I have a 700 dbl. pumper that loads up.Are there 1 or 2 power valves in this carb?Have replaced the front one ,dont know if there is one in the rear

Take the bowl off and see. Make sure they are 2 inches less than idle in gear vacum.

Do some of the Holleys have power valves on the rear?

If it is an off the shelf double pumper it should have a PV in the rear, unless it has been plugged.

I have a 850 dp (4781) that does have a power valve in the rear. I believe all 4150 series carbs have rear power valves unless someone has plugged it.
Jeff

my 700 DP had a PV in the rear.

Get the list number off the carb and check this chart from Holley. If it has a sec power valve there will be a reference number in parens next to the pri power valve number. Go to the bottom and reference what PV to use... The chart is done this way because most carbs don't have a sec PV so it wasn't worth building another column in the chart...

www.holley.com/HiOctn/ProdLine/CarbList.pdf (http://www.holley.com/HiOctn/ProdLine/CarbList.pdf)

Thanks DjD,My carb list# is 4778-2 and the primary power valve is 125-65 according to your chart,and thats what Ive been putting in.There is no # in parenthisis next to it so this means I dont have a second power valve ,is that correct?What would cause this carb to load up? Does it just need a rebuild?Thanks for all your help.

Doug you need to be more specific. Where in the carb's operation does the problem occur? Idling, but a good romp and it clears out? Wide open passes and then it craps out? Try to describe what happens, say you just put a new set of plugs in... What happens next?

Hi Doug,
I think you'll need to provide some specifics on the engine, (ie cam specs, CR, intake, ign, timing, etc.) and also describe the problem in a little more detail.
FWIW, my 4777 650 DP does NOT have a seconday power valve.

Just put a new set of plugs in,electric choke seems to work ok,carb seems to load up at idle,when you get on it seems to clear out.Always have a lot of black carbon in the tailpipe tips.When cold have to keep my foot on the gas otherwise it will stall.Have adjusted the air idle mixture screw on the metering block ,doesnt seem to make any difference.Screw it all the way in engine stalls.Old plugs didnt look to bad ,more grey than black.Engine is original block LS-5 TRW forged pistons,10.44 cr.Original heads with stainless valves and seats.Power plus cam,.544,.544,lift,230,230,duration.Crane gold roller rockers,Old edlebrock hi rise,MSD 6al,pro billet dist.with blaster 2 coil.Hedman headers,M-22,3.73 ratio.Not sure about the timing.

To adjust idle mixture screws, turn them in until the engine starts to stumble and then back them out until it smooths out. Having a vacuum gauge and adjusting for highest vacuum would help dial it in better when backing the screw out. Do one side at a time and then shut the car off and check where you are on each and set them to meet in the middle. Example: 1 turn on one and 3/4 turn on the other, set both to 7/8 of a turn. I have found that most Holleys on stock to somewhat warmed over SBC's like less than one turn. I almost always start at 3/4 turn and rarely need much more adjustment. Every mill is a little different though.

I highly recomend going through your carb and setting everything back to factory spec's. It's always easier to start from a known base. If you're a bit gun shy check out www.camaros.net/techref/series_2.html (http://www.camaros.net/techref/series_2.html) and see if the "Understanding your Holley" articles give you some confidence and a better understanding of your carb.

Hey guys, I am in no way a carb tuner but couldn't it be possible he has too large primary shooters in it. Isn't the higher the number the larger the shot of fuel is right away but then peters out, and the smaller the number the smaller initial shot but strong shot all the way through? Or is it possible your floats are misadjusted? Too high a fuel level and it could be pushing it out through the vent tubes and then clearing out as you get on it. Like I said I'm not a carb tuner, but maybe something to check.
Good Luck, Jeff

Also couldn't it be possible he just can't get enough air into it at idle? Possibly have to drill the butterflies or uncover the transfer slot slightly? Just another thought.
Good Luck, Jeff

Originally posted by quikss:
Also couldn't it be possible he just can't get enough air into it at idle? Possibly have to drill the butterflies or uncover the transfer slot slightly? Just another thought.
Good Luck, Jeff His cam isn't big enough to warrant drilling the blades... I see drilling the blades as a last ditch effort to make carb work on a combination that is too much for the carb.

As for your squirter question, it only squirts when you give it gas, not when idling. It could be part of the problem though which is why I recomended putting the carb back to the way it came from holley.

Typically when someone is having a problem with a carb I find they have had several friends and even shops involved trying to make things better. When asked I typically find that no one has even broken out the factory spec's and put the carb back to how it started life. Most seem to know how to set the floats and that you need .015" in the accl pump but most just start tweeking from where the carb was when they got involved.

How does my combination sound.Would I be better off with a different carb?If so what would you recommend.Thanks again for all the help.

I'm sure that 700cfm 4778-2 is fine on your engine. I'd make the most of what you have and if it's not enough once you have it at it's best then let the site know how it runs and what you want it to do.

I totally agree with DjD. The carb needs to go back to the factory specs, and go from there.
The Holley web site will list all of the info you need regarding jet size, etc.
We're missing a couple pieces of vital information here....
First, we NEED to know what the initial timing is set at. Also, is the vacuum advance connected to a ported source, or full manifold vacuum?
Second, we need to know how much Manifold vacuum you have at idle. (in gear if auto)
If you don't have, or can't borrow a Vacuum gauge, set the air/fuel idle mixture screws to achieve the highest rpm at idle. Both screws should be about the same. I think you'll find that 1&1/2 turns out will be a good place to start. Once you get those set, then re-adjust the idle to where you want it.
That is not a huge cam, so I would think that a 6.5 (stock) power valve would be fine.
Check the float levels also...it should just dribble out of the site hole when properly adjusted. You could have a stuck needle/seat, and the float level is too high, causing excess fuel to enter the carb.
With the air filter removed, after you shut the car off, jump out, and look to see if any fuel is dripping from the boosters...
These are just some basic things to check/adjust to get you in the ball park.
Let us know if any of this helps.

Thanks for the help Ill play with it this weekend and let you all know.

I would definitely check the vacuum, my 350 has a moderate cam in it but when we checked the vacuum it was down around 6. The power valve was the stock 6.5 and it for sure was a problem. You might be experiencing the same - remember to check it in gear at idle if automatic trans.

Thanks, I have an M-22 4spd.

Originally posted by DougA:
Thanks, I have an M-22 4spd. DUH...I guess if we would have looked at your sig.... graemlins/clonk.gif
graemlins/beers.gif

Here is what I found this weekend.Float levels ok,primary pump squirter at.015,vacuum at 9 in. at 8degrees timing bumped it up close to 10 degrees,vacuum at 10 in.(mechanical advance pro billet MSD dist.)Idle air screws both at 1 1/4 turns,idle at 800 rpms.Carb calls for 6.5 power valve which is what is in there now,should i try a 5 or 5.5 p.v.?

Just looking for some help.Thanks

Put the biggest bushing in the dist. you can, then adjust your static timing up to 14. Make sure you have enough battery/cable/starter for this. This should give you around 32-34 degrees total timing. Now you can adjust your static timing up 2 degrees at a time until you have pinging problems. Then go back 2 degrees. Best to do this in the summer btw. Now if it won't start with this much static timing. You can but a different bushing in until you get to 14 or 12 etc with the same total timing as you ended up with. This will get your idle vac up and allow you to tweak the carb some more. More than likely, the low idle vac has caused you to turn the idle speed screw up and exposed the transition slot. Which will richen up the idle.
With more vac, you can turn the screw back out and close the throttle some. You can also flip the carb over and adjust the secondaries open a little to allow the primaries to be closed some more. The proper throttle blade position is .040-.060 of the primary slot exposed and the secondary slot just barely showing. Flip it over and you'll see the slots in the throttle bores. Just measure with a feeler gauge. Note, .040 -.060 or .020 change is only about a 3/4 of a turn on the idle screw.
Also, if you have vac adv, hooking it up will raise your idle vac.. 9-10" seems low to me for a 230@.050 454 cam. Stock to + - 4 numbers on the jets should be sufficient. If not, something else is wrong.

In short:
verify jetting, stock will work for short time if wrong (lean)
set timing
Adjust throttle plates for .040-060,
adjust idle mixture screws for highest idle/vacuum.
Repeat until all is correct.

Thanks Scott,willtry this weekend.

I found on my 461 BB Olds with about the same cam that my idle air bleeds were not big enough. It ran rich at idle and lean at the strip. Just a suggestion. I know its not apples to apples but it helped mine.
Later