I just rebuilt my 400 in my 77 f250. It has new timing gears and chain. New mild cam. New distributor. New pistons. New fuel pump. New carb. I got it back in the truck and got it to fire up when I timed it at 8* btdc. It lugged so I started advancing the timing. It got to 22* btdc before it smoothly idled. It starts fine and runs fine but it seems very high for the timing. I hooked up the advance vac line revved to 3000 rpms and it goes up past 40* btdc. I already checked the timing marks to see if balancer slipped and timing gears to see if I'm a tooth off. Anyone have any ideas?

 

Distributor either to advanced or carb turned up to high?

 

When I turn the distributor down it runs bad and when I shut off the truck it diesels. The carb is a 2bbl holley 500 cfm. Checked the plugs and they barely looked used. Doesn't appear to be running rich.

 

Hmm... is 500 cfm enough?

 

I was going to go with something in the 600's however, the cost of a new carb and intake put me over the amount that the commander of household affairs would allow. Man bugets suck! So that was the biggest found. It ran a 2bbl before.

 

Lol I hate budgets too!
Well unless it happens to be a tooth off, my guess would the new parts made that carb to small

 

Yeah today I tore the timing cover off and checked its dead on. I did read somewhere that a lean mix would need more advance. Would this be true?

 

http://www.projectbronco.com/Technic...FM_formula.jpg

 

Thanks for the info. I called them prior to buying the carb and was told the 500 would work. They said the larger with intake would be better performance wise but for a 2bbl it would work.

 

Not a problem. It probably would of but changing cam and pistons is probably whats getting u for not having enough cfm now