I have an off idle stumble that I believe is not related to the pump shot. I can tune this out by richining the idle mix screws but that is obviously not the direction I need to go according to the afr. Everywhere else is pretty awesome. And the new exhaust absolutely made a performance difference. I think I'm going to go one jet size smaller on the primary's to lean cruise a little bit. Shooting for 14 + right? I'm going to call quickfuel about what to do with the idle. I think the ifr needs to be smaller which means the bleeds will need to change too. Also, I finally got the fast idle to work properly. My secondary blades were completely closed from the factory. I took the carb off and set the transfer slots correctly and now my choke and fast idle works just like it should. Setting the transfer slots also helped all 4 corner idle mix screws to be more sensitive.
I installed smaller Idle restrictions and set transition slots again. I improved a little but im still too rich on idle so I ordered smaller restrictors today and some more air bleeds. I went 1 jet size smaller on the primary and secondaries and was able to burn my tires into 3rd gear (turning from a stop sign) it would load up too much before to burn them into 2nd. From a straight dead stop it still only does about a 10 ft burnout. On WOT runs the afr dips into the 10s briefly. Possibly too much pump shot. But I won't mess with that any further until the idle is right. Was hoping to be done with the idle circuit with the first ifr change but over all I'm happy to be making some progress. Even with the 256 gear I think she's gonna run pretty hard especially once I dial in the transmission governor. And maybe a little stall is all I will need.
Been a few weeks since I messed with the car. But Wednesday I made some small ifr changes along with air bleeds. These changes really helped my low speed cruise afr. But the idle is still eye burning and more I lean the idle the worse it runs. If I want my afr in the 13 range it puts my idle mix screws only a half turn out. It runs best with a super rich idle like low 11s. I am going to make some radical changes to the ifrs and air bleeds like what is mentioned in this link: https://www.innovatemotorsports.com/resources/carb_EFI_mileage.php They describe my situation perfectly. And these changes will allow alot more adjusting with the idle mixture screws. I could live with a rich idle but I also have an annoying stumble that I'm still trying to deal with too. Tuning the carb to run similar to the one here in the article might be the ticket. After this If I cant make this carb and intake perform decent I am going to be swapping to a dual plane intake. I know the right tune will unleash this beast.
Block the wheels well, put it in gear and use a vacuum gauge and tune the idle mix screws to get max vacuum. I never use the AFR for idle.
When I ran the dual plane, I ran a 2" Wilson type tapered spacer under my 830hp. I had a/f readings of 13.5 at idle in park (1,150rpm), 14.0 at idle in gear (750rpm). Cruise at 13.9-14.0 WOT at 12.9 All above readings using the d/p & 2" tapered. Now with SP3, Never misses a beat to 7k. Still run a tapered spacer but only 1" to allow hood to close. Still fine tuning a/f with the SP3 & trying some different filter combos, but no hesitation what so ever.
Yeah I agree but max vacuum is eye burning rich. So rich i really cant even breathe behind the car. And any time I'm cruising really light or coasting it dips into the 11s. I also have a stumble that I cant tune out. I'm hoping that following this link will produce good results. I think the sp3 is alot of the problem. It should have never been marketed as a hybrid intake that performs well on a mild built engine. I followed advice to get a 750 double pumper. I think a properly set up 650 would work better. The 4 barrels slam open and it launches good but goes lean like into the 17 range right after the pump shot is done. I know this car could roast the tires with the right carb setup. Smaller air bleeds could bring the mains on sooner but will also richen the cruise. The motor ain't creating enough vacuum to pull the fuel through. I have a smaller shooter in right now to extend the duration of the shot and I'm using aggressive pump cams. Might try the 4500 series yellow pump cam again but it really ain't meant for a 4150.
On your HEI can you change the bushing in the system if you can put the larger bushing to limit the advance then you can advance the HEI to get some more bottom end. when the AFR goes to 17 after the pump shot this would indicate that you need to make the shot longer. I would not read too much into what the afr is at idle but it should be at 14. Again you are not going to make the SP3 work with a low gear set of 256 to 308. that intake wants to go to 2500 rpm to get into it's range that is the way those things work. If you want to stay more stock side with then yes go to the D/P intake but this is for under 6000 rpm after that the power does start to drop off even though mine pushed the rpm to 6100 with max HP. You get that 373 -410 gear in there with the 4speed trans and a good 3000 stall those carb problems will be a thing of the past, I guaronteee it. If you plan on going more later the SP3 is your best bet, mine starts up like nothing even after sitting for a week I start it up and the vac gauge is at 10. ( JUST FOR YOU MART) lol. idles at 800 I had a looser 3500 stall that I swear was the best convertor I have used yet if you want the 350 engine to come out of the hole like a freight train. It is still in the 350 trans I took out when I put in the 200r4 trans. A 650 dbl pump carb would give you a better out of the hole the transition would be quicker but there you would lose some top end power, how much who knows, I don't think anyone has tested this on a 350 but I do know gsjohnny used one for years on his blower motor but there it can use a smaller carb and still get good results with the blower. you have to watch trying to tune out troubles with the air bleeds you can cause other problems within the carb and this may be what you are experiencing now. when in doubt go back towards your original settings and keep damn good records of what you are doing. I have to commend you for what you are trying to do here as we will all learn from this. you are doing a heck of a lot more in your short period of time than some here have talked about doing for 10 years.
Low end power is definitely there. I think with the right carb set up it will produce a nice burnout. I have to tune out that lean bog though. The goal is to get the idle circuit extremely responsive by using smaller bleeds and smaller ifrs. This will hopefully fix the light throttle stumble which should allow me to use a smaller pump shot that will extend the duration of the shot. I can fix the stumble with a massive pump shot but then the shot runs out before the mains are really kicking in and I end up going lean 10 feet into my burnout and it bogs out.
Your thinking right keep on going should be interesting to see how it works out. What you need is one of those old G-Tech monitors that give you 60 ft and 1/8 or 1/4 mile times. the 60ft readout would let you know if you are going the right way.
