heads, cam, carb, nitrous

[VTStang66]

I'm trying to build a street car. Not a daily driver, but something I can drive around town when I want.

'66 fastback
8 point cage
currie 4.10 8"
street tires (late model v-6 16" wheels)
tremec 3550
302, forged flat-top pistons
RPM air gap manifold
probably a pan-hard bar
lowered a little

I want about 400 hp on the 302 NA, maybe a little less, with some nitrous on top of that. I'm looking at the NOS sportsman fogger kit.

My biggest hangup is with the cam and the nitrous. I'm looking at big cams to give me some top end, and big cams like high compression. However, I don't think I want to run the compression too high with the nitrous, right? I'm thinking somewhere between a 150-200 shot. I'm not worried about the rear end because the tires will be the weak link in the powertrain.

So here's my question. What kind of compression/cam combo should I look for to give me the NA power I want while still being able to handle the nitrous? Also, what size carb? I think I'll get a holley double pumper. I figure maybe about a 700 cfm, but I can get anything in 50-cfm increments. What does the all-knowing stangnet say?

 

[5.0ina66]

I'd use a 650cfm carb, clean up the ports on the intake, good headers, AFR165s (clean up if needed), Comp beehive springs, a true shaft mount rocker setup like T&D Machine's setup, low tension piston rings, a windage tray, 10:1 compression (if it were NA) and expect very near 400hp with the right cam. You may also consider a small single plane intake like the Wieland excellerator for better nitrous charge distribution than a dual plane, and with the single plane and a well built engine I'd expect 410hp or so, if not a tad more. I'd look at a small solid lifter cam or a hyd. roller (my favorite is the Speed Pro CS195R) and investigate a custom cam if you can afford it. The valvetrain stability will give you some 'free' high RPM power and let you wind it tighter, while the rings and oil control devices will unleash otherwise-lost HP (15-20 or so) and it ought to be a total mother on the juice. Matter of fact, you might be in the shatter-the-block range on spray.
HTH
--Kyle
EDIT: With a single plane and smallish solid lifter custom cam, I predict 420hp NA + however much N20 you want to run, but much N20 and you'll probably be picking hunks of the block up in the next county.

 

[coolblue65]

If you want to get near 400hp with out the nitrous, you are going to need fairly high compression. Your power band will end up being pretty high up as well, which in turn will take away some of that streetability by making it a dog down low. If your doing all this, why not just stroke the motor?

 

[rbohm]

since this will be a street car, and a toy, you can make slightly more aggressive choices. i make the following recommendations;

performer rpm heads. these heads have a 60cc combustion chamber and will give you about 9.5:1 compression with flattop pistons.

performer rpm intake, perhaps even the air gap intake. this till compliment the heads nicely.

edelbrock 750 cfm performer carb. very tunable, and flows enough for this motor. the air valve secondary will prevent too much airflow for best driveability.

for a cam probably a comp xe282hr cam with a set of crane link bar roller lifters. this is still a streetable cam, that will boost midrange power nicely, and wont lay down on the top end of this motor.

headers, i recommend a good tri-y header with a 1 5/8" primary tube dumping into a 1 3/4" secondary tube that dumps into a 3" collector, and runs out through a 2 1/2" dual exhaust system run out the back with a good turbo muffler.

for nitrous, i would limit the level of nitrous to no more than a 125 shot. this will push the engine over the 450hp mark, without overstressing things.

 

[VTStang66]

I didn't mention that it's a mexican block, so it is a bit stronger than your average 302. The 200 shot isn't set in stone, the kit is adjustable from 50 to 250 so I'll figure that out later. I already have the short block built, so that's why I'm not stroking it. I already have the performer RPM air gap intake too, so I'm pretty sure I'll stick with that. Nitrous distribution won't be a problem with the fogger system (1 nozzle per port). I also already have hedman elite hedders (1 5/8" primaries, 3" collectors). I'm running 2.25" exhaust now but I might change that later if I feel like it's corking it up.

But back to the main question, is compression ratio an issue with the nitrous, or should I just build as if it will be NA and then just add the nitrous and not worry about it?

 

[Z06killinSBF]

10:1 comp is fine on the bottle. Just remember that with all that compression and the nitrous, your cam will act really small. I would get a cam around 107-108LSA as well to keep the NA manners up a little. With a big lift cam, you'll need it.

Lose that tiny exhaust as well. Thats gonna be HURTING you.

 

[VTStang66]

Thanks Z06. What does LSA do? I know it's lobe separation angle, but what are they talking about exactly, and how does it affect the engine?

Another question: I already have the performer 1.90" edelbrock heads. I like the sound of the AFR 165s, but looking at the specs it looks like those are almost the same heads. The edelbrocks have 170 cc intake runners (vs. 165 for AFR), and the intake valve is the same. My heads are emissions legal though. If I machined the edelbrocks a little, would they flow nearly as well as the AFRs? I know edelbrock isn't known for their heads but in the interest of money if I could get it pretty close I could save a thousand bucks. What do you think?

here are some 302s making 400+ hp with the AFR 165s.

 

[brianj5600]

2 of those look like the same motor all but the intake. The Vic jr made 43 more hp.

 

[10secgoal]

FWIW I ran a 302 .040 over with about 9.3 to 1 compression. AFR 185's with an airgap,4.11's, a 750 DP and an X-303. 12.1's all day, very streetable. I had the X in there from years ago and didn't see a point in changing it when I had the bottle to make up the difference. You can make 500 with a 200 shot and have a mild 300hp motor. Or 75 shot with a hotter build. 302 or stroker I would go 185's on the heads. One of the best mods I ever did.

 

[VTStang66]

2 of those look like the same motor all but the intake. The Vic jr made 43 more hp.

The first one with the performer RPM made 421. After the 3rd one they're all stroked and/or blown.

 

[brianj5600]

Oops, I had a dislexic moment. 34hp is what I meant. And it did have 185's too. Oh well. I was looking at 1 & 3.

 

[Z06killinSBF]

The 165's in my opinion are "beginner" heads. Great for a mild, near stock motor. Your trying to reach high HP with little cubes so your going to need something to have great port volume and flow a TON up top. You can send those Edelbrocks out to get ported and have bigger valves installed or you could sell them and get a set of TEA ported Trick Flow Track Heats. They will out flow a set of AFR 205's all day long yet still retain some down low torque from the little motor. Since you have the Mexican block, I recommend a solid lifter cam. Here is one I think would work great for your app.

http://cgi.ebay.com/ebaymotors/Madd...ItemQQcategoryZ33614QQihZ019QQitemZ8033224303

Also recommend a 650DP carb on top of that Air-Gap.

These heads> http://www.totalengineairflow.com/products/fordhead/tfstw/

 

[BullittStangV8]

FWIW I ran a 302 .040 over with about 9.3 to 1 compression. AFR 185's with an airgap,4.11's, a 750 DP and an X-303. 12.1's all day, very streetable. I had the X in there from years ago and didn't see a point in changing it when I had the bottle to make up the difference. You can make 500 with a 200 shot and have a mild 300hp motor. Or 75 shot with a hotter build. 302 or stroker I would go 185's on the heads. One of the best mods I ever did.

10 sec, what is .040 over in a 302? Also, what HP did you make? I have a stroked/bored 331 with 10.1-1 compression, AFR 185, x-303 and the same air gap. Carb Still to be determined. Any guess on HP 1/4 times? Its gonna have 4.11's and a 4spd toploader most likly for the rear/tranny set up.

 

[Z06killinSBF]

A .040 302 = 308

.030 302 = 306

 

[DK832]

For inspiration with that Air Gap and Fogger setup: this is what I'm building for my 351W. 90% finished, still missing some stiffening brackets and the electricals. This is in a 10:1 full roller, all forged, Sportsman block and is jetted to 175HP to begin with.

AirGap with Fogger setup

 

[rbohm]

Thanks Z06. What does LSA do? I know it's lobe separation angle, but what are they talking about exactly, and how does it affect the engine?

the lobbe seperation angle has an interesting effect on engine performance. remember first that the higher the dynamic cylinder pressure, the better an engine will perform, assuming you stay out of detonation. the lsa will allow you to "trick" an engine into thinking it has a higher or lower compression ratio, given that the rest of the cam specs are the same. how does it do this? good question. let me use my old viking 100h cam as an example, .460 lift 289 advertised duration, 78 degrees overlap, and 110 degree lsa. this cam would come on like gang busters at about 2500rpm, and pull hard through about 6500 before it dropped off. the engine had 10:1 compression. but lets say i had detonation problems with that engine that timing, and higher octane fuel couldnt cure. what i could do is narrow the lsa so the i get more overlap to reduce dynamic cylinder pressure. if i went to say a 108 lsa cam, everything else being the same, the overlap now becomes 80 degrees, and the dynamic cylinder pressure drops at lower rpms. this might be enough to kill my detonation problem, but it will hurt low end power a bit, and improve the top end power a bit. a little like retarding the cam on one lobe and advancing the cam on the other lobe. at this point my engine now thinks it has a dynamic compression ratio of something more like 9.7:1 or so. now lets us say the same engine, but 9:1 compression ratio. if we open the lsa up to 112 degrees, this reduces the valve overlap, and we bleed less pressure at low speeds, thus we have raised the dynamic compression ratio, as now our overlap is 76 degrees, and again we have advanced one cam lobe, and retarded the other lobe, but we have gained low end power, but not necessarily lost top end power in this case as the engine "thinks" it has a higher compression ratio.

the lesson here is that you need to look at all the cam specs before selecting a cam, as the lsa does affect the rpm range as well as the dynamic compression ratio. so if you are going to build a normally aspirated engine, you want a higher compression ratio, but you want to avoid detonation in the normal driving range, use a slightly narrower lsa angle. if you want to build a turbo or supercharged motor, you want a lower compression ratio, but you also need more low end power as well to get over the boost lag, so you select a cam that has a wider lsa angle. by the way, if you really want a large cam, and want to make streetable, you also want a wider lsa.

remember that the devil is in the details.

 

[VTStang66]

Since you have the Mexican block, I recommend a solid lifter cam.

Why? I'm just trying to understand all the ins and outs.

 

[enferno]

i have a brand new holey 650 cfm double pumper and a brand new NOS powershot system complete from bottle to the intake, including a WOT switch.

i'll sell you both for cheap if you're interested

 

[Vinyl66]

With a 302 I would run:
650 carb
Air Gap
AFR 185's (way better than Performers) If you keep the Performers at least change the weak valve springs to match the cam.
Shoot for 10:1 or so compression
Solid Flat Tappet Cam (with matching springs) if you want to rev to 7000(go custom for most hp and let them know you will be using N20) Camshaft innovations likes solid flat cams.
Hydraulic Flat Tappet Cam if staying under 6500 and do not want to adjust valves every now and then.
1 5/8" full length headers
2 1/2" exhaust

This is the same basic setup on my 347 except I run the Vic Jr intake. I only have 3.55 gears and small drag radials and have run in the 11.8's shifting at 6200 rpm.

With the older Mexican block I would stay with a flat tappet cam because of the expense of converting to a roller setup. There are guy's running 9's with these blocks so a decent shot of N20 (150) should be no problem. For the block anyway.
Just be sure you are running forged pistons.

 

[Vinyl66]

10 sec, what is .040 over in a 302? Also, what HP did you make? I have a stroked/bored 331 with 10.1-1 compression, AFR 185, x-303 and the same air gap. Carb Still to be determined. Any guess on HP 1/4 times? Its gonna have 4.11's and a 4spd toploader most likly for the rear/tranny set up.

Bullitt,
My 347 is similar to your 331. I have 10:1 compression, AFR185's, my cam has a little more duration at .050" and yours has more lift, flowmaster exhaust....
With 4.11's your car should really scoot!! I have 3.55's and mine does pretty well.
I used to run the Pro Products air gap and ran as low as 12.01 at just under 110mph. After switching to the Vic Jr. I ran 11.8's at 112.5mph. All with a 650 vacuum carb. I hope to try out a 750 this fall but have been impressed with the 650!

So you should have an easy low 12 second car. If you can really get it to hook up (good luck) you have the capability to run 11's.