impressive numbers .. what rear gears are you running ?

 

3.73 rear.

 

same here..excellent choice

 

whats the numbers on the cam and how much timing are you running at idle?

Neal

 

The cam numbers are in my signature and I am running a programmable 6 al with a locked rotor at 34 degrees. The more I give her the more she likes it. 34 initial.

 

mr skull thank you,thank you, i sense you were rather adament on your on the use of a spreader bar to correct left front wheel coming off ground on power brake start with car veering dangerously to right. i installed a VP&P spreader bar (the kit you weld yourself for best fit) unbelievable i launch at 2500 rpm perfectly straight and the car is 100% better on high spirirted street driving. i still have slight bog between idle (900) rpm and 1800 rpm. i think LARS gave me a hint now that my vacuum is 16" and needle jets set with vacuum, acelarator pump (red spring) is set to .015, squirtors unknown new stock holley 750 ,4160c ,vacuum secondary with 76 primary jets. A/F gauge shows slightly rich when secondaries cut in like 12,5 to 13 . i think the power valve that LARS mention (use office staple in power valve jets may be next step. engine 408" all forged,10'5 cr,AFR 195 heads, air gap,headers,cold air intake,lunati roller 541 lift,231/241 @.050 ,112 CL. 700R4,3.55 gears.

 

Update:
With the holes filled, the carb is much more tunable now. I have my secondaries open just a tad right now to dial in my idle without opening up my primaries any further. The primary blades are right where they need to be on the transfer slot. I reduced the size of the IFR from 0.035" dia to 0.0345". I also reduced the primary jets to 77. The car has never driven better. Need to get her on the highway to see how high speed cruise looks. Wonders a tad lean at light low speed cruise but probably would not notice it without a wide O2 meter. The conic rich condition a low loads is all but gone. Just transient episodes which is to be expected when abruptly changing throttle positions and piston loading.

950 cfm w/mechanical secondaries
pri jets 77
sec jets 88
Pri IFR .0345
Pri vac adv. 6.5
Sec vac adv 5.5
Idle air bleeds 075
Hi speed air bleeds 035
pri squirt 21 (drilled to 32..another surprise)
sec squirt 32
Secondary blades are open just a tad at idle
Primary and secondary blades have been drilled approx 1/16" diameter (holes have been filled)

 

idle air bypass so you can set the idle transfer slots where they should be. holley bought barry grant to get this patent

 

Yes, I like that idea. The struggle with a big cam is to dial in a good idle speed while maintaining proper throttle blade orientation. Another issue I dont completely understand or agree with is the notion that all 4 idle screws must be adjusted the same amount..... It seems to me this is true to a point. I think once you get it close, just using the primaries to fine tune would be better. I find just the smallest adjustment on all 4 screws has a big impact on my numbers. I am shooting for about 12.5 to 13.5 AFR range for most driving conditions. I am close but still have this annoying condition when I let of the throttle from a light cruise it goes rich momentarily to as low as the hi 10's. My guess is my vacuum at idle is about 10" and when I close the blades at a higher operation speed, the vacuum spikes in the plenum and pulls lots of fuel through the idle circuit during a low load event. It quickly burns off but you can feel it when it happens. Not sure I can stop it from happening. If I lean out the idle circuit then I go lean at low load cruise speeds. That is probably why the holes were drilled on the blades to mitigate this issue somewhat. If I open the secondaries to let more are in, then my idle is too high. I cant close my primaries anymore than they are and still be on the transfer slot. The only option I can think of at the moment is allow the car to idle at a higher speed. I have been trying to keep it at about 11-1200 but may need it to be at 13-1400. seems crazy high. I will give it a shot today just to see if it behaves down low. I may post a chart showing the issue. My LM-1 monitors MAP, AFR, RPM and throttle position (homemade sensor).

 

I downsized my IFR just a tad more and took her out for a drive. Getting real close. I did a short light load part throttle run in 4rth gear which I would imagine had me into the primary boosters. The car wondered rich into the high 11"s AFR. At load load, low rpm cruise in 5 gear where I was mostly still on the idle circuit, the car ran lean in the high 14's to low 15. Because my 5 gear is 0.82 instead of 0.64 allows me to use 5 gear around town, not just highway. This is my lean trouble zone. My throttle blades are just barely open but the idle circuit can't furnish enough fuel under a light load low rpm condition. I think I am going to dial back on my main jets one more size and richen up my idle screws more to help feed the lean condition. I need to get her on the highway to make sure I have enough primary jet to feed the beast under load into the secondaries. Once I get that, then it is off to the dyno to check out the secondaries.

 

Do you think that your idle mixture screws are too sensitive? I had this issue with my QF carb out of the box yet when on the transition slot the mixture was too lean causing a flat spot. I entrusted the car to the local American car specialists who disguised the flat spot by having one idle screw at 1 turn out and the other at 3/4 (they didn't bother to tell me that the engine was running pig rich at full throttle either). The mixture screws were so sensitive that an 1/8 of a turn made a huge difference to the A/F ratio received by the engine.
To "desensitise" the mixture screws I have made the idle jets smaller and then reduced the idle bleed size to correct the lean condition on transition. Runs much better now and no flat spot.
It took me a while to realise that you aren't changing the AF ratio of the idle mixture coming out of the port in the carb when you adjust the mixture screw,the idle screw just changes the quantity fed into the engine, you have to change the air bleed size or the idle jet to change the AF ratio.

 

Changing the idle screws will impact the AFR at idle and to a lessor degree cruise. The idle jets have a greater impact when you are into the transfer slot and beyond for low load cruise.