please help carb question

[sleekcraft76]

i have a 460 .030 over stelth intake holley 750 with vacume sec clay smith cam with 560 lift 231 duration.i have ben haveing a real hard time finding the correct jet sizes and power valve for it to run good .it does not seam like it has much vacume and a strange surg at 3000 what kind of vacume should i looking for? whould a power valve plug help ? need help bad i have been pulling my hair out with this.
thanks a lot!!!!!!

[Floored]

dont use power valve plug. put boat in water and warm it up. check vacuum at steady idle. you want a power valve approx. 2" below your idle vacuum. 750 should have around a 72 jet and i'm using 79's on my primaries on my 455 olds and still a little lean :confused: .get a quick change secondary housing and secondary springs to adjust secondary opening rate.you want them closed at cruise and when they open you shouldn't feel the transition :cool: if you are still a little lean you may have to change the secondary metering plate to richen it up. find a calm spot and do a hard pass and shut down engine to get plug reading. make sure timing is set approx 8-12 initial and 34-36 total my .002

[OMEGA_BUBBLE_JET]

do yourself a favor and ditch the vacuum secondaries. A mechanical secondary would work much better for you with less heartaches. Especially with a hot cam like you have. Just a suggestion. vacuum secondaries are natorious for running lean which can lead to meltdown in your engind. It is much easier to "fatten" up a mechanical secondary. And they seem to be more responsive. If you have to rig it with spring kits that should tell you something.

[1Bahnerjet]

OBJ a Thumb nail pic makes a good Avatar. :cool:
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Drive What You Own And Like What You Drive

[BK]

OMEGA_BUBBLE_JET:
do yourself a favor and ditch the vacuum secondaries. A mechanical secondary would work much better for you with less heartaches. Especially with a hot cam like you have. Just a suggestion. vacuum secondaries are natorious for running lean which can lead to meltdown in your engind. It is much easier to "fatten" up a mechanical secondary. And they seem to be more responsive. If you have to rig it with spring kits that should tell you something. Sorry but I have to disagree with this. Not saying a mechanical secondary carb wouldnt work just as good or better but you can make that carb work just fine with what you have. If im not mistaken isnt the stealth a dual plane intake? If so you should have plenty manifold vacume, and like floored said the quick change kit is a good idea for tuning and a metering plate change may be something to try as well. :)

[OMEGA_BUBBLE_JET]

Alright Byron I don't want this to get nasty but for the time and money and effort he would spend screwing with the vacuum secondary he could sell it on ebay and buy a mechanical secondary carb and not have some much tuning (headaches). I guess it really is personal preference. I just like life to be as simple as possible. And I am no proffesional tuner by any means so I wouldn't attempt to swap metering blocks unless I knew what I was doing.

[OMEGA_BUBBLE_JET]

thanks bahnerjet. I guess the big one is a little over the top....
Kris

[BK]

No worries, I wasnt trying to bash ya or discredit your advice as I think a mechanical secondary carb is the way to go if you have a choice, just saying the carb he has will work just fine with some tuning. As far as changing the metering block, you wouldnt have to change metering block (most vacume secondary carbs only have one in the front) just the metering plate witch is not much more difficult than doing a jet change. BTW, im not a "professinal tuner" either, just trying to help. :)

[Hotcrusader76]

I have seen both types of carbs work very reliably.
Surge @3000RPM? Could you have a vacuum leak somewhere? Don't rule it out. IE Throttleshafts, baseplate matteing surface, intake/carb surface, etc.
You can block off the powervalve at first to find your perfect cruise jetting for the primary, temporarly eliminating the acceleration circuit.
The secondary plate? Leave it alone for now.
Also make sure you have nothing pluggin up those airbleeds on top of your caburetor. Sometimes little pieces of crap get caught up in there.
Get a good vacuum check at idle then properly select the PV.
Also note- 76 Jets are an average size for your type of set-up (with knowing only what you have stated so far)
Now as far as mechanical secondary? If you can master a vacuum secondary, you will be a pro on a mechanical.
Just my 0.02 :D
~Ty

[Floored]

I made my suggestions based on the equipt. that the man has to work with. Part of posting questions is to learn and also get different opinions.My spare carb is a 3310-3 holley that has vacuum secondaries, my normal carb is a 3310 with 4 corner idle, gear drive secondaries, 50cc accel pump and center shooters. This is what we used to build before holley made double pumpers. I learned to do carbs by trial and error and asked alot of questions, read a lot of books and hung out at drag strips alot. Once sleek76 does get his tuneup set, if anything goes wrong on lake he knows more of what to look for so maybe a weekend isn't shot. you guys can flame me now