Briggs oil filler cap threads

[B.Ikard 2]

Gents, I need to modify a 16hp Briggs block to accept a dipstick. What diameter and pitch is the oil cap thread? I plan on boring in the cast in dipstick boss near the cylinder fins and using the factory grommet. Any help would be appreciated, Brent

[HubbardRA 19]

Brent, I think it is a 3/8 pipe thread.

[PatRarick 1]

Rod, I think he's speaking of the standard Briggs oil fill cap with the two little nubs on it. That is standard NC bolt thread. If I remember correctly, it's 5/8", but may be 3/4".

[MPH 12]

Sounds too me like he's planning on installing a newer version dipstick that comes up about to the head. If so, your a lucky man Brent as I left the 16hp with the rod out in the shop, the rubber groument that the tube slides through is 3/4 course bolt tread, happen to have a bolt in the junk tray.

[B.Ikard 2]

3/4 coarse-thanks !!! This one is going in a 914, not sure if the earlier dipstick design will clear frame. Brent

[HubbardRA 19]

I installed a dipstick into the 13 Hp engine that I put on my 713S. I bought the factory dipstick for that. It had a tube which appeared to just be a piece of 3/8 pipe. That screwed into the original hole, then the dipstick screwed onto that. As far as I could tell, the tube had pipe threads. There was no shoulder and you just screwed it in till it got tight. There is not gasket on this one. I also have a couple of the long plastic tubes that screw into the same hole and use an o-ring gasket. I thought the question was about the short dipstick with the tube that is only about 4 inches long. Sorry! There must be a pipe thread and a straight thread that both have the same pitch and are used for these dipstick mountings.

[PatRarick 1]

There were a few different types and locations for the oil fills. The oil fill in the oil pan is 3/4" pipe thread. The oil fill in the LOWER crankcase, just above the oil pan and opposite the carb side of the engine, is 1/2" pipe thread. The oil fill in the UPPER crankcase used bolt thread, verified to be 3/4" by MPH. The 3/4" oil fill in the oil pan had two types of fill pipe. The early ones had no threads on the inside and a flat cap held in place by a spring. You simply flipped it open to check or add oil. The later types were threaded inside with the 3/4" bolt thread for the little plastic screw in fill caps. Since the oil pan is reversible, this oil fill could be on either side of the engine. The 1/2" oil fill in the lower crankcase used a pipe nipple and a cap with a dipstick. This oil fill was only opposite the carb side, on the lower crankcase, just above the oil pan. The oil fill in the upper crankcase was on the upper left of the crankcase, just below the cylinder cooling fins as you face the rear or PTO side of the engine. It used a threaded rubber grommet that screwed into the hole, and a "press fit" hole in the center. The dipstick/oil fill tube was forced through the gromment and secured by bolting it to the cylinder head. Early engines had no provisions cast in the blocks for the oil fills in the crankcase. Later engines had the provisions cast in the block, but not all had the holes drilled and tapped. On engines with the provisions, but no holes, I have drilled and tapped both areas when necessary. Doing so on the lower crankcase isn't too bad as you have room for error if your angle is slightly off. The fill in the upper crankcase is kind of tricky to get the correct angle, and the angle is much more critical as the dipstick or fill tube is bolted to the head. An incorrect angle will not allow the pressed in dipstick or fill tube to seal. There may be other locations and types of oil fills, but these are the only three I'm aware of.