Ring Gaps

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kemp1942
Posts: 100
Joined: Tue Jul 15, 2008 8:54 pm
Your interest in the forum: Lifelong interest in Jowetts
Given Name: Ian
Location: Lockerbie

Ring Gaps

Post by kemp1942 »

Anyone know what ring gaps should be for 7 and/or 8 HP ? On my good piston (from the recon engine that started to sieze just before the Rally, damaging a piston and destroying the rings) the gap is 22 thou - this is an '8' std piston. I have gotten some replacement rings which have a 13 thou gap - wondering if I can leave them or should I gap them at 22 thou ( In the back of my mind is 4 thou per 1" of barrell bore which would equate to about 12 thou ?????????
A Bulldog is for life
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Peter Holden
Posts: 140
Joined: Tue Sep 02, 2008 7:45 pm

Re: Ring Gaps

Post by Peter Holden »

Ian
Does the attached help[img]
SWScan00030a.jpg
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Forumadmin
Site Admin
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Re: Ring Gaps

Post by Forumadmin »

Hi Peter,
You will see that I edited the post by resizing your pic so that it could be read. however a rescan or resize from your end might be better as some definition has been lost. Aim for a file size of about 100 to 150 k. Since it is black and white a GIF file may be better than jpg.

Seems like Ian is going for a race engine, semi air cooled.
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Leo Bolter
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Your interest in the forum: Proud owner of:
1 x 1951 Jowett Jupiter
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Location: R. D. 2, Palmerston North, 4472, New Zealand.

Re: Ring Gaps

Post by Leo Bolter »

. . . . or download this (340 kb): :)

http://60.234.149.204/Leo/Forum_Files/J ... ions_1.doc

NOTE: The original of this document was included inside a carton containing an unused set of “Repco” brand (Australasian company) semi-finished Jowett Javelin pistons. (This .doc is normally available on my section of the Gallery, but it is not at the moment, "due to maintenance being done"). :(

The ring gap recommendations are found at the top of page 2. I quote:

Recommended Ring Gaps.
[b][u]Air Cooled Racing Engines: -[/u][/b] Not less than 0.005"|[b][u]All other engines: -[/u][/b] not less than 0.003" I hope this helps . . .
Leo
Last edited by Leo Bolter on Tue Jun 29, 2010 11:04 pm, edited 1 time in total.
R. Leo Bolter,
Palmerston North,
New Zealand.

JCC of NZ - Member No 0741.
JOAC - Member No 0161

Car: Jupiter (E1-SA-513-R)

Skype name = jupiter1951
Messenger name = r.l.bolter"at"massey.ac.nz
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kemp1942
Posts: 100
Joined: Tue Jul 15, 2008 8:54 pm
Your interest in the forum: Lifelong interest in Jowetts
Given Name: Ian
Location: Lockerbie

Re: Ring Gaps

Post by kemp1942 »

Thanks all - since it seems they should be at least 003" x 3in = 009", looks like I can leave them at 013" - can't add any metal back on !. I'll replace the pair on the 'good' piston which are circa 022"
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k. rogers
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Joined: Thu Feb 23, 2006 9:43 pm
Your interest in the forum: 1933 7hp Kingfisher
1935 7hp Weasel
1928 7hp Sports replica
1952 Bradford special
Given Name: Ken
Location: Cornwall

Re: Ring Gaps

Post by k. rogers »

I don't want to add confusion but in a 1935 'Practical Motorist' it states the gap should be 0.002in between the slotted ends of the rings when positioned in the bore - firstly, that is considerably less than the 3thou per inch formula; secondly, what do they mean by 'slotted ends'?
7hp Weasel & Kingfisher
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