Thanks Billy and Charlie... That's what I needed to know. I'll continue on. There is a good used Barry Grant Mighty Demon 750 CFM blow thru carb with mechanical secondaries on Epay that I think I'll go for to top things off.

Rono

  Ron Lane,  Meridian, ID

Am I confused (happens a lot anymore)? - isn't the spacer suposed to be made with the 4 holes matching the carb baseplate bores and then opening up and tapering away as air leaves the carb? This seems upside down to that concept.

On the other hand - I sure can see the advantage of smoothing the edges of the air entry into the manifold too. Seems like you need two transitions - one out of the carb - and one from the open plenum into the manifold passages.  

 
 Steve Metzger       Tucson, Arizona

Steve, Think you're right. The object being to slow the Fuel/air down after it leaves the carb and before it impinges on the manifold plenum bottom and seperates. I've seen polycarbonate manifolds with little rivers of fuel running down the intake runners. Doubt if that burns very well.   

Frank/Rebop

Bristol, In ( by Elkhart) 

Now I'm really lost. Ted, are you talking about using 2 tapered spaces small holes in the center and large holes on the outsides? So you have a large opening under the carb AND at the maniflold, sort of an hourglass setup? I know I'm getting old but I'm completely lost in this thread. Chuck

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

Chuck, I think he meant try them the other way around with open end together, but a try both ways may show some interesting results.



Frank, I don't think the idea is to slow the mix down anywhere down the line, slowing it down is what causes the molecules

To fall out of suspension, too smooth a port job will also cause this when not in wide open throttle. I recently installed the 1.08 carb I got from Glenn and my car does not bark as load as it did Exhaust wise with a 1.12 but it is a lot smoother power all around, can't tell if it has more power but definitely smoother with the increase in velocity from the smaller bores of the carb!

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?

Rono.  You’ll need to slot the four hole gasket so that there is no unsupported gasket material under the carb or over the intake opening depending upon which way you install the spacer.

 

Billy.  Boosted applications are completely different when it comes to air flow requirements.  While I’ve reams of data for naturally aspirated carb setups, I’ve only a smattering of information on some of the various blow-thru applications in regards to spacer demands.  Because many of the engines I test with superchargers already have fixed carburetor setups, there’s not much opportunity to test a variety of carb spacers on those.  There are undoubtedly some learnings to be had in that area but the complexity of many of those setups prevents their owners from spending the time on the dyno to test some of the variations in those setups.

 

Chuck.  Here’s a picture of the tapered spacer and looking at it from the bottom side.  The general idea is to have the four hole portion at the carb base which eliminates some of the flow eddys that form which in turn inhibits flow through the carburetor.  These spacers work really well on the smaller sized carburetors in that the flow through the carb is increased simply due to the reduction of the turbulence that occurs under the carb.

 

 

There is not a carburetor spacer that is a ‘catch all’ for all applications.  For the Y, I find that the Mummert aluminum intake prefers one design of spacer while the Blue Thunder intake prefers another.  And then the ECZ-B iron intake seems to be up in the air on which spacer works best depending upon the intake and engine modifications themselves.

Lorena, Texas (South of Waco)

Ted -

(1) Is the above picture inverted to the way the spacer goes under the carb and shown this way for clarity?

(2) Assuming so, would it then simply discharge onto the the carb mounting surface of the manifold (slots in particular)? Does the center divider get reduced - removed to certain depth  - "sharpened" edge - what sort of manifold match?

 
 Steve Metzger       Tucson, Arizona

I had a  1" thick square hole spacer on my engine for a while but recently changed to this slightly modified 1" tk 4 holer. This is the surface that contacts a Blue Thunder manifold. The purpose of transitions is to provide smoother flow out of the bottom of the spacer reducing turbulance in the plenum allowing the A/F mixture an easier time turning to the horizontal runners.  It also should help A/F reach the back of the engine when running on the front barrels.  Remember the front and back of the BT manifold is curved to the radius the carb throttles. 

 I drive mostly on the street and this spacer is somewhat more forgiving at Idle and off idle. I didn't notice much loss in acceleration but I have not tried it on the track. The BT has a medium size "window" between the oval holes, if that window was not there the idle would probably be even better. 

Doug T

The Highlands, Louisville, Ky.

Well I put a Mummert 2 slot spacer on the Blue Thunder, and while it may not be optimum neither is the BT manifold without some exhaust help.  The machinist who milled the back of the manifold also fit and polished the spacer with the BT which did have some edges he said had to go.  I'm not racing but I'll take what I can get and it runs real nice.

Ted, Redding, CA

very interesting thread

been looking at HVH website,  surprised they say plastic/phenolic spacers not for street only drag/marine use!

ally for street/strip use  why ...any coment please. i would have thought plastic would have been a better heat blocker

stuey