[kyle_blake]

I run the 3310-4.. from waht i gather they came from factory with 72 iin the front and plate in the back which is equivlent to 76.

You mentioned a stumble and trying to a new power valve to fix it. I belive the website i read "mortec.com" or something says that a stumble is an off IDLE lean condition.

recently i did the same thing, went from STOCK(72) to 67 and I found out what this stumble is. I went up to 69 and still stumbles. So I think 70 will work.

I don't believe jets are a factor at idle.. the idle circuitry is in effect. Not a 100% sure , maybe some one can verify for me.

Oh ya withrespect to your leaking problem. I HAD the same thing , secondaries were dumping fuel on passenger side. Adjusted floats down and it went away.

At that time my gasket in the holley that connects the holley's base plate to the main body of the holley was soaked so i got a rebuild kit and made sure i adjusted the floats to the "DRY" setting in the instructions. Typically i've had good luck with that setting and when running on level ground the floats were really really close...they call this the "WET" setting I believe.

the secondaries should come in without feeling any pause in transition.

[BILTIT]

Have you checked into your accelerator pump adjustment, cam, pump size? I found i have to adjust my pump arm every now and then as it vibrates loose (needs new nylock nut) and will cause a stumble/hesitation.

[kyle_blake]

very good point.. about pump cam arm adjustment
in the holley rebuild kit the instructions say to make sure it is 0.10 or something..
you have to use a feeler gauge
The pump cam(plastic pieces) are to tailor the shot but I'm not sure how they cause a hesitation yet or something that I could control for a specific solution

I suppose the squirters also play a roll to.

Here are some links I read:

http://www.bob2000.com/carb.htm

http://www.nastyz28.com/perftune.html#carb

http://www.mortec.com/carbtip1.htm

[tremo]

Good reference sites Kyle and thanks for the feedback! Once I reinstall my 750cfm, I'll drop the floats a bit lower to see if that helps w/ the fuel pooling issue.

My 3310 (not a -1, 2, 3, or 4, just a 3310S) had #70 jets installed and has a 21 secondary metering plate which equals a #75 jet. I dropped the primaries down to #67's (1 jet size per 2000+' in elevation) but have not touched the secondary plate (yet).

Update
I'm done with my timing adjustments and have got it down to where she runs the best. The 600cfm carb is still temperamental (I have to keep the idle at 1000rpm and it barely stays running when I drop it in gear), but it has proven to be a good test using a smaller carb. Now it's time to swap my 750cfm back.

In doing some reading on Power Valves, Holley says:

If the vehicle is equipped with an automatic transmission, take the vacuum reading with the engine thoroughly warmed up and idling in gear. In either case, the power valve selected should be 1/2 the intake manifold vacuum reading taken. EXAMPLE: 13” Hg vacuum reading divided by 2 = 6.5 power valve. If your reading divided by 2 lands on an even number you should select the next lowest power valve. EXAMPLE: 8” Hg vacuum reading divided by 2 = 4 power valve. Since there is no #4 power valve you should use a 3.5."

I measured my vacuum off the manifold at idle (~1000 rpm, but not in gear cause it will stall) and it was 6 inches. Divided by 2 = 3, so that means I need a 2.5 PV?! Hmmm...quite a difference from my current 6.5. A smaller PV may very well explain the running rich problem I've had as well? The local auto parts store only had a 4.5 so I bought it and also ordered a 2.5. It's worth a shot to see what the results are...

Thanks again for all the advice!

Jim.

[Tom Vaught]

There should be NO CLEARANCE between the pump arm and the accelerator pump lever when the throttle plates are in the IDLE position. There should be some clearance (.010 minimim) when you are in the wide open position on the blades. This is to keep the diaphragm from rupturing from over-travel.

Many many people have developed a hesitation in their Holleys after reading the Holley instructions incorrectly.

NO CLEARANCE at idle.

Tom V.

ps I used to be a Holley guy at their research/ engineering complex.

[BILTIT]

I think you are getting some errors in your vacuum readings. May be a vacuum leak or misadjusted idle mixture screws. You should be able to get the car to go from neutral to gear with very little rpm drop (maybe 100-250)without stalling. My RAIV cammed 400 w/3310 had about 8-10'' of vacuum.

[kyle_blake]

I agree with Tom, well said!

The whole situation of not being able to get it to idle properly and stalling in drive could be the power valve being activated. I'm not 100% sure, i've never been in a test situation like yours.

Let me know what happens with the 4.5 power valve

mortec says :If you have an automatic transmission, take the vacuum reading at idle in "Drive" (with the emergency brake on and the wheels blocked) and chose the power valve 1-2 inches below that figure.

[tremo]

Update
Some success and an interesting finding! Put my Holley (4160) 750cfm vacuum secondary carb back on today and continued some methodical testing. e.g Straight swap, float adjustment, then new 4.5 Power Valve.

Tested the vacuum and it jumped up to 9 inches (from 6) with the 750cfm @ 800 rpm, but still seems low to me. In gear it dives to 3-4 inches. Either my gauge is messed up or I have a vacuum leak I'm unaware of. (Manifold to heads?). I've checked and checked and can not detect a leak. Hmmm...may need to dig deeper on this one...

Test #1 - Straight swap
The engine did not feel as strong as with the 600cfm. Driviability was much improved; drove "smoother", idled better and of course did not nearly die when in gear. However, a right turn, power brake on concrete only yielded a ~5' patch. Decided not to readjust the timing just yet (will be getting a new timing light next weekend). The car just felt kinda lazy when getting on it. Also, I waited 15 minutes to test the fuel pooling issue and it did start after a good crank on the first try vs. 2-3 tries. Some improvement.

Test #2 - Float adjustment
Adjusted the primary float a tad below the bottom of the sight hole. Moved to the secondary and this is where things get strange. Could not adjust the float; ended up adjusting it so far down the 5/8" adjustment nut came off the keyed adjustment shaft that goes to the needle valve.

Took the bowl off and found a silver colored, odd-headed small bolt inside the bowl! WTF?! At first I thought it fell off the float adjustment shaft, but nope - looks like the factory gave me some extraneous hardware!

Managed to back out the adjustment shaft, put it all back together and the thing leaked like a sieve out the site hole. Took it apart again and had to bend the float tab up to give me enough adjustment externally. Perhaps the screw bouncing around messed up the float setting?

Slapped it together, adjusted the float level just below the site hole like the primary and the friggin' car runs GREAT now! I'd say it runs as good if not better than with the 600cfm. It pulls strong thru all the gears and right-hand turns don't require as much gas to get the tires to break loose. Power braking also laid a nice 40' patch (on a back road of course). Progress!

Now, I just went back out to the garage to test the fuel pooling issue and discovered the passenger side primary is bleeding fuel. This is the culprit. Any ideas on how to resolve it? Back down the float a bit more???

I didn't have time to install the 4.5 PV, but will do that next weekend. (Something to look forward to!) Kyle, I read that quote on mortec.com and decided to go with what Holley recommended (1/2 your vacuum = PV, next size down for even number). So if I go with what mortec says, 6 inches (when I used the 600cfm) would be around a 4.5 PV. 9 inches (750cfm) would be around a 6.5 PV, which is what I have installed currently. Guess we'll see if the 4.5 makes any difference...

Next steps
- Baseline timing with advanced timing light.
- Check mechanical and vacuum advance and make adjustments as needed.
- Install new 4.5 PV

Seee-ya!

Jim.

[BILTIT]

Just to clarify, vacuum should be measured in inches of mercury not lbs. You probably have a vacuum (inches) and fuel pressure (lbs.) gauge in one.

Glad your getting things worked out.

[tremo]

Ooops, you're right. It is a combo gauge - inches and lbs.