Right now ive got a 750DP thats actually jetted to 780 with a proform main body it was set up for a 406. I think its too much carb for the motor right now, 355 vortec heads, hot cam 520 lift, performer rpm intake, hei dizzy. Spark plugs are all sooty, smoke out of exahust, bogging, getting like 6mpg.

I've got a 600VS carb which I think will be too small, but my buddies got a 650VS i could try and another 750DP i could try. I'm thinking a 650 or 700DP would be the best way to go cuz dont the DP's make more horsepower than a VS carb? Also what about eldebrocks? I heard they are good for the street but suck at the strip. I'm willing trade some streetablility for horsepower.

 

"Jetted to 780" - there is no such thing.

Tune what you've got on now. It's the best choice of anything you listed as long as you can live without a choke. See the Holley sticky in the top section of this forum.

VS doesn't make more peak power than DP - DP just makes more power "under the curve". In other words, more power quicker. Edelbrocks are good for those who are willing to sacrifice performance to save money - typically the "shiny" crowd.

 

it turns out that "double pumper" is really just a dual feed 750VS 3310 carb. Should I go DP? It takes so long for the four barrells to kick in, and sometimes i get a bog when i punch it, it has 72 jets in it.

 

Get a spring kit and experiment with the secondaries first. If nothing else it's a good learning experience before you move on to something else.

 

I ran a 12.16 with a 750vs on my setup. You have to tune the carb. I had the choke flap removed, and installed a rear metering block. I played with jets, squirters, and PV's for a while to get things right. You can play with springs and pump cam also.

What size squirter do you have on it?
Have you had a vaccuum gauge on it to set the air screws?
Which Power valve does it have in front?
What does the spark plugs look like?
Did you set the floats?
What rpm is the idle set at?

 

set the floats, and idle screws, its got 72 jets in the primaries not sure about anything else. Sometimes itll bog and the secondaries take too long for me to open. I will swap my buddy for his 750DP, cuz i dont want any VS junk slow carb. My buddy keeps telling me the 750 is too big and i should get a 650 for it. Is the 750 too big?? For street use?? I mean bigger is gonna mean more HP. he told me the 750 will be too big and ill burn the valves from dumping too much fuel i told him i would jet it down and he said id have to jet it down to a 650 anyway

 

oh yeah the plugs are black but that was probably from running 8* locked out timing for a while

 

A 750 VS isn't too big, it'll only be as big as it needs to be. Bigger doesn't necessarily mean more HP, but in a DP too big does mean less throttle response, worse mileage, and more tuning headaches.

You don't "jet down" from a 750 to a 650. Jetting alters the fuel metering, that's completely independent of the air flow rating of the carm.

 

yeah thats what i tried telling my buddy but hes got all the experience so he knows everything. Haven't put a vacuum gauge on it b/c the only vac port on the carb is ported spark and brake booster on the manifold.

so is 750VS the way to go or should I try the 750DP or a 650DP or I also got a 650 single inlet. I think 600 would be way too small. Problem around here is there are a ton of experienced gearheads/mechanics in my neighborhood telling me what to do but wivestales and uneducation seem to reign supreme around here. Alot of people are telling me to go "eldebrock" for the street. I wanna stick with the holley though. and actually TUNE it unlike everyone else.

Also alot of people are telling me to disconnect the vac advance. also a question when you set it for total timing thats with the vac advance disconected right? B/c im worried with the vac advance its gotta be pulling like 50 degrees of timing in, but no pinging it seems..weird.

 

You've already got the 750 VS, so try working with it first. The process isn't that much different to tune the VS than it is to tune the DP, you're just tuning the secondary opening rate instead of the secondary accelerator pump shot. For that matter, the process isn't that much different if you were tuning any other carb.

Total timing is with the vacuum advance disconnected. For anything on the street, you want to keep the vacuum advance. You could easily have 45 degrees or more of advance under high vacuum and high RPM, that's no problem when you're not under load.

 

Use the 750vs. Try some 68 jets in the front and see what powervalve you have while your at it. What size squiter does it have?

There should be 3 vaccum fittings. One in the back for the brake booster, one on the side of the metering block for the vaccum advance and one on the base plate on the side or front. If for some reason it only has two, you can test off the brake booster fitting. You need to tune for best vaccum

The rear metering block should be the same as 75 jets. Depends on the model of the carb. You need to try 34* timing all in by 3k with the vortec heads.

Oh yeah, what is you fuel pressure set at. You should be close at 6 psi.

 

the brake booster is off the rear manifold port. The ONLY vacuum port on the carb is the ported spark on the metering block and that shows 0HG at idle. I don't know why it doesn't have any other vacuum ports im running breathers now because of it, also the choke is gone. The manifold seems to suck pretty good. I screwed them in until it sounds like its gonna die and back it off a turn, thats how my buddy said to do it. The fuel pressure is at 5psi, should I change it to 6? I read anywhere from 4-7 is good. The primary fuel bowl says "72" on it in marker so im guessing it has 72 jets, and the secondary bowl says "4.5" on it, powervalve perhaps? how do i find out what size squirter and stuff is in it? This came off a 450+HP 406

 

http://www.holley.com/data/Products/...199R9934-3.pdf
Read this if you havent already.

The "squirter/shooter/pump discharge nozzle" is were the fuel squirts out in the front. It has a large phillips screw in it. Just bump the throttle and you will see were the fuel comes from. It should be stamped with the size. If it has a #31 then try a #35.

You cannot tell what size jets or powervalve it has without taking the fuel bowls off.

If it is a 3310, factory settings are in the link above. Stock it should hav a 31 squirter, 70 front jets and a 6.5 powervalve. It should have a plate in back instead of jets. The plate should be a # 21 which is the same as 75 jets. Oh yeah, stock the secondaries should be a black spring.

You need to put a vaccum gauge on it to adjust the air screws.

 

My Proform wasn't drilled for the port in the metering block.

There should be a port on the front of the throttle body for manifold vacuum. But, it's a small port, not big enough for PCV or brake booster.

 

I'll look again today cause im going to put in my new starter and get the motor running again (last started cracked the other day) but i looked all around and could not find any vacuum ports. I don't think its a profrom main body like my buddy said cause it has a choke horn, either that or could it be a really old 3310 that doesn't have any vac ports? The 600VS carb i have has a bunch of ports, this one just has ported spark but ill look again today.

 

yep no vacuum ports on the carb, the baseplate says 4233 on it

 

Proform main bodies don't have a choke, so it must not be a Proform main body.

 

yeah i guess it is not, it says holley list 3310 right on it. So you guys think I should put 70 jets and a 65 powervalve in it (basically restore factory settings) and possibly a 35 shooter? I checked and it has 72 jets and a 45 powervalve. Had to fix my idle screws as they were really loose

 

okay guys i found a book on holley's laying around and was reading it so learned quite a bit. Set my accelerator pump to .015-.020 of play at WOT, reset fuel pressure to 5.5psi and set float level. Started playing around with the mixture screws and then i found:

There is a small hole drilled in each of the primary throttle blades, also the secondary throttle blades are open quite a bit, I can't get this thing to idle down without really leaning it out.

Aren't the secondaries supposed to be CLOSED at idle?? I know the holes in the primary are for a big cam with low vacuum. Also I have really good vacuum like 15Hg. So I adjusted the secondaries down then screwed the stop screw in until it touched then went 1/2 turn more. Re-set idle and mixture screws everything seems like it should be good now.

I found out it is a 32 shooter, 72 jets and 4.5 powervalve. Going to try some 70 jets and a lighter spring and do the vacuum test to see what powervalve i need. Also gotta set my total timing when my buddy loans me his light. Just got it set to 10* base right now

 

Sounds like you are on the right track now. Its easy to tell someone how do do something, but its better to just learn how to do it.

Keep working and fine tuning.

 

No. As the sticky and Holley information tells you, they are supposed to be open slightly.

Holes drilled in the primary throttle blades probably means this carb isn't going to ever be quite right on your engine.

 

so five7 my buddys got a 650 single inlet I could try, I think the 750 might be too much. do you think its worth trying a 650VS even though its a single feed

 

You can try it and see what it does.

 

I think its a 600 actually it says "list 1850" on it. My plugs actually don't look too bad anymore and it stopped sucking gas so much after I adjusted it right. It just bogs when you stomp it and there is a big flat spot, you can hear all 4 barells opening it just goes "wahhh" sucking in air and falls on its face for a second and then it goes.

 

Try a 35 shooter in the front. It should help some with the bog. Might even play with the pump cams. Try the shooter first.

Make sure you dont lose the washer under the shooter and the one under the screw head!!!!!!!

 

i changed the spring from a yellow to a purple and it got rid of the bog and it seems to run pretty good right now