oil recommendation for 40 flathead

I use 10W40 in my 40 ragtop flathead. I either use ZZDP additive or likely switching to Amzoil 10 W 40 with extra zinc. You should use zinc additive on any car w/o roller cam which includes most cars up to 1989 or so. My 90 Silverado I am uncertain as to the cam so play it safe and use the additive. My engine buildr and mechanic friends only use sythetic whereas I had been using Valvoline Syn-tec (blend) but considering all Amzoil, especially being able to by it at whelesale dealer cost. Pricey stuff.
 

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I use Castrol 20W50. I believe most will work fine for occasional driving...just remember to change the oil once in a while! :)
 
I like Pat/Ohio, use Castrol 20/50W in my flathead. If you drive where the RPM's are up there for long stretches and day after day, perhaps adding Zinc is the proper thing to do. For most of us, with several oil changes in the course of a driving year and limited use....why??? LouB.
 
I've heard the best oil to use with 1300PPM+ zinc is Chevron Delo LE,you can get it by the gallon at wall mart i thinks it's a 15 40W too.
 
here in california diesel oil is low zinc also (for a few years), if it says "low emission" on the jug then welcome to our world :). i still have a jug and a 1/2 of the old delo for my moms and girlfriends new cars (i use 1qt with the regular oil). i use valvoline VR1 "race oil" in my '47, it has high zinc.
"High zinc/phosphorus provides extreme wear protection, including flat tappet applications"


http://www.valvoline.com/products/consumer-products/motor-oil/racing-motor-oil/6
 
I doubt there was much zinc in the oils of the forties. With the low spring pressure in the flathead, no where near as much zinc is needed as in a modern flat tappet engine. As I understand it, there is still zinc in the oils, but at a reduced level. sufficient for us.
 
I also use Castrol 20w50 in all of our flatheads. Some get driven at highway speeds 65,75MPH for long trips (600+ miles) and some just get driven around town. I've installed top oilers in both our '39 Ford CS and '39 LZ CP and I use MMO in them.
 
I have used Castrol 20/50 for well over 35 years even in older diesels. I put it in my 39 over 30 years ago at start up on a new engine and it has over 103,000 miles with alot of highway (Columbia 3:78) traveling at 65 to 70 MPH. Had the pan off for an oil leak at 85,000 and the bottom end was clean and no sludge at all in the pan. G.M.
 
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