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6/25/14 11:02pm - Original Message: 'Carb Spacer needed?'
bcousins
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Jacksonville, FL - USA

Vette(s):
79 L-82 4-speed. Engine stock except long tube headers. Previous owner replaced upholstery and carpet with OEM. I replaced and upgraded steering and suspension.

Joined: 12/15/2009
Posts: 36
Wondering what the members thoughts are on the use of a spacer between the carb and manifold? My stock Rochester on my stock manifold on my 79 L-82 has a 3/8" spacer but I am not sure if the spacer was added by one of several previous owners.
I am replacing with a Holley 670 cfm to set on top of an Edelbrock RPM Air Gap. I understand hood clearance issues and that's not a problem. 
Is a spacer needed or helpful for air flow? Temperature reduction? What is it for?
Can I do without one?


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6/26/14 3:55am - Reply: 'Re: Carb Spacer needed?'
Joanne Gold Member
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Joined: 11/30/2006
Posts: 441

spacer help keep fuel from get hot.and I found also smooths out running a fair bit.

I'm  sure others will chime in with their views too..



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6/26/14 12:07pm - Reply: 'Re: Carb Spacer needed?'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19454
 Different design spacers provide different "advantages". You have the open hole spacers, where the center is completely open, and you have the four hole spacer that has 4 holes presumably the same approximate size of the carb throttle plates. The open hole spacers help with higher rpm(hp) gains, while the 4 holers provide a slight torque increase at lower rpm. The height of the spacers is equally important....changing the height will move the HP/torque curve up/down the rpm band. Going from a 1/2" spacer to a 1" spacer makes a definite change on dyno tests...usually the taller the spacer, the more top end HP, up to a point.
The spacers also will provide a bit of insulation from engine heat that is transferred from the intake manifold to the carb base, but here the material the spacer is made of makes the biggest difference. Metal(aluminuminum) spacers will still transfer heat, just not as much. Phenolic(plastic/resin) type spacers provide much more heat insulation, and are normally the best choice if heat is an issue.
The design of the intake manifold needs to be considered when choosing a spacer plate. An open plenum intake will work best at higher rpms with the open hole spacer, but an open plenum intake with a 4 hole spacer will increase the torque all across the board.
On a stock type, 4 hole intake, an open hole spacer is basically useless for anything other than heat insulation...the combination of open spacer/4 hole intake will not provide ANY performance gains, and in most cases will loose both torque and horsepower.
4 hole intakes need to use 4 hole spacers....this combo will help hp AND torque in the mid range rpm, but will usually drop hp in the higher rpm ranges.

There are also adapter/spacers that adapt from a spread-bore carb to a straight bore intake, and versa-visa. The only real benefit, if any, of those things is the heat insulation properties.


I'm spaced out now.....Wacko
LOL

Well...almost...
bcousins said:"My stock Rochester on my stock manifold on my 79 L-82 has a 3/8" spacer but I am not sure if the spacer was added by one of several previous owners."


Are you sure what you see is not the normal, stock gasket? The base gaskets for quadrapukes are normally aboot 3/8" thick, and are made of a fiberboard-like material....mostly for heat insulation, but also for a good seal to the intake. Thumbs Up 
Doesn't really matter since your are changing both intake and carb...just wonderin. Approve


|UPDATED|6/26/2014 10:07:07 AM (AZT)|/UPDATED|


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Joel Adams
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6/26/14 2:58pm - Reply: 'Re: Carb Spacer needed?'
bcousins
Former Member
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Jacksonville, FL - USA

Vette(s):
79 L-82 4-speed. Engine stock except long tube headers. Previous owner replaced upholstery and carpet with OEM. I replaced and upgraded steering and suspension.

Joined: 12/15/2009
Posts: 36
Joel,
Thanks for the info. It does look as you described that I am looking at the stock gasket, not a spacer. 
The real reason I asked is because when ordering the intake and carb from Summit they show suggested things you may need and one of them is spacers as shown here http://www.summitracing.com/parts/sum-g1405-1. It is phenolic and is 1/2 inch.  They also sell the 1 inch. 
I have read elsewhere about some of the pros and cons of using spacers and the various types but I always like to see what other C3 owners have to say. Thanks again for your input. 


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6/27/14 12:53pm - Reply: 'Re: Carb Spacer needed?'
nosal1 Gold Member
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Dunedin, FL - USA

Vette(s):
1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.

Joined: 3/21/2006
Posts: 237

Bcousins am I to understand that you are installing an Edelbrock 

''AIR GAP'' intake and if you are,forget about the spacer as the design of the intake takes into account the heat problem,as it does not incorporate exhaust cross over ports thereby relieving the heat under the carb.Secondly the design of the AIR GAP intake improves on the "low end torque" and due to it being a raised chamber,off of the oil galley and not a dual plane design,you will get the top end increase as well.I have used these Edelbrocks Air Gap and Professional Products style AIR GAP many times on my 383 stroker engines and they are great intakes if you have the hood clearance.I have an '80 and would like to use one,albeit not going to buy another hood...Good Luck....
 Sal C


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6/27/14 10:27pm - Reply: 'Re: Carb Spacer needed?'
bcousins
Former Member
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Jacksonville, FL - USA

Vette(s):
79 L-82 4-speed. Engine stock except long tube headers. Previous owner replaced upholstery and carpet with OEM. I replaced and upgraded steering and suspension.

Joined: 12/15/2009
Posts: 36
Thanks for the info about the heat transfer Sal. The L-82 stock manifold is 4.75 inches high. The Edelbrock RPM Performer Air Gap 7501 is 5.25 inches high, a difference of 1/2 of an inch. I know it will not clear the stock hood with the stock air cleaner but I believe it will with the Edelbrock Low-profile air cleaner that is reportedly 1 inch lower. 
Any other members have experience with this combo?




|UPDATED|6/27/2014 8:27:53 PM (AZT)|/UPDATED|


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6/28/14 8:43pm - Reply: 'Re: Carb Spacer needed?'
Norsky Lifetime Member
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Twin Lakes, CO - USA

Vette(s):
SOLD - "The Toy" - 1970 Convertible
SOLD - "The Beast" - 1990 ZR-1 (#682)
"BLKBRRD" - 1978 Trans Am, 400ci/285hp, 4 spd, Black w/black interior, Hurst t-tops

Joined: 1/23/2002
Posts: 6714
I was having hot start issues with "The Toy" several years ago.  Turned out the carb was getting too hot to touch and boiling the fuel.  I bought a Mr Gasket spacer kit which was a mix of aluminum and fiber layers.  I added as many layers (alternating the fiber and aluminum) as I could without bumping the hood.  The hot start problem went away and the carb stays WWWAAAYYY cooler than before.  The only modification I had to do was to make a slightly longer choke linkage (I used an old clothes hanger - yea I know - can you say "BUBBA"!).

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6/28/14 9:48pm - Reply: 'Re: Carb Spacer needed?'
bcousins
Former Member
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Jacksonville, FL - USA

Vette(s):
79 L-82 4-speed. Engine stock except long tube headers. Previous owner replaced upholstery and carpet with OEM. I replaced and upgraded steering and suspension.

Joined: 12/15/2009
Posts: 36
Jim,
Thanks for the info about boiling fuel. By my calculations, and I used some of my grandson's Play-Do to measure, I have about 3/8 or so to play with so I can use a small spacer before having to spring for a new hood that will accommodate all the goodies. 
Any idea how much spacr you created using the layers?
Best regards,
Bill


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6/28/14 9:50pm - Reply: 'Re: Carb Spacer needed?'
bcousins
Former Member
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Jacksonville, FL - USA

Vette(s):
79 L-82 4-speed. Engine stock except long tube headers. Previous owner replaced upholstery and carpet with OEM. I replaced and upgraded steering and suspension.

Joined: 12/15/2009
Posts: 36
I admire your ingenuity by using the coat hanger to solve a problem. Always helpful to be creative!

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