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Engine Specific Info and Questions => IDI Engine => Topic started by: rs899 on September 29, 2009, 04:39:22 pm
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OK, so I picked up the 91 Jetta NA with 140K miles that was the victim of somebody else's timing belt error.
http://www.vwdiesel.net/forum/index.php?topic=21204.0
I got all the pistons out and everything looks OK, except #1 has an s-shaped rod and a really messed up piston. The top end has been rebuilt and is ready to go.
I was going to re-ring and re-bearing the rods after honing the bores.
I read somewhere that Goetze made much better rings than Grant. I put together a nice order for Arizona Autohaus. It came in today.
I goofed. I only bought one piston's worth of Goetze rings. ( website is kinda misleading- the pricing is for Grant Rings in sets for 4 pistons- the Goetze is price per piston. The price is $25 for ONE Goetze piston set and $22 for FOUR Grant piston set :'()
I opened the package, so I don't think AZAH will want to take them back, so I either have to buy $75 more of Goetze rings, $22 of Grant rings, or just use what I have on the other 3 good cylinders.
Unfortunately, I have no idea of what this engine was like. If I knew it burned little oil and had good compression, I would probably just fix #1.
Being cheap, had I read the website properly, I would have just bought the Grants from the get go. I hate to put $75 more in an engine that probably will need a rebuild in 100k miles anyway.
Opinions?
Rick
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jeez it needs a rebuild now, you might as well just drop the coin while its out and apart.
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Get a set of 4 for sure I wouldn't be afraid of the Grant ones and believe me there is nothing wrong with having a spare set for 1 piston on hand. But also do't get disgusted after you rebuild it and it uses a little oil even after it's broken in. These things all use a little oil no matter what you do, I've had 2 of them bored with new pistons and both used at least a quart in 3,000 mi. but it runs 70-75 on the interstate everyday. $22 does seem awfuly cheap though for a set of rings though ::)
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I've been running a set of grant rings in both my cars now.. THey seem to be working just fine.. Actually great for the price.. THe top line rings they replaced were definitly more costly, and complete garbage.. AS Rabbit TD mentioned though, don;t be too disgusted if it does still use a bit of oil not matter what rings you opt for.. ..
Both my Bunnies went from burning a quart every 400 miles to a quart every 2-3K miles after changing rings..
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Thanks guys, maybe I'll get the Grants as long as your experience isn't too bad. I am sure it is going to burn some oil anyway with the mileage it has.
Looking at the 3 good pistons, though, I was surprised at how clean they were. The rings on those were very free and there isn't much , if any, coking of the ring lands ( unlike most of the pistons in my parts collections that are really coked up). That's one reason I was just thinking of leaving those alone at this point.
Macka- no the engine is not out. I would certainly do the whole thing right if I did have it out, but its more a question of not wanting to take the time to do it at this point
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OK, but IMO if you mangled a piston, you may have other damage. I'd either swap out the engine with a known working engine, or do the rebuild. I don't like guessing if the motor will last for 50 seconds or 50 years after a catastrophic failure like that. If you do swap out a known working keep the block for a spare and rebuild it.
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What "other damage"? With the possible exception of the crank, ( and I will look at the main bearings at least) I am willing to gamble that investing about $100 in rings/rods/bolts (and a day's work) will get me 50 to 100K miles vs investing closer to $1000 (and a couple of weekends) to get 200K. I just don't get a sense that this engine is that close to worn out based on a lot of 1.6 NAs that I have seen over the years ( including the one in my Rabbit Pickup).
That must also have been the opinion of the deceased machine shop owner who owned this car. The car came complete with a head that he rebuilt and a used piston/rod ( I had a better one). He could have pulled the engine and reworked it himself for nothing but new parts costs...I am just following his lead.
Rick
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What "other damage"? With the possible exception of the crank, ( and I will look at the main bearings at least) I am willing to gamble that investing about $100 in rings/rods/bolts (and a day's work) will get me 50 to 100K miles vs investing closer to $1000 (and a couple of weekends) to get 200K. I just don't get a sense that this engine is that close to worn out based on a lot of 1.6 NAs that I have seen over the years ( including the one in my Rabbit Pickup).
No way did your crank get damaged from the piston eating the valve... maybe your cam has a crack that might fracture at any time (Did you test it for cracks ? Magnaflux or the chemical crack detection?) I would do the rebuild too, but don't discount your rebuilt engine so much... The last one I rebuilt did not use oil after break-in and went on for another 100K miles until I sold it - still running like new.
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Unfortunately (or fortunately) I am going to have to use a mechanical cam on this hydraulic head (unless someone has definitive evidence that it won't work). The original hydraulic cam was left in the leaky trunk for about a year, and several of the lobes are pitted beyond salvage.
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Unfortunately (or fortunately) I am going to have to use a mechanical cam on this hydraulic head (unless someone has definitive evidence that it won't work). The original hydraulic cam was left in the leaky trunk for about a year, and several of the lobes are pitted beyond salvage.
Great ! So there is no worry about the cam cracking then. All of my IDI's have had mechanical lifters so I have no idea what the differences are for the hydro - Provda.
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Won't work, the lobe circles are completely different for mechanical vs. hydro.
Brendan
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Won't work, the lobe circles are completely different for mechanical vs. hydro
Please educate me further. My rough measurements indicate the lobe (non-contact part) are maybe .050" thicker on the mechanical. Is that going to contact the lifters?
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I have been running mechanical cams in hydro. heads for literally thousands and thousands of miles...certainly NOT a problem.
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I am glad to hear that, DK. I am willing to confirm your experience, but I was hoping somebody can tell me more about hydraulic lifters and cam theory and why having a slightly different cam will matter.
I have 11 vehicles and so far only this one and my old F-100 have hydraulic lifters. I would just as soon use a solid lifter head with any of a pile of good solid lifter cams I have, but the late PO has already reworked this hydraulic one , and it seems a shame to "waste" it
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Welp, I can be wrong. I didn't think you could get a thin enough shim to make the clearances right if you were putting a hydro cam on a mechanical head, but you're going the other way around so I have no idea how that would work.
Brendan
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you mean thick enough shim, the hydro cams have a smaller base circle.
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Shim? What shim? See, I am really confused...are there shims on a hydraulic head? If so, those weren't included in the kit of parts I fell into....
I know my way around mechanical heads just fine...why did they have to mess up a good thing...progress (mutter mutter) .
Rick
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no, hydro heads have no shims.
we were just saying that the hydro cam has a smaller base circle, so if you installed one in a mech head, you would need VERY thick shims.
a mech cam in a hydro head will compress the lifters more than they are designed to be, might work, but not the way they designed it.
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Is the normal condition for the hydraulic cam to contact the lifters at all times (360 degrees)? Or is there some clearance as on a solid lifter system?
The last thing I want to do is have #1 (or any) piston and valves meet again. I am not too concerned that running a mechanical cam is less than optimal , as long as will it work without damage....
Rick
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on both solid and hydro you should not be able to see any gap between the lifter and the cam.
when the hydro engine is running the oil pressure will keep the lifter in contact with the cam at all times, and when off they should be touching, or so close you cant tell the difference.
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Well of course, on the mechanical , there is the normal clearance, whatever the spec is .006" intake /.014" exhaust or whatever it is (not reading from the Bently).
So on the hydraulic, with the oil pressure up , the lifters are in constant contact with the cam...hmmm. Shows how much I know....
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well, this is not entirely true, when the cam pushes the lifter down it will force a small amount of oil out of it, and the oil pressure will take a small amount of time to fill it back up to contact the cam again.
this is a very small amount of time, and usually the lifter is in contact with the cam long before the next time it is pushed down again, but if the motor is spun fast enough the oil pressure cannot keep up with the oil being pushed out of the lifter by the cam, making the gap get bigger and bigger, sometimes called valve float.(this can also happen when the valve springs are not strong enough to push the valve back up fast enough in a mech engine)
but for all purposes other than high RPM(which our diesels rarely see) the Hydro lifter is in contact with the cam at all times
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Unfortunately (or fortunately) I am going to have to use a mechanical cam on this hydraulic head (unless someone has definitive evidence that it won't work). The original hydraulic cam was left in the leaky trunk for about a year, and several of the lobes are pitted beyond salvage.
http://www.oregoncamshaft.com/
We've used this place twice with good results, if they have cams in stock you can buy one and use your's as a core or just send it in and get it ground. The cam in my rabbit came from there.....