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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Bitzer! on April 15, 2012, 03:18:02 pm

Title: Holley 750
Post by: Bitzer! on April 15, 2012, 03:18:02 pm

Hi guys,

Either a silly question, a senior moment or I have a problem!

The 454 fires up lovely on the key, I have the throttle cable hooked up to the front linkage.

The two rear barrels aren't taking juice unless I opererate the linkage manually. Am I just missing a spring or should they run on vacuum?

cheers as always

Andy

Title: Re: Holley 750
Post by: ralphhemi on April 15, 2012, 07:55:41 pm

If you have a mechanical 4 barrel ,then it will be a double pumper 2 accelerator pumps , if you have vacuum secondaries  they will not open until under load     

Title: Re: Holley 750
Post by: Bitzer! on April 16, 2012, 11:08:08 am

Aha that would explain it!

Yes they are vacuum, can I / is it worth it to change them over to fully mechanical?

cheers

Title: Re: Holley 750
Post by: bake74 on April 17, 2012, 06:20:24 am

Quote from: Bitzer! on April 16, 2012, 11:08:08 am

Aha that would explain it!

Yes they are vacuum, can I / is it worth it to change them over to fully mechanical?

cheers

     It would be worth it if you want to stand there and throttle the truck to wide open to see the secondaries open.  Otherwise when you drive it you will be able to tell if they open.  They work just fine being vacuum operated as long as the vacuum hoses are hooked up and you have good vacuum.

Title: Re: Holley 750
Post by: Bitzer! on April 17, 2012, 09:41:39 am

Cheers Bake, I guess I'll leave em as they are. All new vacuum hoses and tight fit so should be fine. One less thing to worry about!!

Title: Re: Holley 750
Post by: TexasRed on April 17, 2012, 09:30:55 pm

Howdy Bitzer! Have you seen this regarding holley carbs: http://www.bob2000.com/carb.htm

Title: Re: Holley 750
Post by: Bitzer! on April 18, 2012, 04:28:10 pm

Cheers TexasRed

I hadn't seen that but it's well and truely saved!!!