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Machine shop head work
- Thread starter Boyd12
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What did they charge? Just curious. Picture is kinda difficult to see. If you can't feel a ridge with your fingernail you should be OK. If you have a flat stone you might want to pass it across the head. I probably would but that's me. LOL I think you're OK from what I can see. This might help allay your worries. SeaDoos workmanship so I am told. Not as critical as the head though but the tool marks are just tool marks. Good Luck
You better not run that head unless you know the shop specializes in the Seadoo DI.
On a 2-stroke and especially a DI you can't just cut the head to get more compression like on a car, you have to reshape the dome to get the proper squish.
This should never be done by a local "machine shop" you should only have this done by a shop that specializes in 2-stroke watercraft and has experience with your engine. As far as I know the only shop that tested performance mods on the DI engine was Group K. I have Group K do all of my machine work and they are happy to take your calls.
On a 2-stroke and especially a DI you can't just cut the head to get more compression like on a car, you have to reshape the dome to get the proper squish.
This should never be done by a local "machine shop" you should only have this done by a shop that specializes in 2-stroke watercraft and has experience with your engine. As far as I know the only shop that tested performance mods on the DI engine was Group K. I have Group K do all of my machine work and they are happy to take your calls.
Sometimes the cutter is not dialed in properly and is not the same height on opposite sides. Usually about .001 is how close you want it. Optimum is when you see evidence of tool marks in the opposite direction but no metal removed. 
Personally, I don't like milling machines for that reason. Lathes don't do that but there are issues no matter what you do. Most likety it will seal Ok. Bring it back to the shop and tell them your concern. They will be cooperative. If they do engines chances are they know what works and what doesn't. Hopefully. Again, Good Luck.
Personally, I don't like milling machines for that reason. Lathes don't do that but there are issues no matter what you do. Most likety it will seal Ok. Bring it back to the shop and tell them your concern. They will be cooperative. If they do engines chances are they know what works and what doesn't. Hopefully. Again, Good Luck.
DanSquires
Well-Known Member
that rough machined surface is intentional, and I know for fact that Fullbore puts swirling on all RV faces in engines they build. It confuses the airflow between cylinders, which results in no air bleed and you get a much snappier throttle response.
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Sometimes the cutter is not dialed in properly and is not the same height on opposite sides. Usually about .001 is how close you want it. Optimum is when you see evidence of tool marks in the opposite direction but no metal removed.
Sometimes the cutter is not dialed in properly and is not the same height on opposite sides. Usually about .001 is how close you want it. Optimum is when you see evidence of tool marks in the opposite direction but no metal removed.
I sent them an email and I have not heard back. To me the work looks like a visually impaired person did it. It looks like the used a surfacing table first, then milled it but didnt finish the milling. If you look inside the red rectangle, the is a metal filing in the hole on the right side. Arent they supposed to blow filings out when they are finished?
I'm not going to argue for them. I think they should have deburred the port openings with a little chamfer. I surely would not have called that a complete job. Always expect a shaving here or there even when you do your best you may find one clinger. LOL That isn't acceptable though in my book. Why did you get the head machined??
I got the head machined because it was warped and didnt seal. the warpage is odd since the engine ran fine before disassembly and when i installed the head it leaked bad. so i sent it to an experienced machine shop and $119 later i get this. they responded to my email that the ridge was necessary. that doesnt make any sense. they started machining the head and stopped part of they way through leaving a ridge that is necessary.
It doesn't look like they stopped from the picture but like the cutter moved away or the piece moved away. Could have been cutter breakdown but on aluminum? .... ya never know. Hmmmmm.... "The ridge was necessary." I suppose it would be dumb to ask why the ridge is necessary. Necessary because the screwed up. I don't want to judge though because I can't see it in person. As I suggested... It may seal. I have heads around here for 951s. One is an R&D. Are the DI's different ?
sadly, the Di is different. The head MAY seal and it may not. A big risk if you ask me. It is almost impossible to find qualified people in the machine shop business.
Well qualified with the proper tools anyway. I wouldn't try to machine one of my heads in a mill without the proper equipment. Good shops do too nice a work for cheap compared to the amount of time I'd spend and not as good an end result because I don't have the tooling. I still think you should stone the head.... carefully.
I am not sure bolting on and praying is a good idea on the Di engine. It is a very high strung and temperamental beast.
This is what Group K had to say....
Increasing Power
Besides making the choice to not modify the fuel mapping, we also made the choice to maintain our modified Di as an 87 octane safe platform. We tested with many of the top end modifications that had netted good results on the carbureted version of the 951, but the Di reacted quite differently because it had a different set of needs. In the end, the most effective modification was increasing the compression ratio and reshaping the combustion chambers to stave off detonation. The combustion chamber design that worked best on our Di was considerably different from what worked best on the carbureted 951s we have developed in past years. However (again) our testing showed us that the Di engine had very different needs from the older carbureted engines. Our “Di Specification” head mod gives the 951 Di much stronger acceleration through the entire rpm range, and slightly increases peak speed as well.
About Cylinder Head Installation
The Di head can be removed with basic tools. The head is sealed to the cylinder with a multi layer steel head gasket that can easily be reused with good long term results. When re-using this head gasket, we recommend to thoroughly clean both the head and cylinder surface, and then apply a very thin coat of 3Bond 1211 Gasket Sealer to both sides of the head gasket. This gasket sealer is available from Group K with your order.
This is what Group K had to say....
Increasing Power
Besides making the choice to not modify the fuel mapping, we also made the choice to maintain our modified Di as an 87 octane safe platform. We tested with many of the top end modifications that had netted good results on the carbureted version of the 951, but the Di reacted quite differently because it had a different set of needs. In the end, the most effective modification was increasing the compression ratio and reshaping the combustion chambers to stave off detonation. The combustion chamber design that worked best on our Di was considerably different from what worked best on the carbureted 951s we have developed in past years. However (again) our testing showed us that the Di engine had very different needs from the older carbureted engines. Our “Di Specification” head mod gives the 951 Di much stronger acceleration through the entire rpm range, and slightly increases peak speed as well.
About Cylinder Head Installation
The Di head can be removed with basic tools. The head is sealed to the cylinder with a multi layer steel head gasket that can easily be reused with good long term results. When re-using this head gasket, we recommend to thoroughly clean both the head and cylinder surface, and then apply a very thin coat of 3Bond 1211 Gasket Sealer to both sides of the head gasket. This gasket sealer is available from Group K with your order.
True. With good people and good management, a QC guy is unnecessary. The work will speak for itself.Ha.... We never had a QC guy.
Thanks for the posts!
noviceskier
Active Member
Wow
.002 ain't all that bad as long as it isn't a quick drop off. The shop could have grabbed the head and induced the stress during machining. Then when they released the clamps they used it sprung a bit. I'd worry more about the ridge.
I agree with you but all I keep thinking is how the quality of the work is bad and then the head isnt even flat. I can deal with the issue of it not being flat a lot more than the ridge!
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