Moparts
bogs and stumbles
Posted By: mopar dave
bogs and stumbles - 06/16/09 02:51 PM
lashed the valves on the 408 .003" tighter(.017-.019) than spec(.020-.022) and now i have a bog in low gear only and seems to go away as engine gets up to operating temp(180), but not completely. i have a prosystems 1000hp on it with 40 squirters. i tryed 35 squirters and its worse, 45's are about the same as the 40's, but feel kind of mushy.
i talked to patrick at prosystems and he told me to drill out the idle air bleeds til i could get the mixture screws in the 2 turns range. well i drilled them .017" to take them from .076 to .093, now the mixtures screws were at 1 1/8 and now are at 1 3/4 turns out. this has helped alot and now with 40's in it the problem is almost gone, but still has a quik stumble that i can not seem to get completely cured. any ideas what else i might try? i'm thinking the problem may not be in the carb at this point, but in the convertor. 727 with a 9.5" tight 4500 and 4.10 gear. patrick also mentioned tuning the power valve, but not sure which way to go with it. the slight hesitation is now from dead stop to about 25-30mph after that no problem and no problems in park either.
Posted By: mikemotorhead
Re: bogs and stumbles - 06/16/09 03:19 PM
Dave I had a problem just like that several years ago that had me pulling out my hair for awhile. Turned out that the gasket between the front bowl and metering block was partially blocking the flow to my squirters and causing the bog. Don't know if this could be the problem but you might want to check just in case!
Mike
Posted By: RemCharger
Re: bogs and stumbles - 06/16/09 03:59 PM
That and your check valves in the accel pump system. The one in the bowl mostly, but try a new needle in the squirter hole too. I assume the pump screws are drilled?
Posted By: MR_P_BODY
Re: bogs and stumbles - 06/16/09 04:06 PM
patrick also mentioned tuning the power valve, but not sure which way to go with it. the slight hesitation is now from dead stop to about 25-30mph after that no problem and no problems in park either.
He is saying to get the PV closer to your vac point
so there is less time for it to open during your
transition (most likely you would need to raise the
PV number)
Posted By: mopar dave
Re: bogs and stumbles - 06/16/09 05:09 PM
you may be onto something charger with the bowl gaskets or check valves as i notice the throttle has to travel about 1/4" to squirt fuel out either squirter. i adjusted the pump levers to .020" and still does the same thing.
my pv now is a 6.5 and my vacuum in gear is between 5-6". so maybe a 4.5 would be better?
what i don't understand is how tightening up the cam/valve lash could cause these issues.
Posted By: RemCharger
Re: bogs and stumbles - 06/16/09 05:18 PM
Cowinkidink?
Posted By: MR_P_BODY
Re: bogs and stumbles - 06/16/09 05:29 PM
Quote:
you may be onto something charger with the bowl gaskets or check valves as i notice the throttle has to travel about 1/4" to squirt fuel out either squirter. i adjusted the pump levers to .020" and still does the same thing.
my pv now is a 6.5 and my vacuum in gear is between 5-6". so maybe a 4.5 would be better?
what i don't understand is how tightening up the cam/valve lash could cause these issues.
If you change the vac in the engine it would change
the way it runs and basically you changed the
cam events ... with your vac being 5-6" and your
running a 6.5 theoretically its already dumping fuel...
it should be 1" less than your in gear idle vac
Posted By: emarine01
Re: bogs and stumbles - 06/16/09 06:02 PM
When you tightend the intake lash you make the cam a little bigger in lift and duration it may not be much but it changes the valve timing
Posted By: BradH
Re: bogs and stumbles - 06/16/09 06:14 PM
"Bogs and Stumbles"... sounds like a Country & Western duo.
Posted By: mopar dave
Re: bogs and stumbles - 06/16/09 06:42 PM
yeah, if i could just wright a song maybe i could make enough money i could buy the baddest car on here and would'nt be bothered with bogs and stumbles. so ya think i should have a 4.5 pv in it? i just got back from a hot 30 mile ride with the engine temp running 195-200 and the 35 squirters in it and its for sure worse than with the 40's in it. not by much, but theres alittle more stumble than the 40's. at a couple traffic lights i tryed footbraking at 1500, definite bog and at 2000 just alittle stumble, but i may try the 45's again later and see how it acts. it looks like the 40's are the best squirter, but there's more adjustments somewhere else. i'll pull the front bowl and change the pv and check the gasket and check valve for now and go from there.
Posted By: emarine01
Re: bogs and stumbles - 06/16/09 07:08 PM
Hey I am not a carb pro but you said the squirters dont start till 1/4 throttle, that sounded a little late for me, any one else wanta step in on this , my squirters come on when I move the throttle, I flash a 5k vert off a 1200 idle and need the fuel early, I dont run any part throttle execpt loading on the trailer
Posted By: MR_P_BODY
Re: bogs and stumbles - 06/16/09 07:11 PM
Quote:
Hey I am not a carb pro but you said the squirters dont start till 1/4 throttle, that sounded a little late for me, any one else wanta step in on this , my squirters come on when I move the throttle, I flash a 5k vert off a 1200 idle and need the fuel early, I dont run any part throttle execpt loading on the trailer
Thats alot late... should start to squirt as soon as
you start to open the blades
Posted By: emarine01
Re: bogs and stumbles - 06/16/09 07:18 PM
Quote:
Quote:
Hey I am not a carb pro but you said the squirters dont start till 1/4 throttle, that sounded a little late for me, any one else wanta step in on this , my squirters come on when I move the throttle, I flash a 5k vert off a 1200 idle and need the fuel early, I dont run any part throttle execpt loading on the trailer
Thats alot late... should start to squirt as soon as
you start to open the blades
Thats what I thought, This squirter thing is kinda new to me ,It sounds like turbo lag on a diesel 
Posted By: mopar dave
Re: bogs and stumbles - 06/16/09 07:20 PM
yeah, i agree. all of my past carbs squirted as soon as the throttle was moved. the pumps are adjusted properly and the pump levers are moving as soon as the throttle is moved, but no squirt til 1/4" of movement. maybe i should contact patrick about this, it seems weird. it has 50cc pumps also, do think that would be a charactoristic of a 50cc pump?
Posted By: mopar dave
Re: bogs and stumbles - 06/16/09 07:24 PM
i just called patrick and left a message on this, will see what he thinks about this.
Posted By: mopar dave
Re: bogs and stumbles - 06/16/09 08:53 PM
patrick got right back with and had me remove one of the metering blocks. he has a modification in the squirter passage that consists of drilling a pin hole in this passage to bleed off some pump shot. it seems my motor wants the extra fuel, so i plugged the holes in both blocks with jb kwik. once it sets up will see if this helps. suppose to rain tomorrow, so it'll be a couple days.
Posted By: mopar dave
Re: bogs and stumbles - 06/17/09 08:05 PM
i patched up the bleed holes in the pump shot passage that prosystems had modded. now i have pump shot as soon as the throttle is moved. will see if this helps with the stumble. also pulled a couple plugs and found they were almost black, so while i was in there i dropped the pri. and sec. jetting two sizes. was 84/92 and now 82/90.
when i had it on the dyno the air/fuel was 12.8 avg in 65* weather. should run alittle cleaner. i'll know more tomorrow when the roads dry up.
Posted By: mopar dave
Re: bogs and stumbles - 06/22/09 03:55 PM
ok, the stumble is completely gone after engine is at operating temp. (180*+). i tried the 35 squirter first and the stumble would'nt completely go away, so i tried 40's and stumbling issues are gone. the leaner jetting also made a world of difference as now from a 15-20mph roll in first gear i can hammer it and the 325/50 mt/drag radials fry thru 1st and sometimes all the way thru 2nd
gear@7000rpm. this indy headed 408 is finally coming together. its becoming a real beast.
Posted By: sshemi
Re: bogs and stumbles - 07/02/09 06:47 PM
Quote:
patrick got right back with and had me remove one of the metering blocks. he has a modification in the squirter passage that consists of drilling a pin hole in this passage to bleed off some pump shot. it seems my motor wants the extra fuel, so i plugged the holes in both blocks with jb kwik. once it sets up will see if this helps. suppose to rain tomorrow, so it'll be a couple days.
exactly where did he put the bleed holes (why would you wanna do that?) reason i am asking is I also have a pro system carb and i to have a bog.
And i have tried everything squirters, cams.
Wonder if i also have the bleed holes.
Thanks
Joel
Posted By: mopar dave
Re: bogs and stumbles - 07/02/09 07:01 PM
take your metering blocks off and lay them pv side down, look at the pump shot passage and follow it up to the middle of the block where it turns and goes into the main body, at the turn is where the .028 hole will be. its hard to see, but if you turn the block around and hold it up to a light, look thru the pump shot hole just above the pv. its hard to see, but if its there plug it with some jb quik.
Posted By: sshemi
Re: bogs and stumbles - 07/02/09 08:18 PM
thanks.
