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87mm piston heat question.
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mark tucker
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PostPosted: Sun Dec 07, 2014 9:40 am    Post subject: Reply with quote

when I got my bug it had 87's. i had never driven it as it was crashed(tire tracks across the roof,intake knocked off the head,crunched quarters front&rear,fenders in peices.etc) so I dont know how hot it ran. I tore it appart and uppon balancing it I decided I wasent going to use a crankshaft that was softer than a lot of aluminum I hade worked with, so i got a 78.8 scat crank&cb rods(rods were a no brainer,arp rod bolts,bushings,time, well time was nothing I could do them in about 30 min....if I wanted to)so I clearanced those who knows how old 87's for the longer stroke added some shim& head gadgets opened the step so the piston could go into the chamber about .030" for a .035" piston to head clearance (quench).added a fk8 and 1.25 rockers and it went for about 3.5 more years.no issues as far as running hot.I still have those pistons with total seal rings and they will probably get used agaiin somethen.
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eschmi
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PostPosted: Wed Dec 10, 2014 1:15 am    Post subject: Reply with quote

alright cool, so I shouldn't have to do any other modifications really. I have pretty much everything for the rebuild minus a crank which the original German one should be fine from everything I was looking up unless I go bigger late on. Also going to put a different fan shroud on so it pushes more air down to keep it cooled.
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Heres what I got for $200
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veedubcrazy
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PostPosted: Thu Dec 11, 2014 9:20 am    Post subject: Reply with quote

If for nothing else, please balance the entire rotating assembly.
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eschmi
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PostPosted: Thu Dec 11, 2014 5:05 pm    Post subject: Reply with quote

what do you mean? sorry it's my first engine build ever so I'm kinda learning as I go
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bugguy1967
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PostPosted: Thu Dec 11, 2014 10:33 pm    Post subject: Reply with quote

He means for you to send your crank, rods, pistons, flywheel, gland nut, clutch, and pulley in to get balanced by a competent machine shop. Prices are around $100-$200 and make the engine run much smoother, quieter, and last longer.
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eschmi
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PostPosted: Fri Dec 12, 2014 12:16 am    Post subject: Reply with quote

so if its brand new pistons and push rods all I have to worry about is the other stuff then correct?
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veedubcrazy
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PostPosted: Fri Dec 12, 2014 8:16 am    Post subject: Reply with quote

If it was all balanced before, you 'could' balance the piston assy yourself. They all need to weigh the same. Even one piston (ring, wrist pin, clips included) that is out a 1/2 gram makes a difference. It is best though to have a competent machine shop to balance it all though...
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jbbugs
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PostPosted: Fri Dec 12, 2014 11:16 am    Post subject: Reply with quote

I built a motor with 87's for a customer over 20 years ago that he logged over 120,000 trouble-free miles on in the blazing South Florida heat. We tore it down after he had me build a new larger motor for him....
we shouldn't have torn it down. Everything looked beautiful inside. I am sure it could have run fine for years to come.
If you're not overheating them, the 87's are fine. Don't believe all the BS that some of the Parrots are Spewing online.

Oh Yeah, the 87's were also run Without any thermostat or flaps either.
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FreeBug
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PostPosted: Fri Dec 12, 2014 4:04 pm    Post subject: Reply with quote

FWIW, i had 87s in a type 3, many years back, and it developed pretty bad blow-by after a couple years, but it was neither well-tuned nor always well- aifiltered.

I just don't see why bother for an extra 56cc...
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eschmi
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PostPosted: Fri Dec 12, 2014 8:38 pm    Post subject: Reply with quote

alrighty, i'll go that route then and just have them check everything to save a possible headache later, and I went 87mm because.... full rebuild kit for $200.... cant beat that. Literally had to drive 1 miles, pick it up, take it back home. lol
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eschmi
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PostPosted: Sun Dec 14, 2014 3:29 pm    Post subject: Reply with quote

sorry guys, hopefully the last stupid question... upon tearing down the engine I've become stuck because it has a thermostat which was holding up the fan shroud from coming off... now I'm trying to decide if it's better to keep it and use a thermostat in a dune buggy or let it run a little colder than normal without it... thoughts? opinions?
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bugninva
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PostPosted: Sun Dec 14, 2014 5:01 pm    Post subject: Reply with quote

i'd like to say it's a no-brainer, use the thermostat to regulate your engine operating temperature, as it was intended..... that said, if you are going to use modified tinwork and delete the "sled" tins used under the engine to create a plenum for the thermostat and spent air, your thermostat will not be working within the parameters it was intended... if that's the case, keep the air control vanes in the shroud, but wire them in the open position.
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eschmi
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PostPosted: Sun Dec 14, 2014 7:48 pm    Post subject: Reply with quote

alright, thanks! wasn't sure if it was worth messing with but I'll use it I guess xP
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Zundfolge1432 Premium Member
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PostPosted: Mon Dec 15, 2014 5:27 pm    Post subject: Reply with quote

Never fails to amaze me, people will show up here ask a question then they don't like the answers given, even though ithey come from members who always give rock solid advice. Ignoring those with 20 or more years building engines, those with formal training, racers, those in business, why would anyone ignore this? Beats the hell outta me. Buy your 87s and see what happens. They are definitely a shortcut item, they do not tolerate heat period. You mentioned blowby and lapping cylinders into the heads. Blowby is a failure of the rings. Not the seal of cylinder to head. You'll get to see it (blowby) first hand when cylinders warp from overheat and you pressurize crankcase. Building an engine is a lot more than just throwing a bunch of parts together.good luck
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