69 350 L-46. PO had it rebuilt, bored .030 over. Heads are stock camel humps he said were 2.02s. Probably close to stock cam. Only obvious mod is an Edelbrock Performer intake. Original points dist. He didn't build it and I haven't had it apart. Seems clean, tight and very functional. Wasn't going to tear apart something working that well just out of curiosity.

The Holley 4160 has a dual feed and it's generally been fine since I rebuilt it a couple of years ago but to get throttle response I found the white pump cam and .28 shooter works best. Like I had to dial down that that 750 quite a bit. Very responsive but now I see it's asking for a new needle & seat for the secondaries. It seems to like eating those. Third one. Float and hanger h/w are new. This needle & seat is visibly gunked up with something so I'll have a look at all that shortly. Yes, I am aware of ethanol use and the problems it can cause but this looks like something broke somewhere suddenly so I'll just take the thing off and look.

Here's the question: seems like 750 was a bit much for that setup. The PO thought he had some horsepower monster and didn't. Thinking of swapping it out for a Holley in the 600-650 cfm range and using a single feed but looking at their website is making my head spin. looking for some real world input, maybe on their Brawlers, QuikFuel, etc. I know about Lars and professionally rebuilt Qjets and other manufacturers. Figured I'd start with what looks like a direct swap.

I can fix the old one and get it running fine again. It's just something that ALWAYS seems to want something from me. I've dumped girlfriends for being too needy so why not carbs.

EDIT: using an electric choke and vacuum secondary

 

i wouldn’t think a 750 is too large properly tuned
. Purchase a genuine Holley kit and see if that will last longer

 

If you start playing around with those accelerator pump shot cams, it can get real complicated. Especially when there could be three screw holes to choose from after selecting one of ten color cams. The experts say to choose a color code cam and run it down the drag strip. Then change the screw location. Then a different color cam. Its just not practical to check your E.T.s a dozen times seeing what works, and what doesn't.
Then you have the shooter size. And the shooter style, with longer tubes on the shooter. Then you have the Power Valve to play with, plus jet sizing. Plus the spring on the secondary opening rate.

Using "seat of the pants" testing, the number two hole in those cams seems to work the best. Maybe one notch lower on the power valve if vacuum is lower than stock.
I can't comment on shooter size because I have the Holley 650 DP.

I think your 750 is fine for your app. It is true that a larger CFM may not have the "instant" throttle response as a lesser CFM. However, always think richer is better than leaner. I would much rather see a puff of black smoke in the rear view mirror than fry an engine from being too lean.
And I would stick with the dual feed Holley. Hard to beat.

If you think a Holley 750 is too big, keep in mind that GM designed Quad is a 750.
Keep tweaking, you will get it right.

 

What is the list# of the carburetor, found on front surface of air horn.

 

3310-4. Below that 2942

Took it off. Clean as a whistle. The float floats. Maybe a piece of gasket material. Nothing obvious. All back together with new needle & seat but it’s pouring rain so starting it will have to wait. Not hard to do but a little tired of doing it

 

650 is plenty I bet a 600 would feed it fine too.
no need for 750s etc. GM used a lot of those on different vehicles (just calibrated differently) to save $.

 

I have a 3310-1, 4150, never had to change the shooter or cam from stock.
Use 72 primary jets and long yellow secondary spring.

 

Tuning wasn't the problem, but since I mentioned it this carb came with the green cam and I forget which shooter but I think I went down at least 4 sizes. Looks like it just got plopped on and not tuned right out of the box. Horrible bog - stomp on it .... wait for it .... that kind of thing. None now. Very crisp and fun to drive. Many many changes & test rides until I got it.This carb runs nice but does seem to want to eat needle & seats on it's secondary only. Flooding it out is no fun and can be damned dangerous.

Just for the hell of it looking at Edelbrock 1411 vs 1406. Leaning towards the latter as being probably OK for a basically stock 350. Any thoughts?

 

The "gap" between the accelerator pump and its linkage, what did you set that at, do you remember?
Holley says 0.015. Sometimes 0.012 better.

Thoughts on Eddys?
They make the best Intakes in the world.
They make great heads.
Their carbs? Mehh. Never had one. Don't want one. Can't work on one.

 

The spec is ZERO gap.....you need additional travel available per spec to be sure you do not bottom out the pump lever at WOT. The butterflies are opened all the way and the pump arm needs to be able to travel further than the linkage is asking it to move. Any change in Idle speed or accelerator pump cam requires the tuner to re-check and adjust the accelerator pump arm travel spec.

ANY gap in the linkage will cause a dead flat spot, bog or "pop" when you try to accelerate.

 

Well, yes and no on the gap. Zero gap will make the acc pump dribble into the venturie at idle from vibration. Even the weight of the gas pedal & cable will make the squirters squirt.

That's why the recommended 0.012 is set real tight at closed throttle and 0.015 at WOT.

 

I will believe that when I see it.

 

The only clearance spec is .015 at WOT to prevent damage to the linkage and pump diaphragm.
Zero clearance at closed throttle.

 

cv67 is correct

 

https://documents.holley.com/techlib...carburetor.pdf

 

Buy the 0-90670 Holley truck avenger. This is the best out of the box carb Holley makes for 300-400 horsepower engines.......
I have installed a dozen of these over the years and they never fail to surprise the hell out of me.......
The primaries are billet mini annular......it has a secondary metering block also. Holley need to scrap the Street Avenger line and start selling these exclusively....best kept secret in their lineup....
https://www.holley.com/products/fuel.../parts/0-90670

I am building a hot little roller 355 this winter for a customer with the new Trick Flow 175 heads and this is the carb it is getting.....I plan on doing a thread on it so stay tuned.

Jebby

 

Just out of boredom the answer was .... vacuum leak. Unsurprising. Replacing it was pure frustration but getting past that and actually looking at the problem was a little more rewarding.

Two things. Once I had it in my hands I found the vacuum pod was actually loose (blame the idiot that put it on) and the intake manifold vacuum fitting which I thought was snug turned out to be held in place with old cheese or boogers or the equivalent. Probably too much teflon tape to get it to seat in a spot where it didn't interfere with the barb on the base plate of the carb. I swapped it out for a swivel fitting.

Jebbysan - thanks for the Holley tip. Nice to get real world input. I had to slightly grind the top of the replacement fitting for clearance under my 4160 and see that going in that direction or converting to 4150 probably means spacer and different air cleaner base for hood clearance. Or I'd have to tee the brakes and everything else off the barb and that would probably work but doesn't seem like the best choice. An alternative I had considered was a Holley Street Demon 625. If nothing else it looks like clearance with the manifold fitting isn't a problem. https://www.holley.com/products/fuel_systems/carburetors/street/parts/1901

Got everything cleaned out, rebuilt and put back together - just in time to get walloped by 18" of heavy wet snow and ice. Will be a day or two before I can fire it up. Assuming I've found the major problem(s) and can keep it idling check for entire intake for leaks - starting in back by the distributor.

 

When I first got my '69 L46 it had an Holley 600cfm with vacuum secondaries and ran with it for several years. I had run it at Lakeside raceway here in Qld, Aust. several times and the best I could get out of it was 100mph, geez I had a 77 Alfa Romeo Alfetta GTV 2.0lt
that would redline in 5th - 125mph. Now I'm running a the correct Quadrajet. Haven't been back to the track, but the difference is like chalk and cheese when on the road. The holley was quite fuel efficient though.