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| | | | Joined: Nov 2010 Posts: 21 Wrench Fetcher | | Wrench Fetcher Joined: Nov 2010 Posts: 21 | Never rebuilt a carb!!! But here goes...has anyone setup a new 4160-390 on a 250 ? It's a list 0-8007 with a -65 power valve, .025 nozzle and a "plain" vac. sec. spring and a -51 main jet size... I have 19.5 to 20 vac. at idle.. I have a stumble at med. thrtl. off idle ...Should I get a 9.5 or 10.5 power valve to help (half the vac. reading) ? Maybe the nozzle s/b bigger? I'm hoping to not buy a pile of parts and do it many times... any help for this newbee would be cool !!!
Bear | | | | | Joined: Jun 2010 Posts: 188 Shop Shark | | Shop Shark Joined: Jun 2010 Posts: 188 | What are you using for a distributor. Try more advance first. Around 12 degrees initial. Carb might not be the problem. | | | | | Joined: Feb 2000 Posts: 5,223 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 5,223 | Pull a plug and check the color, rich will be black, white with purple dots lean, grayish brown just right. Back the accelerator pump off some, if its way worse, give it more fuel via the accelerator pump. You might be able to adjust the accelerator cam around to a differnet hole or you may have to by the next one up for a quicker shot or longer shot of fuel.
A slightly rich idle screw adjustment can help off idle a bit, won't help mid range.
And for the record, owning Holley means, many, many tries at getting it right!
Joe | | | | | Joined: May 2005 Posts: 1,624 Shop Shark | | Shop Shark Joined: May 2005 Posts: 1,624 | There are several threads on this isuue if you will search the forums. I know as I went through all this with mine and no, the flat spot didn't go away with the change to the 9.5 power valve
Six volt guy living in a twelve volt world
| | | | | Joined: Nov 2010 Posts: 21 Wrench Fetcher | | Wrench Fetcher Joined: Nov 2010 Posts: 21 | I switched the cam to the other mounting hole and it helped.... I can run at 65+ fine..and 35-45 ok too...Plugs were grey/brown...I had already timed to 12deg. and switched from the vac port under the front of the carb to the ported one up on the top by the bowl plug...now the total advance is @36...not 46...oooops. It seems as if it's not enough fuel from the acc. pump off idle before there is enough air flow through the carb...Should I get a cam assortment kit first to try?
Bear
| | | | | Joined: May 2005 Posts: 1,624 Shop Shark | | Shop Shark Joined: May 2005 Posts: 1,624 | I also tried the pump cam thing. I never did get rid of the off idle flat spot. I was about to start re-jetting when I sold the 250 and moved on to a 350. Remember the old saying, "There's no substitute for cubic inches except cubic money".
Six volt guy living in a twelve volt world
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