Just finished installing a pcv valve (AC CV-698C) from a 230 cu. in. Mopar flathead military surplus engine (built in 1967) into my 1939 Plymouth pickup which had a downdraft tube. I'm uncertain as too the exact year of my engine? Most likely a 201 or 218. Anyhow, after installing it, I needed to adjust the idle mixture. The engine also seems to run slightly rougher at higher rpm (around 1500 or more) Any opinions on this? Another question; is it OK to drive without the tube going to the air filter? I'll need to do some fabricating to do this. I plan on converting from oil bath to a paper element filter as well. Has anyone made this modification and offer any wisdom or issues I may be creating?
I will assume your breather cap/filler tube will filter the air going into the crankcase so you should be good to go. . So, no need to connect to the air filter on the carb. Engine now runs ruff: Likely the PCV has made it lean so one may have to go to a larger main jet(s) in the carb. Max points given for improving crankcase ventilation on a pre ‘63 engine.
The last of the Chrysler 6 flatheads were 264” and Desoto was 251”. With a port & relieve plus a Chris Craft cam should go like stink. Downside is it’s two or so inches longer than the Dodge/Plymouth block. My grandfather favored them Mopar 6’s.
By venting from the crankcase to the intake manifold have you not created “essentially “ a vacuum leak ? and a lean condition ? I think venting to the air cleaner you would not have the lean condition.
I don't think the Mopar flathead 6s are very popular with most hot rodders, but like your grandfather, I've come to appreciate them. My early short block version makes lots of torque and keeps up with modern traffic just fine with a transplanted BW-T5 behind it. I believe these engines were produced from the 30s to the late 60s and used in some heavy duty military vehicles. I have been accumulating some vintage speed equipment for the 230 engine I purchased which I might install and would be really cool, but my 1939 truck already goes fast enough to kill me. My oil filler cap is filtered and I have been considering opening the main jet a tad?
I still use the draft tube. Mine leaks oil like crazy, after sitting 25 plus years and then getting it running I think the gaskets are at the end of there life.
Our grandfather built an engine for my oldest cousin’s car, a ‘49 Plymouth business coupe. A Desoto as that is what he had on hand in his shop. Relieved, max oversize bore, Chrysler Marine (Chris Craft?) cam and an early floor shift trans. Cut out behind the grill to move the radiator forward. It had enuf snot to trash the transmission unless driven with moderation. Them engines were used in industrial applications well past ‘59, the last year for pass cars.
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