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#1
Lean jetting
ddgonzal
Posted on: 2015/8/17 2:45
Quote:
I have a question regarding the secondary jet mentioned that was slightly running lean and my question is, what jet size did you upgrade too? Mine is a #135 thank you Good Question. 1971 Datsun 1200 was fitted with a small #135 secondary jet. That proved to be finicky, so for 1972-1973, Datsun fitted #140. That will take care of surging while cruising at higher speeds.  
#2
Re: Lean jetting
grover
Posted on: 2015/8/17 2:50
Or go to a #102 Main jet from the stock #97 which is what I did to cure the flat spot when cruising at 65 mph or so in my 1972 coupe.
#3
Re: Lean jetting
ddgonzal
Posted on: 2015/8/17 2:59
Yes, 1972 had its own problem.
1971 - lean secondary 1972 - lean primary Although I must say I never experienced a flat spot with all the working stock equipment. If you modify the engine (for example change exhaust, gap the plugs too narrow, or remove smog equipment) then the jetting can go over the line. 1972-1973 was factory jetted for maximum fuel economy but if anything altered that then it could run too lean. Going to a bigger size jet has a small penalty but gives the engine more leeway in the tuning department.
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