Building a 4.7L low compression, supercharged S65 stroker motor - Page 2 - BMW M5 Forum and M6 Forums
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post #11 of 71 Old 17th November 2011, 08:39 AM
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Theres a lot of wear on the bearings, were the tolerances right? I would check the radius on the crank journals and side to side float clearance of the rod big end to crank.

20000 miles, high revs and a supercharger should not have done this; the oil film separating the bearings and crank has failed so I would be concerned if I was you and would want answers and remedial work done before buttoning up the engine.

The rod pinching at the break line is very strange, were the caps fitted with dowels and was there signs of movement/distortion?

What were the bores like when it was pulled apart? From what I can see of the pistons all looks well there. With such short piston skirts and supercharging especially on a stroked engine puts a lot of load on the thrust side of the piston and bore.

615BHP is pushing things that far so I am surprised at the visual clues I am seeing.

Cheers

Jay

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post #12 of 71 Old 17th November 2011, 05:03 PM Thread Starter
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Originally Posted by ur20v View Post
Theres a lot of wear on the bearings, were the tolerances right?
BMW factory tolerances are very tight. Factory tolerances aren't published by BMW in any of their repair manuals. We had to measure stock cranks and connecting rods to figure them out. The stroker was built using factory tolerances. This was reconfirmed after we pulled the motor apart and measured it up after the fact. In other words, whether right or wrong, the motor you are seeing was built with factory tolerances.

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I would check the radius on the crank journals and side to side float clearance of the rod big end to crank.
All of these issues have been addressed on the rebuild.

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20000 miles, high revs and a supercharger should not have done this; the oil film separating the bearings and crank has failed so I would be concerned if I was you and would want answers and remedial work done before buttoning up the engine.
You're getting ahead of the story. But yes, all of these issues were addressed with the rebuild.

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The rod pinching at the break line is very strange, were the caps fitted with dowels and was there signs of movement/distortion?
No dowels. I'm not sure how to check for signs of distortion and movement. The connecting rod bores all measured up nice and round when we pulled them apart...if that's what your asking. I have all of the rods here at home. If you tell me what to look for, I will check.

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What were the bores like when it was pulled apart? From what I can see of the pistons all looks well there. With such short piston skirts and supercharging especially on a stroked engine puts a lot of load on the thrust side of the piston and bore.
A few hundred pictures are posted here. It sounds like you already checked them out. I photographed just about every hole from multiple angles. There was some side wear on a few holes, but not all of them.
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post #13 of 71 Old 18th November 2011, 12:56 AM
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Hi PencilGeek,

I'm not trying to poke holes in your project or thread, sorry to jump ahead, I'll hold tight and read your updates with great interest.

As for signs of movement in the rod big ends there might be areas polished or gualing from movement, if there had been dowels damage might be present. I'm surprised there's no dowels, what locks the 1/2's alignment? Again if these questions are answered later in your project story I can eagerly wait.

So many questions... oh the wait...

Cheers
Jay
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post #14 of 71 Old 18th November 2011, 01:05 AM
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See here:

con-rods « RET-Monitor

Location of con rod caps, part 2
Thursday, December 16th, 2010
In the previous article on the subject of maintaining the accurate locations of the two parts of a split con rod design, we looked at dowel pins and ring dowels, and the relative merits of the two methods.

The subject of joint shear stiffness was raised, and it was noted that the ring dowel, having a greater cross-sectional area, provides more stiffness to the joint. A stiffer joint is more stable and less likely to suffer from joint face fretting wear. While the con rod bolt may not Read more…

Tags: con-rods
Posted in con-rods | 2 Comments »

Location of connecting rod caps, part 1
Wednesday, November 10th, 2010
In an article published in 2009, I looked at some of the design features of the joint face of a split con rod. One important requirement is that the two parts of the con rod - the ‘blade’ of the rod and its cap - must be positively and reliably located with respect to each other.

It is important that these location features are machined into the rod before the big-end bore is finished to size. This guarantees that when the rod is assembled and the Read more…

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Posted in con-rods | No Comments »
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post #15 of 71 Old 18th November 2011, 06:39 AM Thread Starter
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Quote:
Originally Posted by ur20v View Post
Hi PencilGeek,

I'm not trying to poke holes in your project or thread, sorry to jump ahead, I'll hold tight and read your updates with great interest.

As for signs of movement in the rod big ends there might be areas polished or gualing from movement, if there had been dowels damage might be present. I'm surprised there's no dowels, what locks the 1/2's alignment? Again if these questions are answered later in your project story I can eagerly wait.

So many questions... oh the wait...

Cheers
Jay
It's all good. Nothing wrong with asking questions. Not sure I know the answers. But I will look at the link you gave me, and see if I have a disassembled Carrillo around here to look at...maybe take some pictures to help answer your question.
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post #16 of 71 Old 18th November 2011, 08:43 AM
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post #17 of 71 Old 21st November 2011, 11:22 PM Thread Starter
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Crankshaft journal and bearing adjustments
For the most part, all of the bearings looked great when we disassembled the supercharged stroker motor. There were some discolorations in the bearings, but nothing looked out of place. That's why it was a bit of a surprise when Federico (RD Sport) pulled me aside and told me Carrillo wanted to redesign the connecting rods.

After I gave RD Sport permission to redesign the rods, I left Van Dyne Engineering and went directly back to Auto Talent. I wanted to take a much closer look at the bearings and take as many pictures as possible of every connecting rod and every bearing from every possible angle. I was able to immediately see the excessive bearing wear at the joints, just as Federico had told me. And the more I looked at the bearings, the rattier they began to look to me. But I'm not the engine builder, and I have no idea what Van Dyne planned to do about it (if anything).

As you can see below, the good bearings look pretty good, and the others vary from decent to rather ratty looking. Here's a sample of the bearing pictures. The complete set of all bearing pictures can be found here, starting at the bottom of page-2. If you click on the photos, they will expand to a full screen to get a closer look. The photos actually look much worse than the bearings look in real life. In real life, there's really nothing more than a few discolored spots on the bearings. I think the lighting has amplified the discolorations and makes it look much worse than it actually is. But the lighting also makes it real easy to see what I'm talking about.

Good bearing photos:





















Ratty bearing photos:















Measuring the journals
Since BMW doesn't publish their bearing journal clearances, we measured a few crankshafts and connecting rods to figure out what those factory clearances are. Van Dyne doesn't use platigauge to measure the clearances, they measure it much more accurately and in a more sophisticated manner. Van Dyne pre-assembles and correctly torques the main and connecting rod caps. Using an expanding micrometer that can measure inside diameters of a circle, Van Dyne measures the assembled bearing size. Then using a micrometer on the crankshaft main and rod journals, those measurements are subtracted from the bearing size to calculate the bearing clearance. If Van Dyne doesn't like the clearance they measure, they will recommend to change it.

Many people might have read that and thought BMW knows best and you shouldn't make any such adjustments. But BMW doesn't publish these specs and doesn't offer any different rod bearing sizes to allow you to make adjustments. This means BMW literally has a one-size-fits-all mentality to connecting rod bearings -- even though main bearings come in three different sizes. Van Dyne isn't the type of shop that simply slaps the motor together with the parts available. Van Dyne has a very long and prestigous racing pedigree (see side-bar below). As I mentioned earlier, if they don't like the measurements, they will want to make adjustments.

For weeks we had been getting ready to assemble the bottom end. All of the parts were at Van Dyne and ready to assemble. The only remaining job was to meaure the bearings and journals. Now that everybody's schedule was in sync, Van Dyne made the measurements and wasn't satisfied. 48 hours before we were supposed to assemble the bottom end, everything came to a screeching halt. Van Dyne wasn't satisfied with the clearances and believed they were too tight; they wanted to make some adjustments. Van Dyne recommended to resize the main and rod journals to obtain the exact clearance they wanted. Using an exact journal-by-journal measurement, Van Dyne sent the crankshaft down to the machine shop for resizing, re-treating, and re-balancing. Resizing the journals cost us another two week delay. Hopefully it would be our last!

Unfortunately I don't have any pictures of the measurement process. But I do have pictures assembling the rest of the bottom end after the adjustments were made. The following pictures are just a few of the many pictures I took. To see all of the photos, please view this photo album.

















Who is Van Dyne Engineering?
Stewart Van Dyne was the principle engine builder for Drake Engineering (formerly Meyer/Drake Engineering). Stewart and I worked together at Drake Engineering in the early 1980's. Stewart built Mark Donahue's Indy-500 winning motor, along with motors that have won endurance races in Lemans and Sebring. Stewart's winning race motors are far too numerous to list. Drake Engineering was no lightweight racing shop. The Drake "Offy" won the Indy-500 twenty-six times of which seventeen of those wins were consecutive. During my tenure at Drake, I witnessed our engine designer, in conjunction with Stewart design and build prototype motors motors for Chrysler, Buick, Mc Laren, and Carol Shelby. When I left Drake Engineering, they were in the process of designing a five-valve OHC cylinder head for a small block Chevy. When John Drake retired, Stewart Van Dyne bought all of his engine molds and patents, thus ensuring the ability to remanufacture any of the historic Drake racing engines and other Drake racing engine parts.
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post #18 of 71 Old 21st November 2011, 11:48 PM
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Thanks for sharing. I remember first reading about it over a year ago... it has been a long time coming. Hope to see it done soon!
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post #19 of 71 Old 28th November 2011, 05:14 AM Thread Starter
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Checking the connecting rod side play

After assembling the crank plate and installing the connecting rods, it's time to check the connecting rod side play. The connecting rod side play is the amount of side-to-side play after the two connecting rods have been installed on the same journal. If the clearance is too small, then the connecting rods will rub against each other, create extra heat, and not allow enough oil to escape. It's a vicious cycle of generating too much heat. The side play is measured by spreading the connecting rods as far apart as possible and then measuring with a simple feeler gauge. If the side play is too tight, then the motor must be disassembled and adjustments must be made.



Factory Measurements:

This is another one of those areas where BMW doesn't publish any specifications, so without measuing a few crankshafts and connecting rods, it's impossible to know what BMW intended. A typical measurement is 0.010" (ten-thousanths of an inch). For our application, we wanted a slightly different side-play tolerance. So we first had to measure the factory crank and connecting rods, then measure the stroker crank and connecting rods to see how they compare. The complete set of photos measuring the side play may be found here.





Stroker Measurements:







Adjusting the side play:
Even though Carrillo connecting rods are made to the highest standards, we did find a few of them were 1/2 of a thousanth of an inch different than the others (0.0005"). Since Van Dyne already planned to use his own tolerance specifications, this was our opportunity to make the necessary corrections. To ensure that Van Dyne machines the correct face of the connecting rod, each rod is marked with dye. The dyed face is the side that gets machined.







After all of the connecting rods are properly marked, each one is machined on a high precision grinder to obtain the exact dimensions Van Dyne desired. The entire process took more than two hours because the grinder only removed about 0.00025" on every pass. Each connecting rod is measured and re-measured. If it's not perfect, then it goes back on the grinder for one more pass. The complete set of photos documenting the connecting rod resizing process may be found here.











Once all of the connecting rods are properly resized, then it's time to clean up the parts. Each connecting rod is slightly sanded to remove any burrs, then dropped in the solvent tank to clean it all up. The pistons are reattached and the motor is put back together again.







Once the bottom end is finally assembled, then final measurements are taken. Now that the bottom end is fully assembled and no more adjustments are necessary, the block is sealed by injecting a special block sealer provided by BMW. Once the two halves of the block are assembled, the crank seals are installed. Two one-way check valves are pressed into the block. A sealant is injected through the check valve. The sealant fills a channel that runs between the block and the crank cradle. The injection process continues until the sealant squirts out a tiny opening at each crankshaft seal. You don't want to waste this sealant because it's $100 per tube, and there's just barely enough to complete the job.












Last edited by PencilGeek; 28th November 2011 at 05:41 AM.
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post #20 of 71 Old 28th November 2011, 06:39 AM
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Looks like they are taking the extra time and effort to check and recheck everything. Nice to see the correct tools used too! I like the slide wedge, haven't seen one of them for a while!!

Thanks for taking the time to document the process and post here, I for one really appreciate it as I have a passion for well built engines.

Good luck with the next stage.

Jay
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