Cylinder head location

supascoot
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Cylinder head location Jul 11, 2019 6:39:38 GMT -5 via mobile 90GTVert, oldgeek, and 1 more like this

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Post by supascoot on Jul 11, 2019 6:39:38 GMT -5

I can't seem to find my head....
Just thought I'd share this. With lack of dowels and no proper way to locate cylinder head combined with poor fitting studs, keeping squish tolerances can be a problem. Dowels were an option but i chose a different path. I machined the barrel top down about .080" (2mm) to leave a spigot concentric with the bore of 1.949" (49.5mm) those dimensions are not critical so long as they match the head. I then machined the head to match so it beared only on the spigot leaving about .004-.005" clearance between the head and fin area. I have deleted the head gasket. Because my piston protruded from the deck and I had also changed the angle of the crown, i then machined another recess into the head for the squish clearance with a 1° difference so that the squish band clearance was getting greater towards the centre of the bore. Then I machined the combustion chamber to desired shape and cc,s. Final step was I lapped the head to the barrel to ensure matching surfaces. I use a tiny amount of loctite 515 on the face push them together and separate, clean off any excess then reassemble, so only absolutely minimal sealant is in there to ooze out. Done this for quite some time on various engines with no failure.

supascoot Scoot Member Posts: 32	Cylinder head location Jul 11, 2019 6:42:35 GMT -5 90GTVert and repherence2 like this Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by supascoot on Jul 11, 2019 6:42:35 GMT -5 Sorry had to switch to desktop view to upload photos Disregard circle from painting

ThaiGyro
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Cylinder head location Jul 11, 2019 7:31:37 GMT -5 harleyracer59 likes this

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Post by ThaiGyro on Jul 11, 2019 7:31:37 GMT -5

I say nice machining. I do not quite understand why. Poor fitting studs? OK. Why? Maybe I am missing something. I like to machine "O" ring groove head/cylinder connections. Less work, easy to adjust. Never had issues with that approach. Only need to tune the ring. (Ours rings were aluminum/aluminium) Actually, never recall poor fitting studs.
Again, maybe I do not understand why you required that much machining.
Fun though!

'84 Honda Gyro Up TB50M, TA01E engine, a stocker...still workin' it. '15 Honda CRF250-SL Scrambler project.
'96 Yamaha TRX 850 project, '14 Yamaha Mio MX 125 daily scoot,'02 Thai Nissan NV Wing Road VZ-R, AWD pickup project.
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supascoot
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Cylinder head location Jul 11, 2019 7:42:52 GMT -5 via mobile repherence2 and houseoffubar like this

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Post by supascoot on Jul 11, 2019 7:42:52 GMT -5

Jul 11, 2019 7:31:37 GMT -5 ThaiGyro said:

I say nice machining. I do not quite understand why. Poor fitting studs? OK. Why? Maybe I am missing something. I like to machine "O" ring groove head/cylinder connections. Less work, easy to adjust. Never had issues with that approach. Only need to tune the ring. (Ours rings were aluminum/aluminium) Actually, never recall poor fitting studs.
Again, maybe I do not understand why you required that much machining.
Fun though!

I found with tighter squish clearance that when head was tightened down, the squish would be different in different positions around the bore, loosen the head and move it a little and you will get varying measurements, with bigger clearances not so much much of an issue as you have a bit more give and take. As for poor fitting studs, probably a poor explanation on my part, stud clearance into head is fine, just not able to consistancy locate it, that's all, it all has a bit of give and take. Dowels would do same job. I just found this easier. Only takes me about 20min including setup.

supascoot Scoot Member Posts: 32	Cylinder head location Jul 11, 2019 7:43:59 GMT -5 via mobile houseoffubar likes this Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by supascoot on Jul 11, 2019 7:43:59 GMT -5 Oh and that material on the bed is not all from that.

supascoot Scoot Member Posts: 32	Cylinder head location Jul 11, 2019 7:45:24 GMT -5 via mobile harleyracer59 likes this Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by supascoot on Jul 11, 2019 7:45:24 GMT -5 20min for the that and about the same for the barrel, so about 40min all up

repherence2
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Cylinder head location Jul 11, 2019 10:05:19 GMT -5 via mobile aeroxbud and harleyracer59 like this

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Post by repherence2 on Jul 11, 2019 10:05:19 GMT -5

Jul 11, 2019 7:45:24 GMT -5 supascoot said:

20min for the that and about the same for the barrel, so about 40min all up

40 minutes for someone that knows how to machine

. 4 jaw chuck is a headache to learn, but once you know it, everything is easier.

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ThaiGyro
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Cylinder head location Jul 11, 2019 10:46:06 GMT -5 harleyracer59 and supascoot like this

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Post by ThaiGyro on Jul 11, 2019 10:46:06 GMT -5

Nice regardless. I am a super novice at machining, though I understand the principles of fine work...just a simple brain...I like easy!

As a related note: I have seen "locator" studs on some super expensive engines. They were made to bite the head just a tiny bit, centering and holding the head. The concept was a minimal spline cut diameter to the head holes...OK if newly milled. Not worth anything on old worn ones.

Did not work well.

'84 Honda Gyro Up TB50M, TA01E engine, a stocker...still workin' it. '15 Honda CRF250-SL Scrambler project.
'96 Yamaha TRX 850 project, '14 Yamaha Mio MX 125 daily scoot,'02 Thai Nissan NV Wing Road VZ-R, AWD pickup project.
______________________
Montana projects: 2007 Honda Fit Si - 2.0 liter K20Z3
1994 Suzuki Sidekick 4X4 engine upgrades and cosmetics.

jackrides Scoot Pro Posts: 1,428	Cylinder head location Jul 11, 2019 12:18:45 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by jackrides on Jul 11, 2019 12:18:45 GMT -5 WOW!
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ThomasTPFL
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Cylinder head location Jul 11, 2019 16:18:49 GMT -5 via mobile harleyracer59 and supascoot like this

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Post by ThomasTPFL on Jul 11, 2019 16:18:49 GMT -5

I've seen folks do the other way, make the head drop into the cylinder. Usually to make up for lost compression from using a thick base gasket/spacer to account to adjust port timing.

supascoot
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Cylinder head location Jul 11, 2019 17:39:16 GMT -5 via mobile harleyracer59 likes this

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Post by supascoot on Jul 11, 2019 17:39:16 GMT -5

Jul 11, 2019 16:18:49 GMT -5 ThomasTPFL said:

I've seen folks do the other way, make the head drop into the cylinder. Usually to make up for lost compression from using a thick base gasket/spacer to account to adjust port timing.

Yes have seen it the other way round, some production engines are that way, just not practical in my case.