Back to building the Cutlass... had to find a new 455.

[sadisticsavage]

Hey guys. Just wanted to let everyone know I had to go and find a new 455 for my 86 Cutlass. I initially was supposed to buy one from the guy I bought the 400 trans and 442 exhaust manifolds from but he never returned my calls after awhile so I went ahead and found a new 455. I was a little worried that the transmission I purchased from the guy may be faulty so I also bought another one of them with the motor just in case. If it seems to run properly then I will have a spare 400 transmission I can build up and throw in later. So I got the motor, transmission, exhaust manifolds, and I may have found a radiator. First I plan on refreshing the motor with a re-ring kit and a bearing kit. A fresh coat of paint and a new distributor, plugs, coil, wires, intake and carb. So I was wondering what size carb to run on the 455. I plan on buying the performer edelbrock intake and performer cam. Not sure if I should run the 650 cfm or 750 cfm. Thanks again for your guys help. It is greatly appreciated. Good to be back on the Gbody Forum!!!

 

[rccktmn2]

As far as a carb the 750 would work the 650 is a little small for a big block. Stock 455s came with 800s the w-30s came with 850s. good luck on the build!

 

[84dragcutlass]

Not to highjack the thread but how can you tell what size quadrajet you have. I have a 455 as well i bought with the "original" quadrajet and want to know what it is

 

[sadisticsavage]

No problem we are all here for knowledge haha. And Im not sure but there should be a part number on the part you may have to look up.

 

[88hurstolds]

As far as a carb the 750 would work the 650 is a little small for a big block. Stock 455s came with 800s the w-30s came with 850s. good luck on the build!

Where are you sourcing this information from?
Oldsmobile never used an 850 cfm carb, infact no stock Q-jet was 850cfm
Edelbrock made an 850CFM aftermarket version of the Q-jet.
455's came with 750CFM carbs from 68-72 and the W-30s were the same however the did not use primary metering rods and just used 2bbl jets.
73-76 used 800CFM, may seem excessive for a smog era engine but the metering passages were different.
With Q-jets don't be fooled by a carb being better because it has larger CFM's.

The way you can tell what CFM carb you have is by measuring the ID of the venturi.
An 800CFM will have a 1-7/8" venturi
750CFM is 1-3/32".
or
Look down the primary bores with the throttle held wide open. The 750 models have a ridge all the way around the bores, just below the booster venturis. The 800's only have two raised bumps, opposite each other, sticking out from the sides of the bores also just below the booster venturis.
Here is an 800CFM, notice the lump on the top left at about 11:00:

 

[1bad79]

X2 on the info from 88hurstolds