Carburetor Spacer

[svopel]

I have the "standard" gasket-spacer set up (thin gasket and 1/4 inch fiber spacer) between the carburetor (Weber 32/36) and the manifold on my SCCA ITB Manta. A reputable race mechanic suggested I could add torque by replacing the quarter-inch carburetor spacer with a one-inch spacer. Before I invest in having a chunk of aluminum made into a one-inch spacer, does anyone have experience with running a larger spacer? ... is there a significant improvement over the "standard" spacer-gasket setup. I know longer intake runners = more torque, but I don't know if a "spacer" would be the same. And, if one inch is good would two inches be better, and if two inches is good ... and so on. What's the optium for performance?

Also ... would a one-inch spacer affect current jetting -- or other tuning parameters? Another concern I have is ensuring a good seal to prevent vacuum leaks ... suggestions please.

Thanks for your help ...

Ken

[RallyBob]

Originally Posted by svopel I have the "standard" gasket-spacer set up (thin gasket and 1/4 inch fiber spacer) between the carburetor (Weber 32/36) and the manifold on my SCCA ITB Manta. A reputable race mechanic suggested I could add torque by replacing the quarter-inch carburetor spacer with a one-inch spacer. Before I invest in having a chunk of aluminum made into a one-inch spacer, does anyone have experience with running a larger spacer? ... is there a significant improvement over the "standard" spacer-gasket setup. I know longer intake runners = more torque, but I don't know if a "spacer" would be the same. And, if one inch is good would two inches be better, and if two inches is good ... and so on. What's the optium for performance? Also ... would a one-inch spacer affect current jetting -- or other tuning parameters? Another concern I have is ensuring a good seal to prevent vacuum leaks ... suggestions please. Thanks for your help ... Ken

As an example, I did a back-to-back test with a 3/4" spacer and a 1/4" spacer (1/2" difference), and it made a huge difference in the powerband on a 97 hp 1.9 engine. I lost something like 7 mph top speed with the short spacer, but gained a ton of low and mid range power. Just the opposite of the expected results. Testing was done within 1/2 hour of the spacer swap and on the same stretch of road, so conditions were nearly identical. Both spacers were two-hole spacers too, not open plenums. I have tested the open plenums as well, and found they lose too much torque overall.

Just my 2 cents worth...

Bob

[GTJIM]

Obviously the plenum volume has a considerable effect - and not all good by the sound of it. This ties in with the good effects reducing that volume by fitting a peaked divider into the floor of the manifold has.
Making things inside inlet tracts bigger is not always the way to increase efficient fluid flow - remember the 302 "Boss" Mustang and its HUGE round intake ports which had to be half filled to get them to work ..........

[GT Tim]

I was just wondering where to purchase the correct spacer.I already hogged out the intake thanks to Bob's how to and put a header on my 1.9 GT.I appreciate any help.Thanks Tim

[RallyBob]

Originally Posted by GT Tim I was just wondering where to purchase the correct spacer.I already hogged out the intake thanks to Bob's how to and put a header on my 1.9 GT.I appreciate any help.Thanks Tim

I've always made my own from whatever was available. I've used scraps of aluminum, Corian (yes the countertop material), hard maple, and phenolic. With a bandsaw and a holesaw plus some drill bits, it's not a difficult task. The hardest part is the dimensional layout.

I hate to ask this, but is this an item of interest to other Opelers? I say this because phenolic can be machined like wood, and at my father's company they have a few wood-cutting CNC's that would be able to cut these out rapidly. I've made them before for Subaru WRX throttle body spacers, and they came out pretty nice.

Bob

[GT Tim]

Thanks Bob, I could probably make it at work but I would much rather use something you made.I know I would buy one if you make them.Thanks Tim

[svopel]

Originally Posted by RallyBob I lost something like 7 mph top speed with the short spacer, but gained a ton of low and mid range power. Both spacers were two-hole spacers too, not open plenums. I have tested the open plenums as well, and found they lose too much torque overall. Just my 2 cents worth... Bob

Bob ...

I'm looking for low and mid range power ... so I had better stick with the short (1/4 inch) spacer -- the two hole version. BTW, did you gain on top end with the 3/4 inch spacer?

Thanks Bob ... your "2 cents worth" is always a bargin.

PS .. I'm interested in having a phenolic spacer made, I don't know how many you need to make it worth while, but put me down.

Ken

[RallyBob]

Originally Posted by svopel BTW, did you gain on top end with the 3/4 inch spacer?

Absolutely. My 'stock' 1.9 (flat tops with 1.9H head and 2.0 valves, 38 DGAS on ported intake, Sprint manifold with 2" exhaust, stock hydraulic cam, 3.44 with Getrag 5 speed) pushed my Ascona to 122 mph with the 3/4" spacer. It would only do 115 with the 1/4" spacer. That's nothing but pure top end hp there, since that car is a brick-and-a-half. It also got there noticeably faster. But the down side was it was 'soggier' below 4000 rpms.

PS .. I'm interested in having a phenolic spacer made, I don't know how many you need to make it worth while, but put me down.

It becomes cost effective at 8-10 pieces. Of course, there's the whole thickness issue to deal with. I'm sure everyone wants a different size.

Bob

[azopelnut]

A low-end torque spacer is what I would be after for all my cars.
Seems like all the phenolic spacers i have are opened up and do not have individual openings for each barrel of the the carb.

[baz]

Originally Posted by RallyBob It becomes cost effective at 8-10 pieces. Of course, there's the whole thickness issue to deal with. I'm sure everyone wants a different size. Bob

bob would it be worth while doing sets in 1/8th steps so the racers can "tune" the engine for tracks to get the best without other changes

[BQS4]

Bob;
I think you have proved that going beyond 3/4" is not needed, but, more than 1/4" shows marked improvement, even on stone stock motors. this would give a range of 1/2", or roughly 4 "sizes" if you go by GTJim's 1/8" idea. This would give you a working idea as to what you're looking at. I don't know how much this wood costs, but, it shouldn't be that much is it?
Gene

[RallyBob]

Originally Posted by baz bob would it be worth while doing sets in 1/8th steps so the racers can "tune" the engine for tracks to get the best without other changes

Baz, I used to do exactly this for my friend's old stock-class circle track Opel. There were numerous intake manifold heights over the years for the 1.9, and I had a collection of three different plenum heights that we'd use to tailor the car's power to the tracks we ran on. Worked like a charm, the parts were legal as they were stock, and we were not allowed to use any carb spacers.

[RallyBob]

Originally Posted by BQS4 Bob; I think you have proved that going beyond 3/4" is not needed, but, more than 1/4" shows marked improvement, even on stone stock motors.

The taller spacers do have their place, but it's not on a stock street engine. On a modified engine with a hot cam they can really let them breathe, so I've used 3/4" and taller spacers in those instances. If you have high compression (10.5 to 11.5 or so), then there is less of a 'penalty' for running a tall spacer, the engine's VE can make up for a tall spacer.

I don't know how much this wood costs, but, it shouldn't be that much is it? Gene

Phenolic material is quite pricey in full sheet quantity...I usually buy it in smaller cut-off sizes from the scrap bin from my local supplier. A piece of 3/8" thick 4' x 8' phenolic material is about $400 or so (last time I priced it anyway). But it works awesome to isolate heat from the carburetor.

Bob

[BQS4]

Bob;
This must be the same stuff as I used a while back. I had to re-make one of these are I found out the hard way that there are two types for the "stock" Opel. One has cut outs for access to he 4 bolts holding the intake/exhaust manifolds together. This one is for the solex carb, but, if used with a weber, the cut outs allow a vacuum to come in under the weber carb (ask me how I know ) But, in the need to have one without the cut outs, I made one from a piece of wood from my old oak office desk. It was used to compartment your desk drawers. I made one for Vickie Gage and it cured a problem for her too.
Gene

[Lindsay]

Aware that the discussion is not regarding GT ...

Years ago, when there were Buick/ Opel Dealers, mechanic suggested to use 0.16" thick fiber gasket from bottom of Solex carburetor as heat isolation spacer. Tried using that spacer with std. thick gasket spacer (D32E-9447-AA) using Weber 32/36; GT hood hit top of the air cleaner bonnet. I have shorten my Weber to Solex (aluminum) air cleaner adapter and Opel air cleaner bonnet. Had to remove additional spacer in GT when using Weber 32/36 carb.

Spacer is great idea for non-GT Owners (or GT Owners with more hood clearance).

[RallyBob]

Originally Posted by Lindsay Spacer is great idea for non-GT Owners (or GT Owners with more hood clearance).

This depends on the basic manifold. Some GT's have tall ones, some short ones. The tall intakes have issues when using a Weber carb with stock air filter adapter...this fact used to drive me nuts when I sold the Weber kits years ago, since some cars had tons of room, others hit the hood. Once I discovered the variations in manifold heights it all made sense to me.

[GT Tim]

I checked to see if I had clearance and I have room for a spacer.I have a high comp motor that was just rebuilt and performance cam not sure exactly what one and 32/36. Thanks Tim

[markandson]

Bob,
Why not make the spacer out of 1/8" phenolic, then everyone could put multiple spacers in to get the height they want. Either that or the purchase quantity would be 4 so that anywhere from 1/8" to 1/2" is available. Being that the phenolic I am familiar with is pretty stiff and also very shiny on both sides, almost like formica, I would think that when stacked together they should seal pretty well.

[jeffw]

Originally Posted by RallyBob The taller spacers do have their place, but it's not on a stock street engine. On a modified engine with a hot cam they can really let them breathe, so I've used 3/4" and taller spacers in those instances. If you have high compression (10.5 to 11.5 or so), then there is less of a 'penalty' for running a tall spacer, the engine's VE can make up for a tall spacer. Phenolic material is quite pricey in full sheet quantity...I usually buy it in smaller cut-off sizes from the scrap bin from my local supplier. A piece of 3/8" thick 4' x 8' phenolic material is about $400 or so (last time I priced it anyway). But it works awesome to isolate heat from the carburetor. Bob

Bob,
I plan to replace my Solex with a weber 32/36 dga manual choke
Are you planing to make any of these spacers, if so I would be interested
Jeff

[cherokee]

Back to the original question...are you sure a larger spacer is legal? Don't have the GCR on the work computer and the SCCA site seems to be down but I was thinking a spacer was a no-no.

[Tru-Craft]

I "used to" machine Phenolic!
I made a 1/4 phenolic spacer for my 32-36 carb years ago, good heat insulator!
The problems
Expensive!
Its abbrasive and wears cutting tools!!!!
The chips are a fine powder that get every where, including the ways of the machines! Remember abbrasive!!!!
I don't machine the stuff anymore! Most supply companies won't even cut it!

Im going to make a spacer for my 38DGAS, just wrote a program for the CNC.
I was thinking of using a high temp UHMW Polyethylene. The temp range is -22 to 275F and machines easily. Cost for material 1/4 x 2-3/4 x 4-1/2 is about a $1 per spacer! Lots of plastic choices today! Other ideas?
Should I make a spacer with 2 seperate holes?
What thickness for my GT?
Lyle

[Tru-Craft]

Bob, it sounds like you have spacers!
Do you have a 1/4 or 3/8 phenolic spacer for my 38DGES?
If you have made some, I won't bother making them! Got enough to do.
Lyle

[RallyBob]

Originally Posted by Tru-Craft Bob, it sounds like you have spacers! Do you have a 1/4 or 3/8 phenolic spacer for my 38DGES? If you have made some, I won't bother making them! Got enough to do. Lyle

Nope, never had them made. Sounds like a job for...TRU-CRAFTman!

[Tru-Craft]

Bob, my daughter will like that name! Wonder what my super powers are?
OK if I make them should the holes be 1-1/2 diameter seperate holes?
or an oval cutout?
1/4 thick? Just stack them.
I will make mine out of high temp poly!
No Phenolic, my machines have to last for another 20 years!!!!!

[Tru-Craft]

I like the 1/8" spacer idea! Just stack them together.
My GT with 32-36 has a 1/4" spacer, has hood clearance.
If I make a spacer to fit the 38DGAS bores will it work on the 32-36?
2 hole design?