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  #16  
Old Apr 25th, 12, 10:16 AM
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Default Re: Tuning out an initial hesitation... ?

Quote:
Originally Posted by HwyStarJoe View Post
Thanks Dennis. I've already got dog-eared copies of all the Holley docs on the workbench.


I've seen that chart too. Where did you get the version you mentioned earlier "In position 1 it's; brown is the largest then pink, green, black & orange (same), red, blue white." ?
I have 2 Holley books with the same charts, one by Mike Urich and Bill Fisher and the other just by Mike Urich, both published by HP Books

Amazon.com: Holly Carburetor Handbook 4150 & 4160 Hp473 (0075478007509): Mike Urich: Books Amazon.com: Holly Carburetor Handbook 4150 & 4160 Hp473 (0075478007509): Mike Urich: Books


and an older version of this one...

Amazon.com: Holley Carburetors & Manifolds: HPBooks-339 (9780895864338): Mike Urich, Bill Fisher: Books Amazon.com: Holley Carburetors & Manifolds: HPBooks-339 (9780895864338): Mike Urich, Bill Fisher: Books
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  #17  
Old Apr 25th, 12, 05:40 PM
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Default Re: Tuning out an initial hesitation... ?

Well... the new pump arm and the 31 squirter didn't alleviate the bog totally . Maybe a little bit. I suppose I can play with cams but I think it may be something else. I'll play with the butterfly adjustments some more and make sure I'm not sucking air before trying to tune it. It could also be that it was 45 degrees outside.

Lemme ask ya, the pair of squirters come with new steel "gaskets". The base of the squirter and mating surface are flat. Why are the "gaskets" conical shaped? I realize the screw will shape the top one, but am I to assume the bottom one will get smooshed flat when I tighten the screw?
They're the same part number for both top and bottom "gaskets"
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  #18  
Old Apr 25th, 12, 05:55 PM
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Default Re: Tuning out an initial hesitation... ?

There is spring pressure in the washers that will help keep the screw from backing out, kinda like a lock washer...

Joe you will be freaked out by the amount of effect the different cams have. As an example the Orange cam in position 2 allows 2.45cc per stroke of the pump, in position 1 it allows 1.9cc per stroke of the pump. The white on hole 1 allows 1.7cc and hole 2 allows 1.95cc... then each cam has a different ramp rate controling how fast or slow the pump is activated...

As for your throttle blades, the air you have to over come is not what is getting by the blades at idle, it's what goes down the bores when the blades open up. That pump shot is everything at the point the throttle is hammered...
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  #19  
Old Apr 26th, 12, 04:02 AM
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Default Re: Tuning out an initial hesitation... ?

Alright... cam swaps it is then.
Wish I could play hookie today.
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  #20  
Old Apr 26th, 12, 10:11 PM
97Z4C 97Z4C is offline
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Default Re: Tuning out an initial hesitation... ?

just me but first i would verify timing and then make sure power valve is correct before going into the cam area
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  #21  
Old Apr 27th, 12, 04:02 AM
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Default Re: Tuning out an initial hesitation... ?

Yeah...
Everything was tuned when it was 80 degrees and humid outside last year. Ran great. It didn't want to respond as well once the temps got down toward 50.

As far as the power valve, I get great vacuum... around 16 steady. Maybe more. So I left the 6.5 in there. Maybe step it up a notch or two?
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  #22  
Old Apr 27th, 12, 09:20 AM
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Default Re: Tuning out an initial hesitation... ?

Quote:
Originally Posted by 97Z4C View Post
just me but first i would verify timing and then make sure power valve is correct before going into the cam area
I understand power valve tuning but why go to all the trouble of disconnecting the carb to access a bowl to change a PV when you can make a pump cam change in about 30 seconds...
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  #23  
Old Apr 27th, 12, 10:15 AM
Grabbin2ndgear Grabbin2ndgear is offline
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Default Re: Tuning out an initial hesitation... ?

You know I would add something, but you guys have covered everything here to tune out a hesitation You guys are damn sharp.

Only thing I would add is to keep playin with the cam, you really need a heavy shot to overcome the vacuum drop. Weird that it developed over a 40 degree temp change, you must have been right on the edge when you tuned it while it was warmer.
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  #24  
Old Jun 12th, 12, 03:02 PM
1968camaro123 1968camaro123 is offline
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Default Re: Tuning out an initial hesitation... ?

Well what happened with the pump cams?
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  #25  
Old Jun 12th, 12, 03:39 PM
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Default Re: Tuning out an initial hesitation... ?

Funny you should mention it because I was going to update...

I was messing around with the tune a week ago. Checking timing (almost a year since setting it), cleaning the carb that sucked up glue from the chinese fuel filter, etc., and reading this link I'd saved: http://members.tccoa.com/392bird/tuning.htm

I took the 31 shot squirter off and went back to the 29. The 31 didn't help as far as I could tell. The timing was close, but I needed to play with the adjustable vacuum can a little. Trying to find the sweet spot. I lost my place so I'm still screwing with it.

While I had the carb off cleaning it I decided to see exactly which cam I had on it. I still can't tell because it's weirdly discolored. Maybe a brown one? Could have been white. The accelerator arm is new because it was grooved, so I put the white cam on.
I had an immediate change in acceleration response.
The hesitation\bog (seems like a combination) on initial acceleration moved up the RPM band.
Now instead of being immediate, I get a good off-the-line response, then it hesitates and responds again. Sort of a 'whaaa......whaaaaaaaaa...' (corny, I know).

One thing I'm also still playing with is my idles. Before the cam change I set them again. I have this weird fixation with setting them. I plug the gauge into the port I use for advance and I have a steady 20 inches at about 900-1000RPM idle. But I was surprised at how close to closed I have them. My screw driver is marked so I can count the revolutions and they were both only about 1/2 to 3/4 of a turn from fully clockwise.
My vacuum with someone on the brake and the car in Drive wavers between 11 and 15 inches. In Park it's a steady 20.

Watching the vacuum gauge I have a pretty wide band CW and CCW before I see the needle start to drop and the idle speed change. I went back and forth with them a couple times in the past week just to see if anything changed and it runs best and has best vacuum with the idles set 3/4 of a turn from closed (fully CW). The passenger side seems to like about a 1/2 turn though.

So that's it... I might put a different cam on, or move this white one to the #2 spot. Not sure what color to use though.
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  #26  
Old Jun 12th, 12, 04:18 PM
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Default Re: Tuning out an initial hesitation... ?

Joe 3/4 turn out on the idle mixture screws is almost always where they end up on the carb's I've tuned. If I get one at 1/2 and the other at 3/4 I split the difference and make them both 5/8th. As for the cam results, you can try the #2 position but I think you got it and are now ready to tune the vacuum advance springs because it sounds like they are opening too soon. You can disconnect the diaphram arm and go for a ride without secondaries to see if that is true.
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  #27  
Old Jun 12th, 12, 06:18 PM
1971ls6 1971ls6 is offline
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Default Re: Tuning out an initial hesitation... ?

Agree 100% on the 3/4 idle mixture, I start at 1 turn and always end up at 3/4 on the 3310 carbs, they have large idle feed restrictors . Before you start tuning the secondaries, don't waste your money on the quick change spring kit, spend the $30 and buy the quick fuel secondary vacuum pod, it uses a screw, like an idle mixture screw to dial in the rate that the secondaries open. You can dial it in way more precisely than changing springs, plus it is the easiest way to make changes based on track conditions, keep turning it out until you get a bog and then go back in until the bog disappears . Far and away the best way to dialin vacuum secondaries.the orange cam seems to work the best for me, white is the stock cam
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  #28  
Old Jun 12th, 12, 06:34 PM
markw markw is offline
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Default Re: Tuning out an initial hesitation... ?

All the pump cams I have seen have the last 3 digits of the part number molded into them. If you get a good hit, then a sag, and then it takes off good it may be time for a smaller shooter to stretch the pump shot out for a longer time. Make notes with each change and don't confuse things with 2 changes at a time. What secondary spring are you using?
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  #29  
Old Jun 13th, 12, 04:00 AM
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Default Re: Tuning out an initial hesitation... ?

The secondary is all factory spec parts from the kit.

Quick Fuel seems like the way to go with a lot of the upgrades. Or a whole new QF carb.

I definitely need to play with the timing some more. Maybe I'll make a short video of the curves and let y'all diagnose.
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  #30  
Old Jun 13th, 12, 04:13 AM
2001 Pewter WS6 2001 Pewter WS6 is offline
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Default Re: Tuning out an initial hesitation... ?

On my friends 69 camaro he had a hesitation as well. He had a new BG Demon 750. His motor was a fairly stout 408 Big Block solid roller. His problem was in the timing. He needed more base timing in it and less vacuum advance. Soon as you hit the throttle the vacuum advance goes away and you are left with what ever the base is at. We ended up setting his base to 26 degrees and limited the mechanical advance to 10 degree for a total of 36 degrees and did away with the vacuum advance all together. The car runs like a raped ape now.
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