Moroso 1.00 " Carburator Spacer Installation

https://www.summitracing.com/parts/hly-0-9381
https://www.jegs.com/i/Holley/510/0-9381/10002/-1

Keep checking ebay Brian. I picked up a brand new in the box Holley 0-9381 years ago for a great price.
It is the matching carb for the Smokey Yunick SY-1 intake manifold.

Those are Koolest Vintage Intakes for a SBC.
I seen one on a 1970 Base Firebird a guy transplanted a SBC into.
I was at Winners Circle Speed shop Joliet IL maybe 2011.
Sounded real good . He opened the hood and showed off to me.
Same SY1 intake !
 
Not so much the Offy Dual Port the issue Right now Mike.
Take a photo for you be back to post.

Might bite the Bullet and buy order the Holley 9380 850 Annular Booster carb.
Googled more old forum posts. All Positive reviews.
Guys all amazed at lighting fast throttle response and excellent top end Hp.
11 second ET some at track.
 
KzvLY9p.jpg
 
WYkGkOc.jpg


Once the Secondaries open it runs real hard.
Power brake to get it going.
I feel inconsistent mixture stumble going on.
Not misfire ignition.
Gets rolling keep it floored.
 
I can't see the images in work. Will have to check at home.
I am familiar with the OFFY dual-port. Was an attempt of trying to make a performance intake and yet still meet emissions - hence the reason for dividing the primaries and secondaries. Back then idle only testing was done.
Have you considered a modified QJet or even a Predator carb to work with that dual-port?
 
My guess is that the stumble you are feeling is the delay coming from the secondary half of the ports being activated.
If so, there is no way around that using that manifold.

Not for an OLDS, but it illustrates the concept just the same.

images

 
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Those are Koolest Vintage Intakes for a SBC.
I seen one on a 1970 Base Firebird a guy transplanted a SBC into.
I was at Winners Circle Speed shop Joliet IL maybe 2011.
Sounded real good . He opened the hood and showed off to me.
Same SY1 intake !

I think the SY-1 intake might work really well on a large CI small block.
 
I can't see the images in work. Will have to check at home.
I am familiar with the OFFY dual-port. Was an attempt of trying to make a performance intake and yet still meet emissions - hence the reason for dividing the primaries and secondaries. Back then idle only testing was done.
Have you considered a modified QJet or even a Predator carb to work with that dual-port?
A Q-jet does not have enough tuning flexibility for the odd Offy Dual Port.
When you get home you will see my burnouts. Twin strips.
3.23 gears. TH400 with 2.48 1st gear.
4200 lbs 63 Pontiac Widetrack.
 
My guess is that the stumble you are feeling is the delay coming from the secondary half of the ports being activated.
If so, there is no way around that using that manifold.

Not for an OLDS, but it illustrates the concept just the same.

images
My late bud Bill swore by Offy Dual ports.
He had one made custom for 81 Stingray Corvette. Dual Quads. 572 ci.
I remember him telling me he drilled large holes around 7/8 " through the divider walls.
He must have drilled bottom side of intake. Closed up bottom by Welding.
He had a friend that was a Master welder.

Some Mopar 440 guys used Offy Dual ports.
Read they cut the plenum divider back 1 inch into the port.
 
Here's a thought - still running wide open exhaust, correct. Might that have anything to do with the stumble?
 
My late bud Bill swore by Offy Dual ports.
He had one made custom for 81 Stingray Corvette. Dual Quads. 572 ci.
I remember him telling me he drilled large holes around 7/8 " through the divider walls.
He must have drilled bottom side of intake. Closed up bottom by Welding.
He had a friend that was a Master welder.

Some Mopar 440 guys used Offy Dual ports.
Read they cut the plenum divider back 1 inch into the port.

Like this?
 
Here's a thought - still running wide open exhaust, correct. Might that have anything to do with the stumble?
Maybe.
It's a transiston stage from idle to off idle slots to main primary boosters working.
Hard to describe.
Like lean.
Rich.....more of a burble.
The Holley Street Avenger 770cfm on now has Straight high mounted boosters.
Not dog leg like modern Hp Holleys sold and used by most racers.
 
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