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Discussion in 'Engine Topic' started by Vortec80, Mar 4, 2019.
Where is this plastic bushing? Never seen one.
Ordered several different carbs through a buddy of mine to try and see. Ordered the tried and true 3310. Ordered the quick fuel slayer 750.... seemed pretty solid with all the tune abilities. And 670 avenger just to compare. Thanks for all the suggestions guys! I hope all the testing goes well this weekend. I hope the 750 carb is able to give me a solid power band. I hope I have a good low end. That's my biggest concern at the moment!
What gear do you have in the car? To get the best bottom end power, you need a stall that will lock up at the engines best torque RPM and a gear that will keep it at that RPM once you launch.
One thing when you get the Holley's it looks like the 670 has the cover where you can change the sec. spring. Put a small wire tie or paper clip on the diaphragm so you can see how far it opens, I like to use the purple spring in most street application. If you have a healthy converter then you can go to the Long yellow or white spring. One thing to note look down to see if the 3310 has the little brass tube poking out of the primary bore if not some of the newer 3310's and other 750's just don't work right with out it. Good luck testing.
The bushing is on the throttle shaft. They wear out causing the shaft to bind and also leak air.
Holley 80783...it's a 650 vac. Sec.
Similar to a 3310, with same base plate but smaller main body bores...great carb for a street car...light years better than the 670, which is basically a 600 with cathedral bowls.
Has the testing been done/completed ? Any results that your willing to share, such as vac. readings at WOT between carbs?
I would put money on the Holley 3310 if all was OK out of the box. 2nd would go to QF 750.
The only time I use the vacuum gauge to check is at WOT to see if the carb is too small IE: the higher the number the more likely the carb is too small My 750 on the current 461 showed 1.5 hg. so I went to the 850 Mighty Demon and it was less than .5 after the change. I am not sure if I am one of the unlucky ones that had a bad experience with a QF 750 VS, but that thing was terrible out of the box.
Was there a ET or MPH performance gain in going from the 750/1.5hg to the Demon 850/0.5hg? If so, that would lead down the path of booster style/location and fuel sheering differences in the fact your engine/inlet runner/car combo liked it better overall. Not to mention the actual CFM ratings of both carbs.
It's strange sometimes how all the tests and results point to a clear carb/size "winner"on the dyno, only to find that the other 2nd or even 3rd place carb is faster at the track.
Thanks for sharing 1980RS, By the way, just a wild ass guess, are you in the 530-580 HP range??
PS: Your not alone in your QF 750 VS experience.
A famous racer once said "we don't race dyno's" can't remember who it was however.