Flathead Overhaul - I'm Stumped
This is a bit off Hudson topic, but my issues apply to any engine overhaul...
Finally finished the full overhaul on my '40 Cadillac 60 Special late last week.
I got in, hit the starter, and after about 20 seconds the old gal roared to life, running as smooth as can be.. Unfortunately, in less than a minute the engine seemed to be loading down, I tried to give it a bit of throttle, but finally it just came to a halt.
When I tried the starter again, it wouldn't budge the engine. I let it sit 30 minutes or so.. starter turned briskly and the engine cranked right up again... same scenario, ran about a minute, then just tightened up and quit.
I've done this exercise 3 times, with same results each time. It seems as though something in the engine is heating and expanding, and tightening up.
I pulled off the oil pan and heads, removed one piston.. mic'd the piston diameter, it was well within the book specs (.30 over). Then I removed one of the rings, slid it into every cylinder to check ring gap.. pretty consistently .012, at the wider end of the specified range.
Before I assembled pistons and rods, my crank could be turned by hand, so I don't think I have a main bearing issue.
Also, every cylinder seemed to be getting a good supply of oil.. the camshaft was dripping, and all the rod journals seemed to have oil.
I did not check every single rod bearing for proper clearance on initial assembly, so I am going to go back and do that now, but it seems unlikely to me that a tight bearing would heat up in less than a minute with the results I'm experiencing.
Just wondering if anyone else on the forum has ever encountered an issue like this and might have some sage advice?
Phil - Austin
Finally finished the full overhaul on my '40 Cadillac 60 Special late last week.
I got in, hit the starter, and after about 20 seconds the old gal roared to life, running as smooth as can be.. Unfortunately, in less than a minute the engine seemed to be loading down, I tried to give it a bit of throttle, but finally it just came to a halt.
When I tried the starter again, it wouldn't budge the engine. I let it sit 30 minutes or so.. starter turned briskly and the engine cranked right up again... same scenario, ran about a minute, then just tightened up and quit.
I've done this exercise 3 times, with same results each time. It seems as though something in the engine is heating and expanding, and tightening up.
I pulled off the oil pan and heads, removed one piston.. mic'd the piston diameter, it was well within the book specs (.30 over). Then I removed one of the rings, slid it into every cylinder to check ring gap.. pretty consistently .012, at the wider end of the specified range.
Before I assembled pistons and rods, my crank could be turned by hand, so I don't think I have a main bearing issue.
Also, every cylinder seemed to be getting a good supply of oil.. the camshaft was dripping, and all the rod journals seemed to have oil.
I did not check every single rod bearing for proper clearance on initial assembly, so I am going to go back and do that now, but it seems unlikely to me that a tight bearing would heat up in less than a minute with the results I'm experiencing.
Just wondering if anyone else on the forum has ever encountered an issue like this and might have some sage advice?
Phil - Austin
0
Comments
-
Something similar happened with my 57 Willys. Ran out of gas...Michel0
-
Charging issues? Basically running off the battery till there's not enough current to run. Waiting allows the battery to recover a bit, and if your engine starts really easy you might get a few run-stop cycles before the battery is truly discharged. Just a thought.0
-
Well,to me the fact the the engine won't crank after it dies is pretty telling that its not an ignition
or fuel/carb issue. Just guessing that the 40 uses the same(or near same) flathead V-8 that was used in WWII and immediate postwar production. Are you sure you don't have a rod or two in backwards? Assuming that all the rod caps stayed with their respective rods. I'd check rod side clearance on the crank with a feeler gauge before I pulled much more apart. Maybe verify that the starter drive is disengaging after the start also. Please share with us what you find.0 -
Unfortunetly, I've cranked my engine til it wouldn't crank no more... Letting it set for a bit gave me a little more cranking.0
-
Are those new pistons? Ken U-Tx said they are "cam ground" . Pistons that were cam ground were generaly tapered too. The idea being to make them smaller in the skirt by a few tho and as they warm up proper fit will be obtained.
If this is not done or done incorectly I can see how you could have just this problem,
Roger0 -
It's just my opinion, but I think that a piston seizing up on your Cadillac would leave some fairly recognizable galling on a cylinder wall. I recall that back in the '60s my brother did a lazy man's bearing job on an engine in a '55 Pontiac. By that I mean remove the pan, lie on your back under the engine and fiddle with shim stock or next oversized bearings in order to quiet knocks. I should add that a lot of what he knew at that time came from a sloppy,retired Depression era neighborhood mechanic who absolutely lived to cut corners. After he buttoned up the engine, it started and ran fine and didn't slow to a stop, but when he shut it off and tried to restart it, the engine barley turned over and would not rotate fast enough to fire up. After it cooled, it would start again and run fine. (It wasn't a starter issue, something in the engine was clearly seizing). It's been decades so don't recall the outcome, but I think that it got better to the point where it no longer was an issue. But if that was the case, then you know that the overheated bearing and journal was not going to last long before failure. I'm not saying that this is the situation with your Cadillac, but in my brother's case it turned out that he had made a mistake in assessing the tolerances for a bearing. Insufficient clearance caused one specific bearing to overheat and begin to seize. I hope that there's another answer out there for you, but it might be possible that there's a clearance problem with a rod or main bearing. Running it repeatedly until it seizes up may do some real damage to a bearing or a journal. I don't envy you having to lay under it with small pieces of Plastigauge that always disappear before your eyes, but it might come to that.0
-
i am no pro mechanic but i have had ,2 seperate times on different engines, when assembling con rods it just didn't feel right. had slightly more drag than when each other one was tightened down. once i took it apart i saw what happened in each instance. it only takes a bur on the edge or back the thickness of a hair to throw it off. if i get spooked i just pull it apart and check it. plastigage is a hassle and you have to go by feel the second time. hope you get it figured out.0
-
I just want to add to my prior post that it's important to remember that while oil is critical to lubing a bearing, it's vital to cooling it. An under cooled bearing and journal surface will expand quickly into the little clearance that's there to begin with. In some case a faulty oil pump or damaged pick up arm could prevent a sufficient supply of oil to keep the bearings lubricated (and of course cooled). I don't have the time now to look up how the engine lubricating system on your Cadillac works exactly, (babbitt splasher or drilled and pressure fed crankshaft), but double checking the oil pump output pressure with a separate and trustworthy gauge is imperative with any rebuild.0
-
Gentlemen, I only suggested Plastigauge because the engine is apparently in the car. Maybe the plastigauge would indicate some repair that could be made now before having to remove the engine from the car and placing it back on a stand for a postmortem.0
-
Thanks for all that valuable input, most thoughts mirror my own. No, it's definitely not a starter issue, I could barely turn the engine with a bar on the crank pulley. I've got both heads off now, pulled out one piston, removed and checked ring gaps.
Today I'll check all the remaining con rod bearings with plastigauge, if I don't see anything then I'll remove each piston one by one, mic it for size and remove the rings and check each gap.
I've already confirmed that every cylinder is dead-on for size (using a single ring and checking ring gap in each cylinder)
Just hoping I find something definitive today that doesn't involve pulling that engine back out!
Phil
0 -
Hi---It sounds to me like one of the rod bearings is not fitted correctly. Hope you get it straightened out.---Cliff Minard0
-
If you think one bearing is tight ,you said it barely will turn with a bar. Maybe you could loosen each bearing cap one at a time till it frees up. That should be the one with the issue - even if its a tight piston . I dont want to distract from the issue but the motor was unbolted from the transmission. Is there anything in re-installing it that could be in a bind?
Roger0 -
As I said earlier, I am doubtful that the issue is related to pistons and rings, but I've been wrong about things before. If it should happen that you need to remove any or all pistons, though, remeber to check the pistons carefully for cracked ring lands. I imagine that few ring lands would survive the rings seizing up.0
-
Gentlemen, just want to tell you how much I am amazed at all the knowledge you guys collected over the years. This is of a great value for some of us, myself to begin with, who do not have 1/10 of this knowledge. There will never be enough thanks for all the help you provide here! Hope I can learn enough to give back some of it one day. Michel0
-
I know that I'm in the minority here, but I simply disagree that the motor has to be removed to undergo a substantial tear down. What if the problem is as simple a bit of debris behind a bearing shell? Even if that bearing shell looked like it had been quite overheated, it could easily be replaced as long as there wasn't much in the way of damage to the journal. Doc, one of the things about this and other forums that I've been aware of for a long time is that others will strenuously emphasize the importance of doing things the "proper and righteous" way as long as you're the one doing the labor. Don't let them fool you. I doubt if there's a one of them that ever heeds their own advice.0
-
that's the nice thing about these old Caddies... just drop the pan, pull off the two heads and everything is in front of you.
Fortunately I have a 2 post lift so access has been easy.
I've removed every piston, measured diameter, removed every ring and checked ring gap in the same cylinder, pulled all the bearings and checked with plastigauge.. I find no issues with the machine work, and all cylinders, bearings, and camshaft were dripping with oil, so I think there is good supply. All the ring gaps were pretty much a maximum spacing per the Caddy manual, so that doesn't seem an issue, and all the bearings are well within the tightest limit.
There is some question about the taper measurements on the pistons, and there was some evidence of scuffing in several. I'll have a call into the tech support guy at my parts supplier tomorrow, hopefully he can shed some light.
I'll keep the forum posted on the results. Sure am anxious to get this old babe back on the highway!0 -
Have you checked the depth of the rings in the grooves? I've just stripped down an engine that had been overhauled about 30 years ago, and never run. Two of the pistons had no clearance at the back of the groove, and this was causing the pistons to bind. it would have run, but not for long. There should be at least .015" clearance behind the ring.0
-
Did you bore the engine and install new pistons? If so are they stock type pistons.. i knew a fellow once, that bored a 308 hudson engine, and used the "Clifford" solid skirt pistons. BUT the machine shop set them up with stock skirt clearance instead of "racing" clearance, so the engine would lock down when it warmed up. Sounds just like your problem.0
-
Geoff... regarding checking groove depth in the ring lands... someone else suggested that.. how would you go about measuring this?
Thing is, I'm seeing some scuffing on several pistons just below the ring land line and toward the skirt, but just along the thrust line.. about 1 - 1 1/2" wide, so that doesn't look like restricted ring travel?0 -
You measure the ring groove depth and then measure the thickness of the ring. There must be at least .015 relief behind the ring. Also I have seen spring-backed rings with too shallow a groove, and the spring and ring bottom in the groove, causing excess friction. The ring lands also must be .015 smaller in diameter than the piston skirt.0
This discussion has been closed.
Categories
- 36.9K All Categories
- 103 Hudson 1916 - 1929
- 19 Upcoming Events
- 91 Essex Super 6
- 28.6K HUDSON
- 559 "How To" - Skills, mechanical and other wise
- 993 Street Rods
- 150 American Motors
- 172 The Flathead Forum
- 49 Manuals, etc,.
- 78 Hudson 8
- 44 FORUM - Instructions and Tips on using the forum
- 2.8K CLASSIFIEDS
- 599 Vehicles
- 2.1K Parts & Pieces
- 77 Literature & Memorabilia
- Hudson 1916 - 1929 Yahoo Groups Archived Photos