I just recently put a 750 vacuum secondary Holley model 3310 on my 355ci.SBC. I have Vortec heads,Comp 268 extreme cam(225/230@50-477/480 lift,performer RPM intake, full lenght headers, flat top Hyper. pistons-about 9.5 to 1 compression). I'am in Arizona and with the heat it is rare to see air below 3000ft. and the air temp. is usually high. The carb. came with 72 jets in it and I have already went down one size to 71 on the primarys and it still acts a little rich, the secondarys have a metering plate right but I plan on getting a conversion kit to put a metering block on it so I have some control over the secondarys. What would you folks suggest that I should run it in the front and the back? Also with my RPM intake there is only one vacuum supply in the manifold and that is right behind the carb.. I need to have two large vacuum ports in order to run my brakes as well as one so that I can run my PCV valve. The holley carb. as you know is much longer than a Carter and it just about covers my vacuum port and when I put the metering block on it , it will be over the vacuum port. If I had room I could put a spacer under the carb. and it would solve all my problem. But as you know they didn't leave any extra room under the hood, I know that there has to be a bunch of people out there that are running this set up and I would like to know what you heve done? I know that this is long and not the best discription in the world but if it makes any sense to anyone please get back to me. Looking forward to hearing from anyone!!! Thanks NORT P.S. If you need any more info than this just let me know. NORT

 

I'm down to 68 primary jets and have some 66 jets in the box. I too still have to secondary plate and plan to go with a block. I've heard 78 jets are a good place to be around with that. It's hard to compar with various engine types/specs though...

As for the vacuum situation, I run a Y-fitting to both the PCV and the brake booster off the carb. I have a fitting from a hardware store that I might use for the brakes in the future though. I think it is called a "banjo fitting" or something.

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

I have the same setup from carb to headers as you only I have more compression. I tried the 70's and it acted good. I changed them to 71's and the 70's were better. Tonight or tomorrow I am going to try 69's. I'll try to post the results on here. Are you using 1.6 roller rockers?

Have you ran at a track yet? I'm just curious to see what kind of times I'll get.

 

As far as the vac. line is concerned, do what biochem said. I plugged mine with an allen type pipe plug 3/8". I then ran a line from the booster to a "T". Take one to the PVC, one to the carb, and the other is the booster. Works great for me.



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Joshua Johnston
1991 Z-28


350, T-5, K&N, Ported Vortec heads, Edelbrock RPM, Holley 750 D.P., HEI, 11.07:1 CR, Comp Cams Roller-.510"/.520"-282*/288* dur., Shorty Headers, Dual 2.5 Exhaust,Dynomax Bullet Mufflers, T&R Motorsports custom air intake

 

The way I usually tune my carb is by reading the plugs. The condition of the plugs will tell you how your engine is running. Also I recommend you use a vacuum gauge to see how much vacuum you've got at idle so you can figure out which power valve to run and also to set your mixture screws correcly. The metering block is a great idea.

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383 86 Camaro Z28 ---1/4 mile et>13.65@103mph,,
10.5:1compression Dart Pro 1 Aluminum heads 215cc>2.05/1.60 valves,400 steel crank,cam specs:224/234 at 050 525/525 lift,3500 stall converter,shift kit,4.10 gears,770 Holley Avenger,Victor Jr. Intake,true dual exh,Hooker headers with 40 series Flowmasters,MSD Coil and Module.ALSO SECOND GEN Z28---mods:454 BBC,.546 max lift(doug herbert cam ) 750 Holley vac sec. ,Edelbrock Performer manifold,Holley electric fuel pump,Hooker headers,Flowmaster mufflers,beefed up 700r4 tranny, 3.90 gears, powertrax unit, B&M console shifter.

 

Also just to give you an idea I currently have #67 on primaries and 78 on secondaries.

 

I have the same setup with a little more compression and I'm running 69's or 68's, I forget which with looking at what's left in the box.

I hooked my brakes up to the manifold and my pcv valce up to the air cleaner base. Works very well except you have to pull the hose off if you want to remove the air cleaner base, PITA! to do this 1000 times.

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350 Vortec, forged flat-tops, CompCams XE268, Edlebrock RPM, Holley 3310, TH350 w/Holeshot 2400, 3.23 posi, Heddman shorties, HEI