can't pass emissions

[buckn' bronc]

I have just dropped in a freshly rebuild 302 in my bronco and it won't pass emissions (has about 300 miles since rebuild). At first the carbon monoxide levels were too high so I put smaller jets in my carb. When I went back, the carbon monoxide levels were great but, now the hydrocarbon levels are too high. I was told that the valves and piston rings have not yet seated and my break in oil is getting into the combustion chamber causing the failed emissions. Is this true? Do I have to wait until the motor has more miles before I try to retest it?

 

[Seabronc]

Who told you that, a buddy or a mechanic? Do you at least have a CAT on the exhaust?

 

[buckn' bronc]

Who told you that, a buddy or a mechanic? Do you at least have a CAT on the exhaust?

[/quote

Its a '73 so there is no cat and it was the machine shop who suggested the oil change.

 

[Seabronc]

Who told you that, a buddy or a mechanic? Do you at least have a CAT on the exhaust?

[/quote

Its a '73 so there is no cat and it was the machine shop who suggested the oil change.

Then I'd follow their suggestion and wait until you finish the break in. In most states it has to meet the emissions levels that were in existence when it was built. In other states there is no requirement for classic and older vehicles.

Good luck,

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