More Tunnel Ram Help

[71GSSDemon]

Holley 4224 660cfm center squirters. 1:1 linkage for both carbs and secondarys. 50cc accelerator pumps, center squirter to all 4 barrels

Any help is greatly appreciated. I have a question or many. My combo is below. It idles great, starts great and if going moderately to WOT, it accelerates awesome. But, if stab to WOT, it has a bad stumble then recovers. I adjusted the accelerator pump cam to #2 hole to see if that helps and it did, some. Also the cams were upside down riding on the near vertical ramp instead of the gradual ramp. Also, with no load, stab to WOT is great but slowly increasing throttle it misses badly about 2700-3000. I can watch in the throat of the carbs and the fuel doesn't seem to be atomizing well from the booster on both carbs. The fuel is acting erratically during this time (too much emulsion or because the transfer slots are covered by the blades?) This happens both in park and while driving. I think it is a bad spot between transfer slots and jets??? Moderate throttle is good here. So, light throttle acceleration (in park or while driving) at 2700-3000 is an issue, passed that it works. And the sudden stab to WOT is an bad stumble but recovers. In Park, it revs freely so it tells me that I need a longer accelerator shot, maybe. I think of this a comparison of light car (park) and a heavy car (load on engine while driving). I did try running one accelerator cam one way and the other carb cam the opposite in thoughts to have a big shot of fuel, and a longer shot to help carry it. No modifications have been done to the carbs. #76 jets in primaries, no PV, #12 jet plates, brown 336 accelerator cams.

1971 Demon, 440 with Hughes whiplash cam (specs below), shaved and ported #250 iron heads, Weiand tunnel ram with Holley 660s, MSD pro billet ready to run distributor, 2" fenderwell headers, 2500 stall and 3.91sg and 29.5 tire.

Initial timing is 18⁰ with full in 36⁰ coming in at 2200. Vacuum advance is hooked up to manifold vacuum as there are no ported vacuum ports. Plugs looked a bit on the lean side. I was at 1 turn out in idle mixture. It is much happier at 1.5-1.75 turns out.

I got to wondering if the air is just lazy due to lack of motor and booster signal. It worked better with some small air cleaners I used to run. Maybe the restriction on the air increased the booster signal? Maybe why it works great if stopping at 3/4 throttle?


Cam Specs:
Lobe Separation 107 installed at 102
.518" lift I/E
232/245 @0.50

Posts: 2
Joined: Mon Dec 12, 2022 3:53 pm

[71GSSDemon]

I have ordered pin drills to measure all the air bleeds. At this point, the carbs do not appear to be modified in any way. Also, I am unsure how much advance is being added at idle right now with manifold vacuum being used. Distributor is MSD pro billet ready to run.

[71GSSDemon]

My pin drills showed up, so I could measure the air bleeds.

Primary
IAB 0.70
MAB 0.29

Secondary
IAB 0.31
MAB 0.020

Emulsion has 2 bleeds each 0.026. Bottom of slot and one about 3/4 the way up. Top of slot has 0.022 jet. Below the emulsion slot, in their own cavity there are 2 jets, 1 per side, 0.037.

[71GSSDemon]

I would upload a pic, but i don't know how.

[rgalajda]

Emulsion has 2 bleeds each 0.026. Bottom of slot and one about 3/4 the way up. Top of slot has 0.022 jet.
In the middle picture you are referring to # 22

Below the emulsion slot, in their own cavity there are 2 jets, 1 per side, 0.037. #25

[rgalajda]

Reducing the IAB by .005 to .010" may richen up small throttle opening up to cruise to cover the lean transition.

Also a larger HSAB could could start the mains a little earlier to cover the lean transition .

Since you won't have screw in bleeds , you would have to drill and tap . You could try just drilling the HSAB about .005" larger.

The old trick of inserting a piece of wire into the IAB to reduce it's size . Just pull a strand out of some braided wire long enough to go into IAB and over choke to where the air cleaner sits. The air cleaner will hold it for a test drive. About a .010" strand will work.

[GTO Geoff]

A larger HSAB will start the mains later, not sooner.

[71GSSDemon]

There does seem to be some confusion about the size of MAB and if it comes in sooner or later. I was under the impression with a wire on MAB they would flow sooner, but I was corrected.

Question..the reference of high speed air bleed (HSAB) is also main air bleed (MAB)?

[GTO Geoff]

HSAB & MAB, same thing. Both refer to the air bleed for the main system [ high speed system ] as opposed to the low speed system which is the idle system.

Putting a wire in the MAB will start the system earlier.

[rgalajda]

Is this setup intended for street use?