lightemup

I am having problems getting answers to questions I have about my Holley spread bore (#80555c) I purchased this spring for my '70 L46 350. Before I installed the carb, I equipped it with a secondary metering block to replace the secondary plate. (passages and gaskets all looked to line up) I am now having trouble sorting out the high-end performance of the carb. It now runs out of fuel at the top end of first gear and sometimes second. Idle and cruise performance is great. Jetting seems to make no diff except for plug color. ALL fuel lines, filters, pump and passages and ignition have been triple checked. The only thing that seems to make any diff is the level of the secondary float. If I raise it high enough to start to keep the bowl full at high rpms, it floods through the vent at quick stops, of course. I called the Holley tech line and got very little help. Basically the gentleman at Holley told me he was surprised that the car ran at all with the secondary block installed and then he told me that the block conversion (part #34-6) was not compatable with my carb. He urged me to re-install the plate. I however, seem to think that I am only maybe a vent baffle and some experimentation away from a good carb. Has anyone else succeeded at this combo? Thoughts, please!

Matt Gruber

the 4165 is the 1 to get, not the 4175.
Even so, compared to other VS holleys, the 4175 is excellent for those with overdrive.

i saw a 4175 at a swap meet for $50. i was tempted as an experiment, but passed. have 2 4165.
.
does yours work with the jet plate? put it back in. they sell plates for tuning.

lightemup

Isn't that what I essentially did was to more or less convert this carb to a quasi-4165?

Matt Gruber

no. there is no such kit.
was the plate too rich?

69Vett

something I just relized with the holley on a stock manifold, there is a Hot exhaust passage, in the front which must be blocked off with a stainless heat sheild. you might want to check that out.
good luck...69VETT

lightemup

The plate that came in the carb was too lean. Now, with the block it acts like it runs out of fuel above 4000-4500 rpms no matter what jets are used. It feels like it's draining the secondary bowl. I think that I'm going to go ahead and raise the secondary bowl fuel level and install a vent baffle back there and see what happens. I guess if that doesn't work, I'll try putting a plate back in. I just thought that there mighta been someone else out there that had tried this with a 4175.

Matt Gruber

exactly how do u know the plate was too lean? o2 sensor at WOT past 3000 rpm?
34-6 converts a 4160 to 4150. the 4175 is quite different. the advantage is quicker jet changes; u can try drilling the plate larger if u r sure it is too lean. r both planes too lean or just 1?
sell the 34-6 to a 4160 owner