800 cfm Holley base line jetting

[HOLESHOT]

SWAPPING THIS 800 CFM #4780 ONTO A 69 S BEE WITH 451,10.5 CR,2500 STHAL,4:10 GEARS WITH 4 LINK SUSPENSION. LOOKING FOR STARTING POINT SO AS NOOT TOO LEAN OUT CAR ON TRACK(DRAG ONLY NO STREET).Has M1 and do not want a power valve in rear block,choke horn was removed before I got it.

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[Streetwize]

Don't have my Holley list book handy, but I do Know my 830 Annular 4 hole idle circuit Holley came with 78's jets all around. That should be in the ball-park- you can call Holley and give them the List # and they can tell you for sure.

Hope it helps,

Wize 1

[rat roaster]

For stock Holley jetting go to.
http://www.mortec.com/carbs.htm

[rat roaster]

If you remove the rear power valve, jet up 6 to 8 sizes . If you run a sealed hood scoop you may want to jet the primaries 2to 4 larger to start. Check idle vacume and adjust power valve accordingly, also dont forget to use jet extensions on the rear jets . Make sure the rear float will work with jet extentions , the float should have a recessed area so when it dropps it will drop fully without touching the extentions.Put in new spark plugs make a pass and check all the plugs really look at #7 .Make sure timming is not more than your fuel and compression can handle.I guess what Im saying is be conservative on the timing till you get a base line on the jetting.Dont play with the jets and timing at the same time get one right then work on the other. Dont detonate it with cheap gas and lots of timing . If its detonating it may appear to be lean.Watch for detonation signs like silver specks on the plugs or melted electrodes or the porcelane on the electrode may look like its bubbly and burnt. Use good gas and you wont have to worry.

[This message has been edited by rat roaster (edited January 07, 2001).]

[This message has been edited by rat roaster (edited January 07, 2001).]

[Leigh]

4780-2 had 70 primary, 85 secondary. Post complete # and I'll list the older version, if thats what you end up having. Sealed scoop info was good.

[Justdartinaround]

ratroaster:
In your reply you said expecialy close to plug #7. Is this usually the lean cylinder on a 440? If not do you know what is?
Thanks,
Justdartinaround

[PRO]

My 4780(800 dbl pump)doesnt have 4 corner idling capability and therefore uses no rear power valve,I run #72 jets in all 4 corners(10.5:1 360,alum heads)@ 4800 ft above sea level,My educated guess is youll want to be on the rich side rather than lean,so Id start with #84"s and work up or down depending on plug color.....PRO...

[rat roaster]

#7 is the leanest cylinder on 440s and all other dodge and chevy engines with a fireing order of 18436572 , What happens is #5 cylinder fires just before #7 in the fireing order so this means that #5 is taking the intake charge just before #7 so it steals some of #7 cylinders intake charge.And guess what #5 & #7 intake ports are together (simesed) so #5 is closer to the big hole the carb covers. I believe single plains can be worse than dual plains for fuel distrubution , you will see some tech articles on using a bit larger jet in that corner on some intake manifolds.Every engine is different so just keep an eye on it till your happy with your performance and plug color.Like Pro said jet a bit fat and work each way till the car runs the fastest then run it for a few runs and have a look at things.