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RevsBaja Samba Member
Joined: July 20, 2016 Posts: 4 Location: Nebraska
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Posted: Sun Mar 29, 2020 8:20 am Post subject: How many broken cylinder fins are too many? |
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I am working on building up a 1200 and have a brand new set of 83mm big bore pistons. The outdoor cats got into the garage and knocked the boxes off the shelf resulting in 3 out 4 cylinders with broken fins.
I've included pics of the two worse cylinders.
The engine will go into a baja bug so it will get plenty of air. Are these cylinders now too far gone to use?
Thanks for any input or advice.
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glutamodo The Android
Joined: July 13, 2004 Posts: 26306 Location: Douglas, WY
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Posted: Sun Mar 29, 2020 8:36 am Post subject: Re: How many broken cylinder fins are too many? |
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Me, I draw the line at one cracked or broken fin.
Those are big bore 40HP, so they have thinner walls than was stock -but not terribly so- and they have more fins overall than the original 1960s engines had in them, and larger fins (holes in them and not 'winged out'). But all of that is there because it is rather needed, and your example is more damaged that I would want to use. _________________ Andy T.
IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox. |
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TDCTDI Samba Advocatus Diaboli
Joined: August 31, 2013 Posts: 12846 Location: North Carolina
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Posted: Sun Mar 29, 2020 8:52 am Post subject: Re: How many broken cylinder fins are too many? |
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Weld them back on.
Is it a great solution? No, but are you willing to toss them & get another set? _________________ Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.
GOFUNDYOURSELF, quit asking everyone to do it for you!
An air cooled VW will make you a hoarder.
Do something, anything, to your project every day, and you will eventually complete it. |
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6T5 square Samba Member
Joined: September 15, 2005 Posts: 1083 Location: Dover, DE
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Posted: Sun Mar 29, 2020 8:59 am Post subject: Re: How many broken cylinder fins are too many? |
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Get rid of the cats _________________ John
65 square 1500S (weezer) sold but always on my mind
60 beetle (Ned)
Quoting John Muir -- Open the rear boot. Get out the stool and sit down. Contemplate the air-cooled beauty before you. - How to Keep Your Volkswagen Alive -- Step-By-Step Procedures for the Compleat Idiot |
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bluebus86 Banned
Joined: September 02, 2010 Posts: 11075
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Posted: Sun Mar 29, 2020 9:00 am Post subject: Re: How many broken cylinder fins are too many? |
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get new cylinders. the part broken is near the high heat source,, the combustion area. also.... kill the cat
if those are indeed big bore, old stock cylinders could I supposed be bored for the pistons you have. but as other guy noted, the fin design is different from stock to big bore, but even stock fins are better than missing fins.
the vendor might be able to supply cylinders only if you ask nicely.
Bug On! Fully Finned, like a Fish! _________________ Help Prevent VW Engine Fires, see this link.....Engine safety wire information
Stop introducing dirt into your oil when adjusting valves ... https://www.thesamba.com/vw/forum/viewtopic.php?t=683022 |
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RWK Samba Member
Joined: June 24, 2009 Posts: 1347 Location: S.W. MI
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Posted: Mon Mar 30, 2020 5:13 am Post subject: Re: How many broken cylinder fins are too many? |
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Keep the cats, they kill the mice that get into engine and build nest in the shroud, end up with same problem but won't know about it until its too late, braze the fins on, work's better with cast iron. _________________ 73 Type 181
63 Type 113
63 Type 261- 428 071
62 Type 241-378 025 178 530 |
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Rome Samba Member
Joined: June 02, 2004 Posts: 9638 Location: Pearl River, NY
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Posted: Mon Mar 30, 2020 10:19 am Post subject: Re: How many broken cylinder fins are too many? |
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Weld them back on. |
TDC has the benefit of much welding experience and his own welding equipment. I would be confident that he could make them usable again, at least by welding one fin back on if not both.
His response got me interested on what is the best method to fix cast iron. Just a few articles searched came up with either MIG welding, or brazing. I have no experience at all with MIG welding, but some minor experience with brazing sheet metal using a rented OA (oxy-acetylene) system. If you have neither the equipment nor experience, nor have a friend or relative who is, then IMO the most "expedient" solution would be to buy another set or at least the cylinders if sold separately.
My layman thoughts are these:
With MIG welding, my concern would be the sudden burst of heating to which the cylinder is subjected. Would that localized heating cause such stress in the thin fin material that it would crack by itself during the cooling? Would you just apply many tack welds (spots) to the fin break instead of continuous bead? You'd have to make sure that the fin fits exactly back onto the cylinder so that you'd have metal-to-metal contact along the entire fin break. Such direct contact maximizes the heat transfer into the cooling air stream.
Would you slightly open the break edge on both the cylinder and the fin by grinding it to a "V" shape, so that the MIG filler has more surface area for successful penetration?
For brazing, you'd need to grind a V so that the brazing rod has more surface area to create the joint. If you just butt the broken fin against the cylinder edge without dressing the edge at all, the braze just bridges the fin and seems there is much less inherent strength. Since you need to heat up the work area until past red hot, how will you hold the broken fin to the cylinder? On the cylinder with the 3 broken fins, you'd probably only be able to get 2 of them back on- the bottom and top one. If you are able to get the bottom fin remnant back on with brazing, you should continue with the top fin while the upper portion of the cylinder is still hot. When you then position and heat up the top fin area, will the torch heat bleed down to the fixed bottom fin and possibly loosen the brazed joint? You can imagine that lots of skill is needed as well as ingenuity to hold the fins exactly in place...
Paying an experienced welder to do this work would quickly match the cost of a new set. I realize it's hard to swallow just throwing out an otherwise new set of cylinders.
If you do decide to use these cylinders as they are without fixing them, I recommend at least running a carbide bit along the broken fin edges to blunt the sharpness and round the edge corners. |
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Eric&Barb Samba Member
Joined: September 19, 2004 Posts: 24732 Location: Olympia Wash Rinse & Repeat
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Posted: Mon Mar 30, 2020 11:09 am Post subject: Re: How many broken cylinder fins are too many? |
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Do keep in mind that the cylinders are made of cast iron. So will not work with normal welding wire when the cast iron is at room temp.
https://duckduckgo.com/?q=welding+cast+iron&t=canonical&ia=web
On the other hand you could try tack weld those on cold in a few spots, and then heat up for brazing or hot welding. _________________ In Stereo, Where Available! |
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wheel607 Samba Member
Joined: May 30, 2004 Posts: 1847
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Posted: Mon Mar 30, 2020 1:49 pm Post subject: Re: How many broken cylinder fins are too many? |
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Braze. |
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splitjunkie Samba Member
Joined: April 04, 2006 Posts: 4091
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Posted: Mon Mar 30, 2020 4:33 pm Post subject: Re: How many broken cylinder fins are too many? |
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Cast iron can be welded but I doubt the cylinders would still be within spec once it was finished. You would also have to weld the entire seam for them to be fully functional which would increase the heat used and the chances of the cylinders warping. _________________ Chris
You know, a lot of these scratches will buff right out... Jerry Seinfeld |
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splitjunkie Samba Member
Joined: April 04, 2006 Posts: 4091
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Posted: Mon Mar 30, 2020 4:35 pm Post subject: Re: How many broken cylinder fins are too many? |
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They are toast. Pull the pistons and put them in the classifieds and buy a new set. Even if you could get someone to weld them and not warp the cylinders you would cost at least as much if not more than just buying a new set. _________________ Chris
You know, a lot of these scratches will buff right out... Jerry Seinfeld |
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motofly196 Samba Member
Joined: June 01, 2008 Posts: 1467 Location: Eastern WA
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Posted: Thu Apr 02, 2020 8:51 am Post subject: Re: How many broken cylinder fins are too many? |
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If those were mine, I wouldn't junk them. Do you have access to an oxy/ acetylene torch? You cant MIG weld that. Cast is full of so many impurities, it will just pop and burn back. But you can braze the fins back on. There are plenty of you tube videos on how to do it. Silicone Bronze rod is what I'd use. Things in this world are not always junk because they are broken. What have you got to lose? |
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TDCTDI Samba Advocatus Diaboli
Joined: August 31, 2013 Posts: 12846 Location: North Carolina
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Posted: Thu Apr 02, 2020 9:50 am Post subject: Re: How many broken cylinder fins are too many? |
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Holy hell, it's not that difficult.
Here's a broken cylinder that I was playing with...
No, welding to cast iron is not ideal, but it's not like the fins are under any stress or are relied upon to keep something together. Here, I tacked the broken fin back on, no tools, clamps, or fixtures.
Then I ran a bead on it, flux core mind you.
And after cleaning it up with a grinder...
You could try to heat the cylinder first but they were kinda designed to dissipate heat quickly & they did so as the inside of the cylinder bore only got warm to the touch, hardly enough to worry about warpage.
You'll only have access to one side of the fin so start with the furthest one in & work your way out.
This took five minutes, it took longer to take pics, download them & peck the reply out.
Keep the cats, you might have to eat them soon. _________________ Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.
GOFUNDYOURSELF, quit asking everyone to do it for you!
An air cooled VW will make you a hoarder.
Do something, anything, to your project every day, and you will eventually complete it. |
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motofly196 Samba Member
Joined: June 01, 2008 Posts: 1467 Location: Eastern WA
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Posted: Thu Apr 02, 2020 10:10 am Post subject: Re: How many broken cylinder fins are too many? |
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Perfect repair TDC. I honestly think if you put the broken fins down, you wouldn't notice a thing. There you go...flux if you've got access to MIG, and Braze if you've got a torch. |
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splitjunkie Samba Member
Joined: April 04, 2006 Posts: 4091
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