Ok so I recently put a Holley 800cfm spreadbore double pumper that I rebuilt on my stockish 350. My engine is stock except I have put on a set of headers and have cut out the dividers on the intake so it is more of a conventional dual plane (leaving the center one). I also have a 1" phenolic spacer that I matched to the intake topped with a factory style thick open 1/4" gasket. My problem is that it seams to run lean when I punch the throttle no matter what I do. I do have an AEM air fuel gauge installed and can watch it lean out when I floor it as well as the engine studders. My jets seem to be dead one because at cruising at 30mph (primaries) I am at 12.5-13 and if I slowly roll into it to the point I am on my secondaries I am also at 12.5ish. My jets are 60 front 78 rear with 8.5 PV front and rear. My float bowl seem to be about perfect height as well. Just the problem with the stuttering backfiring. I also switched my 50cc pump and cam to the primary side to try a help.some to which it did improve. So far I have gone from a pump squirter size of stock 25/37, 37/31, 31/35 (backfired so bad my car caught fire), 35/37, 35/40, 37/40, 40/40, 40/45 and lastly 45/45. I can definitely say my car did not like the smaller sizes as it would backfire and die, and did start doing better with the bigger ones but when I got to the 40/40 size there was no more improvement when I went to 45/45. Car does not backfire now but does stutter pretty badly at sudden WOT. If I roll into it it does seem to be fine but I can not do any decent launches or burnouts. Any ideas anyone? Thanks, Ryan
One more thing, when I went to 37/31 (which I accidently put backwards meant to be 31/37) the car seemed pretty good, it would still bog on hard launches but would normally catch itself and burn the tire. This was also before I put on the thick open gasket, is it possibly hurting fuel flow?
#6213 and yes all matching part numbers... Well now I'm second guessing but I believe they are. I'll double check later.
reason for asking about bowls is that if someone put standard holley dual feed/dbl pump bowls on it the acc pump shot holes do not match up between the bowl and metering blocks . would really cut down on shot or maybe no shot at all .
Hmmm, I'll take it off tonight and check them out. I bought the carb from a member on here and the rear bowl inlet threads are stripped so I took off the nylon spacer and used Teflon tape to make it work for now. I contacted the seller and he said 4150 bowls are the same and he would send me one (still waiting). So kinda worried now, you might be on to something.
ok , just thinkin - i dbl checked some pics . i was not familiar with that particular number and looks like it had originally dual feed style bowls - but - pump shot location may still be dif than standard holley carbs . worth checking . i have pics of that area down in thread "sbb cruiser carb idea" . pointer shows new hole location i drilled to match standard bowls . the small magic marker dot is location of original hole . at some point someone may have just replaced the bowls without checking . also , right above original hole location there is a small casting lump above pump shot passageway . that is a check valve in the original 650 spreadbore metering blocks . not sure if your carb number used those or not . clue maybe ? also , the gasket alignment pins on my metering block are a slightly different orientation so i had to trim standard bowl gasket . stock specs to go by in case you don't have them : jets 62f , 85r - needle n seat , .110 - nozzles 25f , 37r - 800cfm . will have to check power valve specs out of holley catalog when i get home .
Thanks, I set it up originally with the stock jet sizes and pump shots but was not sure of the PV size so that would be nice just to see how they set it up. Being a spreadbore is making this a little more difficult for me and I'm having to keep changing my mindset on how to set it up and not just square it. I'll double check to make sure it's all kosher and lining up but I will also try to get a video of the pump shot. It seems like it is not getting a secondary shot, because I can jump on it maybe 1/2 pedal and it seems strong and will spin the tire but if I try to dump more it starts to sputter and stall and afr gauge says lean. Just out of curiosity do afr gauges ever like? For example if I gun it and it stalls while watching the gauge it always reads lean. Just wondering if it could be more of a default reading if no exhaust is flowing?
yeah the internet holley info - I could not see the notation page with PV info . catalog , found it . anyway : front PV - 8.5 rear PV - 6.5 that carb is sorta designed for a BBC basically . so for a stockish small block may be a little rich etc . will just have to make some adjustments i'm sure . already doing that obviously .
Ok, I took it apart and double checked the blocks and bowls. The blocks are stamped 6213 and the bowls I could not tell but they lined up perfectly and gasket matched perfectly. I put it back together with a 7.5pv in the secondaries and left the primary at 8.5 and also removed that 1/4" open gasket spacer. When I get at it from a dead stab it seems fine until I get into the secondaries then it sputters. I can stab it to about 3/8 maybe 1/2 pedal and it seems fine but if I go for the full onion and put it to the floor from a stop it will go lean and sputter every time. I took a video today of me opening the blades and watching the pump shots and they seem strong. I am just curious if I should go to the blue cam for the rear to move the shot on earlier? It sounds like a should go with a bigger shot but it has 40/40 squirters and would be surprised if I need to go bigger.
I think I would increase rear pump nozzle size first ( +3 maybe ) . the nozzle size does not control amount of fuel but rather duration and volume of shot . then maybe switch rear power valve for a little more fuel shot . stumble = lean normally . may have to try a couple of each . just reread first post , did try bigger nozzles . still maybe except you said no better with the 45's ? that should have 50cc rear pump correct ? correct diaphragm and spring ? arm ? Oh yeah , you switched the 50cc pump to front . So , two 50's ? Air bleeds cleaned out ok ?
Well the block numbers seem good . I always wonder about those . I would probably consider disassemble , reclean , dbl check and back to stock spec parts as a fresh start up point . I've got a 650 DP spread bore in carb cleaner now . If it seems good could send out to you as a comparison carb . Would be an easy swap over . Winter here shortly so I won't need it before spring . I'll probably be in Kirkland area in December . Close ?
Right now I have the 50cc on the front and the 30 out back and both have correct springs, cams and diaphragms. This did seem to help when I did this. When I got the carb it was pretty good shape but I still I went through and cleaned it thoroughly and went through all the orifices then rebuilt it to stock specs (just didn't know the PV size so originally I put 6.5 f & r) and still had a stumble. Yesterday I drove it to work while watching my AFR very closely and even though it cruises right around 12.5-13 as soon as I press the pedal more (not mashing it) it does lean out to 15-15.5 which I know isn't really lean but still leaner then I thought it should be at. Maybe I should jump up my jet size? But I was under the impression that accelerator pumps are in charge of fuel under acceleration to hold it over until the jets are flowing. So not sure if that would help at all? One more thing is I can not get it to stall with the air bleed screws all the way in. I have taken the carb off and squared up the transfer slot everytime I take the carb off just to give me a good starting point and have also opened and closed the secondary blades to see if it helps. Right now i am a half turn out on either side. Watching my vacuum gauge that is the best which comes out to be 21hg. That's a very nice offer and if I can't get things figured out beforehand than I might have to take you up on that just to see how it runs as a baseline. Yes Kirkland is about 1 1/2 hrs away so not too far and I would be happy to buy you beer for your trouble. If I can't figure it out I might just switch to a quadrajet down the road. Thanks, Ryan
the air bleeds are the 8 ( 4 front , 4 rear ) small holes up top . each corner pair does two things , 1 is for idle mix signal , 1 is for main mix signal . if they are clogged with dust etc it can cause run problems . if the main bleed is clogged = low signal = less fuel when on throttle . you are thinking of the idle mix screws . those I usually set about 1 or 1.5 full turns out as a start up point . probably a hair rich but i'd rather start out that way . and correct , only a small square of the transition slot should be visible when linkage is at full rest ( be sure your choke cam etc is all the way off or that will throw your setting off ) . on a stockish motor that should be very close with correct timing etc . if too open then the idle circuit is bypassed ( idle screws will have little or no effect ) and it will start to pull fuel through the main circuit out of the boosters . so in other words if you see fuel dripping out of the boosters at idle something is off .
I was pretty thorough when I rebuilt it on cleaning the air bleed holes and when I had it apart the other day I spray cleaner through them and got steady streams coming out. But after I put the carb on the car and adjusted idle mixture screws for Max vacuum my idle was way high so I adjusted the idle setting (changing the transfer slot exposure) and readjusted the mixture screws before driving it. Do you think that could be my issue? Maybe I do not have enough of the slot exposed? Also maybe o have my secondaries cracked too much?
the slot exposure is pretty much just gonna effect the low rpm idle adjustment end of it . not the mid range punch-bog you are noticing . although with the linkage pulled back initially you may be losing some of your pump shot due to the cam being partially rotated . that seems like it should be kinda minor . maybe 50cc front and back ? trial n error . like I said , back to square one might be a good spot to go from again .
Well I did take back to square one a couple of weeks ago and just like when I first put it on it was way too Rich and bogged horribly. I will mess around with it some more and see. We're a bit brokish right now since I just had to cut my hours so I'll have to wait on the 50cc pump kit.
I think I would leave it 30 front and 50 rear . 50 on those small front primaries just seems outa wack to me . ? . bog or hesitation ? light pump shot can cause a hesitation . and in that direction , I was going over me 650 DP SBore parts and noticed the nozzle screws are dif than standard holley nozzle screws . these have threads all the way to head . regular screws have threads about 2/3 up then a shank portion up to head . regular screw in the sreadbore anti pullover nozzles will cover and probably restrict fuel flow from nozzle . those holes are alot higher up inside the nozzle . worth checking I think . have to check my other 650 SB also for that . and lastly ( and truthfully I should have thought of it sooner ) is fuel pressure . could your pump be dropping off at a higher demand/rpm ? or maybe a line restriction ? rubber hose collapse ? tank filter ? etc . edit : pic added . on left is the spreadbore nozzle and screw and on right is standard holley nozzle an screw . the little "X" on each nozzle is approx. location of inner feed hole of each . Edit : rear jet extensions ? Long shot probably . edit : also noticed today while working on the 650 DP that my holley book calls for a "light weight" plunger under the pump nozzle . was checking because mine were maybe a no show ? Plus someone had previously installed the primary throttle blades incorrectly and they wouldn't close down all the way .
Last night I was able to drive it a bit at WOT and apart from the stumble, once at wide open it runs hard. My AFR gauge at wot is reading rich at 10.5ish so I might jet down my secondaries to help with that. On the note of the screw, since I am running 40 tubular shooters front and rear I am running the hollow screws they came with. Maybe I am not clearly understanding how a squirter works? I was under the believe that bigger is more fuel but keep hearing that the size just changes the duration of the shot and not the amount of fuel? But wouldn't that be the cam changing that not so much the squirter?
