Little update. I got the car tuned pretty good. It does not like a lean idle at all. The cam I chose along with the sp3 idles best with a 11.5 afr. The in gear afr is around 12.5 my light cruise is in the 14 range. Highway speeds I'm right around 13.5. WOT is in the 12s. Probably wont mess with the main jets any more cause I'm already down 7 jet sizes. Jetting down so much could be the cause of an occasional lean tip in stumble. But it's not consistent. I have a power blast plate coming this week that is a mod for the pump shot. It might alleviate the occasional lean stumble. I could try increasing the mains a couple of sizes and see if it fixes my stumble and then delay the circuit from starting with a larger high speed air bleed...lots of options but over all my efforts have seemed to make it faster and drivability seems pretty good. I may end up with a different power valve. Im currently running a 4.5 but have tried a 6.5 and an 8.5. Maybe a 5.5 would be perfect. The others loaded the carb up even after putting smaller power valve jets in. there may be another issue that I need to address. The driver side 02 sensor reads a whole point lower than the passenger side 02. And the plugs are showing more color on the driver side. The carb is jetted evenly. The gauges read more evenly when Cruising but seem to be a point apart at wide open and low speeds. Not sure what to think of this. One thing is for sure I don't want to cause harm to my engine by running too much of a rich idle mixture. I will experience rich conditions anytime I'm coasting down the freeway or extremely light throttle around town. This car is ultimately supposed to be a driver not a race car. I'll probably end up switching to a dual plane. I dont believe the sp3 is a street friendly hybrid intake like they claim. Maybe my carb is just too much. Not sure.
14 initial and 36 total. I'm all in by 3000 or a little under. Advance is set up to add about 10 degrees. Do you think I can run the car with the real rich idle without any issues? Why do you suppose the driver side will read in the 12s and on the passenger side I'll be in the 13s? I swear I've heard the throttle shaft leak like a vacuum leak. Thinking about running a different carb for a day to see if the afr equals out. If it don't I'll be pulling the intake at some point to check for leaks and inspect lifters. Btw the sp3 has tons of bottom end torque and now burns rubber 10× better than my stock 350. I can hammer it at 25 mph and feel the tires break loose. I think I'll miss the single planes power if I switch to the D/P. Better Drivability or power???.... maybe I'll find that my carb is jacked up. I might be driving it 6 hours on Friday. See how she does.
It sounds like you're getting good at tuning the carb, I wonder if a dyno tune might be a good investment?
I haven't broke it down completely but i have blew through all the passages in the metering block with carb cleaner.
I would invest in a high quality 3000 stall converter. It won’t slip much when cruising and it will make that engine combo work with the 2.56 gears. It will let the engine flash up into the power band instantly. A low quality high stall converter will create a ton of heat and slippage but a good one is much less noticeable until you stomp it.
I swapped back to ngk ur4 plugs today to see if it would make a difference on the afr. It didn't really seem to affect much. With shaved heads and higher initial timing is it safe to assume that I should stick with the ur5?
I'll say what I said 20 pages back. There is something else going on here. There is no way you should have this much trouble dialing a carburetor in. It should be close right out of the box.
Everything is tuned pretty good other than the rich idle. Which is apparently so common that there is thousands of message board posts all across the internet about the issue. It's not an autozone holley. The jetting on this in comparison to a regular street carb is way richer out of the box. And the idle feed is in the upper position on the metering block which tends to cause issues. I've compared specs on a few other carbs. This one had .059 power valve restrictors those are massive in comparison to the more common .045 restrictors. I down sized to a .052 and saw the 10s disappear from my afr gauge. It might just be that my 750 quickfuel is just too much carb. Would like to try a 650 double pumper eventually. Or a vacuum secondary with a tunable opening rate. Or a dual plane intake.
Granted I'm running 10:1 comp., roller cam and alum heads but I have a SP3 and Holley 750DP and my cold idle is 11.9-12.3 AFR. Hot idle AFR is 13.0-13.5. I don't have adjustable air bleeds but this is the leanest idle AFR I can get. I run 68 primary and 79 secondary jets, around town street tune is #25 front shooter and #28 rear shooter. It has a slight hesitation off the light but if I go bigger it's to rich for around town. Track tune is same jets and #31 front shooter and #35 rear with a 12.2 WOT and no hesitation. Believe me I've been messing with it for months and this is the best set-up i've found so far. And I'm happy with it. My last combo was real close to yours except I was using the dual plane intake and I could never get idle AFR higher then low to mid 12's. The SP3 wants alot of fuel to go to WOT without hesitation but for running around normal driving the big shooters are just to much. Sometimes you just can't have your cake and eat it too, unless you want to spend countless hours tweeking it.
Thanks for your input. I am not alone lol. I have it running pretty awesome over all. I have a stock stall and a 256 rear so it took me a while to get where I am. Just wish it didn't idle so rich. I ordered one of these blast plates it should be here today. It atomizes the fuel quicker. It might help your .025 squirter perform like the larger shot. I dont have an off the line bog at all but I'm running a 50cc pump.ATTACH=full]522648[/ATTACH]
Not sure off hand. I have been messing with it too much but there really isn't any bog. Currently it goes too lean right after the pump shot runs out. But I am experimenting with bigger high speed air bleeds that delay the mains a little.. the 50cc pump was a life saver. But with the proper tune it shouldn't be needed. When I lowered my idle bleeds it helped my off idle stumble alot and was able to use a smaller squirter
Try to see what AFR is when you floor it, you may be to rich. You shouldn't need the big pump, I'm flowing alot more air and I don't need them. How lean does it go when the pump shot runs out, your jets should be well into play by then. With the big pump and small shooters that shot should last a long time.
