First thing I would do before I spent a bunch of money chasing my tale with the motor combo is, pull the motor and bring it to a nearby dyno service that’s known for legit numbers and retest the motor.

A fresh set of dyno numbers would verify you have what you think you have, as well as where the peaks are occurring.
I have re-tested several motors where the owners have spent thousands of dollars trying to get the car to go as fast as their dyno sheet said it should....... only to find after re-testing that it didn’t have the power they were told, and the car was actually running just what it should.

You need to test the converter flash.
What the converter “should” be and what it actually is could be very different.

I’m not a converter builder, but if the motor really makes peak tq at 6300, you’re going to want like 6500 stall.
I can’t imagine an 8” converter flashing to 6500 behind a 451, and still be efficient enough to provide an adequate level of lock up going down the track in a 3100lb car(unless you were shifting at like 8200+).
I don’t know what you have, but it sure sounds like a combo that would need a 7” unit to meet that criteria.

Well I gotta ask what B1 head is this? An original, or a BS? For a "race ported" original those would be sub standard numbers for sure. Also an original on a 451 is a LOT of head and I'd guess wants a LOT of RPM to be happy. Been there done that as my first B1 engine was a 451. Also you are not running anywhere near almost 800hp worth of MPH, you are likely close to 10MPH off for that HP and weight. So something is quite a bit off in the combo and numbers

just to put this out there... I have a pair of originals that were done by a very reputable shop, per the previous owner, that go 372cfm at .650 on my bench. Point being the port job, if any, could be the issue here. Maybe cross section/cubic inch/flow, makes for a lazy engine. Not to mention the 2 dominators.

Everything is apart right now. I do shift at 8000 with this 8” converter. Maybe it wants more. I’m just trying to see if one of my problems is the exhaust. There is no flow gain above.550 lift with these b1 originals. It seem odd that a race head tops out at this lift.

With your combo 32x5.13 gear and only 648fwhp@3100 this is what the ticket would look like>

60 Foot E.T. : 1.36
1/8 Mile E.T. : 6.19
1/8 Mile Trap Speed : 109.76
1/4 Mile E.T. : 9.81
1/4 Mile Trap Speed : 137
1/4 Mile Trap RPM : 7,360+slip

At 790hp it would be

60 Foot E.T. : 1.28
1/8 Mile E.T. : 5.80
1/8 Mile Trap Speed : 117.25
1/4 Mile E.T. : 9.19
1/4 Mile Trap Speed : 146
1/4 Mile Trap RPM : 7,862+
just for reference, The Moroso slide rule shows less hp.

Thanks for that info

A 451 pump gas engine with Trick Flow heads will run 9.90's in a 3100 lb car if everything is working right so that combo is way, way off somewhere.

Fast is correct, get the engine on a known good dyno to sort it out. If the engine is all apart then look it over for clues. Maybe the Dominators were set up wrong and the engine was going down the track at 9:1 air fuel ratio? Maybe the firing order was switched up? If it was my engine I'd get rid of the sheet metal intake and the carbs and put a single 4bbl on there. I bet it goes faster and works better.

Also sounds like the drivetrain might not match the engine. I know Mazzolini used to run a 383 with B1 heads and he shifted at the moon. Just crazy RPM with those big heads on a smaller engine.

Were the ex ports tested with the appropriate sized flow tube attached?

I really wouldn’t too be concerned with the ex flow flatlining at .550 lift........I’ve seen heads that came off good running hemi motors that do the same thing.
IMO, that’s not your problem.

I also agree with Andy on trying the single 4500 intake.

Very shortly after B1’s came out I dyno tested a 446 with a set that just got a mild bowl blend. It made just over 700hp, which seemed fantastic at the time.
In a 3000lb back half Cuda it went 9.40’s........this was in like 1991.

I rairly even bother checking exhaust flow numbers on my bench. My ears tell me more than flow numbers on exhaust side then I fine tune the air speed to get it where I want it.

Looking to send the heads out to someone who knows b1 originals for a second opinion. Then adjust my combo

Check this threadB1 heads
Do you check your pm's

Yes thanks for that

Lots of people have experience with B1 heads. My opinion for what it matters, just use someone who knows heads period. Guys who know how to make power will make it. With the stock block not sure I'd get to concerned with to much power. Sounds to me like you have some mismatched pieces. Id be looking at tuning the thing to try and find hidden potential, but in the end MPH tells the HP story. Me thinks you are well short of that HP number.

there is a fair bit wrong that engine should be close to 150 mph 9 flat just a comparison my sb at over 3550 lbs runs a 9.57@142 mph witch shows close to 800 hp ,get your box and converter checked for crazy slippage or something going on

For reference...... original B1’s prepped by Koffels.
Bowl and chamber work only:

28”, 4.375 bore, clay radius entry, no tube on ex:

Lift———in/ex
.100——78.9/58.5
.200——148.0/106.1
.300——216.0/146.4
.400——275.6/187.1
.500——326.1/219.2
.600——357.7/242.6
.700——378.4/257.7
.800——389.6/266.4

These made about 830hp on a 526 on our dyno with a single 1050 carb.

Dyno numbers aside, I think a cam swap and the single carb manifold would have improved the ET.

I was at the track a while back and a nice early B body with a Hemi and crossram was running 12's. So sometimes a combination just gets too complex and stops working right. When that happens you need to take it apart and work your way thru it. I highly doubt that the exhaust ports are the culprit but maybe that is the case. Send the heads to Fast and see what he says.

There are a lot of bad sheet metal intakes floating around. I've seen a few come across the dyno that wouldn't make squat for power. They look nice, but some guys building them focus more on the looks than how they work. It is the first thing I'd suspect when an engine isn't making good power.

I’ll be the first to admit that I haven’t really figured out how to get magic to happen on the flow bench with B1 heads.

I think I’ve only tested one set that had what I thought had really good exhaust flow..... and my recollection is they were huge(run on a 572 with spray).

This is more like what I see......
Some older bowl ported heads, mild “full” porting on the exhaust.

On the intakes I opened the bowls up and tweaked the short turns.
On the exhaust the primary thing I did was to narrow up the guide boss...... which was more work than it should have been for what I gained.

As rec’d:

Lift———in/ex
.100——75.6/53.6
.200——149.2/112.2
.300——220.8/165.9
.400——282.3/209.8
.500——336.6/236.2
.600——374.5/242.6
.700——371.7/241.9
.800——352.1/241.9

After rework:
Lift———in/ex
.100——73.7/54.2
.200——148.8/115.9
.300——219.6/165.9
.400——284.2/212.2
.500——338.4/245.7
.600——375.6/257.8
.700——408.0/258.9
.800——400.8/258.9

The thing with the ex flow is, you only need what you need, and blowing out the size of the port chasing a number on the flow bench isn’t likely going to get the car down the track quicker.

I guess the questions I’d ask are, what are the goals/expectations out of the build?
It would seem the OP must be pretty far off from where he wants to be if the motor was still running fine and he elected to remove it and pull it all apart rather than tweak on the combo in the car.

Just trying to eliminate one problem after another to gain more hp. There are quite a few combos out there similar to mine that make more hp.

If there are quite a few people running original B1 headed 451 type builds making more than 800hp, and running like 800hp should in a 3100lb car...... I think it would be in your best interest to chat a few of those folks up and see where they had their heads done.

Why try and reinvent the wheel?

BTW, did you discuss the performance(or lack of it) with Ray?
Did he offer any insight?

'shave run B1 stuff off and on for quite some time. For the performance you are getting from them I would say something is really wrong with the combination you have or the health of the engine in general. I personally would not build a 451 using them these days, but did back in the dark ages. Be interesting to see more info on the current combo, came compression etc.

Have you don e the basics? Leak it down, do a compression check, look at the plugs etc?