Wood and Steel Posted September 18 Report Share Posted September 18 Hi all, My '51 has been running rough lately, so I figured it was as good of a time as any to do some delayed maintenance. I haven't polished the valves since I've owned the car (7 years or so), so I figured it was definitely overdue. I started by checking the vacuum, and sure enough it was low (16+/-) and fluttery. I also checked compression for the first time while I was at it, and was disappointed to see how low it was. Dry they mesured 85, 90, 77, 50, 75, 80. unfortunitly 50 is not a typo. Wet they all measured between 80-90. Not great news, but it does explain some things. I popped the head off and found a pretty gnarly gouge on cylinder 4. All things considered, it looked pretty clean inside other than that. The motor was replaced at some point in the past. The serial number indicates it's from '56. I have no history on it, but the pistons are marked .03 over. I busted out the micrometer and measured the top, middle, and bottom of every cylinder both in line, and perpendicular. The measurements were surprisingly consistent. The largest deviation was less than .0015. There is virtually no taper on any cylinder. I have no experience with engine cylinders, but that seemed pretty good to me. I can even still see the cross hatches from the last hone job on the front and back of each cylinder, but it is worn off on the sides. I'm sure cylinder 4 really needs a fresh bore, but I just don't have the time or money for that right now. What are my options aside from pulling the motor and having it machined? Would a fresh hone job and new rings help much? I'm sure the gouge is deep enough I won't be able to remove it completely. If it is worth honing, would it be worth honing all the cylinders and changing all the rings, or are the other 5 probably good enough? I also have a spare (locked up) engine from a '53. Would it make sense to get the car back on the road with a weak cylinder and rebuild the spare motor as I have time, or would I be better off investing my time and money on the working engine? Quote Link to comment Share on other sites More sharing options...
Sniper Posted September 18 Report Share Posted September 18 I guess it really depends on your budget and your time frame. Myself I would just put your engine back together and run it as is while I rebuilt the spare. That's essentially what I'm doing Quote Link to comment Share on other sites More sharing options...
Los_Control Posted September 18 Report Share Posted September 18 Just curious what the oil pressure is when running? Will tell you the condition of the bearings. To grind the valves will probably help a lot with compression .... whats a set of rings cost for this engine? While you have the head off, drop the pan and spend $200 for a set of rings .... these old cast iron rings do not last that long. While the compression is low, lapping the valves and a new set of rings will improve it for $200 and you now might drive the car for a few years before installing the fresh rebuilt. I get it, # 4 cylinder has a gauge. This will create a puff of smoke now and then and depending how bad it is .... not be a real problem. No it is not a perfect solution to run it ..... but it is not bad either. For the price of the gasket set, rings, lap the valves .... you can keep running that engine while you rebuild another. Quote Link to comment Share on other sites More sharing options...
Young Ed Posted September 18 Report Share Posted September 18 I think I'd freshen up the valves and see what the numbers are then. While it won't be perfect I bet you can get many years out of it 1 Quote Link to comment Share on other sites More sharing options...
Veemoney Posted September 19 Report Share Posted September 19 15 hours ago, Wood and Steel said: I can even still see the cross hatches from the last hone job on the front and back of each cylinder, but it is worn off on the sides The sides of the cylinder wall are thrust surfaces as the piston goes up and down and also the way the piston is made it will show on the piston skirt in the same locations. 16 hours ago, Wood and Steel said: Dry they measured 85, 90, 77, 50, 75, 80. unfortunately 50 is not a typo. Probably not far off from stock with the exception of number 4 for that motor. Do you drive the car pretty regular or is it possibly cylinder 3,4,5 have some rings sticking issues that may benefit from some seafoam soak or marvelous mystery oil. Since you planned on doing the valves and the head is off proceed as planned and also get the head shaved .050-.060". With your compression numbers the head is likely never been cut and that will bump the compression up across all the cylinders. 16 hours ago, Wood and Steel said: I popped the head off and found a pretty gnarly gouge on cylinder 4. Where on the cylinder is the gouge? If it lines up with the wrist pin then I would be concerned otherwise carry on. Quote Link to comment Share on other sites More sharing options...
keithb7 Posted September 19 Report Share Posted September 19 (edited) The gouge in the cylinder wall is a permanent scar from an earlier injury. There is no cheap simple fix that I know of. Oil and combustion gasses will get around your piston rings, through that gouge void. New piston rings won’t help. A lower priced repair could mean boring out the bad cylinder and inserting a sleeve. Won’t be easy or that cheap honestly. Rebuilding the spare engine will be best, but pricey. Be prepared. Machining costs were among my biggest expenses in rebuilding my engine. I also agree with other comments here about lapping the valves and putting it back together. Milling the head .040 or so will increase combustion, but also have a larger effect on oil consumption and crankcase blow-by gases. I don’t think I’d mill the head at this point. Take your time and rebuild the spare engine. As time and money allow, progress slowly. Strip it right down and send the block in to a machine shop. Hot tank it. Get all machining performed as needed. New valve guides too. Then build it up from there. It is a ton of fun and extremely rewarding. Budget $4K USD or so when doing the rebuild yourself. If you wanna do it right. Edited September 19 by keithb7 Quote Link to comment Share on other sites More sharing options...
JBNeal Posted September 19 Report Share Posted September 19 (edited) Sometimes them combustion chamber imperfections can fill up with carbon, kinda like a scab on an open wound...not the best sealing surface for piston rings, but can substantially reduce blowby enough that the extra oil changes per year would still be cheaper than extra machining, and with less downtime Edited September 19 by JBNeal typo corrections Quote Link to comment Share on other sites More sharing options...
Wood and Steel Posted September 19 Author Report Share Posted September 19 18 hours ago, Los_Control said: Just curious what the oil pressure is when running? A hair over 40 at idle, 50+ at anything above idle. 3 hours ago, Veemoney said: Do you drive the car pretty regular... Where on the cylinder is the gouge? If it lines up with the wrist pin then I would be concerned otherwise carry on. It's rare that it sits more than a day or two. It's my daily driver unless I need my truck or weather prohibits. The gouge is on the front of the cylinder (towards the radiator). It seems like it might be a little worse at the bottom, if that's relevant. 1 hour ago, keithb7 said: Take your time and rebuild the spare engine... It is a ton of fun and extremely rewarding. It's honestly a project I've been looking forward to eventually. Thanks in large part to your videos, by the way. The timing is just never right, of course. What rings would you guys recommend? It looks like I can get Hastings or Sealed Power from RA for a reasonable price. Is there a better source? I assume I'd just want plain old cast rings, given the circumstances? How much over can I hone the cylinder? I know honing is a slow processes, but I could order some coarse stones. Right now the piston is marked .03 over but I haven't measured it. The cylinders all measure right around .281+/-. Quote Link to comment Share on other sites More sharing options...
Veemoney Posted September 19 Report Share Posted September 19 Devil is in the details. You haven't provided any details on what you're calling a gouge. A picture and measuring the length width and depth would help since you provided mic readings for the bores but nothing for the gouge to determine if this is more of a scratch than a gouge. Based on the wet compression numbers coming up to match the other cylinders I assumed it to be not so bad and could be used as is. If you decide to hone it measuring the depth will help determine how much you would need to hone to clean up (figure twice the depth of the gouge if it works out evenly during honing), The hone finds the best center for what is left there. Once the head is milled it could be swapped to the other motor if down the road you decide to rebuild that one. Also the cam profile is likely better to in the motor your running. Quote Link to comment Share on other sites More sharing options...
Los_Control Posted September 19 Report Share Posted September 19 6 minutes ago, Wood and Steel said: What rings would you guys recommend? It looks like I can get Hastings or Sealed Power from RA for a reasonable price. Is there a better source? I assume I'd just want plain old cast rings, given the circumstances? How much over can I hone the cylinder? I know honing is a slow processes, but I could order some coarse stones. Right now the piston is marked .03 over but I haven't measured it. The cylinders all measure right around .281+/ I would suggest the cast rings and your sources are fine. I believe you really do need to grind or lap the valves .... use to be a simple test to rotate the engine until the valves were closed .... then pour some gasoline around the valves and watch to see if the gas leaks past the valves. .... good seating valves are air tight and should not leak past .... Very unscientific, but will tell if you do have a problem and which ones. I figure replacing the rings now for 2 different reasons .... As you said they are reasonable .... all but one cylinder is in good shape. I want to know why that cylinder has a gouge in it ..... If it is a loose wrist pin that the clip broke and the pin is causing it .... you want to fix that now. If it is a ring that broke and caused the damage, it can continue to break and cause more damage. Pulling that piston for inspection is the only way to find out. Or it is possible the gouge has always been there and you're just now finding it because of the valves leaking? One thing I'm confused on is the .03 stamp on the pistons. ..... I first assumed it was a typo and meant .030 .... maybe that is a shortcut for 30 over pistons? Quote Link to comment Share on other sites More sharing options...
dpollo Posted September 28 Report Share Posted September 28 I would not normally recommend this BUT it will do no further harm to hone and reassemble the cylinder with the score. If, as my experience has proven, the engine runs well then it will likely give good service. 1 Quote Link to comment Share on other sites More sharing options...
Wood and Steel Posted October 10 Author Report Share Posted October 10 Sorry for such a long delay on updating this thread. A medical emergency pulled me away from it for a while. I'm back to work on it now. I've lapped all the valves and I'm starting on honing the cylinders now. Unfortunetly one of the valve keepers from cylinder #6 vanished on me. I'm hoping it turns up, but I've spend quite a bit of time looking for it already. On 9/19/2024 at 2:30 PM, Los_Control said: If it is a loose wrist pin that the clip broke and the pin is causing it .... It was indeed a loose wrist pin. Here's a picture of the damage after quite a bit of honing: I think I'll be able to remove the smaller scratches that are faintly visible, but there's no way I can grind it enough to get rid of the two large gouges. Quote Link to comment Share on other sites More sharing options...
JBNeal Posted October 10 Report Share Posted October 10 Maybe it's time to invest in a PCV system to harness them blowby fumes and route them back into the charged air stream, reassemble the engine, and see if that does the trick 🤔 Quote Link to comment Share on other sites More sharing options...
Los_Control Posted October 10 Report Share Posted October 10 Well whip my britches and send me down the road as a tramp hillbilly .... I probably should be black listed from the forum for this suggestion. What is the downfall of filling the grooves and honing the cylinder? They make some really good epoxy now days, choose the best .... do a clean job and a proper hone to make the old cast iron rings seal. Whats going to wear first .... the cylinder, epoxy, or rings? You can pull the engine and spend $$ to have it rebuilt, or spend $20 and fix it yourself .... might last a year or 20 years .... who knows? Future damage would be no more worse then it is now. If it fails in the future, would lose compression and start burning oil on 1 cylinder .... not the end of the world, you will make it home. These old engines are nothing more then a old Briggs & Stratton lawn mower engine .... they have 5 extra cylinders. Not like if the repair failed you would never be able to fix the engine correctly .... would be right back where you started .... all cylinders needing to be bored out. Just saying! Quote Link to comment Share on other sites More sharing options...
keithb7 Posted October 11 Report Share Posted October 11 Lol. The Briggs & Stratton was merely a stripped down single cylinder Mopar flathead engine with no pressurized lubrication system, silly. 1 Quote Link to comment Share on other sites More sharing options...
bacelaw Posted October 11 Report Share Posted October 11 This forum is the best. It's a spectrum if you ask me - there's a perfect rebuild on one end, a ring and valve job on the other, and everything in between. From everything I've read, I bet with new rings that motor outlasts all of us. You have good oil pressure, decent compression, and you don't want to pull the motor - so try to repair that cylinder wall, new rings, seal the valves better and do the PCV upgrade. Drive and smile while you rebuild the spare. Quote Link to comment Share on other sites More sharing options...
Veemoney Posted October 11 Report Share Posted October 11 On 9/19/2024 at 9:21 AM, Veemoney said: Where on the cylinder is the gouge? If it lines up with the wrist pin then I would be concerned otherwise carry on. I was afraid of that as well. Now by trying to fix one problem you will be creating another. Meaning to clean up the scratches and lines in the cylinder your opening up the bore size to a point your piston has to much clearance all around and you will then have some piston slap and poor ring seal. Best check your bore size and piston size before moving forward to see what cylinder wall clearance you have at this point. Quote Link to comment Share on other sites More sharing options...
Young Ed Posted October 11 Report Share Posted October 11 Here is some real world experience. Dad got a 50 coupe. Somewhere he found a decent engine. When we took it apart water had gotten into #6. The machine shop gave him used pistons that someone had put new rings on only to discover they needed an overbore. I don't recall if we used those or transferred them to the existing pistons (I feel transferring them is more likely)but either way it got honed and new rings. That cylinder still has deep pits from the rust but it ran perfectly except for a little smoke. So if I was in your shoes I'd make sure the pin won't hit the wall again and run it. Quote Link to comment Share on other sites More sharing options...
soth122003 Posted October 12 Report Share Posted October 12 On 10/10/2024 at 6:11 PM, Wood and Steel said: I think I'll be able to remove the smaller scratches that are faintly visible, but there's no way I can grind it enough to get rid of the two large gouges. Being visible and interfering with engine operation are two different things. The 2 large grooves will be a very light problem IMHO. The light scratches can probably be honed out. The large ones however? You didn't list the depths of them. If more than .006" then bore the cylinder. .005" or less, put it back together and run it. The oil will partially seal them and the blow by will be minimal because they are under the rings at full compression. Also you didn't state the valve condition on that cylinder before cleaning. Was it sealing good or not? Between the valve job and honing and new rings (or old rings if they are still good) I'll bet that compression will come up pretty good if the cylinder grooves aren't that deep. You had 50 psi before on that cylinder right? or was it a different one? Just my thoughts on your situation. Joe Lee Quote Link to comment Share on other sites More sharing options...
Dartgame Posted October 16 Report Share Posted October 16 My chemistry lab experience working with epoxies tells me I'd hesitate to use an epoxy in this situation. Epoxy will burn at 350F; lower than the temps inside a cylinder. Quote Link to comment Share on other sites More sharing options...
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