The BBC RPM Performer test next year

[1980RS]

Since I now have a baseline for my BBC test with the RPM intake I am going to test two others that I have with different depths of the divider being cut down.
1st test was out of the box
2nd test will be with the divider cut down another 1/2" for a 1" divider drop
3rd test will be the divider cut down all the way except for a little lip at the bottom

This will be a very good test as my SBC air gap with the divider cut all the way down did so well last year. Will be interesting to see what carburetor responds better on each combo also.

[rgalajda]

Can you tell us the engine specs and intend use , street, street /strip or drag?

[HQM383]

Since I now have a baseline for my BBC test with the RPM intake I am going to test two others that I have with different depths of the divider being cut down.
1st test was out of the box
2nd test will be with the divider cut down another 1/2" for a 1" divider drop
3rd test will be the divider cut down all the way except for a little lip at the bottom

This will be a very good test as my SBC air gap with the divider cut all the way down did so well last year. Will be interesting to see what carburetor responds better on each combo also.

What are the details of that first test?

Could you run us through the SBC air gap testing done in the past? Might serve as a good reference going forward in this thread.

[1980RS]

Can you tell us the engine specs and intend use , street, street /strip or drag?

My current peanut port 454 that ran 11 teens@119mph Almost all strip testing.

[1980RS]

Since I now have a baseline for my BBC test with the RPM intake I am going to test two others that I have with different depths of the divider being cut down.
1st test was out of the box
2nd test will be with the divider cut down another 1/2" for a 1" divider drop
3rd test will be the divider cut down all the way except for a little lip at the bottom

This will be a very good test as my SBC air gap with the divider cut all the way down did so well last year. Will be interesting to see what carburetor responds better on each combo also.

What are the details of that first test?

Could you run us through the SBC air gap testing done in the past? Might serve as a good reference going forward in this thread.

My SBC 358 with the divider cut down ran 11.30@118mph which I though was outstanding for a dual plane. I would have liked to try my 8" converter with this intake but it was hurt and I will need to wait until next year for anymore testing. I have also run my Holley 300-36 Contender dual plane with pretty good results also. One thing I know for sure the cut down divider will need to be cross jetted.

[HQM383]

Since I now have a baseline for my BBC test with the RPM intake I am going to test two others that I have with different depths of the divider being cut down.
1st test was out of the box
2nd test will be with the divider cut down another 1/2" for a 1" divider drop
3rd test will be the divider cut down all the way except for a little lip at the bottom

This will be a very good test as my SBC air gap with the divider cut all the way down did so well last year. Will be interesting to see what carburetor responds better on each combo also.

What are the details of that first test?

Could you run us through the SBC air gap testing done in the past? Might serve as a good reference going forward in this thread.

My SBC 358 with the divider cut down ran 11.30@118mph which I though was outstanding for a dual plane. I would have liked to try my 8" converter with this intake but it was hurt and I will need to wait until next year for anymore testing. I have also run my Holley 300-36 Contender dual plane with pretty good results also. One thing I know for sure the cut down divider will need to be cross jetted.

And the above in red?

What was the full divider results for the sbc test or another way, what we’re the cut down gains?

[rgalajda]

A true dual plane intake which has a full divider , where the plenums are divided, sees about half of the carbs CFM capability.
Cutting the divider between the two plenums, you allow cylinders to draw from all four barrels. This leads to the question of how much do you cut out.
If the cutout is large , extending to the plenum floor , it converts a dual plane intake into a single plane intake that has longer runners with many turns and changes of direction. Any advantage of the dual plane intake , vacuum and low speed torque ,is almost lost.

On a BBC approaching about 600 hp the single plane intake is usually an advantage along with a short cam, and will usually out perform the output with a dual plane , divider cutout, and a longer cam.
If the build involves making good torque ( who doesn't want to ) 500 to 525 hp , a good dual plane intake with an 850 cfm or larger carb may be the way to go.
If you are performing tests ,top end output, on a dual plane intake you should use as large a carburetor as possible first, before cutting the divider .
Some of the low performance aluminum dual plane intake manifolds ( OE replacement ) lacking a raised pad and better runner shapes , do not have enough cfm flow to respond to large cfm carbs.

[Tom68]

A true dual plane intake which has a full divider , where the plenums are divided, sees about half of the carbs CFM capability.
Cutting the divider between the two plenums, you allow cylinders to draw from all four barrels. This leads to the question of how much do you cut out.

Even with the divider cut to the upper plenum floor it still stops the cylinders that have significant intake timing overlap from pulling on the same corner of the carb, i.e you still get some of the dual planes low speed advantage plus an open plenum to pull from at higher revs, still has all the shitty bends and the flow still smashes into a flat plenum floor so can't deliver tall long runner single plane performance.

On the carb sizing, 8 intake valves are not open at the same time, with a single plane and race cam they see 4 open valves at the plenum, a dual plane with the same cam only sees two valves open at the same time to half the carby, a dual plane can handle a bigger carb not because it needs it but because it can handle it due to less egr overlap contamination, that also means it has less misfires at low speed with manifold vacuum, that's why Henry had to go to a Dual Plane in 1934 and the rest is now history.

[F-BIRD'88]

"larger carb". Can be multi carbs on a dual plane high rise. "dual Quad". "Tri-Power"
2x4. 3x2. 4x2 5x2. Most intakes also like carb spacers too.
You could evaluate multi carbs on your single 4 bbl hi rise by adding a multi carb adapter.
Carb height becomes an issue with flat hoods but you do get the benefit of more air flow and added carb height. This multi carb adapter spacer could be divided , open or partially divided.
With this you can avoid cuttung out the plenum divider in the intake, while evaluating various amounts of added carb(s) cfm and plenum styles and heights.

The more powerfull the test engine is the more likely it will respond to increasing carb(s) cfm capacity

[Bigchief632]

"larger carb". Can be multi carbs on a dual plane high rise. "dual Quad". "Tri-Power"
2x4. 3x2. 4x2 5x2. Most intakes also like carb spacers too.
You could evaluate multi carbs on your single 4 bbl hi rise by adding a multi carb adapter.
Carb height becomes an issue with flat hoods but you do get the benefit of more air flow and added carb height. This multi carb adapter spacer could be divided , open or partially divided.
With this you can avoid cuttung out the plenum divider in the intake, while evaluating various amounts of added carb(s) cfm and plenum styles and heights.

The more powerfull the test engine is the more likely it will respond to increasing carb(s) cfm capacity

Thanks Captain Obvious, lol

[1980RS]

What are the details of that first test?

Could you run us through the SBC air gap testing done in the past? Might serve as a good reference going forward in this thread.

My SBC 358 with the divider cut down ran 11.30@118mph which I though was outstanding for a dual plane. I would have liked to try my 8" converter with this intake but it was hurt and I will need to wait until next year for anymore testing. I have also run my Holley 300-36 Contender dual plane with pretty good results also. One thing I know for sure the cut down divider will need to be cross jetted.

And the above in red?

What was the full divider results for the sbc test or another way, what we’re the cut down gains?

I have to look but I think the car ran 11.59@115mph with the full divider on the SBC

[1980RS]

So you all know what the stock Performer RPM looks like
Here is No.2 cut down 1" and No.3 cut all the way down

[F-BIRD'88]

Do you happen to have a Dominator carb (and 4500 adapter) to try out? For grins

[Old School]

Since I now have a baseline for my BBC test with the RPM intake I am going to test two others that I have with different depths of the divider being cut down.
1st test was out of the box
2nd test will be with the divider cut down another 1/2" for a 1" divider drop
3rd test will be the divider cut down all the way except for a little lip at the bottom

This will be a very good test as my SBC air gap with the divider cut all the way down did so well last year. Will be interesting to see what carburetor responds better on each combo also.

What was the et and mph with test 1? Test 2? Test 3? Also give the dates and location of each test.

[skinny z]

So you all know what the stock Performer RPM looks like
Here is No.2 cut down 1" and No.3 cut all the way down

I may have missed it but do you intend to experiment with any spacers?
And on your SBC with the modified air gap, were there any spacer tests done then? This is on my agenda for what I hope will be next year's testing. Pending the details.