Well, my '36 made the trip back to it's old homestead about 160 miles away with no issues. We got to drive Grandpa around some but Grandma wouldn't even try to get in. My father and aunt drove it as well, both feeling like little kids as they hadn't been in the car since '59. All went well on the way home until we got about 20 miles from the house when something let go in the engine. #4 piston now has a hole and a missing section of ring land. It looks like the light noise I'd been hearing for a while might have been detonation on that cylinder. I should have caught it but honestly, I just never expected that issue with the low static compression ratio. Now I'm disassembling the engine and I have a few questions.
How are the retainers for the front hood lace bent over so nicely? Some of them have to be bent after the radiator is installed but what tool is used? Can it be bought today?
Is the D shaped water distribution tube normally a loose fit in the block? This one looks like it's in good shape but it rattles around in the block pretty good.
The pistons have the original mopar logo, the letters APR, the number of the cylinder they're installed in, and a single letter between A and C. Is there a reference that explains the letters? In my experience this typically represents factory sizing but I didn't see this in the maintenance manual. The engine number does not indicate oversize pistons or undersize bearings for this block. Of course, once the piston is out I'll be able to measure it directly but I'm curious just the same.
What are the odds that I can remove the valve springs while the block is in the car? If the rods and mains look ok I don't want to pull the engine out but it does make sense to replace the valve springs and touch up the valves and seats, and if needed replace guides.
There were 4 "undercut" studs for the head in seemingly random places. Is this a case of Plymouth using whatever was around or should I suspect that someone has already replaced the head gasket?
TIA.
Shannen
Can't answer all your questions but maybe help on a couple.
Having the top ring land break and then getting a piece of the now broken ring between the piston and the head seems to be a fairly common failure mode. One theory I've heard is that if there is even a slight ridge at the top of the cylinders and you drive it at a little higher RPMs than that ridge was formed at then top ring hits the ridge and can break. Once the engine is overhauled then it should not reoccur.
On my '33 the split brass rivets holding the hood lacing can be set using hand tools like a flat bladed screw driver and pliers. Turns out there is enough slack in the hood lace to get in and set the rivets with a lot less effort than you'd expect.
Don't know about the fit of the water distribution tube, '33 and '34 don't have it. But I've heard horror stories about them getting rusted into place so it seems they might be a close fit.
I don't know if the factory inspector numbers were documented. Might be due to weight rather than diameter...
Not sure on the '36 as the fenders are higher, but on the '33 once you remove the manifolds you can get the L-head spring compressor in and remove all the keepers, valves and springs with the engine in the car. Be careful not to drop the keepers through the holes into the pan.
No idea about the under cut on the studs. I don't recall that at all on my '33.
Interesting theory on the pistons. After reading it I got curious enough to go out and pull #4.
This engine appears to be in very good shape other than the broken piston and some scuffing on the #4 cylinder wall. Cylinder diameter is 3.128" with no ridge. The rod bearing is serviceable should I want to reuse it. Piston clearance where I could measure it was .020". I fully expected to find carbon in the ring grooves but everything was clean and even the sludge buildup is small. The broken section of the piston was under the quench area in the head which, combined with the carbon on the piston, leads me away from detonation as the primary cause. I have a couple of ideas about what happened but I'm going to do more checking to see if I'm on the right track.
It is not uncommon for these engines to suffer that type of failure. And other than when a hole gets poked through a piston, run for many miles this way. I have seen as many as four pistons with broken rings, broken lands, and sections of rings missing, Probably blown out the exhaust.
Detonation can take more than just the common form of spark knock or pinging from timing that is too advanced. It can happen with out any audible symptoms, especially if there is carbon deposits which can end up in a piece acting like a glow plug in a diesel. Todays fuel mix can also contribute to the situation. It can result in a combination of flame fronts, one lit by carbon and the other ignited by the plug. When the fronts colide, much like a warm front and cold front colliding in weather, bad things can happen. Over pressure from the collision plays hell with the piston top, but does not caus the knock associated with the piston still travelling up while the flame is trying to push it down.
With your observation of carbon build up, this might be the cause of your damage.
A lean mixture from a vacuum leak between the manifold and block can also cause a situation where the flame front is fast and more violent than ignition in a cylinder with a richer fuel air mix. this also hammers at the top of the piston. A lean mixture also burns hotter which can hasten metal fatique.
Shannen,
I looked up your post from a while back, where you said that you had been driving your '36 at 60-62 mph for 1/2 hour. My '36 has the original 201 cubic inch engine and the original 4.12 rear end and 114000 miles. If I drive it above 50-52 mph, it starts to sound unhappy. Just a thought.
Pat O'Connor
I had a slight knock, but drove it carefully for a couple months (1939 Plymouth 201 ci.) I finally got parinoid enough waiting for something to happen and tore the engine down, I had a broken land between two rings. Still parinoid enough, I replaced all the pistons, figured if one broke the others were not far behind. lol My cylinder walls were perfect also and the rod and main bearings, however I did take the block and crank to the machine shop to clean out the block and polish up the crank, with new rings, cam brgs, rings, Rod and Main brgs, worked over the valves, I now have the engine back together, Started it for 5 seconds, long enough to have the fuel pump spewing gas out the side. Now I am waiting for a fuel pump before I start it again.
With .020 clearance on your pistons is quite a bit, you can have the skirts knurled if you don't want to replace them, knock out a couple soft plugs to see how much crap is in the water jacket (mine were plugged up pretty solid) might as well do the new brgs also if you have it this far pulled down. lol Never ending on these ole girls. Good luck with yours.
SD Glenn
This car has 4.12 gears and although it has 17" wheels the current tires are smaller than original. I've calculated rpm at the speed I was driving to be 3400 to 3600. Yes, it's very high and I have no doubt that it contributed to the failure. The return trip consisted of over an hour on "high speed" roads with engine temps running a tad warm and I will accept full responsibility for setting this engine up to fail. I am keeping an eye open for a differential carrier with numerically lower gears. If I'd realized this was a common failure I might have opted for a slower trip home and some extended cool down periods along the way. But the devil's advocate reminds me there are many modern small displacement engines that will withstand this kind of rpm. So, provided I can understand the situation, I may be able to make changes to prevent future occurrences.
Unfortunately for me, if I identify a problem I feel driven to understand it and find a solution. :(
The piston clearance was measured just below the lower oil ring. That's the only part of the piston where I can get a measurement. Clearance is spec'ed at .005" at the skirt, all the way up to .022" at the crown. Since pistons are tapered this measurement seems within limits. It's not the correct place to measure but it's a good enough to get a rough idea about "OK" or "too big" which was my goal.
SD Glenn, now you've gone and scared me. I'm planning on pulling all the pistons but I'd fully expected to find no damage. I guess I'm going to have to prepare myself before pulling the rest of them. As far as cooling system corrosion I've already flushed a bunch of junk out of the jacket and radiator prior to the long trip but I'm sure you know it's a long, drawn out task to get everything so I'm going to try using a suction device to pull out more while the head is off.
I'm backing off my initial theory that detonation was the main issue. I didn't find any of the usual suspects in place. The piston top wasn't cleaned off, the carbon on the head and piston didn't show any indication that it had been hot and glowing, the plug was seated properly and the ground strap wasn't discolored. There is a hole in the piston which often occurs as a result of detonation but the scuff marks on the sides of the piston at the skirt and in the cylinder bore tell me there's probably more to the story. Unless something indicates I should do otherwise, I'm going to treat this as a simple problem which hasn't been investigated properly.
In '37 Plymouth bragged about how cool the oil remained due to the large water jacket and they were proud of their engines' reduced oil consumption. Sustained driving at "high speed" with modern fuel is likely to heat the piston considerably but the block tends to stay cooler. The only way for heat to exit the piston is through skirt/cylinder wall contact, piston/ring/cylinder wall contact, and through engine oil if the squirters in the rods are oriented to direct oil at the piston. I'm currently looking at this with an eye toward insufficient clearance for operating conditions due to unplanned heat accumulation in the piston. Although the high side clearances on the rings and pistons seem ok compared to modern engines, the minimum specs seem a bit low. Other engines with similar bores have minimum ring end gaps in the .010" to .012" range and higher. Piston clearance of .022" at the top may be ok but what happens to .005" when this piston gets hot? And if the ring end gap is pretty close to zero at that time, all it takes is a small ridge or bump from metal transfer on a cylinder wall to butt the ring ends then pop! Lost a land.
FWIW this is just a theory that I'm working with for my car. Please don't think I believe I'm some kind of miracle worker. I'm just looking at my car and asking questions to try and make it more reliable.
BTW Glenn, I think you've got a lot of determination judging by the fight you've had getting your car back together.
Sounds like you are being thorough and I'm sure you will come to a satisfactory solution.
Quote from: 1project2many on July 31, 2012, 08:21:49 PM
This car has 4.12 gears and although it has 17" wheels the current tires are smaller than original. I've calculated rpm at the speed I was driving to be 3400 to 3600. Yes, it's very high and I have no doubt that it contributed to the failure.
What size tires are on your car? With my 17-5.25/5.5 tires and 4.375 final drive I figure 3200 RPM is 62 MPH.
Quote from: 1project2many on July 31, 2012, 08:21:49 PMAs far as cooling system corrosion I've already flushed a bunch of junk out of the jacket and radiator prior to the long trip but I'm sure you know it's a long, drawn out task to get everything so I'm going to try using a suction device to pull out more while the head is off.
If you pop off the core/welch/freeze/expansion plugs on the side of the block you'll have a much better chance at getting the sludge out of the water jacket...
QuoteWhat size tires are on your car? With my 17-5.25/5.5 tires and 4.375 final drive I figure 3200 RPM is 62 MPH.
The tires on the car now are T135/90D17s. They're a 782 rev/mile tire at full inflation but I'm only running at 45 psi. Rolling circumference is under 80" and revs/mile works out to 797. 65 mph equals 3560 rpm.
Tod has this right, I pulled all the side soft plug, dug around with probes and got a lot more out. (I did the flush thing first) I figured it would be easy to just replace the soft plugs, and it was easy. This was before I pulled the engine. After pulling the engine and removing the rear soft plugs, things were packed solid around the back side of number 6 cylinder, I don't understand why the cylinders weren't completely melted down. Take care,
SD Glenn
Quote from: 1project2many on August 01, 2012, 12:45:41 AM
QuoteWhat size tires are on your car? With my 17-5.25/5.5 tires and 4.375 final drive I figure 3200 RPM is 62 MPH.
The tires on the car now are T135/90D17s. They're a 782 rev/mile tire at full inflation but I'm only running at 45 psi. Rolling circumference is under 80" and revs/mile works out to 797. 65 mph equals 3560 rpm.
Interesting, it never dawned on me that a tire designed for spare use on a SUV could fit on antique 17" wheels. On the other hand, I'm using 17" motorcycle tire tubes as the most readily available tube with a center line valve stem so I guess other alternatives to the usual antique car suppliers should have occurred to me.
Finding mounted tire diameters for those is not as easy as for the normal use tires. I did come up with a diameter of 26.5742 which works out to a bit under 83.5" circumference which makes your RPMs a bit less for 65 MPH. Not sure if the number I found was accurate though.
I was using this reference for the tire:
http://simpletire.com/goodyear-t135-90d17-818052253-tires
The tire is recommended for a 4" wheel and mine are near 3 1/2". These tires are already designed to have a high center rather than a flat contact patch and the narrower wheel tends to aggravate that. I actually measured rolling circumference before and after adjusting tire pressure to try and gauge deformation.
The motorcycle tubes are working well? I thought of using them but the bike guys didn't think they'd last.
QuoteTod has this right, I pulled all the side soft plug, dug around with probes and got a lot more out. (I did the flush thing first) I figured it would be easy to just replace the soft plugs, and it was easy. This was before I pulled the engine. After pulling the engine and removing the rear soft plugs, things were packed solid around the back side of number 6 cylinder, I don't understand why the cylinders weren't completely melted down.
I'm really trying to limit how far I tear this engine down but if I can't get it clean enough I'll pull the core plugs. The suction tank has hard plastic hoses that are small enough to get around the cylinders. It will probably take more time to do this than pulling the plugs but if you saw how many projects I've got going right now it might make more sense. What I'd love to do is get it back together so it's usable then in a couple of years pull the engine and do a real thorough job of freshening it up.
BTW, have you guys noticed wires or small diameter rods left in the water jackets? Both the block and head have these. I'm guessing they're left over from the original molds.
Quote from: 1project2many on August 01, 2012, 08:53:34 AM
I was using this reference for the tire:
http://simpletire.com/goodyear-t135-90d17-818052253-tires
Wow! Those are more expensive than some of the antique brand tires for the 17" rim.
Quote from: 1project2many on August 01, 2012, 08:53:34 AMThe motorcycle tubes are working well? I thought of using them but the bike guys didn't think they'd last.
So far, a few years and a few thousand miles, okay. Only issue has been that the valve stem leak a little on some of them so I need to check/fill the tires more often than I'd like.
Quote from: 1project2many on August 01, 2012, 08:53:34 AMBTW, have you guys noticed wires or small diameter rods left in the water jackets? Both the block and head have these. I'm guessing they're left over from the original molds.
I haven't seen that in my engine but I understand that it is fairly common to find those and, yes, my understanding is that they are the remnants of the wires used to hold the sand core in shape and/or in place when casting the parts.
Re; the water distrib tube, the one I've got for my '36 I believe is zinc plated or galv. metal . Have seen one made of a brass or bronze looking alloy but can't remember where I saw it and not sure if it was stock or aftermarket.. There is some info. in the repair manuals about how to get the old one out with a hooked rod, etc..and suggests to replace the tube every time a rebuild occurs. I've seen a couple that were corroded almost as bad as a domestic water heater anode!
Also, I have 17" Firestone tires on my car with tubes obtained some years ago from Coker or Lucas tire companies (not sure which). They may still carry them.
Good luck with the rebuild.
Yes, those tires are expensive new. If you go where the supply is high and demand is low the price is better. I had four shipped in from a junkyard Michigan and the total price was $43.75 each. Source vehicle was a 2004 Ford Five Hundred. There's a larger 17" compact spare that's a better match but I only found those tires on Honda SUV's and ford Mustang Cobra's so the pricing was not as good. I do hope to put correct reproduction tires on one of these days.
Progress report of sorts. The machine shop returned the cylinder head after machining .010" off. The NOS Mopar piston and replacement rings has come in. The piston appears to be a later design with different relief slots and different size rings but I won't sweat the small stuff at this point. My friend at the machine shop thinks I'm over engineering this because he's got plenty of these old engines on the road without doing anything special for clearance or heat reduction. But when asked he admitted that he only uses new pistons on rebuilds and follows the piston and ring manufacturer's guidelines for clearance. As an aside, when I mentioned paying $35 for a piston he informed me he had a set of pistons made for a Customer's Packard which cost $150 each. Ouch! Rings from the broken piston have marks on the end which may have been from the ends butting, but also may have been from loose parts floating around. As the other pistons come out I'll check those rings as well. I've got a dial indicator and valve spring compressor here so I'll be checking the guides once the pistons are out then pulling the valves for inspection. As long as no other major projects come up I might have this back together before the end of August.
Quote from: 1project2many on August 02, 2012, 11:55:18 AMThe NOS Mopar piston and replacement rings has come in. The piston appears to be a later design with different relief slots and different size rings but I won't sweat the small stuff at this point.
In my younger and poorer days I attempted to replace just one piston. It came in and was, like yours, a different design. Which in itself I did not care about. However the weight was significantly different than the one it was to replace. There was no way to adjust the weight of the new piston to match the old ones: Way too much material would have had to be removed to balance it. In the end I got a complete set of new pistons. Even then the weight variation was beyond the original specification and I had to get them balanced out.
I lucked out with my pistons, they were the newer sloted type however, they wieghted out good. I had a problem with the Rod and Main Brgs, even packed in the NOS cosmolien they had rust corrosion on the back sides, I had the machine shop polish them out for me, they thought that would be OK.
I have my 39 engine running, sounds great. I went to the paint shop and brought my fenders and front clip home. He has had it for 2 months and not even started... lol . I am going to install these back on the car, think I will just run the original pattena throught the rest of this year, and maybe paint it myself this winter. lol I wanted to get a few miles on the engine before winter.
Good luck with your engine, I'm finally happy with mine.
SD Glenn
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