Two differing articles on allpar.com, (both by knowledgeable POC members,) are quoting the cylinder specifications on the ?33 Plymouth PC motor. One says 3 ?? Bore X 4 1/8? Stroke, one says 3 ⅛?Bore X 4 1/8? Stroke, but both say 189.8 Cubic Inches. Kanter?s website quotes both a 3 ?? bore and a 3 ⅛? bore on their engine kits page, (http://www.kanter.com/p24-mon.html#mo1) but the year information is confusing. Todd Fitch?s website says the 3 ⅛? bore is correct for the PC.
When, (and if,) it comes time to order pistons, (late November, this year,) which is the right bore size on my PC? Also, if I end up needing pistons/rings, am I at the mercy of Kanter?s prices or is there a secret stash somewhere? Any help appreciated, thanks in advance. GA
Check with EGGE, they might be able to help
Quote from: Plymouths on September 24, 2010, 01:01:02 PM
All 1933 Plymouth engines,PC or PD, are 3 1/8" X 4 1/8". Displacement is 189.8 c.i. or 3.1 L. They are 4 ring aluminum pistons. In fact I believe 1934 and on for several years, all the engines used 3 1/8" pistons they just played with the stroke to increase or decrease the displacement.
Yep. The pistons, wrist pins, wrist pin bushings, rod and main bearings, etc. are the same for 1933-41. They stroked it in 1934 to change the displacement from 189.8 (call it 190) to 201 in 1934. The change from 201 to 218 in 1942 was a bit more radical and so it uses different bearings, etc.
I did buy pistons for my PD from Egge many years ago. Turns out they were quite a bit heavier than the CPDP stamped ones that were in the engine and the weight variation between them was higher than the 1933 specification. So be prepared to either balance them yourself or have your machine shop balance them.
Thanks for the replies. My plan is to tear into the motor in late Nov. or Dec. The old car runs so well, but the oil pressure is only 20 to 25# when warm at 40 MPH, and the rear main seal is leaky leaky all over the garage floor. 'Course we all know how it goes: "Well, I might as well do the whole motor as long as I have it apart. . . . " :D
My '36 rear main seal doesn't leak (the pan gasket does). My oil pressure is also 20-25 pounds with a warm engine. I've driven it 25000 miles that way since I bought it in 1990. As long as I don't go over 50-52 mph, no problems.
Pat O'Connor
Yes!! This is the kind of confidence building information I'm looking for! Thanks, both of you. It is also funny you'd talk about "just drive it," as a very good friend of mine and I were talking about that very topic today. He and I go a ways back, both with Model A's, both with old HD motorcycles, (in other words, both with leaky motor experience! :D) He has nearly convinced me to just drive the old Plymouth as it is. "Go over to Grainger's and get one of those oil absorbing mats they sell, stick it on your garage floor, and take the thing out for a ride," he told me today. Now, I read your suggestions and ideas, and this feels the "best" of what I've come across.
BTW, Is obsessive thinking part of being an old car "guy?" When I'm driving the car, I have a great time, and when I'm tinkering with it in the garage, the same. My "problems," (and, apparently the car's,) seem to come late at night when I'm trying to get to sleep!! Then, the "you better get it 'right' or you'll regret it" goblins come calling. The plain fact is at my age and with the 35 to 50 miles of local 45 MPH driving that I'm using the car in any given week, it more than likely will run for as long as I need it to and past that point. Sheeesh! I guess I'm not "happy" unless I'm worrying about something! Is it just me? Anyway, thanks for the rant, and thanks for your excellent input. GA
Quote from: Plymouths on September 25, 2010, 11:31:35 AM
20-25 psi at 40 mph is just fine. It should be about 35 psi at 'cold' start-up and it should hold about 15 psi at idle. If it does I would leave it alone and drive it. ...snip...
Not quite. Or maybe rephrased, it depends on his engine number.
There were three different oil pump/oil pressure relief systems in 1933 with a factory retrofit kit for the middle one which gives you four sets of numbers to puzzle you way through in the parts book. The last one is what they settled with for the next few decades where the flow through the oil filter was shut off if the pressure drops too low. On those and later engines you should have a pretty high (15 to 25 psi) idle oil pressure.
The first iterations are pressure relief only. First on the oil pump cover, then inside the pan and the variation to replace the one in the pan with a different style on the oil pump. Since all the 1933s are fitted with oil filters (a pretty direct path from the oil galley to the sump) and since these early ones have no mechanism for shutting off flow through the filter on low pressure conditions, your hot idle oil pressure can be very low. You should have 30 psi at 30 MPH and ("30 to 40 lbs" at "normal driving speeds").
But they suggest checking the oil filter for blockage at a lower pressure than is possible on later cars: "When the engine is running fast enough to register 10 lbs. pressure on the oil pressure gauge, the return connection on the oil filter should be removed .... A steady flow of clean oil should then be observed..." Basically the idle oil pressure on a early 1933 engine that is hot can be below 10 psi.