletproof bottom end I'm one of those types of guys that goes the extra mile and gets the stronger stuff anyway (4340 crank and girdle). Just out of curiosity whats an estimate amount of torque this thing will be putting out? Thanks alot for your help man.

Originally Posted by MustangMatt96GT My new motor is getting a 9.7:1 compression ratio on E85 as a street car. Its getting a dart block, big bore, eagle crank, scat H beams, custom Diamond pistons, Trick Flow 240 High Ports, and a custom cam setup from me... On 20-23 psi I should be able to crack the 900 range pretty easy in my street car!

Damn nice!

[fogged306]

A 225 head is about where you want to be for a 408" street engine. You can make 500 to the tire all day long on a pump gas 9.5 deck stroker with no power adder, especially being close to sea level in FL. If those are your goals, I'd skip the blower all together and get some 225 highports, a super victor, and a good valve train set-up along with all the other supporting stuff you'll need like suspension, fuel, trans, ect. and just run it N/A.

[MustangMatt96GT]

Originally Posted by fogged306 A 225 head is about where you want to be for a 408" street engine. You can make 500 to the tire all day long on a pump gas 9.5 deck stroker with no power adder, especially being close to sea level in FL. If those are your goals, I'd skip the blower all together and get some 225 highports, a super victor, and a good valve train set-up along with all the other supporting stuff you'll need like suspension, fuel, trans, ect. and just run it N/A.

I do like this idea too, the only difference is that the cam will dictate if its streetable or not. the KB can have a factory cam in it if need be and it will still make power. The N/A route and the KB'd route will probably cost the same in the end.

[tmoss]

The 351 GT40 lower flows right at 270cfm with a 27 cfm spread right out of the box and is easily taken a little over 300cfm - last one I did for a 1250 size port went 302 cfm average with a 19cfm total spread. 1262 size port should flow 325+ cfm.

[WildStang88]

Originally Posted by tmoss The 351 GT40 lower flows right at 270cfm with a 27 cfm spread right out of the box and is easily taken a little over 300cfm - last one I did for a 1250 size port went 302 cfm average with a 19cfm total spread. 1262 size port should flow 325+ cfm.

Thats alot of flow. An to be sure that I have the GT40 lower I rechecked the casting. Got RF-F87E-9K461-BA. As a matter of fact TMoss, you're mentioned in this post That website made me want to recheck it.

Intake Identification - Mustang Forums at StangNet

Now I just have to decide which way I want to go with this. I love the whine of Kenne Bells for sure. I'll keep you guys updated. One last thing.. what casting on the block should I look for? I know F4TE is a good one but gonna be hard to find. C8ZE? C9ZE? Any others around the 60's... 70's, and should I stay away from the 80's? Probably won't matter much and that is if I can't find the F4TE's...

[69fastback]

Go big or go home



And 408s suck

[tmoss]

Wild - you must use the 351W casting from a Lightining on a 408W. That's the one I posted about. It's a much better casting design becasue it's wider than it's little brother for the 302-347 engines.