RFMustangGT
Member
18mustangs said:You can get twist in caps like the cap I posed earlier in the FRPP catalog to fit your 60's era valve covers. Contrary to what others may say (I've run open breathers and closed and stopped after learning how exactly the PCV system is set up and works) you cannot use a PCV valve and the open filtered breather cap. The reason is the PCV draws air from the crankcase, and with a closed cap the air from after the MAF is diverted to the crankcase to prevent a vacuum and to put fresh air into the crankcase in place of the corrosive vapro laden air drawn out by the PCV. This is a 1 for 1 swap so the air fuel ratio is not thrown off. If you run an open filtered breather cap the air is drawn out of the crankcase, and unmetered air is drawn into the crankcase along with 100% of the intake charge. This extra air leans the air fuel ratio. The computer can only compensate so much with the adaptive fuel strategy (adaptive fuel limits) , if the A\F ratio goes too far out of tolerance you're pinging.
Tim
Thanks! now I know what to do!