7 June 2010
Every engine I've every built, the oil pan eventually leaks. Cork gaskets are the problem. This engine was assembled with nogaskets other than the head gasket and oil pump. I used Right Stuff (by Permatex) exclusively. Here's the assembly process and minor changes I made with the goal of an absolutely leak-free engine.
The oil pan is ordinary enough, but with decent baffling. Too bad the 232/258 isn't this well done. That engine gets air under the pickup in very hard turns.
I bought a new pan gasket and rear pan seal from BEST (brand) but though labelled correctly, it was the wrong part. I ended up re-using the old rear pan seal, which was supple enough, but I used enough Right Stuff to ensure it would not leak.
That nice looking drain plug is no accident. I spent a lot of time getting that right! I bought a magnetic drain plug (thanks Nate for the suggestion), and filed the mating surface perfectly smooth.
The oil pan seals to the timing chain cover at the front, which is of couse 90 degrees from the bottom of the block. This will require a back-and-forth tightening sequence to pull it into place. Easy enough.
The oil pump pickup is supposed to have a little plastic clip that keeps the pickup from touching the pan floor. Even the TSM warns about not losing it. Mine was pre-lost. I solved this by wiring a small block of teflon -- aerospace surplus -- to the pickup. Since I'm not running a pan gasket I was concerned about the pickup hitting the pan. It's close to the teflon block but doesn't hit.
The single biggest change to the oil pan system was replacing all the bolts with studs. Pan bolts seem to loosen with time, I'm sure it's related to shrinking and shifting gaskets, so I did this pan with studs and serrated face locknuts without washers.
I was very generous with Right Stuff around the rear main and seal, if you look closely, you can see that I got it to extrude between the casting and cap, eliminating yet another leak source. The rear pan seal has Right Stuff under and over it.
Here's two of the nuts visible, one on one off. The stud system was cheap, it's just grade 5 hardware from MSC Direct. The pan cannot be tightened yet, the timing cover base plate must be installed and sealed first. This was done within a few minutes of these photos.
The timing cover of this engine is slightly fussy, but nothing serious. This is one area AMC really improved in the new six; all of the little annoyances here were eliminated.
The timing cover is in two halfs; a base plate that bolts to the block and a more ordinary cover. The base plate seals to the oil pan. Pressurized oil passes through the base plate too, and there was a gasket behind it; I simply circled the passageways with Right Stuff and assembled. I did a partial assembly (may or may not be visible in the photos here) so that I could torque up the oil pan before I completed the stuff behind the cover.
I didn't photograph the base plate before assembly, but you can discern which passages flow oil by the intrusion of Right Stuff into the hole which I wiped out before it cured.
When I got it assembled to this stage, I inserted the base plate to pan bolts, tightened them in sequence (pan, plate, pan, plate, ...) up to torque and let it sit overnight.
The timing cover proper was modified to mount the EDIS spark sensor. The 36-1 wheel mounts to the damper with an adapter shown here as a partial blank.
The harmonic damper has an internal seal with a bunch of peculiar parts. This is the correct assembly order. Note that once again, a bead of Right Stuff seals it. It would be an unpleasant place for an oil seep, since the pulley would fling the oil all over the place!
The damper simply slides onto the crank nose, it's not a press fit. The timing cover seal is the same part as the later six right up through the 21st century.
Note that the correct damper bolt is the one with the short shoulder! I forget offhand what the other bolt is for, but it is from this motor. I cleaned all the hardware and small parts and sorted them out at assembly time.
The very existence of these covers I find quite hilarious. What's under them? Nothing! They're a vestige left over from when this was a flathead -- then, the adjustable cam followers were under there. There is no reason to ever take these covers off during the lifetime of the motor. I sealed them with Right Stuff and loctited the covers on. Done and done.
What I thought was a leaking rear seal in the old engine turned out to be this rear cam plug, seeping down the back of the block under the bellhousing plate. It's at the end of the pressurized oiling system, at full gallery pressure. There's an ugly smear of sealer there that looks worse than it is. When I installed the engine, at the last second, I put a bead of Right Stuff in a circle around this plug so that the plate would be an additional oil seal, should the plug leak. I put a piece of tape across it to remind me when I'm flat on my back under the car. I don't expect it to leak in the first place, but this double-fix is trivial to do.
It's a tight fit. A very tight fit. Allegedly the engine and trans goes in from the bottom at the factory. I forged on with a topside install.
The engine has to go in without the flywheel and rear bellhousing plate. (It has to come out that way too.) Torquing the flywheel properly while under the car is no small feat. Even without the junk on the back of the engine, it has to go in initially somewhat diagonally and rotated into place. The timing cover noses under the front brace. It's better if you remove the heater box; I did not and broke the water inlets to the heater core. A hoist with one of those longitudinal mass-shifting jobbies (shown here) makes it fairly easy. Just slow and careful.
I was very paranoid about head sealing. The block deck and head surface were double-checked for flatness (.001") and immaculately clean and degreased. The gasket got three light coats of Permatex Copper, both sides, and I brushed on Permatex Copper around the steam holes. I bevelled holes in the head and block, but there was no sign of thread pulling, but what the hell.
The gasket was coated and allowed to more or less fully dry between coats. I assume that once in place, the solvents in the gasket cement are difficult to evaporate. The final coat was slightly tackier, and with the brushed-on spots around the holes (I mainly did that so that the micro-surface in those areas would be wetted with cement) I'm quite certain it was tight steel-cement-gasket-cement-steel sandwich.
Head installation was actually a bit of an adventure. I did not want to drop the head on the sticky gasket and slide it around to find the bolt holes! My plan to install two studs and use those as guides was foiled by the fact that the thermostat pod needs to be fit under the from fender brace.
The solution was simple. I placed the gasket on the block, carefully aligning the holes by eye. I then used the engine hoist and a chain bolted to the rocker shaft bosses to lower the head within an inch of the block, but not touching. I then ran a couple of head studs down a front and a rear hole, aligned the head wit hone hand while I installed a stud with the other. Then I could just lower the head onto the gasket and block and install the other studs. It was actually easy to accomplish, and the hoist made dropping that fat chunk of cast iron a lot easier than wrastlin'.
Just some semi-random photos of the block. Note that the old drivers-side distributor hole is still there! It met the same camshaft gear, from 90 degrees away.