The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post

burnin oil · 08-27-2015, 07:44 AM

I cammed my motor back a little and run a 274 duration solid cam. The 830 double pumper is barely to big for this cam but worked well with the old one. I ran around for about 2 months on the primaries only, disconnected the secondaries, while tuning and it ran alright. Once I rehooked the linkage I gained a mile to the gallon and it runs a lot better. She just wants more than 400cfm that is available on the primaries. Do some digging and you will find that the Holley vac secondaries will never hit the full potential unless you run the lightest spring. The heaviest spring will nearly never open the back side.

08-27-2015, 07:44 AM	#102
burnin oil Registered User Join Date: Jan 2013 Location: Eastern TN Posts: 1,921	Re: 400/406 Builds I cammed my motor back a little and run a 274 duration solid cam. The 830 double pumper is barely to big for this cam but worked well with the old one. I ran around for about 2 months on the primaries only, disconnected the secondaries, while tuning and it ran alright. Once I rehooked the linkage I gained a mile to the gallon and it runs a lot better. She just wants more than 400cfm that is available on the primaries. Do some digging and you will find that the Holley vac secondaries will never hit the full potential unless you run the lightest spring. The heaviest spring will nearly never open the back side.