Visit The Dirt Forum for More Information

Author Topic:   Carb Jetting
killermiller
Dirt Roller

Total posts: 24
posted January 01, 2002 02:55 PM
Hello, I am new to racing and have tons of questions! Think this place will be a great help! First question I have is how do you determine what jet to run and when to change them? What performance changes come with smaller or larger jets? I race a IMCA stock car,355,dart iron eagle heads,and mandated Holly 350 carb...Thanks for any advice! Much more questions to come!

------------------
killermiller

mitch
Dirt Full Roller

Total posts: 27
posted January 01, 2002 05:44 PM
quote:
Originally posted by killermiller:
Hello, I am new to racing and have tons of questions! Think this place will be a great help! First question I have is how do you determine what jet to run and when to change them? What performance changes come with smaller or larger jets? I race a IMCA stock car,355,dart iron eagle heads,and mandated Holly 350 carb...Thanks for any advice! Much more questions to come!



Read your spark plugs,start with about 3 sets of new plugs. By reading your plugs, I mean, put them in, run the engine hard, then pull the plugs and look at them. If they are dark colored, or black, you are running too rich. If they are white like when purchased, you are too lean. It is best to start with too rich and work your way down to what you want. What you are looking for is a light carmel color on your ceramic. The plugs you used to get your jetting right will still be good plugs to use, but you need the new plugs to be able to gauge the color. The other option would be, do you have access to a dyno! I used to run a nitrous oxide drag boat, and learned how to jet.Ran 9.38sec 1/4 mile

BK19
Dirt Freak

Total posts: 285
posted January 01, 2002 06:27 PM UIN: 40696038
1 thing too ad is hot air is thinner so you jet down
cold air is denser so you jet up
if the temp drops10 degrees go up 1 jet size
if the temp rises go down 1 size for evry 10 degrees this is for holley jets

killermiller
Dirt Roller

Total posts: 24
posted January 01, 2002 08:08 PM
Thanks for the help guys! I will have plenty of questions and appreciate all the input!

------------------
killermiller

bbracer17
Dirt Freak

Total posts: 256
posted January 01, 2002 08:40 PM
where i run is at sea level so when I run gas I go to the Holley website and cross reference my carb number and see what jets Holley put in the carb. Holley sets up the carb for sea level and this has been extremely close for all my cars.

OvalRocket34
Dirt Roller

Total posts: 24
posted January 02, 2002 07:21 AM
www.parkercarburetion.com

this site will help you out and there is a tech cd available that is well worth the money. on top of that Earl is a **** of a guy!

BK19
Dirt Freak

Total posts: 285
posted January 02, 2002 07:47 PM UIN: 40696038
yes he is in fact he is the one that told me about the rule of thumb in changeing jets for every 10 degrees of temp

go4win
Dirt Full Roller

Total posts: 61
posted January 02, 2002 08:55 PM
i ran the 350 carb all year
ran 74 jets with a 350 with double humps
hope this helps

killermiller
Dirt Roller

Total posts: 24
posted January 02, 2002 11:48 PM
Yes thanks everyone for the input I will check out the website and have allready learned alot..am sure I will have many more questions as the season goes on ! Thanks again!

Back to the Archives