Twin SNs?

[Buck-Strickland]

Joe,

What was the size/makeup of the motor that you ran two SN’s into a box on, and that had surge problems? Do you remember the pulley ratio (crank and blower pulley diameters)?

How did you pipe the twin SN’s into the 502?

What was the setup on the 875hp 383?

Thanks for your time.

[Granatelli]

We actually tried it several times. Above is the 502. I did it on a 302 in a '85 mustang as well and made 714hp

If you have a specific application you are inquiring about let me know. If you want twins that look cool ...have at it. If the goal is power and reliability - don't let the blowers fight each other. Have each blower feed have the cylinders

As for 383 - we did it both ways common box and split manifold

[Buck-Strickland]

I was going to add a second SN-2000 HO to my 406 sbc.(see Thumnails below) I was thinking of using dual 3" inlet y-pipe with a 3.5" outlet to the carb enclosure. I'm starting to understand the fighting each other. But, I wonder if a large chamber like the enclosure on your 502 might help. Or is using a dual quad manifold and two carburetors a must?

[Granatelli]

if you want wow factor it is fine - if you want pure performance divorce them. it is the nature of the centrifugal design to fight. the real reason twin turbos don't fight like this is because they exh balanced them out. But with belt driven blowers balls or gear, they are far less forgiving

[Sponge]

if you want wow factor it is fine - if you want pure performance divorce them. it is the nature of the centrifugal design to fight. the real reason twin turbos don't fight like this is because they exh balanced them out. But with belt driven blowers balls or gear, they are far less forgiving

Even with dual carburator?

[Aggressor]

Error

- Geary

[Aggressor]

Perhaps Mr Granatelli would explain this better than I can. I understand that if you force boost air from 2 blowers through 2 carbs into 1 common intake plenum a reversion condition may take place. I believe that is why the Edelbrock X-F66 crossram was used on the original Shelby/Cosby cars. It effectively splits the engine into 2 uneven-firing 4 cylinder engines connected by a common crank. Each Paxton has no reference to the existance of the other.
I don't fully understand the reversion term but it may be what was descibed earlier as the blowers fighting each other. In this case the fight would not be above the throttle plates but would be in the plenum after fuel was added to the pressurized air. I also wondered if one carb could be backfed bottom up by the blower winning the push/pull contest at that moment.

I used the X-F66 solution in my dual Paxton build and the results are spectacular. With 2400 pounds and a 90 inch wheelbase you use light toe pressure on the accelerator for street driving to arrive safe.

- Geary

[Sponge]

I did have received this from Cobra Automotive:

Hello Dylan,
We do not currently make a twin Paxton set up for small blocks: however we could if it is something you wanted to do. Please contact our sales manager, Scotty Hackenson, to discuss further. His direct e-mail is sales@cobraautomotive.com or call him at 203-284-3863.
Our kit uses the old style "ball driven" blowers as it is a re-creation of the twin set up that Carroll Shelby did on the two 427 Cobras he built in the 60's for himself and Bill Cosby. Two blowers are required to feed the intake requirements of the big block engine. Here is some info we have on our kits. Best regards,

Carl Vogt
Cobra Automotive Inc.
37 Warehouse Point Road
Wallingford, CT 06492
203-284-3863 phone
203-284-3897 fax
info@cobraautomotive e-mail
www.cobraautomotive.com web site

[Granatelli]

There were 3 cars not 2. The third car went to Glen Campbell the singer

[Granatelli]

Perhaps Mr Granetelli would explain this better than I can. I understand that if you force boost air from 2 blowers through 2 carbs into 1 common intake plenum a reversion condition may take place. I believe that is why the Edelbrock X-F66 crossram was used on the original Shelby/Cosby cars. It effectively splits the engine into 2 uneven-firing 4 cylinder engines connected by a common crank. Each Paxton has no reference to the existance of the other.
I don't fully understand the reversion term but it may be what was descibed earlier as the blowers fighting each other. I this case the fight would not be above the throttle plates but would be in the plenum after fuel was added to the pressurized air. I also wondered if one carb could be backfed bottom up by the blower winning the push/pull contest at that moment.

I used the X-F66 solution in my dual Paxton build and the results are spectacular. With 2400 pounds and a 90 inch wheelbase you use light toe pressure on the accelerator for street driving to arrive safe.

- Geary

BINGO:huge:

[Buck-Strickland]

So, two blowers into a enclosure will fight each other.
Does the pressure go up and the volume drop? The air just stops flowing through the units. Is that how they end up stalling each other out (In front of the Surge line.) What if they were pulleyed down to match the motor and prevent exceeding the surge line?

Joe,

How/what did you guys do on the 875hp 383 Chevy? What was the engine combination, and the blower setup? Blow through or draw through?

Perhaps I would be wiser to wait until a VR4 unit comes up for sale again.

Thanks