BG Carb Questions-Tuning...
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Instructor
Joined: Feb 2001
Posts: 217
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From: Suwanee GA
Barry Grant Carb Questions-Tuning...
I am running a 3 year old BG Silverclaw 750 cfm mech. sec. (similiar to Race Demon). Recently, I switched from a Torker II to an RPM Air-Gap intake and better flowing exhaust and have had serious driveability problems. BG actually flowed and revised the fuel curve (to match the Race Demon) for me-at no charge. They did not touch the jets. The car runs better, but seems rich at idle and lean under part throttle (hesitates until sec start to open). It has 75/81 jets and a size 31 squirter.
During this process I bolted on a 750 cfm vac sec Holley with 74 primaries and it ran well. My next move is to try 78's in the Silverclaw and enlarge the air bleeds to lean the idle circuit. Any other suggestions?
[Modified by Doug Brandon, 11:13 AM 2/11/2002]
During this process I bolted on a 750 cfm vac sec Holley with 74 primaries and it ran well. My next move is to try 78's in the Silverclaw and enlarge the air bleeds to lean the idle circuit. Any other suggestions?
[Modified by Doug Brandon, 11:13 AM 2/11/2002]
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Instructor
Joined: Feb 2001
Posts: 217
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From: Suwanee GA
Re: Barry Grant Carb Questions-Tuning... (Doug Brandon)
Cam is .527/.553, 224/232 @ 0.050. I get about 14-15 inches of vacuum at idle (800 rpm). Motor has oval ports with mild work and big valves. Carb has a 65 power valve. No changes to air cleaner, no spacer under the carb.
[Modified by Doug Brandon, 2:12 PM 2/11/2002]
[Modified by Doug Brandon, 2:12 PM 2/11/2002]
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Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Barry Grant Carb Questions-Tuning... (Doug Brandon)
In my 750 speed Demon the stock jetting was 76/83 6.5 power valve. It was so rich at idle I drilled .125 holes in the primary blades so I had more adjustment on the four corners. Of course setting them with a vacuum gauge. I had off idle bog So I drilled out the squirters to .044 or .045. My secondary blades are open slightly more than my primaries at idle. Which help with the transition to WOT.
I drive at higher altitude so my 74/81 jetting settings would be lean. You would need 75/82 or 76/81 My 900 rpm idle has a 13-14 inches of vac. Driving on level ground is 18 or so.
I drive at higher altitude so my 74/81 jetting settings would be lean. You would need 75/82 or 76/81 My 900 rpm idle has a 13-14 inches of vac. Driving on level ground is 18 or so.
Drifting
Joined: Jul 2001
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Re: Barry Grant Carb Questions-Tuning... (Doug Brandon)
The carb is now getting a stronger signal.Try 8.5 primary power valve and pull the carb to crack open the secondary plate a little with the screw provided under the base plate to lean the idle some.Leave the jets as is until you get the idle and part throttle ironed out.Changing too many things you will not know what did what.
Thread Starter
Instructor
Joined: Feb 2001
Posts: 217
Likes: 1
From: Suwanee GA
Re: Barry Grant Carb Questions-Tuning... (mountainmotor)
Thanks, and one thing I forgot to mention-the engine is now getting air with a L88 hood. Before the carb (with Torker II) was operating under a factory BB hood. Perhaps cooler air is allowing more air into the engine, which would require more fuel?
[Modified by Doug Brandon, 10:33 PM 2/11/2002]
[Modified by Doug Brandon, 10:33 PM 2/11/2002]
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Joined: Dec 1999
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From: Sierra Foothills CA
Re: Barry Grant Carb Questions-Tuning... (Doug Brandon)
Doug,
The carb I'm running should be very similar to yours- Stage 3(pretty sure but bought it years ago) Barry Grant modded 750 DP flowing up to 1140 cfm, not that I can pull that much w/ my combo. It's always run great right out of the box- so good that I've been afraid to touch a thing. When I went to the L88 hood it didn't change a thing except for more power due to cold air. Sorry you're having probs...wish I could help but it's a mystery to me, especially since they went through it again for you.
The carb I'm running should be very similar to yours- Stage 3(pretty sure but bought it years ago) Barry Grant modded 750 DP flowing up to 1140 cfm, not that I can pull that much w/ my combo. It's always run great right out of the box- so good that I've been afraid to touch a thing. When I went to the L88 hood it didn't change a thing except for more power due to cold air. Sorry you're having probs...wish I could help but it's a mystery to me, especially since they went through it again for you.
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