Which carb for 425? - ClassicOldsmobile.com

Which carb for 425?

Old June 27th, 2018, 06:55 PM
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Which carb for 425?

I have a 425 out of a 66 toroonado in my 65 442 with a 600 com carb that I think is way to small. The engine is a fresh rebuild with forged 10.5 -1 Pistons , edelbrock o4b intake , maybe alittle bit hotter cam than stock and headers. Currently has a 600 cfm edelbrock on it which i think is to small. I was looking at the quick fuel 750 slayer carbs or 750 e Brock's . Should I go with a 750 or 850? Double pumper or vacuum 2ndry? Also seems like it came stock with an 800cfm q jet. Thanks
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Old June 28th, 2018, 05:12 AM
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When I had a 66 Delta 425, duals, I used a 650 Holley Double Pumper spreadbore. No issues and performed very well. It was perhaps a bit small but with mechanical secondaries I had no stumble or bog issues. The 600 may be a little small for the 425, somewhere around 700 cfm in my opinion should be fine.
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Old June 28th, 2018, 07:51 AM
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I'll probably get flamed for this, but throw away all of those junk carbs and go back to a well tuned Q-jet. It's what that engine was designed for and it will give the best all around performance and economy. Unless your engine is only a race engine needing the performance qualities of Hollies, Edelbrocks, or any other carb, stay with a good, well tuned Q-jet.
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Old June 28th, 2018, 09:11 AM
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Edzolz..... you won't get flamed by me.


65rocket.......... Try a Quadrajet and jet it accordingly. They used them on 350's up to 455's. There is no mystical magic in those aftermarket carbs. They need sizing correctly and playing with.
Bogging is usually due to improper secondary air valve spring. A very small screwdriver and 3/32" allen wrench is all you need to adjust the tension.
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Old June 28th, 2018, 09:16 AM
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My intake accepts 4150 flange so I'm pretty sure q jet is out . Not worried about economy just looking for best performance and drivability
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Old June 28th, 2018, 05:45 PM
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Originally Posted by 65oldsrocket View Post
My intake accepts 4150 flange so I'm pretty sure q jet is out . Not worried about economy just looking for best performance and drivability
Quick fuel 750 Slayer or if you want to move up a QF SS830.
But whatever you do, buy a wideband O2, itíll be the best $200.00 youíve ever spent.
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