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Squirter Fuel Pullover on 4150
Posted: Mon Oct 08, 2018 9:38 pm
by 63qcar
Since it was raining today, fired to car off to check some carb settings and looked inside the carb as I brought the rpm up very slowly so the accelerator pump circuit didn`t come into play ..... trying to see at what rpm the main circuit started to come in. At 2000 rpm , I started seeing some fuel running out of the primary squirter and as rpm came up , flow increased . I understand that there will always be some fuel pullover , but is there a good way to minimize it as that appears to be uncontrolled fuel flow . There are stainless checks under the squirters on primary and secondary. I have some brass ones out of a 950 HP that are a little heavier . Maybe that would help , or am I just chasing my tail on this .
I haven`t tried the anti pullover squirters from Holley yet , just looking for some comments/suggestions .
Thanks
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 6:06 am
by grandsport51
Interesting Topic
Just looked this up pretty relevant!
https://youtu.be/2VOXXRtyG3E
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 9:27 am
by 427dart
Are you using the anti pullover type nozzle or straight brass tube type?
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 9:32 am
by 427dart
Hmmm... Maybe some type of thin brass deflector is needed in front of nozzle to break up the air flow around it??
Doesn't seem to do it on the primary.
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 9:34 am
by Barry_R
Holley (and other carb manufacturers) have known about pullover for decades. Look at it as an additional tuning tool rather than as an uncontrolled event. The squirters with the brass tubes will have more pullover than the ones with the simple drilled holes. The anti-pullover ones will significantly reduce the pullover fuel. You are already working with check ball (or check pointer) weights...
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 10:01 am
by 63qcar
Not using the anti pullover ones yet , but plan on ordering some today .... just the standard drilled ones . I have some brass check valves/plungers that are slightly heavier than the SS ones in the carb now that I plan to try . Have to make sure they`re the same length as I have found some oal differences in the checks over the years .
Does anyone know what`s involved in changing over from the flapper in the accelerator pump to the old style ball check ? Seems that may be worth trying if the "easy" fixes don`t work .
The pullover is causing the most problem between 2000 and 2500 rpm , which is right where the main circuit starts to take over on the street . Trying to eliminate one variable here.
Barry , you brought back something from way back when I was racing Porsches in SCCA . We had to use the Zenith 32 NDIX carbs so we modified them so the accelerator pumps supplied additional fuel at WOT , but that was strictly for the track . Didn`t work at all for the street ..... way rich .
Looks like starting tomorrow afternoon , things will be a washout as the TS/hurricane passes over us , so it may be a few days before I can try stuff on the road , sp , thanks for the ideas .
Also , BTW , this carb has the BLP mini annulars in it.
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 10:08 am
by grandsport51
Be safe !!
Michael looks like a big one .
I miss living in Fla. everyday except for hurricanes .
2004 was a tough year 22 days without juice .
Though I did enjoy breakfast from the Grill!!
Dave B.
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 10:18 am
by 427dart
OK ...I looked again and see the primary pulling as well.
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 11:33 am
by pamotorman
drill out the needle check and fill it with lead. this will add weight.
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 12:26 pm
by BigBlocksOnTop2
How about a ''tuned'' spring. Something like out of an ink pen. True Valve Hardware stores have assortment of springs. They have to be soft enough so that accelerator pump can push the ball/ needle off its ''seat''.
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 2:14 pm
by Ks Fats
If you don't want to use it to your advantage a small "kill bleed" can be drilled on the jet side of the metering block. I've used .018 in a 4-40 brass set screw on the flat where the two passages intersect. I used to worry about it on the 350 carbed limited engines until I discovered it only added about .5 afr percent at w.o.t.(350 iron head engines) . The flapper valve bowls do seem to be worse but it can be compensated for; I've never modified the later bowls for the check ball,just replaced them with earlier bowls.
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 4:06 pm
by Casper393W
63qcar wrote: ↑Tue Oct 09, 2018 10:01 am
Not using the anti pullover ones yet , but plan on ordering some today .... just the standard drilled ones . I have some brass check valves/plungers that are slightly heavier than the SS ones in the carb now that I plan to try . Have to make sure they`re the same length as I have found some oal differences in the checks over the years .
Does anyone know what`s involved in changing over from the flapper in the accelerator pump to the old style ball check ? Seems that may be worth trying if the "easy" fixes don`t work .
The pullover is causing the most problem between 2000 and 2500 rpm , which is right where the main circuit starts to take over on the street . Trying to eliminate one variable here.
Barry , you brought back something from way back when I was racing Porsches in SCCA . We had to use the Zenith 32 NDIX carbs so we modified them so the accelerator pumps supplied additional fuel at WOT , but that was strictly for the track . Didn`t work at all for the street ..... way rich .
Looks like starting tomorrow afternoon , things will be a washout as the TS/hurricane passes over us , so it may be a few days before I can try stuff on the road , sp , thanks for the ideas .
Also , BTW , this carb has the BLP mini annulars in it.
What are your thoughts on the BLP mini Annular boosters? Im getting ready to send my 4224's center squirters down and have them installed..
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 5:50 pm
by 63qcar
Ksfats ... the problem with the pullover is that it occurs between 2000 and 2500 rpm and then tails off . It never really squirts out of the nozzles/orifices .it just leaks from the orifices and then runs down the inside of the carb and never really gets atomized from airflow . It just flows down on one side and really screws things up in that rpm range .... which is where I have to be in the pits or around town in traffic sometimes.
Engine is smooth at idle ( 1100 rpm ) until it hits 2000 rpm and then it gets rough and clears up again around 2500 to 2700 rpm .
Thats the area I`m trying to clean up . I`ll weigh the brass checks vs the SS checks on my reloading scales hopefully tonight and see if there is a significant difference in weights . If so , I`ll go with the brass ones as a trial and then try the anti pullover squirters after that .
Casper , I like the annulars .... the engine seems to respond quicker and atomize the fuel better , at least in my application .
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 6:19 pm
by JonKaase
Most of the time what you are seeing is resonant pumping from the accelerator pump diaphram vibrating enough to pump fuel through the circuit. This really is bad with a sheet metal tunnel ram. and it will get worse or better with rpm, depending on the shake of the engine. You can throw a washer on top of the orange rubber check valve that will push it closed when the lever is all the way maxed out at WOT, but in our experience its better to have the fuel and tune around it. Its more vibration than air over the squirter!... Kaase
Re: Squirter Fuel Pullover on 4150
Posted: Tue Oct 09, 2018 6:36 pm
by cgarb
Jon,
How did you discover this? Make a pull with the pump arms off one time? It makes perfectly good sense to me when you think about it. Kind of micro pumping because of the engine shake. A good example of one problem camouflaging itself as something else. Also as a side note...What did the inside of the intake port feel like on the running engine? I watched that on youtube and was like wow...that's scary but cool. Were you trying to get an idea what the reversion was doing or just because you can?