Rich or Lean? or in between?

66StangGuy · 10-03-2003, 09:39 PM

my next project.

carb.

trying to figure it all out.

is my motor running rich or lean?

installed new plugs. old ones looked new not very old.
ran the motor for a week or so driving around normally.
checked the plugs and they look like brand new. very clean.
put my car on the smog machine at work and a\f ratio was 25:1
reved the motor and went up to about 27:1

this reads lean right? plugs read lean right?

also read that extrealy rich will "wash" the plugs as well.

well i get about 8mpg. so i was hopeing it was running rich.
but the motor will be most efficient when it is tuned properly right?

any ideas on what jets i should use?
currently running holley 4160 600cfm #66 main jets stock power valve.

motor seems to have more power at part throttle and really no power differiance from half to full throttle.

what are symptoms of a blown powervalve.

im lost guys what way to go?

Rev · 10-04-2003, 02:20 PM

I don't think the car would even run at 27:1 or 25:1. Ideal is about 12-13:1. The plug insulators should be either ash gray or tan for ideal fuel air ratio. BTW, air/fuel ratio does vary between idle, cruise, and WOT. Also when reading plugs, it is hoped that they all look pretty much the same indicating that the air/fuel ratio is about the same for each cylinder.

Rev

66StangGuy · 10-04-2003, 07:26 PM

thanks for the reply rev. yeah all the plugs are the same. and i know the the 25:1 ratio was really off thats why i was not sure what was going on. i know how to read the motor and unsually find it its rich or lean but im at a 50\50 here and just dont know what way to go. guess ill just order a set of 60's and 70's and see what way works better or if i should just stay with the 66's i have in it now.

10-03-2003, 09:39 PM	#1
66StangGuy Registered Member Join Date: Feb 2002 Location: Diamond Bar Posts: 258	Rich or Lean? or in between? my next project. carb. trying to figure it all out. is my motor running rich or lean? installed new plugs. old ones looked new not very old. ran the motor for a week or so driving around normally. checked the plugs and they look like brand new. very clean. put my car on the smog machine at work and a\f ratio was 25:1 reved the motor and went up to about 27:1 this reads lean right? plugs read lean right? also read that extrealy rich will "wash" the plugs as well. well i get about 8mpg. so i was hopeing it was running rich. but the motor will be most efficient when it is tuned properly right? any ideas on what jets i should use? currently running holley 4160 600cfm #66 main jets stock power valve. motor seems to have more power at part throttle and really no power differiance from half to full throttle. what are symptoms of a blown powervalve. im lost guys what way to go? __________________ 66 mustang-292-Holley 4160-World Castings Windsor Sr.-Hooker super comp headers-MSD box & Coil.3.55 gears. B&M Z-Gate-Black leather racing seats with 4pt harnes.

10-04-2003, 02:20 PM	#2
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	Somethings wrong? I don't think the car would even run at 27:1 or 25:1. Ideal is about 12-13:1. The plug insulators should be either ash gray or tan for ideal fuel air ratio. BTW, air/fuel ratio does vary between idle, cruise, and WOT. Also when reading plugs, it is hoped that they all look pretty much the same indicating that the air/fuel ratio is about the same for each cylinder. Rev __________________ '66 Coupe, 306, 350-375 HP, C-4, 13.07 e.t., 104.8 mph, 1/4 mi. O.B.C. #2 '66 coupe Last edited by Rev; 10-04-2003 at 04:21 PM..

10-04-2003, 07:26 PM	#3
66StangGuy Registered Member Join Date: Feb 2002 Location: Diamond Bar Posts: 258	thanks for the reply rev. yeah all the plugs are the same. and i know the the 25:1 ratio was really off thats why i was not sure what was going on. i know how to read the motor and unsually find it its rich or lean but im at a 50\50 here and just dont know what way to go. guess ill just order a set of 60's and 70's and see what way works better or if i should just stay with the 66's i have in it now. __________________ 66 mustang-292-Holley 4160-World Castings Windsor Sr.-Hooker super comp headers-MSD box & Coil.3.55 gears. B&M Z-Gate-Black leather racing seats with 4pt harnes.

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