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Author Topic: Possibly entering the 378 club!  (Read 4707 times)

Offline Sderbyshire

  • Posts: 254
  • Into Sailing, classic Triumph cars and motorbikes.
Re: Possibly entering the 378 club!
« Reply #30 on: Jun 20, 2018, 08:52:00 »
Collected barrels and pistons from the machine shop this morning, and so couldnt wait to test fit and measure up for gaskets!

With a new base gasket in place and the barrels bolted down im seeing :

Pistons sticking up .045 from the barrels
Base gasket measuring 0.018

So if i went for a base gasket at 0.063 from Lani then id have pistons perfectly flush with the barrels.

A 0.042 head gasket would then give me clearance of 0.42.

Is this correct and the right approach?

Steve




Online irk miller

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Re: Possibly entering the 378 club!
« Reply #31 on: Jun 20, 2018, 09:10:13 »
Yep.  That's the way to do it.

Offline crazypj

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Re: Possibly entering the 378 club!
« Reply #32 on: Jun 20, 2018, 11:16:08 »
Yep, numbers work out
Did you check gasket after it was compressed? I doubt if it would be more than 0.001" but it's generally easier to clamp cylinder down without gaskets then work out what combination will get you closest to 0.040" clearance. Having thickest gasket on base is a real good idea as there is way less pressure 'down there'.  ;D I'm really interested to see how a 70mm bore turns out. When I did my CJ250 to 70mm I used GS1000 pistons and flycut the head. Using stock 360 head gives a different combustion chamber shape and probably volume? I was actually on TV with it in 1995 (or 6?) There was an event at LLandow  Circuit with a RWYB 'sprint' Thanks to the 'magic' of television, I was filmed during a run then it was cut into the Welsh Champion drag racer doing a huge wheelie off the line making it look like I was 'winning (even though filmed on different days) only another 14 mins, 55sec to get my full '15 minutes of fame'  ;D
 
« Last Edit: Jun 20, 2018, 11:25:34 by crazypj »
'you can take my word for it or argue until you find out I'm right'
Best thing I ever overheard
"yep, PJ's my boss, he taught me everything I know, just didn't teach me everything he knows"
Brian Morgan, 1982

CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline Sderbyshire

  • Posts: 254
  • Into Sailing, classic Triumph cars and motorbikes.
Re: Possibly entering the 378 club!
« Reply #33 on: Jun 20, 2018, 11:24:33 »
Thanks both.

I did measure base gasket after removing it, so had been compressed.

Ill order the copper gaskets and hopefully get rebuilding soon!

Im a little unsure on piston rings.

I have a three part oil control ring, being two thin rings and a wavy centre, and two thicker compression rings.
Both compression rings are stamped 100 on what i think is their upper face. One ring is black edged and one silver.

Have you seen this before?, ive not take a picture yet nor contacted the seller.

Steve

Offline crazypj

  • Posts: 13199
  • Split personality, I fake being smart
Re: Possibly entering the 378 club!
« Reply #34 on: Jun 20, 2018, 11:29:18 »
Rings are completely normal, marked as 1.00mm oversize. Expander ring goes in between side rails. Make sure ends are butted and not overlapping (sometimes they look 'too tight' assembled correctly) Side rsails don't haver up or down face
Top ring is chrome face, second ring is 'black'
 Numbers up.
 Oh, stagger the oil ring rails and have gaps 'opposite' the 'join' on expander,(I only go about 1/2" either way)  it only makes a tiny difference but can seal 'better'.
« Last Edit: Jun 20, 2018, 11:34:04 by crazypj »
'you can take my word for it or argue until you find out I'm right'
Best thing I ever overheard
"yep, PJ's my boss, he taught me everything I know, just didn't teach me everything he knows"
Brian Morgan, 1982

CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline Sderbyshire

  • Posts: 254
  • Into Sailing, classic Triumph cars and motorbikes.
Re: Possibly entering the 378 club!
« Reply #35 on: Jun 20, 2018, 12:01:20 »
Fantastic, thanks CrazyPJ!

Offline Sderbyshire

  • Posts: 254
  • Into Sailing, classic Triumph cars and motorbikes.
Re: Possibly entering the 378 club!
« Reply #36 on: Jun 23, 2018, 06:10:30 »
Gaskets ordered from Lani at Coppergaskets, he was very prompt in responding and in making and posting the gaskets too!

While i wait for those to arrive ive painted the head and barrels, and built the head back up with new Viton seals.

Cant wait for the gaskets to arrive so i can rebuild and fire up the CB389 😀

Offline MiniatureNinja

  • Posts: 480
Re: Possibly entering the 378 club!
« Reply #37 on: Jun 23, 2018, 14:06:00 »
Moving right along there. I had quite a bit less meat on my build, and that's what I did went with a thicker base gasket. You could probably get away with shaving some off the case but gaskets is more reasonable solution.
Factory valves and guides?

Sent from my SM-G955U using DO THE TON mobile app

'75 Honda CB360 - thread

Offline crazypj

  • Posts: 13199
  • Split personality, I fake being smart
Re: Possibly entering the 378 club!
« Reply #38 on: Jun 23, 2018, 15:34:15 »
Stock valve guides are actually real good. It's only if you fit oversize stainless valves the guides need changing (something they don't tell you when you buy stainless steel valves, the stemscan  gall in cast iron and need bronze guides) Really though, it isn't worth the extra expense of oversize exhaust valves but the+1 (35mm) intakes will make all the port work better as it's already oversize.With a '390' is should be good to 'cruise' around 85~90 with top end around 120 on stock gearing (17/34) I got confused the other day with the CB550 591cc 'kit' and 70mm 389.46cc of 360 (35x35x3.14159x50.6x2 = 389.4629)
'you can take my word for it or argue until you find out I'm right'
Best thing I ever overheard
"yep, PJ's my boss, he taught me everything I know, just didn't teach me everything he knows"
Brian Morgan, 1982

CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline Sderbyshire

  • Posts: 254
  • Into Sailing, classic Triumph cars and motorbikes.
Re: Possibly entering the 378 club!
« Reply #39 on: Jun 30, 2018, 04:05:01 »
Gaskets and new dowells arrived in the week so guess what im doing this weekend 😎