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cracked piston
Posted by: Gleason (IP Logged)
Date: June 18, 2006 03:00PM
<HTML>Hi,
I wrote in last fall about the poor performance I was having with my 735 Stanley. After spending the winter refurbushing the empire burner I was hoping that I had fixed the problem.
After taking it out a couple of times this spring I found it still lacking in performance, only slightly improved from before. I put a therocouple on the steam line to the engine and was getting good superheat when the pressure was high (500-550 psi; 650-750 f).
When I parked the car I opened up the drain valve on the feed water heater in the exhaust, set the brake and cracked open the throttle with about 200 lbs in the boiler, just got a pronounced hiss out of the drain valve. Previously I had noted that Steam would come out the condenser with the cap removed and the brake set. Figured there must be blowby past either the valves or the rings, so pulled the engine ( I was pretty sure the valves were OK because I had checked them last year).
Anyway I unscrewed the cylinder caps and found one of the pistons slightly loose, I could rotate it on the shaft about an 1/8 turn. When I put the engine on end liquid leaked past the piston ( not really fast but more so than the adjacent cylinder). So, I removed the retaining nut (alarmingly easy to do!) and unscrewed the piston. It seems to be in good shape with an intact ring, the cylinder bores are pretty smooth with just a little rust pitting. Then I looked at the inner piston and it was cracked completly in half as was the ring!
I guess this was the cause (I hope ) of the poor performance. It looks like there is no damage other than the piston and ring.
Now I need to know what caused the break, was it from the 2 pistons not being tight together, or just metal fatigue?
Does anyone make replacement pistons and rings for a 740 engine?
What is the best way to get the rest of the cylinder block apart (the treads are "staked" on the engine rod ends) so I can look at the other set of pistons?
Thanks, Eric</HTML>
I wrote in last fall about the poor performance I was having with my 735 Stanley. After spending the winter refurbushing the empire burner I was hoping that I had fixed the problem.
After taking it out a couple of times this spring I found it still lacking in performance, only slightly improved from before. I put a therocouple on the steam line to the engine and was getting good superheat when the pressure was high (500-550 psi; 650-750 f).
When I parked the car I opened up the drain valve on the feed water heater in the exhaust, set the brake and cracked open the throttle with about 200 lbs in the boiler, just got a pronounced hiss out of the drain valve. Previously I had noted that Steam would come out the condenser with the cap removed and the brake set. Figured there must be blowby past either the valves or the rings, so pulled the engine ( I was pretty sure the valves were OK because I had checked them last year).
Anyway I unscrewed the cylinder caps and found one of the pistons slightly loose, I could rotate it on the shaft about an 1/8 turn. When I put the engine on end liquid leaked past the piston ( not really fast but more so than the adjacent cylinder). So, I removed the retaining nut (alarmingly easy to do!) and unscrewed the piston. It seems to be in good shape with an intact ring, the cylinder bores are pretty smooth with just a little rust pitting. Then I looked at the inner piston and it was cracked completly in half as was the ring!
I guess this was the cause (I hope ) of the poor performance. It looks like there is no damage other than the piston and ring.
Now I need to know what caused the break, was it from the 2 pistons not being tight together, or just metal fatigue?
Does anyone make replacement pistons and rings for a 740 engine?
What is the best way to get the rest of the cylinder block apart (the treads are "staked" on the engine rod ends) so I can look at the other set of pistons?
Thanks, Eric</HTML>
Re: cracked piston
Posted by: Ben (IP Logged)
Date: June 18, 2006 05:04PM
<HTML> Hi, Drill out the stake marks,,,chances they are of marginal use,,and back off the nuts,,,clean up the threads w/a small 3 corner file or the like,,,, Now pull the block right off , [ after disconnecting the valve rods ] ,, The bigger problem is that PROBABLY the pistons have been off before,,,and the piston threads were dammaged at that time,,,,,,Nergaard has written on this I believe,,,,make a top hat bush for the piston,,steel to steel will be better anyhow,,,Still keep looking for the problem,,,I don't think all that much steam could leak past the ''good'' piston,,, How much is the performence off ??? Did the broken piston score the block??? Boy,,,you got to that one just in time,,,Was there any sound,,,,It is my opinion that steamers do not give much audible warning of impending doom,,,,Good luck,,,,Ben // oh yes check for bent parts,,ie/ crankpin,,piston rod,,,anything that could be a casualty of a water slug,,,CB</HTML>
Re: cracked piston
Posted by: gleason (IP Logged)
Date: June 19, 2006 01:17AM
<HTML>Well,
Thanks for the advice, got the block loose and apart except for one of the back side cylinder heads, I will let it soak some in penetrating oil for a while. The staking did not scew up the threads so things should go back together with out too much trouble. Do folks just use locktight these days?The other pistons seem to be in good shape and still tight on the rod.
The bores look pretty good, just a little bit of rust pitting. The valves are still in place so havn't yet checked the seats although they seem to be in good shape.
So, does anyone know where to get a replacement piston and ring?
Thanks, Eric</HTML>
Thanks for the advice, got the block loose and apart except for one of the back side cylinder heads, I will let it soak some in penetrating oil for a while. The staking did not scew up the threads so things should go back together with out too much trouble. Do folks just use locktight these days?The other pistons seem to be in good shape and still tight on the rod.
The bores look pretty good, just a little bit of rust pitting. The valves are still in place so havn't yet checked the seats although they seem to be in good shape.
So, does anyone know where to get a replacement piston and ring?
Thanks, Eric</HTML>
Re: cracked piston
Posted by: Howard Randall (IP Logged)
Date: June 19, 2006 12:35PM
<HTML>Try Howard Johnson in Lamont , IL
630-257-5783
Howard Randall</HTML>
630-257-5783
Howard Randall</HTML>
Re: cracked piston
Posted by: Ben (IP Logged)
Date: June 19, 2006 06:58PM
<HTML>Locktite is temperature sensitive,,,,thats how you get it apart,,,, Did the engine make any funny noise, last time it ran??,,,Cheers Ben</HTML>
Re: cracked piston
Posted by: gleason (IP Logged)
Date: June 20, 2006 04:33AM
<HTML>There was no noise that I noticed, it did squeak a bit at low speed under stress but I think it has done that as long as I have owned the car. Who knows the piston could have been cracked when I bought the car, I have only put a couple of hundred miles on it. There was no knocking, with the wheel jacked up and the throttle just cracked open the engine ran fairly smoothly, maybe just a bit of variation in speed from one stroke to the next.
Anyway, hope to get her back together, will have to clean things up some, check the valves and seats, etc.
Thanks, Eric</HTML>
Anyway, hope to get her back together, will have to clean things up some, check the valves and seats, etc.
Thanks, Eric</HTML>
Re: cracked piston
Posted by: gleason (IP Logged)
Date: June 28, 2006 03:14AM
<HTML>Well I have a new old piston on the way thanks to Alan Kelso. Today I finally got around to taking the valves out and looking at them, they were pretty well pitted with just a bit of scoring. Is it just that the castings are fairly porus or is all the pitting due to rust? Anyway just got a start on cleaning them up. The valve faces on the block look really good. Can you use valve grinding compound for the final polish to get them to seat just right?
Thanks, Eric</HTML>
Thanks, Eric</HTML>
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