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Discussion Starter #1
Hello all. I have finally gotten my 68 Malibu up and running. I have about 5 to 600 miles on the car so far and honestly I'm pretty happy with the way the car is running out. I have one issue i would like to clear up. Cruising between 55 and 65 lightly pressing the go pedal there is an ever so slight hesitation. Once past that the car seems to pull ok. All other situations the car is pretty good, starts great, idles nice, launch is strong. the car does seem a bit slow on a power pull but the weather here this summer has been pretty tropical.

The specs on the car are as follows. 68 Malibu, all steel, full interior, 434 big block (4.155x4.00), 10.2:1, 049 heads with 2.19- 1.88 valves, moderate home grown port and pocket cleanup. Cam is a Lunati 60203 HFT set to the cam card which iirc is at 108 icl. Engine has an old Weiand Accelerator single plane with a 3310-1 carb. Quick Fuel adj vac sec can @ 1 1/2 turns out. 72 pri. and 76 sec. jets 65 pv both sides. I cant recall the pump nozzle but would assume it is a 25. Timing is 19 deg initial with 35 total. 42 deg with vac adv hooked @ manifold. Idle vacuum is at 12 in. Steady cruise (55-60) vacuum is at 16-17 in. 1 3/4 long tube headers w 2 1/5 exhaust,

Any thoughts on the hesitation? Pump shooter? Pump cam? Power valve(s)? Thanks for any input.
 

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Either 8.5 or 10.5 power valve would likely be a better fit.

Stock pump shooter should be a 28 on the 3310-1.

What colr pump cam is on it??
What hole is it installed in??

If you adjusted the idle mixture screws for highest vacuum you could obtain at idle it will make the transition too lean, back them out richer 1/8 turn or so from that best vacuum point for most all performance applications. Typically cruise you are not running on the main jet(especially if less than 3.73 gear), since throttle is not open much, you are still in the transition circuit. You get a hiccup at slifght acceleration from the too lean transition circuit until airflow picks up and the mains become active.
 

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I will second what Ericnova72 stated go up in the power valve number.
You could drive the car with a vacuum gauge hooked up and inside the car where you can watch it and see what happens at what vacuum.
I will bet at 6.5" or close to that it clears up.

I had that same issue with a few cars and making the enrichment circuit come in sooner was all it took.
Power valve for Holley step up springs for Qjet or AFB/AVS type carbs
 

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Discussion Starter #4
The pump cam is white and is in the #1 position. according to a 2005 Holley Performance catalog the 3310-1 should have had a .025 pump nozzle. Also the power valves are listed as 85 primary and 105 secondary. This was a swap meet carb that I rebuilt over 5 years ago so who knows what was in it and how it got put back together other than the notes I taped to it when I assembled it. I think my first change will be a bigger pump nozzle. 1 or 2 sizes? Move the cam to position 2?
 

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Try swapping pump cams, get the kit with all the different colored cams if you don’t have it yet. I never would have expected they change the behavior of a carburetor as much as they do. Easy to swap, and easily reversible if they don’t give you the result you want.

IIRC, the pink cam is very similar to the stock white cam, the difference being that the pink cam keeps on going for a little longer as the throttle blades open. You might need just that little bit of extra fuel to cover that last little bit before the secondaries open.
 
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Discussion Starter #7
I pulled the carb tonight to verify the pv's. The pump nozzle was a 25 which I swapped to a 31, that will be the first change I will try. I didnt want to pull the bowls and blocks till I have the parts in hand to button it back up. I checked the transfer slots and they are pretty close to if not square. I do have the pump cam assortment so that will be an option also and as stated a pretty easy, reversible change. The idle screws are 2 turns out @ 14 in., there wasn't much change in vacuum while adjusting them. I'll give the nozzle change a try and go from there.
 

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Hi
PV set up for 45-50 mph road speed starts to actuate . Play with different pv around that vacuum reading at that road speed .
Set uplight throttle cruise ie primary main jets at 45-50 mph . Typically the leanest the AF ratios ever get .
Change/drill/jet primary PVR pwr valve restrictor to suit 60mph AF ratios
 

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31 might be too much, try a 28. You may also want to try a quick opener PV, like a 105 or 85. Make sure the fuel level is up, low fuel levels equal carb slow to respond to acceleration.
 

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Am I wrong in reading his issue when he stated "lightly" pressing the go pedal there is a slight hesitation"

I do not feel pump squirter or pump cam needs changed as lightly pressing the go pedal gives slow throttle opening and the jets and power valve play in that area not so much the squirter.

I thought the squirter was for covering up a quick throttle opening rate.
 

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When you say lightly pressing on the pedal, is that a slow movement or quick movement?

Either way, you should have a primary PV half of your cruise vacuum, so based on your info an 8.5 for sure. Your 3310-1 came with 10.5 PV primary, and 8.5 secondary, so the holley book you have has it backwards.

I would change both PV to the way the 3310-1 came. Then double check accel pump adjustment. Lengthen the bolt which pushes on the accel pump arm, so that at full throttle you can just slide a .015" feeler gauge between the head of the bolt and the arm, without compressing the spring.
 

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I have one of those carbs on a mild BBC that I’ve tuned quite a bit with a wideband. With a 70 PMJ the AFR would go above 17:1 before the 6.5 power valve opened. I solved this with a 10.5 power valve. Although your carb is jetted richer with 72’s, it also sits atop a single plane intake which I understand will tend to need more jet. I suspect what you’re feeling is leanness before the PV opens.
 

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Discussion Starter #13
Thanks for the help everyone, this is the input I was hoping for when I posted. Pockets you are right the catalog was right, I read the footnotes wrong. I did question whether it is an accelerator circuit issue. The power valve choice is sounding more logical so i am gonna get the right pv's for the carb and try that. I will go back to the 25 pump nozzle or try a 28 that I found in my parts box. Thanks again all.
 

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Discussion Starter #14
Out of curiosity, while looking at the list of 3310's in my old Holley catalog all of the 3310's listed which goes up to a -7 call for a 65 PV. What would make the -1 version use the higher vacuum value? I know The -2 and beyond use a secondary plate which I believe does not use a PV.
 

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Out of curiosity, while looking at the list of 3310's in my old Holley catalog all of the 3310's listed which goes up to a -7 call for a 65 PV. What would make the -1 version use the higher vacuum value? I know The -2 and beyond use a secondary plate which I believe does not use a PV.
The -1 was originally designed for the 1965 high performance 396 BBC available in Chevelles. It’s calibration is more specific to that application. The later versions were generic aftermarket carbs designed to work on a variety of applications. Most people that tune Holleys for the street end up with leaner primary jetting and/or smaller IFR’s and higher number power valves than stock.
 

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Discussion Starter #16
The -1 was originally designed for the 1965 high performance 396 BBC available in Chevelles. It’s calibration is more specific to that application. The later versions were generic aftermarket carbs designed to work on a variety of applications. Most people that tune Holleys for the street end up with leaner primary jetting and/or smaller IFR’s and higher number power valves than stock.
Finally reporting back on my situation, Between my procrastination and trying to find a couple of Holley power valves from the same vendor in a reasonable time frame. I got the carb back together to the original configuration except for a 28 pump nozzle in place of the stock 25. The hesitation I had is gone which is great. I still have some full throttle tuning to do as I don't feel the car is pulling as hard as it should. could be my imagination or not. I do have a quick fuel adjustable secondary can on the carb so that will be my next move.
 

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Finally reporting back on my situation, Between my procrastination and trying to find a couple of Holley power valves from the same vendor in a reasonable time frame. I got the carb back together to the original configuration except for a 28 pump nozzle in place of the stock 25. The hesitation I had is gone which is great. I still have some full throttle tuning to do as I don't feel the car is pulling as hard as it should. could be my imagination or not. I do have a quick fuel adjustable secondary can on the carb so that will be my next move.
I may have missed it because I didn’t read every reply.
What transmission are you running and what rear gears? If automatic trans what convertor stall?
 
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