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which bronze is used
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Topic: which bronze is used (Read 4299 times)
nicolas
Hero Member
Posts: 4010
which bronze is used
«
on:
April 15, 2012, 19:20:30 pm »
i have been looking at the possibility of fitting new bronze lifter guides in my case and i can't seem to figure out which material to use, or what is the correct clearance when cold. the reason being the copper and bronze usually expands more then metal. i am also wondering what fitting you would suggest when i machine the case and the inserts.
thanks
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ibg
Full Member
Posts: 140
Re: which bronze is used
«
Reply #1 on:
April 16, 2012, 13:12:46 pm »
I can't advise on the material to use, though rocky Jennings sells silicone bronze bushes. I did some testing on my sleeved case in the oven, and the bores expanded much faster than the lifters, so i would suggest very close clearance, around 1 thou. A lot will depend on your ambient temperature on start up, over here in Melbourne Australia in is not less than 12 deg C. so at 12 deg I have 1 thou clearance. If your startup temps are colder you may need more clearance.
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K-Roc
Full Member
Posts: 194
Re: which bronze is used
«
Reply #2 on:
April 16, 2012, 23:14:39 pm »
Ampco 45 Nickel -Alum-Bronze
Also makes unreal valve seats.
Here's a good link to info on the material
http://www.matweb.com/search/DataSheet.aspx?MatGUID=388203f1c3034fb8b0362c3f7cdd6e46&ckck=1
Cheers. K-Roc.
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nicolas
Hero Member
Posts: 4010
Re: which bronze is used
«
Reply #3 on:
April 17, 2012, 05:44:11 am »
thank you.
so to get this right a clearance of 1thousanth is 0,0254 mm? i looking at temperatures in the average of 20°C up to 30°C when cold. but that can't be decisive on engine 'needs'. the clearance needs to be right to keep enough oil pressure and allow lubrication.
and what fitting is used to press them in the case. case heated up and dropped in or pressed in?
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didi
Jr. Member
Posts: 75
Re: which bronze is used
«
Reply #4 on:
April 17, 2012, 07:43:51 am »
Hi
have a look at the end of this blog page.
http://didivw.blogspot.com/search?updated-max=2011-03-13T15:30:00%2B01:00&max-results=7&start=7&by-date=false
cooled the sleeves down and heated the case up.
Didi
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Didi - Aircooled VW
http://didivw.blogspot.com/
Bruce
Hero Member
Posts: 1420
Re: which bronze is used
«
Reply #5 on:
April 17, 2012, 08:24:01 am »
Quote from: ibg on April 16, 2012, 13:12:46 pm
i would suggest very close clearance, around 1 thou.
Better than guessing is to use VW's spec.
Lifters: 18.96-18.98mm
Bores: 19.00-19.02mm
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ibg
Full Member
Posts: 140
Re: which bronze is used
«
Reply #6 on:
April 17, 2012, 11:09:59 am »
Whilst Bruce's, suggestion is good, the VW specs are fairly wide, from .02mm to .06mm, my testing led me to work on the close side, 0.025mm is about 1 thou. When my case was at operating temp there was 4 thou clearance between the lifter and bore (0.1mm). I would suggest reaming or preferably honing the lifter bores to size after fitting the bushes. I found small differences between lifters and honed to suit.
I didn't fit my bushes, but I have read that only 1 or 1.5 thou interference should be used when fitting the bushes due to the chance of cracking the case, a machinist may be able to advise you. I like the idea of heating the case/chilling the sleeves and pressing them in easily.
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didi
Jr. Member
Posts: 75
Re: which bronze is used
«
Reply #7 on:
April 17, 2012, 15:06:29 pm »
What is even helpful for an easy and fast starting to the press in procedure, machine a small diameter lead on the bronce sleeve of about 2mm long and a couple of thousandths under size
Didi
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Didi - Aircooled VW
http://didivw.blogspot.com/
nicolas
Hero Member
Posts: 4010
Re: which bronze is used
«
Reply #8 on:
April 19, 2012, 19:58:20 pm »
thanks for all the info. i think i stick to Bruce's advice and take the smallest clearance as a starting point i should be Ok.
and yes i was thinking of honing them to the right size afterwards, or machine them to the exact size. . the idea of a stepped bushing can work as well, but it should be OK with a good chamfer.
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