Oil specifications 37 flathead

[37 ford firetruck]

Have a stock 1937 ford flathead with the cast iron heads. It runs pretty good for setting for twenty years but the oil is black as night. I would like to know what oil or oil additive will work best in this engine...it also has no filter that I could find.

[Lawson Cox]

Most any brand of 30W oil is fine. Drain oil. Put in maybe 3 qts of mineral spirits or kerosene and crank it up. Let it run for just a short period, maybe a minute or two at most. Drain out flush media and fill to full line on dip stick. I prefer Valvoline 30W myself.

These old engines will blacken the oil pretty fast. Use Non detergent oil.

[J Witt]

Remember that close to a quart of whatever you pour in the engine will remain after you drain the flush out. It would probably be good to run it again for a bit after the new oil is in there and drain it again before putting in the oil you want to run long term.

Lots of oil recommendations on this forum, I use Shell Rotella T3 15-40 in mine with a few ounces of moly additive. Works fine. YMMV.

John

[39topless]

Your engine did not come with a filter. You can install one if you want.

[rotorwrench]

Putting a solvent in an engine of unknown condition could be the death of the bearings. No telling how much crud is in the bottom of the old pan. A person doesn't want to stir that nest of mad hornets up right away to go through the bearings. An engine can be flushed by changing the oil more often at lower mileage intervals. Any SAE 30 motor oil will work so buy the cheapest stuff you can find to flush.

[Drbrown]

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Interesting recommendation found in a 1940-1950's Chilton Repair Manual for flushing Ford flatheads .... In a cursory summary "Put in 5 qts oil PLUS 1 Qt of gasoline. Run for about 50 miles. Gas will burn-off. Change oil as a flush and change again as a final."
I always heard and saw about the kerosene method in the 50's.

(I have no oil filter, use detergent 10w-30, and change every 1000 miles)

[rotorwrench]

In that quantity it would dilute the oil to a very low viscosity but will still have a loosening effect on the crud. It might be better to use a quart of Marvel Mystery Oil. Old round motor airplanes used in Alaska and other cold climates had fuel dilution systems that thinned the oil for start up and warm up when the temp gets to below freezing. After it warmed up, the system was shut down. The mix happened in baffled part of the oil tank around the sump so it didn't dilute the whole tank of oil. After you run the engine for a few hour flight the fuel would evaporate out of the oil and it would get back to normal. Those engines had an external tank that could be cleaned out.

A person should know the history of the engine before attempting a flush like this. If the car was driven by a little old lady to the post office & grocery store that were only a block away from her house then the engine can really sludge up bad. In those cases the pan & intake should be pulled and cleaned out manually. If the car was driven on long commutes and always thoroughly warmed up then there will be no problem. If you don't know the history, you have to err on the side of caution. It might be OK or it might start knocking immediately.

[jimvette59]

If it doesn't blow up. It will wash down everything. Not good. IMHO.

[texas webb]

I'd drop the pan and get it as clean as possible first.

[Kube]

Originally Posted by rotorwrench

Putting a solvent in an engine of unknown condition could be the death of the bearings. No telling how much crud is in the bottom of the old pan. A person doesn't want to stir that nest of mad hornets up right away to go through the bearings. An engine can be flushed by changing the oil more often at lower mileage intervals. Any SAE 30 motor oil will work so buy the cheapest stuff you can find to flush.

I could not agree with you more. I saw (personally) way too many the aftermath of engines guys attempted to flush. The issues caused were all too often severe.