how fast have you gone with reproduction 1967-1969 style D PORT long branches
 

have a decent 455 with mildly ported iron heads, xr 288 HR about 9.75:1 and stock un ground on Ames long branch manifolds estimate 425 hp
I know the car will be quicker with headers, but how much quicker? still have some bugs to iron out and have way too much gear in it w the 411s
I have another pump gas e head round port 455 waiting to go in that will have dougs headers on it. I really dont know if i would swap the manifolds for headers but curious to see how fast someone else may have gone. Im guessing 3600ish weight.

I can't answer the speed question, but I talked to RARE this morning and they have left sides only in the long branch manifolds for D-port. They said 8-12 weeks out for the right sides.

I miss-read this, I see you have some in hand.

These long branch ones in this dyno test of a stock rebuild of a RA3 motor made 368 Hp, which was only a 8 Hp improvement over the standard log exh manifolds.

In a previous dyno test of a rebuilt and fine tuned RA4 motor they eked out 400 Hp, so seeing that number came in with the better flowing round port exh manifolds I don’t know how close you will really come to 425 Hp even considering the bigger cubes and Cam difference.

I have a set of the GTO ones I have been meaning to get on my flow bench for years now, as that will be a true indicator of the ultimate level of hp any motor could make with them.

I had long branch manifolds with 2.5 flowmaster cross flow system on my 68 Firebird. 455, similar cam, a RPM with a Thermoquad. Turbo 400, 3.31 gears with 275/60 Drag Radials. Car weighed 3660 with h me in it.
It ran 12.10 @ 114 in Kansas in summer. Sold it to a guy in Pennsylvania. He told me he was running high 11’s there.

Edit, I’ve got oldtimers disease. 12.10’s was with headers & dual dyno max mufflers under the back seat foot wells.

It ran 12.25 with long branch & cross flow exhaust. Had Continental tight 10 inch converter both ways.

That’s about what I was hoping if we sniff your results I’d be pretty happy

Not track times but an interesting dyno comparison that Mike did with the long branch manifolds:

"Now for some numbers: Best with exhaust manifolds, 464.6 Ft. Lbs @ 4700 rpm Peak HP 442.2 @ 5900 rpm. With borrowed 1 3/4 headers from a 74 GTO NHRA stocker: 18" long 3" collector, 481.6 ft. lbs torque @ 4800 rpm. 20-28 more ft. lbs. of torque everywhere. 448.4 HP @ 5800 rpm. Was not tuned to the headers, so 10-15 HP more on top could be expected. No reason to tune to headers because they are not going to be used."

Eric

Notice my edit. Sorry about that. 😀

Looks like with a 12.25 number that Murf was making about 340 Hp at the flywheel.

I’m only showing about 300 at the moment

It’s hard to be very precise with the Moroso slide calculator, and I was being a tad generous.

Just look at the pure stock guys that have to run those manifolds. They can't port them, nor port any other aspect of the engine.

There are a couple of 69 birds using the long branch manifolds running 12's. One in particular RAIV that has been in the 11's going back several years now.

https://uploads.tapatalk-cdn.com/202...de9f37b57a.jpg
This is my best in my convertible. My friend has gone 11.20’s around 122 or so in his 67 FB


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What’s your compression and head flow Dave

??? Murf’s numbers, especially the MPH.. look more like 450 HP?

Only 9.2 and I was told flow was 240. But I have my doubts


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My first time out with 3.08 gears and a TH400 w/13” Continental converter mine went 12.22 at 113. I’ve since upgraded to a 4L80E with a 3200 stall and 3.55 gears but haven’t been to the track. This is with a Holley Sniper EFI, full street trim and crap in the trunk. On the engine dyno with headers and a Holley HP it made 521 hp.

I’m having to shift 4 times because of the gear being a bit steep some changes coming to see if I can get it to mph again
I’m
Trying to stay 52-5500 I don’t want to work on it every weekend, just wring it’s neck once in awhile it’s fun to drive

Here's the ramair II bird that put everyone on notice a dozen years ago in the stock class.

Since then there are several that run 11's in this class currently.

Since you aren't competing with rules and skies the limit, you could technically compare to the FAST class, which has had one in particular max effort dip into the 9's, with the long branch manifolds.

https://youtu.be/KWR0IBTtG80

Round port but yes having had a few sets of repro round port f body manifolds they are much larger Than the d port version especially in the middle of the y
I am also sure they are opened up as much as they could those things are heavy lol

There are D port birds in the stock class using them as well. They (the 68's) typically run in the low to mid 12's. In there case the manifolds aren't limiting them, it's the rest of the D port package that limits the car (smaller cam, smaller heads etc...)

They aren't allowed to mess with them at all, no porting. So even the round port example I used above is a PS racer following the same rules but that really wouldn't apply to your question anyway, you aren't building a PS racer, you don't have rules to comply with, so we are just looking for the fastest car on stock long branch manifolds and the FAST series would also be a good place to look where porting is allowed. In fact I don't think there is a better place to look at how fast stock parts can go than the Pure Stock and Fast racing series. There's nothing else out there like it.

https://www.psmcdr.com/rules#:~:text...0be%20retained.

If you can get Dennis or Dan to chime in I believe he has records of fastest times. I'd be willing to bet no one has gone faster with stock manifolds than these guys.

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

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.

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

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

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.

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