The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Install thread- Holley EFI Sniper on '72 402 big block

davepl · 05-24-2018, 10:50 AM

For anyone following along, two things:

1) That "Notch" in the two-plane intake is important. If your intake is sealed all the way such that the two planes are totally separate, TBI EFI will not run well (or for some brands at all) because the MAP sensor is only on one of those sides. I can't tell if the old 4-hole was separate side to side, but the new one looks OK. The ZZ502 intake from Chevrolet has a notch too, but smaller.

2) Holley offers a linkage extension as well as progressive conversion linkage. I have ordered the progressive kit because otherwise it is VERY touchy. Consider that it opens all four barrels right off the start...

05-24-2018, 10:50 AM	#75
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Re: Install thread- Holley EFI Sniper on '72 402 big block For anyone following along, two things: 1) That "Notch" in the two-plane intake is important. If your intake is sealed all the way such that the two planes are totally separate, TBI EFI will not run well (or for some brands at all) because the MAP sensor is only on one of those sides. I can't tell if the old 4-hole was separate side to side, but the new one looks OK. The ZZ502 intake from Chevrolet has a notch too, but smaller. 2) Holley offers a linkage extension as well as progressive conversion linkage. I have ordered the progressive kit because otherwise it is VERY touchy. Consider that it opens all four barrels right off the start... __________________ 1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible