rejet holley 600

rowingone · 03-22-04, 09:02 AM

My 64 was a Penn. car and now its found its new home in the mountains . . I live at 6000ft and drive up to 10000 on the weekends - is reading the plugs the best way to tell if rejetting is appropriate - and how many miles is appropriate to accurately read plugs after a change? My feeling is the car runs great so leave it but there is definately some carbon on the plugs . . I could also go with a hotter plug?

Ron Miller · 03-22-04, 12:21 PM

I'm in Missouri and run the stock 66 Holley on a 350 engine, using 62/1000 (#62, I believe) jets in mine at an elevation of 500-600 feet above sea level. And, mine still runs a little rich, although most of my driving is short tripping. So, I believe at your elevation you could run smaller jets (stock originals were #65, I believe) than stock and still be OK.

My .02 worth.

Rlm

rowingone · 03-22-04, 12:35 PM

I guess what I"m asking Ron is how you decided which jets were appropriate for you elevation - trial and error?

motorman · 03-22-04, 12:37 PM

Quote:

Originally Posted by rowingone

My 64 was a Penn. car and now its found its new home in the mountains . . I live at 6000ft and drive up to 10000 on the weekends - is reading the plugs the best way to tell if rejetting is appropriate - and how many miles is appropriate to accurately read plugs after a change? My feeling is the car runs great so leave it but there is definately some carbon on the plugs . . I could also go with a hotter plug?

you want to reduce the "AREA" of the jets 2% for every 1500 you are above sea level. post the "LIST" number on the front of the choke housing and i will check to see what you need.

rowingone · 03-22-04, 12:57 PM

Thanks motorman but the original choke housing is not on there anymore - its an electric choke . . the only numbers I can find are 1850-4 and 3903 on the front of the carb.

Ron Miller · 03-22-04, 01:08 PM

Quote:

Originally Posted by rowingone

I guess what I"m asking Ron is how you decided which jets were appropriate for you elevation - trial and error?

The #62 jets were installed in the carburetor when I purchased it, though the correct original jets from the factory were #65. I haven't changed the #62's since they function adequately for my purposes, but the "correct" way to tune the carb is as stated in the above post from motorman. It's worth noting, however, that to my knowledge a single size jet was supplied as original equipment in the cars when shipped from the factory regardless of which part of the country they were going to. JohnZ could probably verify this, along with some of the other good folks on this forum.

Holley has an excellent site with loads of info on various products, carbs included. If you go to http://www.holley.com/HiOctn/TechSer...fo/TI-220.html, they'll tell you exactly how to tune your carb's main metering system for your driving conditions. Their home page (for carburetors) is at http://www.holley.com/HiOctn/ProdLin...FMSC/FMSC.html, with most of the tuning information in the technical section listed on this page. Lots of other info there should you choose to study further. Hope this helps!!

rlm

rowingone · 03-22-04, 01:29 PM

ron - I just found some info from holley - their recommendation is to reduce the jet size one holley number for every 2000ft elevation increase. They say "most holley carbs are calibrated for operation at sea level." I guess the next question is how you tell which jet I have . . . sounds like you might be too lean according to Holley?

Ron Miller · 03-22-04, 01:43 PM

Quote:

Originally Posted by rowingone

ron - I just found some info from holley - their recommendation is to reduce the jet size one holley number for every 2000ft elevation increase. They say "most holley carbs are calibrated for operation at sea level." I guess the next question is how you tell which jet I have . . . sounds like you might be too lean according to Holley?

Holley's recommendations are a starting point, correct jetting depends upon your driving condtions. My plugs read OK as jetted, so there's no problem with being too lean. All else being equal, it's always safer to be a little (emphasize a little) on the rich side than too lean. Also, see my post above, as edited.

rlm

rowingone · 03-22-04, 01:47 PM

Thanks Ron - those sites you listed sound like the best way to figure out what I need.

motorman · 03-22-04, 02:26 PM

Quote:

Originally Posted by rowingone

Thanks motorman but the original choke housing is not on there anymore - its an electric choke . . the only numbers I can find are 1850-4 and 3903 on the front of the carb.

this carb is a aftermarket 600 CFM and the "LIST" number is 1850-4 and came stock with #66 pri jets and #134-9 secondary plate. to jet for a 10% area reduction for a change of 5000 feet from sea level you need a # 63 primary jet and you must buy a # 34R9716-32 secondary plate from holley. the plate will need to be redrilled because the correct size drillings are not available over the counter. you will need to drill the jet hole from .059 to .064 and the idle hole from.029 to .031

rowingone · 03-22-04, 02:29 PM

Motorman - thanks a million - I'm glad you know what you're doing - for those of us that dont!!

rowingone · 03-22-04, 03:14 PM

Motorman - one more question - since the car seems to run fine now - how much difference will these changes make - gas mileage I dont care about but rather performance. Thanks again.

motorman · 03-22-04, 03:27 PM

Quote:

Originally Posted by rowingone

Motorman - one more question - since the car seems to run fine now - how much difference will these changes make - gas mileage I dont care about but rather performance. Thanks again.

your plugs color is your best bet to find out the true story but if you are too rich you could be diluting your oil with excess gasoline.