Have an issue with my '57 and need input !...Just rebuilt carb (float was WAY high) and I had the 283 engine rebuilt last year and purchased a "1957 factrory correct" rochester Carb. The timming was set with the "bad" carb just last week when I had a new Summit Distributor installed. Ran, but was rough. So today I set the float to the correct level the car started up and was SMOOTH but sounded slow. After putting it in gear the Gen light came on and would not idle without a little gas or it would eventually die. So HERE is my question?? Do I need to set the timming AGAIN with the "new" carb. and just advance it just a little bit?
Well you usually do have to adjust the Idle speed and mixture to get it all squared away after you have it apart. They don't automatically reset like electronic FI in your daily driver.
Once the timing is straight, the timing is straight. BUT, you changed the float height ... and that changes the fuel height... which changes the precise idle mixture screws setting. They are precision cut, about an 1/8 or 1/4 turn will alter the AFR a whole point, and you'll probably never hear it. So yeah just about anytime you change anything upstream you want to take a final pass through on the idle mixture and idle RPM.
GREAT ! ! ! I did adjust the mixture screws and running much better, thanks everyone. Now I am (RE)considering the oil I put in the engine. Had an oil change and have been putting in 30 weight (and adding some zinc) , per the engine company that rebuilt it..but some of the guys in my local car club say just put in 10w-30 since it was rebuilt with "modern" parts. Give me some opinions! THANKS ! ! !
Run 20/50 Valvoline VR1 Racing oil and forget the zinc additive it has zinc in it. Unless it's a roller cam you need zinc.
Use a Multi grade oil for small diesel engines. Your engine will stay clean, but the detergents in the oil will go black [which it's supposed to do] I used Castrol CRF 40 in my dry sumped BBC Race Car for 12 years [Recommended by Castrol themselves] I switched over due to an oiling failure with a fancy racing oil. My engine builder recommended this, but I didn't believe him so I contacted Castrol directly [they confirmed this for me] Your idle issue was caused by the idle screws being leaned out to correct the previous float level height. Glad to hear you've sorted this out.