Carb tuning.

Reply Subscribe

Thread Tools

Search this Thread

Nov 2, 2001 | 10:16 PM

fordsnharleys

Thread Starter

Junior User

Joined: Aug 2001

Posts: 61

Likes: 0

Carb tuning.

I wanted to ask someone who has experiences with Holley carburetors about jet sizing. I have a 351 c 2v, with a Holley carb. It is running extremely rich right now, I rebuilt the carb because the float stuck, I thought this would cure it but it did not, so, now I will change Jets to see if that helps. The question is: I have size 73 jets in this thing right now, at 8,000 feet in elevation, right now this car spews black smoke upon acceleration and bogs a lot, I tried adjusting for less accelerator pump spray, and it helped, but minimally, even cruising it smokes black, so how big of a jet stepdown would make a sizable difference? I do not want to underjet, but I don't want to buy 100's of jets till I get it right. I know this is a trial and error thing, but how big of a difference will say a size 67 make?
thanx in advance,
Justin

Nov 3, 2001 | 07:32 PM

thelonerangerxlt

Posting Guru

Joined: Aug 2000

Posts: 1,984

Likes: 2

Carb tuning.

Justin, I went thru the trial and error thing last spring. I have a Motorcraft 2150 2v, but I think it is similiar to your Holley. I was going in the other direction on mine and trying to enrichen the mixture. I ended up with #60's, and I live at 1000' asl. At your altitude, I would start at around #62's, and go from there. If you are running EGR, you can go leaner.

78 Bronco Ranger XLT, 351M, 4 speed, Trailer Special

Nov 3, 2001 | 10:11 PM

Franklin2

Moderator

Joined: Jan 2001

Posts: 56,965

Likes: 2,725

From: Virginia

Carb tuning.

Make sure your float levels are at the bottom of the sight plug, front and rear. I had an oem ford holley that had #62 jets in it originally, so a 62 wouldn't be all that unusual. When you change the jets, if you get new metering block gaskets, carefully take the metering block off and look at the cavity and power valve area next to the main body. If this is wet with fuel a blown power valve may be aggravating the situation. Just some things to look out for, but that high altitude will probably cause a problem that's going to require leaner main jets.

Nov 4, 2001 | 12:27 AM

fordsnharleys

Thread Starter

Junior User

Joined: Aug 2001

Posts: 61

Likes: 0

Carb tuning.

Thanx for The help
today I rectified the situation though, This carb is a 500 cfm 2v (not stock) with the 73 jets that are common in this carb. today I bought some Jets and found that the 67 works very well, It is still a little rich, but not dangerously like it was. appreciate the help though.
Justin
ps: this carb is probably a bit too big huh?

Nov 4, 2001 | 11:10 AM

Franklin2

Moderator

Joined: Jan 2001

Posts: 56,965

Likes: 2,725

From: Virginia

Carb tuning.

Is it a replacement emissions type carb or one of those high performance 2bbls. If it is high performance, it's not really too big, but I think alot of these holley 2bbls are calibrated for racing in racing classes that restrict the engine to a 2bbl.

Nov 4, 2001 | 11:15 PM

fordsnharleys

Thread Starter

Junior User

Joined: Aug 2001

Posts: 61

Likes: 0

Carb tuning.

It is a high performance 2v, non emissions replacement, I am thinking I will spring for the 2v to 4v intake swap, and put a 600 cfm on it, I think it will be more driver friendly.
hopefully!
Justin