MACDAD260

I just installed a new Holley 800CFM (Part #09022) on my Gen V 502 Mag. I have an Edelbrock Performer RPM intake manifold with a 1" open hole carb spacer. The carb came jetted as follows; Starboard Primary-74, Port Primary-72, Both Secondaries-87. Before starting the engine for the first time with the new carb I put a 76 jet in the Port Primary and a 89 in the Port Secondary. Last year, when I was running a 750 Weber, the #4 and # 7 plugs always looked a little leaner than the rest. Since both of those cylinders are fed off the port side of the intake I thought I should start by having that side run a little richer. That is why I changed the port jets to larger sizes than the starboard. What do you guys think of that?

Also, while running it on the hose, it seems to load up at idle. A few blips of the throttle and it idles good again. I adjusted the idle screws for the best idle but I am not sure which way to turn them for rich or lean. Are they air screws or fuel screws?

I am new to Holley carbs so any advice will be appreciated. Thanks.

DanB

Start with the eng warmed up. The 4 corner idle screws are for air. Start with a vac gauge and set all 4 corners to the highest vac you can get without a low speed stumble. Make sure the butterflys have the proper gap at the air bleed slot. Once you do, dont move them. Get it to idle smooth at about 1000 rpm, then put it in the water, tie the boat to the dock and finish it up with it in gear. Should be about 7-800 rpm in gear. This is all for idle only. Jet sizes dont affect idle. They are for running only. You need to do a plug check to get the jets right. I'm not a big fan of unequal jet sizes in pri and sec. Some are.You may have just been having probs with the weber. I'd start off with the same sizes and see what happens. Have a good summer.

Dan

MACDAD260

Thanks, DanB. How's things in sunny Florida? Cold an wet up here most of the weekend, at least. I might get a chance to get on the water Monday. Supposed to be all the way up into the high 60's and sunny that day.

Thanks for the carb help. This 800 does not have a 4 corner idle system, just the screw on each side of the front metering block. I'll try the vaccuum guage and see what happens.

I am using unequal jet sizes to start with just to see how it works. I am probably in for long ordeal to get the jetting right. I want to start out rich and work my way down so I don't hurt the motor. I seized the #4 piston last year due to running too lean so I am going to be real careful to get this right. I am hoping to pick up a mph or two with the Holley.

See ya, Doug

DanB

Hi Doug
Same thing applies for 2 corner idle. Be careful you dont run it too rich, you'll wash down the cyl and then have probs again.
Lovin FL, cant beat summer year round.

Dan

Mr Gadgets

Hi Doug,
I just posted this on another thread, it might apply to your situation. A lot of good info in this book. As Dan said, the amount the throttle plates are open is critical. They need to be covering the idle transfer slot some. If they are open too far, above the slot, you need to close the primarys and open the secondaries some to let enough air into the motor and still be able to adjust the idle circuit.

A hundred years ago I bought a book from S-A design books called Volume 1-carbs: Holley Carburetors, written by Dave Emanuel. I use it as a bible for holley carbs, hope that helps. I dont know if it is still available.

Good luck

Dick

MACDAD260

Thanks Dick, I'll check the throlttle plates before I start it up again. I'll let you guys know how it turns out.

See ya, Doug

Mr. Demeanor

Heres a link to site that I found helpful:

http://www.mortec.com/carbtip1.htm

MACDAD260

Thanks Mr. Demeanor,

Some good general information on that site. I have been there before for engine casting number info. I think I will have to get a Holley tuning book with more detailed information so I can figure this out.

See ya, Doug

H2Xmark

if your engine has a high overlap cam in it, the power valve might be staying open at idle, see what your engine's vacuum is at idle, if it is below 10 to 11 " of vac, you need a lower rated power valve, I think the stock size is a 10.5, but most likely the above post will take care of your problem

MACDAD260

It is a stock Gen V 502 Magnum. I was trying again to get it adjusted today. It pulls 16-17 inches of vacuum at idle with the screws out about 3/4 of a turn. When I pulled off the vacuum gauge it actually ran better with the port unplugged. Something is not right. I took the power valve out and looked for a number. I could not find anything on it, even with a magnifiying glass. Isn't the number supposed to be stamped on one of the flats?