[mysticmissle]

I thought fast could modify everything as long as it looked stock from the outside? I saw one fast 69 copo camaro w tbm brakes for safety I get it but don’t get it

[Formulajones]

Originally Posted by mysticmissle

I thought fast could modify everything as long as it looked stock from the outside? I saw one fast 69 copo camaro w tbm brakes for safety I get it but don’t get it

Yes in FAST you can modify anything, it just has to be stock on the outside. That's a different class.

Pure Stock you cannot. They run pure stock withing the FAST series and then there is Dennis and Dan who run their own pure stock deal that has nothing but pure stock type cars in the event. Those are rules I linked to above.


The pure stock rules in the FAST series are very similar however.

My point was since you're building a street car with no rules, technically anything goes, so a good example of how fast you can go with the OEM long branch manifolds would be in the FAST series, where you can port things. If you want to compare to unported versions, then the pure stock series is a good place to compare. Although they won't be running anything bigger than a 400ci engine with those manifolds since by 1970 when the 455 came out the long branch manifolds were gone in the F-body.

[Stan Weiss]

Originally Posted by SD455DJ

The most recent 455HO that Dan built and Dyno'd is the one for my GT-37. It too is .040 over, 8.6 to 1 compression, Summit 2802 (224/234/114 @ .466"/.488"), untouched stock heads and factory RA manifolds made 430 hp @ 5000 rpm and 535 lbft. torque @ 3500 rpm. So, fairly similar numbers, but this 455HO isn't a max build for the Pure Stocks either. With this cam, it still pulled 20" vacuum at 1200 rpm and 18" at idle...very minimal lope if any...sounded very stock.

Dennis

Stan

[Formulajones]

Originally Posted by Stan Weiss

Stan

That's a nice stock type engine Stan that makes plenty of grunt.

I kept my bird pure to the PS rules with it's RAIII 400 but it's not a max build either. It had to run on pump fuel so I didn't maximize compression like most of those guys do. It made 301/355 on a chassis dyno through a 400 turbo, stock converter, and 12 bolt rear. It's run a best of 12.89 at 106 with a 3890 race weight and 3.31 gear. Stock 70-up style RA manifolds which reportedly aren't as good as the long branch stuff. If I had to guess (haven't had it on an engine dyno) it's probably making around 370-ish HP and 450-460 tq.

I did build a more performance oriented 72 455HO a couple years ago, with round port 7F6 heads, a custom 239 @ .050 hydraulic roller and 10:1 compression that made 507hp 571tq on pump gas through the same stock as cast RA manifolds.

So these manifolds do have the ability to make some decent power right out of the box.

[grandam1979]

There is a FAST 67 Firebird running mid 11’s at 120mph+

[mysticmissle]

I think the 67 has been tens now that you mention it

[Formulajones]

There was a white RAII bird built for the FAST class that had dipped into the 9's. I'm thinking 3-4 years ago.

The pure stock RAII birds like the blue one I linked to above was built for the pure stock class and runs near mid 11's at 120mph. That was probably 10 years ago or more.

[grandam1979]

My buddy’s purestock ram air II car runs mid 12’s at 114-115 mph with long branch manifolds and full 2.5 exhaust. I know Jim’s car went 118+

[SD455DJ]

Originally Posted by grandam1979

My buddy’s purestock ram air II car runs mid 12’s at 114-115 mph with long branch manifolds and full 2.5 exhaust. I know Jim’s car went 118+

I found PSMCDR times in the 12.30 range for Rick's RAII Bird, and I think there is a 12.2-something for the quickest et at one of the races. Rick Mahoney has a couple 11.50 et's in his former Teal Turquoise RAII Bird (TH400) at over 120 mph (takes every advantage the rules allow) and the late Jim Mino's '68 RAII did run 11.80 once, and very low 12's regularly (tough to be consistent with a 4-speed) at over 118 mph (not quite as enhanced as RM's RAII). Both cars weighed at 3475 lbs. with driver. Adrian Beltrame's '69 RAIV Bird run's high 11's at 118 mph, so

We found over the years dyno-ing RAII's, RAIII's, & RAIV's of both A & F varieties that the long branch manifolds make an average of 3-5 hp/3-5 lbft torque more through the RPM range (3000 - 5500/6000 rpm), probably due to their gentle turns vs. the 90 degree turn to the downpipes of the A-body manifolds. So, we're talking 5 - 10 hundredths of the second in the 1/4 mile advantage all other variables being equal.

The FAST guys are cutting their LB manifolds in half lengthwise to port them as much as they can (Greg Gessler used to do those), then weld them back together (not cheap!).

The RAII/IV's are making 450 hp-475hp on the dyno with 12.0 - 12.25 compression (max. 1.5 points over advertised 10.75 allowed).

Dennis