468 BBC with a 950 HP Holley- jet help

[NOPANTS-68]

I'm running a 468 and am having some issues with running fat at idle and slow cruising speeds. The specs are:

ported 990 rect port heads
Comp solid roller - 262 @ .50- .652 lift and a 110 center
10.8 :1 comp.
RPM Air-gap intake
Holley 950 HP carb.
all upper-end supporting parts- Eagle bottom end, fully studded, Holley HP150 electric pump- Aeromotive reg set a 6.5 PSI, etc.- Tremec TKO600 trans.

It's very radical but idles pretty happily at 1100 RPM. I'm running 74s in front with 80s out back, have a 45 power valve in it, mixture screws dialed to make max vac @ 9-10 inches, floats are perfect. The driveability is excellent and it rips pretty hard on the big end. However, at idle it's very fat to the point where I can actually see the vapors coming from the pipes after a short time sitting still. The longer it idles the worse it gets and the tach begins to fall to 900 RPM where it stabilizes and runs pig rich. The regulator is pretty stable at 6 PSI so I don't think it's blowing past the needle and seat. Am I way off or do I have another issue? TIA, Dave

[Shaker455]

Dave,
You are not way off but your HP950 is!

I rework these units constantly

That is one of the most out of balance units you can buy out of a box today and that carb is really too small for your combo as the mainbody has the venturi size of a 750 with 850 boosters.

The passage holes in the boosters that are too large for that venturi size (1-3/8" X 1-3/4")

Metering blocks have too many emulsion holes & too large IFR

Throttleplate holes are too large

Jeff

[NOPANTS-68]

wow thanks Jeff. What would you recommend for my combo?

[Shawn MacAnanny]

I reccomend this. I never made a wiser investment on my whole project.

http://www.rpmoutlet.com/mt.htm

[Shaker455]

Dave,
An 850/1000 is better suted for your combo and is a larger carb than the 950.

I build custom Holleys from select parts so if you wanted to reuse some of your parts and build a new unit I can help.

Email or PM me

[NOPANTS-68]

awesome- I may just do that. Thanks again.

[My427stang]

I agree completely with Shaker, the 950 is a little small, but more than that, the HP series metering blocks just dont cut it for me.

I have relocated and plugged emulsion air passages which helped, but on my own I just swapped to earlier metering blocks.

I have found that the IFR being above float level gets real fussy and requires a larger IFR, as well as the crappy later emulsion that Shaker says

If you look at the crappy picture below, it shows two issues, 1 - the location of the IFR and 2 - The differences in the emulsion passages to the emulsion tubes.

https://static1.pt-content.com/images/noimg.gif

In my case, I drilled the PVCR to match the original area for my 1000, and jetted to match, other than that it was a bolt on from the early 600, and I was able to drop to a .033 IFR from the original .039 (that is a huge difference if you calculate area for each hole)

It runs like EFI compared to the old goofy idle and transition circuit

I bet you could get your 950 running real well, but I do think a 850-based carb would be a better match for WOT power