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Message |
    
polarcreator
New member
Username: polarcreator
Post Number: 1
Registered: 11-2016
| | Posted on Wednesday, November 16, 2016 - 04:15 pm: | 
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Looking for a piston .30 oversize for 4hp St Lawrence engine company marine engine.Anyone with ideas on where to find one. |
polarcreator
New member
Username: polarcreator
Post Number: 2
Registered: 11-2016
| | Posted on Wednesday, November 16, 2016 - 08:25 pm: |
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The serial number for this engine is 7816. Only the first leter of the model number is there. X. It has one piece manifold and lever Ignition. |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 1257
Registered: 07-2002
| | Posted on Wednesday, November 16, 2016 - 09:05 pm: |
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What's the bore on your engine? I have a pattern and core box near completion for the larger engine, I believe it's 3 1/2" bore, it's been a while since I worked on it. |
polarcreator
New member
Username: polarcreator
Post Number: 3
Registered: 11-2016
| | Posted on Wednesday, November 16, 2016 - 09:43 pm: |
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The bore was 3.252 but the machine shop bored it 30 thousand over. The current bore is 3.282. |
robert
Senior Member
Username: robert
Post Number: 800
Registered: 07-2003
| | Posted on Thursday, November 17, 2016 - 01:04 am: |
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Sleeving the bore to match the existing piston would be another option perhaps. Or better yet, sleeve to .025 or .050 under standard so that if the piston needs to be replaced in future a standard or even slightly worn piston could be used. |
polarcreator
Member
Username: polarcreator
Post Number: 4
Registered: 11-2016
| | Posted on Thursday, November 17, 2016 - 01:13 am: |
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The cost to sleeve the engine would run $450 to $550.00. If I can't find a piston I will be doing that. Making it under might allow me to turn down the existing piston and use it. Thanks for that advice. |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 1258
Registered: 07-2002
| | Posted on Thursday, November 17, 2016 - 04:08 am: |
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Here's a link to cylinder sleeving, since it's bored I would try to get a piston. Is yours aluminum or cast iron?
http://www.oldmarineengine.com/discus/messages/5/3051.html |
polarcreator
Member
Username: polarcreator
Post Number: 5
Registered: 11-2016
| | Posted on Thursday, November 17, 2016 - 07:17 am: |
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My piston is aluminium and has four ring three at top and one down at the bottom.Can't seem to find a custom machining place to make one. Has anyone ever tried finding a larger piston and turning it down to size. Is the piston length crucial.It seem that all pistons the right size are way to short. |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 1259
Registered: 07-2002
| | Posted on Thursday, November 17, 2016 - 08:14 am: |
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This is a three port engine, the bottom of the piston times the intake, it is critical. There's a small foundry in Canada that makes pistons, he may take your old piston for a pattern and core, not sure. Someone familiar with his operation may chime in. |
polarcreator
Member
Username: polarcreator
Post Number: 6
Registered: 11-2016
| | Posted on Thursday, November 17, 2016 - 06:32 pm: |
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Do you have the information on who or what the foundry is called. That would be a great help. Also JB thank you for the sleeving info. That was very enlightening. |
bruce_g
Member
Username: bruce_g
Post Number: 17
Registered: 12-2009
| | Posted on Thursday, November 17, 2016 - 10:44 pm: |
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Hello Michel
The foundry is Skara Foundry in Mississaga ON
You will need to use the original as a pattern.
They do not do pattern cores at the foundry.
You would need to build the piston up and cut it in half to use it as a pattern unless you know a patternmaker. Bruce |
polarcreator
Member
Username: polarcreator
Post Number: 7
Registered: 11-2016
| | Posted on Friday, November 18, 2016 - 09:20 pm: |
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Thank you for the foundry information but without a pattern piston of the right size it isn't an option. |
jb_castagnos
Senior Member
Username: jb_castagnos
Post Number: 1262
Registered: 07-2002
| | Posted on Saturday, November 19, 2016 - 08:26 am: |
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If you don't mind sacrificing you're old piston it can be built up with Bondo, machined, cut in half, used for a core and pattern. This is the easiest way for one or two pistons. |
