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I don't see a 600 vac secondary carb doing that combo any justice.

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Either do I, looking for a 750....but it's what I got now

But I think your right on the spring too light, looks like a little trial and error session

Rickster

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Like Quick said, the back barrels don't get a pump shot. So if it bogs the spring is to light opening to fast causing it to lean out.

Holley's got about 5 or 6 different springs for tuning the vac secondaries. They are colored for different spring values so you know what your putting in, weaker or stronger. mike

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Thanks Mike, I have all the springs, actually it's a Quick Fuel Quick Change Kit, I actually think it might be the short spring, which is like having no spring at all for the 1st 1/4" to 3/8" upon opening, going to try the yellow (long) spring next (second lightest) but taller...we'll see

Rickster

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How about some more pump shot????

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I thought about that, but it's adjusted correctly and getting a pretty good shot now....was very crisp on just the primaries, no hesitation at all, gonna try the springs 1st and go from there.....wish I still had the 750 lying around

Rickster

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Just saying..If it were me I'd be throwing some squirter at it too...

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I agree, just got back in from two spring changes and the next to stiffest seems to work well, might try the 50CC pump off the Domi and see if it picks up at all...??????

Got a set of 4.10's with Sure-Grip showing up 1st of the week, so Friday night I will be pleased if we can get it to run low - mid 8's

Ran 9.7 a couple of weeks ago with the 3.55 peg-leg and no secondaries at all...

It was my Son's 1st lap and he is stoked to get back out....

Thanks for the help guys

Rickster

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I doubt whether the secondaries are causing the bog issues , air speed needs to be pretty high in order for the secs to open regardless of spring tension , i can't see they are opening when you hit the gas from a standstill , get hold of a paper clip & wrap it round the secondary arm , go hit the throttle till the motor bogs then go see if the clip has moved up from where you placed it , this will answer you're question , good luck.

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Adam, the heavier spring fixed the bog...it's gone and tips in perfectly now, so it was opening way to soon, going to try a bigger pump shot as Al suggested to see if it picks up any on the initial hit

Rickster

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I doubt whether the secondaries are causing the bog issues , air speed needs to be pretty high in order for the secs to open regardless of spring tension , i can't see they are opening when you hit the gas from a standstill , get hold of a paper clip & wrap it round the secondary arm , go hit the throttle till the motor bogs then go see if the clip has moved up from where you placed it , this will answer you're question , good luck.

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Adam, the heavier spring fixed the bog...it's gone and tips in perfectly now, so it was opening way to soon, going to try a bigger pump shot as Al suggested to see if it picks up any on the initial hit

Rickster

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I doubt whether the secondaries are causing the bog issues , air speed needs to be pretty high in order for the secs to open regardless of spring tension , i can't see they are opening when you hit the gas from a standstill , get hold of a paper clip & wrap it round the secondary arm , go hit the throttle till the motor bogs then go see if the clip has moved up from where you placed it , this will answer you're question , good luck.

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Adam, the heavier spring fixed the bog...it's gone and tips in perfectly now, so it was opening way to soon, going to try a bigger pump shot as Al suggested to see if it picks up any on the initial hit

Rickster

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if it's not bogging I doubt more pump shot will help

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I'll let ya know

Rickster

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See what squirter size is in it now and try a different size (up and down, down will make it squirt longer, bigger will squirt more in sooner)before swapping out the pump size

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Don't have an assortment of squirters but do have some different pump cams....wonder if we might notice an improvement there...

Rickster

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See what squirter size is in it now and try a different size (up and down, down will make it squirt longer, bigger will squirt more in sooner)before swapping out the pump size

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Don't have an assortment of squirters but do have some different pump cams....wonder if we might notice an improvement there...

Rickster

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See what squirter size is in it now and try a different size (up and down, down will make it squirt longer, bigger will squirt more in sooner)before swapping out the pump size

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Don't have an assortment of squirters but do have some different pump cams....wonder if we might notice an improvement there...

Rickster

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I doubt it, only way to tell for sure would be having a 60' timer.

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Well this week I'm gonna just let him make as many laps as he can, since his 1st time out he only got one, we can play with the carb later, it runs good enough now as is

Rickster

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Im not sure I like the idea of tuning late opening secondaries with more pump shot or squirters.

If your running a single plane you could end up over richening the front 4 cylinders while leaning out the back 4 cylinders.

While it may eliminate the bog, overall you could hurt its "launch" performance. By X amount of cyl being rich and X amount being a bit lean. If your running a DPlane intake the effects will be less.


Id tune the secondary bog with the Springs first, witch you did.

Id like to add that even though the Bog is now gone. Id would still try a spring one size heavier at the track to see if it effects ET.

Just because the bogs gone doesnt mean the secondary opening rate is at optimum.

But it very well could be. At this point with the Bog gone, your probably near the top of the carbs Tune

With the combination of Squirters, pumps, pump cams, air jets, main jets, and in your case secondary springs, Do we ever get that perfect carb tune. Probably not but we can get her darn close. mike




EDIT, Id run as is for now, let the kid have some Fun, mike

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Thanks Mike and appreciate the input

Rickster

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i got a mech.750 that works perfect if you want to play with it.

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IS THE LITTLE BALL BEARING still in the housing.it conrols the opeening rate and keeps the secondaries from flopping open too quick

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No it's not and I believe even Holley leaves them out of the newer models nowadays....

Rickster

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i got a mech.750 that works perfect if you want to play with it.

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Thanks Al, might take you up on that in the future....where are you in SWF...?????

Rickster

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i got a mech.750 that works perfect if you want to play with it.

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Thanks Al, might take you up on that in the future....where are you in SWF...?????

Rickster

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right next door BURRITO SPRINGS

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BURRITO SPRINGS , know it well, I built the Prado @ Spring Creek Plaza & Regal Cinema, Congress Jeweler's Building, also Granada Shoppes down the road in Naples.....we should get together one day for some cold ones....

Rickster

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i got a mech.750 that works perfect if you want to play with it.

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Thanks Al, might take you up on that in the future....where are you in SWF...?????

Rickster

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right next door BURRITO SPRINGS

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BURRITO SPRINGS , know it well, I built the Prado @ Spring Creek Plaza & Regal Cinema, Congress Jeweler's Building, also Granada Shoppes down the road in Naples.....we should get together one day for some cold ones....

Rickster

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sounds good if i ever get to take my car out ill give yua a shout,its only been a year so im about due

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i have run that combo
if it has a dead spot because lack of gas not spring
nothing wrong with a 600 vac either
i had both 600 and 750 dpp
600 only 10 off the 750
750 was used but was redone
600 was new
put jets in both
and small(litest) spring in the 600
ran 82 in the 750 in the spring time 80 in
the summer
600 ran 80 in all time
drill the back plate

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