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#90
by
fspGTD
on 08 Sep, 2005 13:16
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Well, I decided I didn't like the way the upper rod bearings looked too much, so I just ordered a set of new rod bearings. You'd never guess who had the best price on them, at only $14 a set. The VW dealer! :lol:
Also for a little added peace of mind at high RPMs, I am also going to throw on a set of new genuine VW 9mmx1.0mm shouldered rod nuts. They also wearen't too bad in price... $1.82 a piece from the dealer (or about $15 for a set of 8.)
2383: As for where to get bearings from, check out this thread:
http://www.vwdiesel.net/phpBB/viewtopic.php?t=1908I'd recommend using the thrust washers rather than the integrated main/thrust. You'd (obviously) need a couple extra main and crank bearings for your 6-cylinder motor.
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#91
by
fspGTD
on 14 Sep, 2005 19:15
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My parts arrived and it turns out what I thought was a "set" of connecting rod bearing shells from the VW Dealer is really just one shell! (IE: not even enough to do one cylinder!)
Needless to say, I sent that $15 bearing shell right back to "the Stealer". Guess I'll just be reusing my old bearings for now. At least they're tight!
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#92
by
QuickTD
on 14 Sep, 2005 20:04
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Kolbenschmidt OEM rod bearings are only $30CDN for a set of 8, mains are $50CDN for all 10, thrust washers are $12CDN for all 4 at any aftermarket parts supplier. I would not suggest the dealer for bearings unless you wan't to dispose of a bunch of money.
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#93
by
fspGTD
on 28 Sep, 2005 14:50
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I did a leak down test on my GTD autocrosser on cylinder number four with my new homemade leakdown tester.
Result: 26% leakdown at 100 psi :shock:
Almost all the leakage seemed to be coming out through the rings. I had the oil pan off and it was really easy to tell that was where all that rushing air noise was coming from. There was very little noise and no noticeable flow through the air intake or exhaust.
I tried filling the cylinder with oil and re-testing, but the oil kept getting blown through. It only held pressure (when it seemed really quiet) for about one second and I wasn't able to see what the % leakdown was. But right after the oil got blown through I think I saw 4-6%, dropping to 10% and below.
Looks like it's time for some new rings at least. I'm just amazed how well the motor pulled considering its 26% leakdown!
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#94
by
fspGTD
on 03 Oct, 2005 02:26
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Update: the head's off, and the pistons are out!
I found the rings have what seems to be excessive ring to piston groove clearance. Bentley says upper end of the range should be .002", but on the one top compression ring I measured, I found .006"-.007"! Could that be the culprit for the low compression and high leakdown?
Any of you guys with experience re-using pistons with new rings check your ring to piston-groove clearance, and what did you find?
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#95
by
fspGTD
on 25 Oct, 2005 20:51
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Update: I had the pistons bead blasted to have them cleaned up, and have a set of new rings here ready to install. With the new rings and bead blasted ring lands, the ring to ring land clearance tightened up to like new specs (.003" on all the compression rings).
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#96
by
935racer
on 26 Oct, 2005 09:50
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Any pics of the final product? I have a bead blaster and would be interested in trying that. Any idea what size of glass shot was used? thanks jake
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#97
by
fspGTD
on 26 Oct, 2005 11:15
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I'll take some pics for you.
My engine builder did the piston prep... I'll ask him what size glass beads he used.
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#98
by
fspGTD
on 27 Oct, 2005 22:23
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#99
by
veeman
on 28 Oct, 2005 06:30
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Very nice! What are the ridges near the top edge of the piston? I don't think I've seen those on gasser pistons... Something to do with the thermal expansion abilities of the TD piston perhaps?
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#100
by
lord_verminaard
on 28 Oct, 2005 07:52
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Holy moly! Those were used pistons??? Good lord, they are beautiful!
I've seen new pistons that didnt look that good...
NICE!
Brendan
84 Scirocco 8v
00 Camaro L36 M49
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#101
by
935racer
on 28 Oct, 2005 17:55
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I am gonna take a wild guess and say that is likely #8 glass shot. I assume you are coating the pistons? If so with what, and do you have any measurements of the diameter before and after the blasting. Bead blasting could be a good thing for these pistons as it hardens them much liek shot peening. I have see tests comparing hardening between both lead and asteel and glass shot and there was hardly any difference between the steel and glass. I'll see if I can find that info again.
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#102
by
fspGTD
on 29 Oct, 2005 11:36
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I am pretty pleased with how they turned out. The service actually wasn't very expensive. I've heard if you do this, that it's important to clean out all the old glass beads from the grooves before installing the rings.
Dave - I didn't know bead blasting gave similar results to shot peening, that is pretty cool! I do understand it roughens the surface, allowing more places for oil to hang out at, which can't be a bad thing for skirt lubrication.
I won't be having these pistons coated, because that kind of investment just doesn't make sense on these used pistons. These ones have actually been smacked into valves on two different occasions! (This is very apparent in their crowns... which you can check out pics of in page two of this thread.) My main goal with this engine work is just to get the car back "ready to race" reliably (with ring leakage issue addressed), and within my current budget. It's going to be good to have the GTD up and running again.
Veeman - according to this online Car Craft article, (
http://www.carcraft.com/techarticles/77899/,) "anti-detonation grooves above the top ring land are said to knock the peaks off shock waves within the cylinder."
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#103
by
v8volvo
on 01 Nov, 2005 15:12
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What do your piston-rod assemblies feel like? Before I rebuilt my 1.6NA, it had, among other major problems (like colossal oil consumption and smoking), a little lower-end tap in it. All my rod and main bearings were in beautiful shape (this motor had a full rebuild only 90k ago; something must have been done to the rings--maybe overheating--to make them lose their tensile strength after that), so I was mystefied as to the possible source of this sound. Then, as I was reassembling it after honing and installing new rings, I noticed that the wrist pin one the #1 rod-piston assembly was a little loose. Not LOOSE, but not like the others. On the other three, the wristpin was fixed--pressed in--to the small end of the con-rod, and then floated free in the piston (held in by circlips at either end, one of which was also loose on #1). On my #1 assembly, the pin floated in both the connecting rod small end and in the piston. I figured this might be the source of the noise; I took the circlip out and bent it so that it fit tightly, and slapped it back together.
What do yours feel like? Are the wrist pins all fixed in the conrods and floating in the pistons? Mine was not loose like rattling loose, it was just able to move inside the conrod end. Also, what do you (all you guys) think could be the consequence of this? I reused the pistons, didn't have the block bored, and replaced no bearings, and I have a spare shortblock so if this goes it won't be a huge deal, just kind of a pain in the ass. But I'd like to make sure the head can't get damaged. I don't suppose it could throw a rod, per se, but I can imagine other bad things happening. The noise was gone for the first few hundred miles after the rebuild, but has now returned. I think maybe the piston pin circlip has come loose again--it was a non-stock clip, not like the others in the engine. If that came out, what would happen, do you think? Just score the hell out of my cylinder wall, I suppose...
Thanks... :shock:
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#104
by
fspGTD
on 03 Nov, 2005 09:57
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On a 1.6lNA motor I recently re-ringed (the 1.6VNTD), I recall all of its wrist pins were a medium/light press-fit into the pistons. I'd describe it as just light enough that you can press the pin into the piston with your hands, no special tools required. Sliding the rod back and forth inside the piston, the rod slid across the pin before the pin slid in the piston. (I actually can't remember if the pin slid in the piston at all for the purposes of this test, it might have not.)
The 1.6lTD pistons seem to have a noticeably looser fit of the piston pins. I have read a reference that on the turbo pistons the pin piston to clearance was increased. Having recently handled both, I think I can verify this is true. The rod pushes in and moves around from side to side noticeably easier in the TD piston than it does with a NA piston. Sliding the rod back and forth inside the piston, the pin slides inside the piston before the rod slides over the pin.
The design of these pins is called full floating. The idea is with everything at operating temperature, the pins are supposed to be able to rotate around and distribute the wear and lubricating oil all around. They get their lubrication from a hole in top of the small end of the rod. What you describe "not rattling loose, but able to move" sounds right to me. The main advantage of them is that they are easy to disassemble and reassemble, as you don't need a press.
Be really careful removing wrist pin clips if you plan on re-using them... if you bend one and put it back in so it could come out while the engine was running, it seems like it would do some pretty serious piston wall damage. Next time you have a bottom end apart if you want extra peace of mind, install new pin retaining clips.
I'm sure new pin clips are cheap... let's see. Looks like the part number is N 012 277 1, known at the dealer parts depts as "lock ring" remarks "C24x1.5", 8 needed per motor. Yep, they retail for under 50 cents a piece.
I know certain types of applications that are pretty extreme (like baja style off-road racers constantly crashing over bumps) make improvements in the piston pin retension department, upgrading the clips to special one-use-only spiralox retainers (since they get destroyed every time you remove them, there is no temptation to re-used them like there is with c-clips).
You also sometimes hear about teflon buttons getting installed near the pin ends to minimize the damage "just in case".
