[Mike S]

While the engine is at the machine shop I am building a 2004r for it. The shift kit has different valve body modifications dependent on HP. Below 350hp and over 350hp.
The engine is a 400 .030 over, 9-1 compression with slightly ported 6X heads ,rpm intake, 750 vacuum sec Holley and 1 3/4" header. Leaning to a 68 cam but still haven't decided.
Do you think this would be over or under 350hp? My guess would be over, but not by much, maybe 380. I am just building a nice cruiser.

[b-man]

Your horsepower guess of 380 seems pretty realistic to me.

[25stevem]

Even with the lightly ported heads, but with the valve lift of the 068 Cam and the 9 to 1 comp and installed in the car driving all the belt driven stuff I really don't see you topping 350 hp.

In the 2000 issue of muscle car magazine they covered a stock rebuild of a RAII motor with is 068 Cam and higher compression then yours .
After a good amount of tuning and finally slapping early F body hp Exh manifolds on it they got the motor to pump out 370 hp, or 4 hp more then the factory rating.

Since this was with a open head pipe, just water pump and a unloaded Alt spinning I gotta say that if you make it to 350 hp your doing good!

[Murf]

Mike, It would be interesting to know what they have you do & why. Seeing how they base the need on HP numbers. If I was that close, I think I’d do the higher HP mods. Unless your sure you’ll never do any other mods to the car. Just my opinion.

Murf

[Formulajones]

I'm with Murf, I'd do what ever mods to the valve body required for the "above" 350hp level and call it done so it doesn't have to be revisited later.

A well built stock 400 with the 068 cam, stock manifolds, 10:1 compression, stock intake, and unported stock #12 heads will probably make around 370hp if I had to guess with mine based on how it runs and what the car weighs. It made 301hp on a chassis dyno through a 400 turbo, stock converter, and 12 bolt rear.

It weighs 3890 with me in it.

https://youtu.be/er1z7PpqsnY

[Jim Moshier]

x2 on what Murf said I can see 370hp and if you are that close just go all in!

[Stan Weiss]

This is an old and very simple program and I just used what I had for input.

Stan

[77 TRASHCAN]

I'm not against Murf's build thoughts, BUT...

My now semi retired enginge builder was/is a Chevy guy, although he now only builds and tunes aluminum hemi's (TAD).
I know a Chevy is not an apples to apples comparison, BUT AGAIN....
He built a small block 400 for my buddies 1966 C10 (as in very heavy, 5000 pounds) pickup.
Engine specs were not far off from Mike's proposed build. Heads were modified by builder (his knowledge is huge), although having seen them, I seemingly couldn't see all that much grinding done to them!!!
It had an early Edelbroch performer(these had the larger runners), a Holley 3310, 1-1/2 O.D. headers ( yes, O.D.) the stock 5.565 rids with the cheapest forged pistons available at the time. Those heads were the large chambered 441 heads BTW. cam was Comp 268H high energy grind. This was in the early 80's, mind you, the XE stuff thankfully hadn't been thought of yet...
I don't remember RPM power peaks, or such. The peak numbers were 300 HP and 400 ft/lbs torque.
The builder ONLY used NET dyno numbers (Superflow) when making pulls. If this had been built by a magazine, I'm sure the HP numbers would have been close to 350...

My point....this engine was a hell raiser in that old Chevy pickup, as conservative as the build sounded. It had a 3.42 gear( the rear was a later model 8.5 pickup rear, adapted to us in the 66). Had a Muncie M20, the the engine builder was a little afraid of using in this old pickup, that weighed TOO much!!!

This Old pickup was a hoot to drive. The engine was a HUG torque maker. It was with him several times when he "stop light to stop light" embarrassed many " hot rodders" in the area.

Mike. I'd run the combo you are contemplating, with the 068 cam. I think it will serve your purpose AND be fun to drive!!!

[25stevem]

Stan, so this program assumes small tube headers with the mufflers bolted right up to the collector?

[Tandyman]

Stan , in the airflow data the exhaust test diameter is 1.66 . Is that a mistake? If so it is probably resulting in higher HP numbers because the cylinder head section lists 1.77 .

Glenn

[Skip Fix]

FWIW my RAIV 400 with a good valve job and flat valves(better flow than the tulips), UD HFT 288/296 231/239 @ 0.050 HO intake 73 SD Q jet headers only made 385 HP on a conservative dyno through exhaust and ran the numbers based on mph at the track. So a stock RAIII and exhaust manifolds is going to be down a fair amount.

[Formulajones]

Originally Posted by Skip Fix

FWIW my RAIV 400 with a good valve job and flat valves(better flow than the tulips), UD HFT 288/296 231/239 @ 0.050 HO intake 73 SD Q jet headers only made 385 HP on a conservative dyno through exhaust and ran the numbers based on mph at the track. So a stock RAIII and exhaust manifolds is going to be down a fair amount.

What would 301 at the tires on a Dynojet compute to at the flexplate, considering a 400 turbo with the stock converter and 12 bolt rear?

I've changed valves in the heads too to pick up some flow (legal per rules and better than the 2 piece garbage anyway) and a valve job that helps flow as well.

But that's nothing compared to what the PS guys are getting out of the RAIV's these days, they blow my RAIII away as the good ones are making 400hp at the tires through a 4 speed and smaller 8.2 rear.

[Skip Fix]

My stock '04 GTO made 285 on a dynojet. Rated 350 by factory.

[Stan Weiss]

Originally Posted by 25stevem

Stan, so this program assumes small tube headers with the mufflers bolted right up to the collector?

Steve,
I don't know. Here are where choices there are for exhaust.

Stan

[Stan Weiss]

Originally Posted by Tandyman

Stan , in the airflow data the exhaust test diameter is 1.66 . Is that a mistake? If so it is probably resulting in higher HP numbers because the cylinder head section lists 1.77 .

Glenn

Sorry. My bad. I keep forgetting when you load a head flow file it doesn't change the valve sizes on the main screen.

Stan

[Formulajones]

Originally Posted by Skip Fix

My stock '04 GTO made 285 on a dynojet. Rated 350 by factory.

That's interesting. I've owned a few LS vehicles, 3 of them were 4th gen Fbody LS1's. One I had a very small 218 @ .050 cam from Crane, and headers on it, still stock exhaust, it did 346hp on a dynojet.

My little stock 69 DZ 302 just on a dynojet a couple weeks ago did 282 hp and 277 tq. I was pleasantly surprised at that one. Factory only rated them at 290 so quite a bit under rated to say the least.

[Skip Fix]

The 04 on a Mustang chassis was 290 ish after a little computer tweaking. I think that dynojet dyno day the 05-6s stock were in the 330- 350 ish range .

[Formulajones]

Originally Posted by Skip Fix

The 04 on a Mustang chassis was 290 ish after a little computer tweaking. I think that dynojet dyno day the 05-6s stock were in the 330- 350 ish range .

Cool, the LS2's 05 and up were pretty healthy. I dropped one in my 72 blazer years ago and had a ball with it.

[KSZR]

Originally Posted by Formulajones

Cool, the LS2's 05 and up were pretty healthy. I dropped one in my 72 blazer years ago and had a ball with it.

The 6.2 in my GMC pickup is amazing!

[Tom Vaught]

346 horsepower

Tom V.