2.0 Type 4 Bearing Bore/Journal Spec.s

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Psucamper
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2.0 Type 4 Bearing Bore/Journal Spec.s

Post by Psucamper » Tue Feb 12, 2013 7:12 pm

Am in the process of building a 2000cc T4 engine. I have most of the necessary parts, case, crank, rods, etc. I have previously built and run several T4 engines that performed well. Used quality parts...no junk. This brings me to the point. Some of my cranks have been undersized (10 or 20) and miking them shows they are not really in decent undersize specs. The rods have also been reconditioned (by somebody) and I can measure the big ends to maybe 2/3 tenths. But..I can"t find factory specs on the big end ID.

I know this is not really necessary since it's bearing clearance that counts and there are ways to get that (no plastigauge please) without knowing the rod bore. However, I do want to check for uniform ID's among the reconditioned four rods. This helps identify possible errors in the thickness of the bearing inserts. Currently available bearings can't be counted on for a set that's in spec or even uniform in dimension. The reason for all this is to try to get back to the Bentley numbers and eliminate excess bearing slop and to get to factory tolerances. I want good oil pressure and I want to know the clearances on each and every mating surface. Knowing those ID's would help.
Does anybody have those big end (sans inserts) dimensions or where to find them? Did I overlook them in Bentley? Thank you. RDL

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Amskeptic
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Re: I NEED SOME NUMBERS

Post by Amskeptic » Wed Feb 13, 2013 9:15 am

Psucamper wrote: Some of my cranks have been undersized (10 or 20) and miking them shows they are not really in decent undersize specs.

rods .. I can"t find factory specs on the big end ID.

it's bearing clearance that counts and there are ways to get that (no plastigauge please)
I do want to check for uniform ID's among the reconditioned four rods.
Time for you to color outside the lines. I cannot find connecting rod IDs either. Yes, there are variations all over the place, and the problem is not getting better.

Here in the U.S., machine shops seem to use the old fashioned .010/.020 etc. undersizes while the rest of the world uses metric .25/.50 mm undersizes. That means a U.S. machine shop starts adding huge slop against our metric bearing over/undersizes as we go up. They will likely tell you how much it doesn't matter. You can either ask a machine shop to damn well use the metric dimensions or you have to play mix-n-match and do terrible things like I do.

#1 Get over your distaste of plastigage. It is a simple quick real world test of actual dimensions. If you have mad skills with an accurate micrometer, yes you can get decent readings if you do four measurements per bore/journal. You have thrust diameter versus parting line diameter in the big end rod measurements, and you have both sides of the bore to check for taper.

#2 A nice piece of sandpaper and a thick optically accurate piece of glass for the cap allows you to snug the thrust clearance a tad. Remember that your accuracy only needs to maintain the minumum acceptable oil clearance of .0008" . This would make a white tile machine shop pass out cold, but good grief, these engines are putting out no more horsepower than your average Briggs and Stratton lawn mower engine with the bearing surface area of a Chevy V-8. Relax! I like tight clearances with these expanding aluminum crankcases, but the forces are well distributed, so cap filing is within my acceptable practices.

#3 I am not Mr. Micrometer, so I do have to dress the crankcase parting line, clean up the main saddle mating surfaces with a razor blade, install new bearings in a hyper-clean environment (dry) and ship the fully torqued-down case to a competent-but-relaxed machine shop for bearing ID numbers.

#4 If the crank has yet to be ground or polished, I will ask that the machine shop provide a full four numbers per main journal and connecting rod journal: forward thrust/parting line numbers and rearward thrust/parting line numbers for a total of 32 numbers (throw in a six-pack of Heineken for their troubles).

#5. If the crank has to be ground, I will ask for the proper metric undersize and let the polishing even up the clearances, but really, ask for the lower end of the range! Shoot for connecting rod bearings at .0015 if at all possible, and mains no more than .0025. LOOK at the specification for #2 main journal! It calls for a tighter clearance! Obey! .002"! NOTICE! They want it tighter than the others because it has all that damn crank-whipping reciprocation bashing at it.

#6 Off the record - so don't tell anyone - I have razored down the main saddle mating surfaces to snug up my main clearances across the thrust surfaces ( that means egg shaped with the narrow part of the circle in line with the cylinders. Sue me! I have never wiped a bearing in my life.

#7 This demands uber-cleanliness! It really does! Clean and clean. Assemble with fresh oil on clean! surfaces. .001" you can feel with your finger tips. If you feel the slightest grit at any time as you assemble, STOP!

#8 The acceptable clearances of the crankshaft and camshaft as you build up the engine WILL tell you that you are good to go by the simple ability of the crankshaft to rotate. If it hangs up as you torque down the main bearing bolts, and again when you do the connecting rod nuts, STOP!
Poptoptom and I had that happen as we built up a Raby-parts-supplied engine. Wouldn't you know it, the prior mechanic had noooooooooooooooooo idea that Jake Raby nailed each connecting rod clearance at .0008" and the merest contamination ground it all to a halt. When we cleaned things up and checked with Plastigage, they were perfect, and they fell so beautifully slowly with 30wt Bradd Penn oil.

#9 Notice that I did not answer your question.
Colin
:withstupid:

p.s. errors in connecting rod insert thickness? Who, pray tell? I use Kolbenschmidt and have not run across anything like that)
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

Psucamper
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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by Psucamper » Thu Feb 14, 2013 5:51 am

Colin. Thank you for the further expansion of the crank/rod bearing clearance dilemma faced in restoring T4 engines to health. Your points noted and appreciated. As a calm and deliberate person, I will not panic if I miss specs by a few tenths (or more). And I will not ask about the "terrible things you do" to tweak clearances. It is most impressive to see that Raby repeatedly achieved clearance of an 0.0008" spec on four surfaces. That's almost air gauge stuff!

PS. OK OK I will try plastigauge

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Amskeptic
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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by Amskeptic » Sat Feb 16, 2013 4:08 pm

Psucamper wrote: PS. OK OK I will try plastigauge
Good. Now the Rules of Plastigage® (misspelled for trademark):

Rods - do it with crank on table.
* Fit a dry rod/insert onto crank journal with all orientation exactly as is to be assembled so that the small end will rest on a block of wood on the table so you can reach the nuts with a torque wrench and socket. This is not to move for the rest of the procedure, no fooling around.

(you may hear/read that the Plastigage has to be laid across the rod portion, but no, we are interested in minimum clearance, the rod side will always be more "pounded" than the cap side)

* Lay a stripe of Plastigage® across the dry insert in the cap so that it is perpendicular to the rotational direction. Press at the edges away from the working surface to "tack" it to the rod. Use green if you have fine .001-.003" clearances (go to red ONLY if you are out of green's range after your check).

* Install cap with a dead straight insertion, no smear motion allowed, nice light taps, no motion of connecting rod allowed, yes, it will want to move, no, you will not let it, I get paid by the, comma.

* Torque to spec across the nuts a little here a little there back and forth, no motion allowed.

* Loosen the nuts and remove. Tap the cap studs down directly in the remove direction, as soon as your Plastigage is free of the crankshaft, you don't have to be so nervous because the reading is set. Read the bearing insert in the cap and read the journal against whatever stripe matches your Plastigage. Whatchoo got?

* If you screw up, clean journal and insert with carb spray on a paper towel. Repeat. Might take a few times. Be happy.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

Psucamper
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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by Psucamper » Sat Feb 16, 2013 6:34 pm

Colin . Thank you. Will follow your protocol to the letter (notice the lack of commas). Numbers to follow as soon as I can get into my cold garage. RDL

Psucamper
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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by Psucamper » Thu Mar 28, 2013 12:45 pm

Colin. Apropos of our previous discussions on bearing clearances I have this to offer: On the Tuna Can website (www.tunacan,net/t4/tech/conrods.htm) there is a figure which exhibits the purported T1 "311B big end and small end" bore sizes. Just what we were both looking for. Except...the numbers are wrong. At least as imputed. The exhibit states that the big end bore is 55mm in diameter and the bushing bore is 22.7mm. But they are NOT. I use the T1 numbers here because my T4 rods are currently unavailable.

If that measurement refers to a reasonably good rod with a new set of standard size bearing shells installed, then the numbers (I get) are very close to the stated 55.0mm. Unfortunately, I cannot "backtrack" my way into finding the actual bore with my current set of (distorted/used?) rods. How does a genuine auto machine shop resize rods to spec if they don't know the correct bore size? Is there some mysterious data base we can't access? Or is it...hey,just shine em up a little and it'll be OK. Hell it's only a VW! Bob L.

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Amskeptic
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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by Amskeptic » Thu Mar 28, 2013 4:52 pm

Psucamper wrote:Colin. Apropos of our previous discussions on bearing clearances I have this to offer: On the Tuna Can website (http://www.tunacan,net/t4/tech/conrods.htm) there is a figure which exhibits the purported T1 "311B big end and small end" bore sizes. Just what we were both looking for. Except...the numbers are wrong. At least as imputed. The exhibit states that the big end bore is 55mm in diameter and the bushing bore is 22.7mm. But they are NOT. I use the T1 numbers here because my T4 rods are currently unavailable.

If that measurement refers to a reasonably good rod with a new set of standard size bearing shells installed, then the numbers (I get) are very close to the stated 55.0mm. Unfortunately, I cannot "backtrack" my way into finding the actual bore with my current set of (distorted/used?) rods. How does a genuine auto machine shop resize rods to spec if they don't know the correct bore size? Is there some mysterious data base we can't access? Or is it...hey,just shine em up a little and it'll be OK. Hell it's only a VW! Bob L.
The 2.0 71mm stroke engines have journals that are a full 5mm less than the above. That is how those VW engineers got to use the same crankshaft forgings as the earlier 66mm stroke crankshafts. They merely offset ground the connecting rod journals.

The Bentley manual has the connecting rod journals at 49.98-50.00mm (1.9677-1.9685"). We want no more than .03-.07mm (.001-.003) oil clearance on top of that.
Every engineer/machinist and his brother knows that there is no connecting rod inner diameter number to be had. It is known that the caps and the rods will be milled down at some point, then the caps will be torqued onto the rods and the hole will be made round again. You would have to rely on the connecting rod reconditioner to get that pre-bearing shell number correct. I personally would bring my box of Kolbenschmidt connecting rod bearings to the machinist and say "size the connecting rod for a .002" clearance after the crankshaft journal diameter is at its final polished number." Or something.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

Psucamper
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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by Psucamper » Thu Mar 28, 2013 5:27 pm

Colin....Thank you for the advice and prompt reply. Now to find a competent machine shop.

webwalker
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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by webwalker » Tue Aug 06, 2013 6:32 pm

I note with interest that John Connolly at aircooled.net offers in-house rebuilt rods, rebored, rebushed, magnafluxed and micro-balanced end-to-end. I'm sure if you provided your crankshaft rod journal dimensions to him and bought the crank bearings from him too, he'd have no problem shipping you a set of 4 perfectly set up con-rods. At two C-notes for the set, that's a helluva good price for all of the labor involved. Just a thought.

I'm going through this exercise myself, kitting up all the parts for a new T4 build, and while I'll still 'trust but verify' when my rods get here, I'll feel a lot more confident that I won't have my time or money wasted by some other slovenly jerks.

Marshall

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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by Amskeptic » Wed Aug 07, 2013 12:17 am

webwalker wrote:I note with interest that John Connolly at aircooled.net offers in-house rebuilt rods, rebored, rebushed, magnafluxed and micro-balanced end-to-end. I'm sure if you provided your crankshaft rod journal dimensions to him and bought the crank bearings from him too, he'd have no problem shipping you a set of 4 perfectly set up con-rods. At two C-notes for the set, that's a helluva good price for all of the labor involved. Just a thought.

I'm going through this exercise myself, kitting up all the parts for a new T4 build, and while I'll still 'trust but verify' when my rods get here, I'll feel a lot more confident that I won't have my time or money wasted by some other slovenly jerks.

Marshall
Note that you lose specificity if the crankshaft is not there at the rod-reconditioning procedure. If everybody is on the metric page, you'll most likely be OK for a couple of undersizes. If you have an American machine shop doing the final crank grinding to our ancient Imperial measurements, however, check those clearances without fail at assembly time. I personally would not go ahead with a lower end rod clearance anything over .003". That takes away the fun of a rebuild to have a sloppy new engine with lousy oil pressure.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by wild man smith » Fri Jan 05, 2018 4:34 pm

Just was in the middle of pulling the rods and pistons out this AM. 50mm rod journals for sure. Thank you for the explanation of how they stroked this engine.

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Amskeptic
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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by Amskeptic » Sun Jan 07, 2018 1:09 pm

wild man smith wrote:
Fri Jan 05, 2018 4:34 pm
Just was in the middle of pulling the rods and pistons out this AM. 50mm rod journals for sure. Thank you for the explanation of how they stroked this engine.
You are welcome.

I was looking at webwalker's post back when I, too, respected AirCooled.Net's "re-conditioned racy-ready" rods that I subsequently discovered were not acceptable . . .
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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tommu
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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by tommu » Mon Jan 15, 2018 12:21 am

I had my Rods rebuilt and balanced by RIMCO before Christmas. They came back with a 10 gram difference between them. I swapped them out for an off the shelf 'rebuilt' set and took them to be balanced with the whole rotating mass. Turns out these off the shelf, rebuilt rods were not balanced end to end, only as a whole. We saw a a variation 5 grams between the big ends of the first two rods we picked up at the shop. When I picked up everything the balancing shop was pretty shocked at how unbalanced the parts were that I paid to have balanced..

Today I began setting up to test clearances with plastigage and noticed that a number of the rod nuts are different. Some seem to be locking nuts and some not. I've ordered a new set of nuts - and some green plastigage.

Which me luck - I'm hoping that all the money I gave RIMCO hasn't been wasted. :pale:

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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by asiab3 » Mon Jan 15, 2018 9:37 am

FAT Performance now owns Rimco. Take the rods and your receipt in; both of those establishments stamp their name into their work so you shouldn’t have a problem getting what you paid for. Ugh.

The end-for-end rod balance is most important, and when they’re all matched that way you might see a slight variation in overall rod weight if you put the whole rod on a scale, but that’s less important as long as the ends are perfect.

Greg Aaronson sold his share of FAT last year; I hope he didn’t take the quality control part of the business home with him...

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Amskeptic
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Re: 2.0 Type 4 Bearing Bore/Journal Spec.s

Post by Amskeptic » Tue Jan 16, 2018 9:20 am

asiab3 wrote:
Mon Jan 15, 2018 9:37 am

The end-for-end rod balance is most important,
you might see a slight variation in overall rod weight if you put the whole rod on a scale,
but that’s less important as long as the ends are perfect.
Robbie
I do so beg to differ.

The big ends of the connecting rods must be exactly the same, so do your grinding down there to achieve your specified tolerance (1 gram is fine).

THEN you see if you botched the overall balance between the rods.

You bring the overall balance back in line up at the wrist pin end. The 1700 rods were so lovely with those generous balance pads above the wrist pin line, They were serious! about it with that 5,000 cruising rpm for the 411s and 914s.

Type 1 engines, you have far less to screw with. Put the two heaviest rod/pistons across from each other, regardless.

Big end perfect weight agreement is important for rotating balance, yes. But overall weight agreement is no less critical . . . every lousy billionth of a gram yanks the hell out of the crankshaft and bearings regardless.
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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