Im new to carbs so I figuring it out as I go. Purchased a used 670 holley.

Current symptoms:
- Hesitation
- Low power
- Engine does not want to rev past about 3000 under load. When not loaded revs fine.
- Put new plugs in, ran about 20 minutes, engine died, eventually started back up.
- Plugs are fairly black and sooty (too rich?)
- Dug into the carb to determine what all the guy I bought it from had changed. Has very small jets on it, 54 on primary, 65 on secondaries. Stock is in the high 60's.
- Power valve was one size too big for my vacuum 8.5
- Squirter was a 37, changed to a 40 when i had really bad hesitation off the line.

Was going to go ahead and order a jet kit for the 70 - 80 range, and a 7.5 power valve and try again but if the engine is running too rich I would think that would make it worse. Thus I am a bit lost, wouldnt think I would want to go any smaller on the jets.

12/13/2009 3:37:25 PM

year/make/model

12/13/2009 4:07:42 PM

87 ford mustang 5.0

12/13/2009 4:10:16 PM

fuel too rich. check spark advance.

12/13/2009 4:20:24 PM

im afraid to go any smaller on the jet, its a 54 on the primary to begin with, timing is at 15 degrees

12/13/2009 5:31:36 PM

I know a LOT about this situation- learned after several years of messing with several Holleys. The best advice I can give you is to pony up and buy a new one. Fresh out of the box you will be happy and above all else you will have started with a clean slate.

Otherwise you will spend all winter trying to figure out the one part on your car that most easily can ruin whatever you hope to accomplish come spring.

12/13/2009 11:47:09 PM

Or you could just find a jet chart and match up with your application. Most carb manufacturers have published info on jetting. You could even call Holley.

Also...you really need to provide the carb number (you know, like 0-1850) because that should tell you its original jetting, etc.

[Edited on December 14, 2009 at 12:13 AM. Reason : blah blah...]

12/14/2009 12:07:15 AM

thats what i figured i would do, after a little research i found the initial jetting is 67 / 78 so I am going to return it to that and start from there.

ive never had a chance to run the car WOT so im thinking my read on the plugs wont tell me anything.

^^unfortunately if I get to February and still have these problems that is exactly what i might be looking at.

[Edited on December 14, 2009 at 6:33 AM. Reason : ..]

12/14/2009 6:31:40 AM

at least get a low-end wideband. just because it's a carb doesn't mean you have to do guess-and-check tuning

12/14/2009 8:49:58 AM

i was considering that, ive already got an o2 sensor from the initial setup. any you would recommend? seems like they are only sold with a 02 sensor and they are all in the $200 range.

12/14/2009 12:58:48 PM

You do need to use the O2 sensor that comes with the wideband kit...or at least the Bosch 5-wire sensor. Standard single and 4 wire sensors will not work. But you've already got the bung there at any rate.

That's my limit on this. Ray...fill him in on the rest.

12/14/2009 1:39:13 PM

I have had the AEM wideband and I currently have the Innovate LC1 wideband. I wouldn't recommend either of them for you--the AEM has no logging software which would be helpful. The Innovate has good logging software but is a PITA to install and not that reliable. The Innovate's installation problems come from its sensitivity to electrical noise, while the reliability issues come from a heater control circuit that I feel is prone to overheating and frying the sensor.

Most widebands use the Bosch LSU series sensor that came OEM on a lot of cars (LSU 4.2, 4.7, and 4.9 are most common now). There are a number of different styles of connectors and harness lengths. http://wbo2.com/lsu/default.htm and http://wbo2.com/cable/lsuconns.htm have lots of info.

I'd just say get something in your budget that has logging software + a display. I mount my display on the steering column by the tach so I can always see roughly what AFR I am getting at a particular rpm (vital on a turbo car). Mounting in an A pillar gauge pod sucks because you can't see the tach at the same time.

Then it's nice to be able and see a graph of the AFR on a laptop. It's good for driveability tuning like fixing stumbles and hesitations.

12/14/2009 5:17:17 PM

Dude... WTF

youreally don't know what you are doing do you?

12/14/2009 11:59:06 PM

If you have it all figured out please share.

12/15/2009 12:35:49 PM

i have an innovate and no problems. i dont use their software, tho. i use megatune for logging.

12/15/2009 1:56:10 PM