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Piston+Cylinder removal together -- possible?
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bnam
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PostPosted: Thu Dec 08, 2016 8:49 am    Post subject: Piston+Cylinder removal together -- possible? Reply with quote

Is it possible to remove the cylinder + piston together (71 stock 1600dp type 1)?

I'd like to clean up the top & bottom seating areas on the cylinder and thought I could put 2&4 at TDC, pull the cylinder out till wrist pin was exposed, remove pin and then remove the cylinder/piston combo. Now I could push the piston back in, seal the top and bottom and wash out the fins well, and then clean the sealing area and perhaps even lap cylinder in the respective head. Then do the same on 1&3.

I got as far as pulling out the rear retaining clip on #2. The wrist pin moved enough to cover the slot for the clip, but no further (I was pulling it with just finger pressure). When it didn't work, I pushed itback and put the clip back in. And cleaned up the bottom as best I could. Would still like to get it out, wanted to check if was possible/advisable before I mess it up.

Thanks!
Byas
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Dale M.
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PostPosted: Thu Dec 08, 2016 9:09 am    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

I have use a section of threaded rod through wrist pin and put a nut on one side and a weigh on other and sort of lightly "slide hammer" them out... Might only be some carbon or crud keeping WP from coming all the way out... Go slowly and gently ...

Dale
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PostPosted: Thu Dec 08, 2016 9:11 am    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

Definitely possible. Some install them that way so removal wouldn't be a problem. I preassembled mine and it worked out great.
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PostPosted: Thu Dec 08, 2016 10:35 am    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

Sure it's possible but why? You have come this far. Why not hone and re-ring? At the very least pull the pistons out and clean everything. If you attempt re-seat the cylinder to head with valve grinding compound you are likely to leave some grit in there. Are you mainly just trying to reseal an engine? Why not buy or make a ring compressor? You can make one out of a large soup can in a pinch. Just a suggestion.
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PostPosted: Thu Dec 08, 2016 11:24 am    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

Yea no big deal. I get teflon buttons so even easier.
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PostPosted: Thu Dec 08, 2016 11:42 am    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

That's one reason to machine for full floating pins from the start.
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PostPosted: Thu Dec 08, 2016 6:05 pm    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

yeah it's possible, that's how I usually assemble the engine.
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PostPosted: Thu Dec 08, 2016 6:26 pm    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

yamaducci wrote:
Sure it's possible but why? You have come this far. Why not hone and re-ring?


Depending on the mileage of the engine, and how well the rings are seated, you can do more damage then good. if you just pull the cylinders, stick them in a vice and hone them, the results will be less then stellar. However, when I hone cylinders, I use a torque plate and a precision Sunnen hone. In this method the cylinders can be just as good or better then when you bought them.
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PostPosted: Thu Dec 08, 2016 7:09 pm    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

yamaducci wrote:
Sure it's possible but why? You have come this far. Why not hone and re-ring? At the very least pull the pistons out and clean everything. If you attempt re-seat the cylinder to head with valve grinding compound you are likely to leave some grit in there. Are you mainly just trying to reseal an engine? Why not buy or make a ring compressor? You can make one out of a large soup can in a pinch. Just a suggestion.


I've considered what you suggest. Problem is that I don't have easy access to ACVW parts here in India -- so I stock up whenever I or my wife go back to Calif. So, trying to get ring set now would delay this till end of Jan. Orderig online would take about 4 weeks and cost about $40 just for shipping. So, trying not to go further than I need to.
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PostPosted: Fri Dec 09, 2016 9:46 am    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

Multi69s wrote:
yamaducci wrote:
Sure it's possible but why? You have come this far. Why not hone and re-ring?


Depending on the mileage of the engine, and how well the rings are seated, you can do more damage then good. if you just pull the cylinders, stick them in a vice and hone them, the results will be less then stellar. However, when I hone cylinders, I use a torque plate and a precision Sunnen hone. In this method the cylinders can be just as good or better then when you bought them.


I have always believed the theory behind the toqrue plate and jigs that simulate heads and cases but I guess you didn't see Pat Downs post this week dispelling that theory.
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Last edited by yamaducci on Mon Dec 12, 2016 9:27 am; edited 1 time in total
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yamaducci
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PostPosted: Fri Dec 09, 2016 9:48 am    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

bnam wrote:
yamaducci wrote:
Sure it's possible but why? You have come this far. Why not hone and re-ring? At the very least pull the pistons out and clean everything. If you attempt re-seat the cylinder to head with valve grinding compound you are likely to leave some grit in there. Are you mainly just trying to reseal an engine? Why not buy or make a ring compressor? You can make one out of a large soup can in a pinch. Just a suggestion.


I've considered what you suggest. Problem is that I don't have easy access to ACVW parts here in India -- so I stock up whenever I or my wife go back to Calif. So, trying to get ring set now would delay this till end of Jan. Orderig online would take about 4 weeks and cost about $40 just for shipping. So, trying not to go further than I need to.


That's right you are in India.... So all the more reason to make a ring compressor and not risk getting grit stuck in your rings from trying to lap the cylinder while assembled.
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PostPosted: Fri Dec 09, 2016 10:19 am    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

I can get a ring compressor and plan to. But, I had read that once the piston was pulled out, it should ONLY be put back with new rings. Sp, was hoping to avoid that. Is my understanding incorrect. (This is first time for me)

And, my plan was to push the piston all the way up to the top when I lap so that no grit gets to the rings.

Byas
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PostPosted: Fri Dec 09, 2016 10:37 am    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

I have never heard that or there would have been thousands of posts on that. You simply just don't want to switch pistons to a different cylinder or install the rings upside down once they have been seated. As long as you mark them in a way that won't wash off you can pull them and put them back in the same cylinder. You can scratch the number or use a punch. I have used oil filter strap wrenches in a pinch to compress the rings if you cannot find one locally.
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PostPosted: Fri Dec 09, 2016 1:25 pm    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

yamaducci wrote:


I have always believed the theory behind the toque plate and jigs that simulate heads and cases but I guess you didn't see Pat Downs post this week dispelling that theory.


No I haven't, please direct me to that post. However, in all honesty, it will be hard for one persons findings to dispel years of what is considered the best practice.
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PostPosted: Fri Dec 09, 2016 2:42 pm    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

Multi69s wrote:
yamaducci wrote:


I have always believed the theory behind the toque plate and jigs that simulate heads and cases but I guess you didn't see Pat Downs post this week dispelling that theory.


No I haven't, please direct me to that post. However, in all honesty, it will be hard for one persons findings to dispel years of what is considered the best practice.

http://www.thesamba.com/vw/forum/viewtopic.php?p=8285758&highlight=#8285758
Take a look down the page at his post or throughout that thread. The reason I now believe what he is saying is because I have known for a very long time that I can put a cylinder bore guage in a cylinder and squeeze it with the other hand and there is a measurable deformation into an oval shape. This can be easily transferred to many things that require even torque-down. Perfect example is you can cross torque a stock Bug with even pressure and it will still deform the drum and give pulse pedal. The best simulation I have seen with torque down like this to hone a cylinder where it simulated being in an engine and set up on the hone. There was the person; maybe NS Racing, who uses a case to put the cylinder onto then has a head that was bored through so that the cylinder can be torques between a head and a case and still run the hone through it. These cylinders are weak and will easily distort with uneven torque surface texture at mating surfaces, stud stretch, heat expansion, etc. etc.
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PostPosted: Fri Dec 09, 2016 3:20 pm    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

yamaducci wrote:
Multi69s wrote:
yamaducci wrote:


I have always believed the theory behind the toque plate and jigs that simulate heads and cases but I guess you didn't see Pat Downs post this week dispelling that theory.


No I haven't, please direct me to that post. However, in all honesty, it will be hard for one persons findings to dispel years of what is considered the best practice.

http://www.thesamba.com/vw/forum/viewtopic.php?p=8285758&highlight=#8285758
Take a look down the page at his post or throughout that thread. The reason I now believe what he is saying is because I have known for a very long time that I can put a cylinder bore guage in a cylinder and squeeze it with the other hand and there is a measurable deformation into an oval shape. This can be easily transferred to many things that require even torque-down. Perfect example is you can cross torque a stock Bug with even pressure and it will still deform the drum and give pulse pedal. The best simulation I have seen with torque down like this to hone a cylinder where it simulated being in an engine and set up on the hone. There was the person; maybe NS Racing, who uses a case to put the cylinder onto then has a head that was bored through so that the cylinder can be torques between a head and a case and still run the hone through it. These cylinders are weak and will easily distort with uneven torque surface texture at mating surfaces, stud stretch, heat expansion, etc. etc.


Sorry but you just made my case, You said that you can deform a cylinder with your hand, so how is the average person going to hold the cylinder when they hone it with out distorting it. This isn't a VW only issue, 30 years ago when dirt bikes were air cooled, we figured that we would lose 30% of the starting horsepower at the end of the race due to heat induced cylinder deformation. Yes I read the post, and I have had discussions with modok and ray concerning this issue in the past. And yes I used to use traditional hone in the past. However, when I scored on my Sunnen hone (mad divorced wife sale), I really saw the difference it made. However, as ray pointed out. It's not just the hone, holding fixture, grit or speed that matters, its all of the above.

That's why I still say if it is a low mileage engine and the rings have seated well, leave it alone.
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PostPosted: Mon Dec 12, 2016 9:36 am    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

The case I am trying to make is that you can deform a cylinder with your bare hands if you squeeze it and you can also deform it if you bolt it into a jig that is not the final engine it will be in. If someone were going to hone a cylinder I am suggesting no external forces be place on the cylinder from any direction. That way the cylinder will get it's hone in a relaxed state.
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PostPosted: Mon Dec 12, 2016 9:58 am    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

yamaducci wrote:
The case I am trying to make is that you can deform a cylinder with your bare hands if you squeeze it and you can also deform it if you bolt it into a jig that is not the final engine it will be in. If someone were going to hone a cylinder I am suggesting no external forces be place on the cylinder from any direction. That way the cylinder will get it's hone in a relaxed state.


But is that not Physically impossible? For a hone to work it has to remove material from high spots, actually ideally on a fresh cylindrical shape you want to manufacture slightly undersized and then finalize the ID through the honing process. Thus removing material from the entire circumference.

To remove said material the hone uses an abrasive stone that cuts through friction. Friction induces torque on the surface being cut. This torque would then cause the, in this instance cylinder jug to to rotate. If no external forces were applied you would simply spin the jug and the hone would never actually cut.

Much like many theories in principle it is ideal. However, in practice it is impossible. I have designed Honing machines for a couple of companies including the one listed in this thread. Through which I have watched hundreds of operators in the US, Germany, and Mexico. No matter a cylinder head, gun barrel, or hydraulic cylinder the part is held in place by a human hand or fixture jig. Why, because unless you want the hone to act like a clutch and the part to act like a drive shaft it has to be held from rotating...its just simple physics.
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PostPosted: Mon Dec 12, 2016 10:22 am    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

Obviously the cylinder will have to be stopped from rotating but not by a clamping force that will distort its shape or a squeezing force that the cylinder normally does not see.
If you design these machines what is your best suggestion since your machine is supposed to correct the problems we are discussing; not create them.
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PostPosted: Mon Dec 12, 2016 1:13 pm    Post subject: Re: Piston+Cylinder removal together -- possible? Reply with quote

yamaducci wrote:
Obviously the cylinder will have to be stopped from rotating but not by a clamping force that will distort its shape or a squeezing force that the cylinder normally does not see.
If you design these machines what is your best suggestion since your machine is supposed to correct the problems we are discussing; not create them.


Since they have been honed traditionally for over 60 years it obviously works. If the clamping force is deforming the jugs, you are clamping way to hard to compensate for trying to remove too much material too fast and probably not lubricating/cooling adequately. Cast aluminum will deform easily, but the clamping forces to hone them should be well below that. I have seen one of the largest domestic honing shops hone 18" long 2" diameter steel hydraulic cylinders with nothing more than hand help pressure, manually moving the cylinder back and forth over the mandrel on some Circa 1970's Sunnen hones to finish out the bore. The forces for aluminum should be far less than Stainless Steel.

If wanting to build a fixture that would match the functional forces the head would see, you would want to simulate how it would be mounted between the head and the block with the same clamping force as applied to the rods/nuts. Basically machine a 2 piece fixture with the case mounting surface and the head mounting surface. Then bolt it together with rods in the exact location as the final head/case. However, this clamping style is meant to resist the linear motion of the stroking piston. If enough force was applied to the jug to spin it in the fixture, now your mating surfaces are twisted. So you are worse off than simply clamping it traditionally and going slow and slight, and especially with sticky aluminum plenty of coolant fluid.
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