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Author Topic:   damb carb
Donnie Ross
Member
posted March 27, 2003 08:11 PM
question for kp or any one else my 406 refuses to run with a 4 bbl runs great with c&s 890 2bbl,tried 3 different 750 double pumpers, one completely stock 73 primary jets 6.5 power valve 80 jets rear wont idle ragged sounding when revved. one guerte 750 off little bros late model 86 and 88 jets ran good on his same cam specs both cars heads only diff, his dart aluminum mine ported 492's 890 has 88 jets 2.5 power valve
as i say great with 2 bbl small amount of black smoke when accelerated not much, both 4 bbls blue smoke almost like oil burning not present with 2 bbl,fuel pressure 6lbs regulated would the wrong power valve do this?


rico 08
Member
posted March 28, 2003 08:27 AM
HMMMM,KP will probably knock this out but i'll give my two cents,sometimes a two barrell will run alot better if there is a problem in the motor somewhere because it is smaller and generates alot better metering signal at the carb which will crutch something wrong and if you have a problem somewhere it will run the best,i'd look into cam out of time or something that will kill the signal the carb is getting,low vacuum.Also it sounds like you're overly rich.


KPLugnut
Member
posted March 28, 2003 10:21 AM
I'll have to agree with the previous post.
Also, you may have a real weak ignition, and because the 2bbl is feeding so much less fuel possibly, the problem doesn't show up as much.
Get a vacuum reading at idle if you can, it may show some evidence of the problem.
Also, I agree, the blue smoke isn't oil, it's probably a "fog" of unburned fuel.
Let us know what your vacuum is doing and we can probably work thru it. I doubt it's anything specifically to do with the carbs themselves, tho (power valve, etc), but rather something either cam timing related (therefore, vacuum-caused) or ignition related.

Hope that starts to help. Just get back to us with vacuum info and we'll go from there.

KPLugnut

Donnie Ross
Member
posted March 28, 2003 08:25 PM
checked vaccum tonight fluctuated between 5 and 6 inches at idle came up to 12 at about 2500


Donnie Ross
Member
posted March 28, 2003 08:28 PM
also cam specs are .615 lift 258 degrees at .050 intake, .615 260 degrees exhaust roller if this helps.


Donnie Ross
Member
posted March 30, 2003 06:48 AM
problem solved installed 2.5 valve engine runs great,Thanks for the suggestions Rico and Kp.


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