VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: oblique on March 22, 2023, 08:22:59 pm
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Hello again and gappy spring.
I hope everyone is well.
Picked up a sketchy shortblock and got into it at the carwash...would love to salvage it.
As an atheist, I don't know what in gods name happened here but that's a lot of force, so what is the proper way of measuring the rods?
The top side looks machined but I don't know if they are all exactly the same there but even if they were, it's really tough to get my caliper in a consistent position. It's a 12" Mitutoyo so plenty of length.
Do I remove the studs and line the rods up on a hard surface side by side?
Again really want to salvage this block...there's also weird gunk in the head bolt holes... it's like silicone...
Had a turbo pan, and the drain boss looks good but it was rather rusty on the outside, I don't know how significant the section loss is but I'll know when I clean it up more.
Yeah, check out the intermediate shaft failure...seen this before?
(https://i.ibb.co/j6qzLDg/20230321-201023.jpg) (https://ibb.co/tmnzbD8)
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What are the head cam to lifter clearances like?
With that much mashing on the tops of the pistons I would venture a guess that they were way too tight.
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I wish i knew...i only received the shortblock. Seller 'doesn't know'.
The block is hydraulic...you're saying it mightve been run with a mech head somehow?
Wrong cam? Timed badly? Valves keepers too high?
But yeah it does look like theres been repeated contact ...i figure this might be more plausible on a hydro head since the oil pressure could soak up some of the.force of repeated contact.
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Those marks on the pistons are due to a broken timing belt, it wasn't running with the pistons slapping the valves.
And this one was going down the road pretty fast when it broke.
Nice find, a hydraulic TD block.
That means you can use a metal head gasket from a 1.9 AAZ block.
Or it's pretty easy to put a mechanical head on it, with a regular head gasket.
Kinda hard to read the numbers but it looks like original pistons so a second over bore to 78mm might get rid of all the rust pits.
Or since it's a hydro block you could put 1.7 pistons into it which are 79.5mm.
I've seen an I-shaft thrust surface break off like that before.
I think it's from a bad injection pump mainshaft bearing, that made the belt ride to the outside.
Then it had to skip across the I-shaft pully to get back in line with the crank sprocket.
That pulls the shaft out, then the oil pump pulls it back to ride against the thrust surface in like normal.
Bang,bang,bang break.
What's in the head bolt holes?
I would think the rod measurement would be from hole to hole.
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I've seen other TB broken pistons...nothing even close to this...these impressions are DEEP and on all the pistons...cam kept rotating after the break?
the pistons are marked 76.48 and are OE. The skirts dont actually look too bad and the ridges on the bores aren't terrible...I will try to bore this 0.5 over...I am finding 1.0mm pistons are a bit harder to come by.
The stuff in the head bolt holes is a silicone adhesive type substance, like RTV. With fine grit mixed in. Where the holes are empty there there is some rust...I will need to find a long tap to get those cleaned up.
I'll post more measurements of the rods and general condition of the block after I clean it up better.
i will be going with a hydro head...I have been collecting them and have found some decent ones.
Thank you!
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Cleaned it up some, pretty typical rust belt corrosion.
Some questions:
How do I remove the dipstick tube? Hammered on it from the pickup side wouldn't budge.
What are the holes in front of and to the side of the vacuum housing? Pics of a 1991 NA hydro block with black paint for comparison.
What is the bolt.on the bottom front of the block? Dont.think I've seen that before.
Still have to clean the head bolt threads.
(https://i.ibb.co/0s1t7fM/20230323-232618.jpg) (https://ibb.co/Y0JZCtk)
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I don't think I've ever noticed that little hole back in the cavity before.
Looks like it's plugged with a rivet,.. so I'm thinking maybe an oil passageway.
Like the one behind the 9/16" plug above it and to the right,.. only smaller. Also close to the oil pump so it might be a passageway.
The one down by the trany mount hole might be an oil pan bolt hole that came through the top.
You are right. I can't find any good pistons that are 1mm over either. I'll keep looking for ya. I have a spare set of new 1mm over pistons but they are kolbenshcmidts and would cost $400 for the set.
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Any ideas to remove the dipstick? Just heat it up and hammer some more?
Those holes by the vacuum pump are a bit concerning to me...i will try blowing air through them to see how theyre connected. On the other NA block (painted black) the rivet does look factory but it doesnt have the other hole like this TD block.
I measured the rods hole-to-hole and they are all within .01mm of each other...98.63mm. Is this even possible with the amount of force those pistons took?
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I'm thinking just heat and beat for the dipstick.
I think they usually are hard to get out.
I broke a belt once and the pistons had some bad marks,.. not quite as bad as yours.
The rods were still good.
How much are you paying for the pistons and what brand are they?
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They will be Hans pistons, pretty sure they are same as PP sells. I bought a set for another block (the painted black NA block in some of the above pics) and the machine shop was surprised at the quality and consistency. They are out of Taiwan and came in "arco" branded boxes. Someone on here said the rings aren't the greatest quality so I just got some German ones immediately.
I picked up another TD motor yesterday, i think I got lucky. Everything on it looked quite original but the block and head looked fantastic inside. Stock bores and pistons. No ridges at all. No visible cracks between valves on the head. The mystery bolt on the bottom is for holding the PS line metal bendy support tabs!
(https://i.ibb.co/DgBPK1G/20230326-213513.jpg) (https://ibb.co/dJNsKfb)
(https://i.ibb.co/GdsNbBq/20230326-213503.jpg) (https://ibb.co/nw3t5ZF)
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(https://i.ibb.co/fSSW0tH/20230326-213800.jpg) (https://ibb.co/8BBw829)
It has the riveted hole just like the rest.
(https://i.ibb.co/7V6CYz9/20230327-074452.jpg) (https://ibb.co/S09ysxL)
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Did you try getting pistons from Spareto? I got a couple sets a few months ago for fairly cheap. I just checked and they have them readily available.
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Not trying to hijack this thread but...
Fatmobile, you mentioned above that since Oblique has a hydraulic 1.6l block it can be bored to take 1.7l pistons. I have a mechanical 1.6 that has cylinder ridges but is already bored out to 77.51 pistons. So, KY engine code pistons are not an option from what you have written?
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The 1.7 pistons won't fit through a mechanical head gasket.
With a hydraulic block you can use a metal 1.9 AAZ head gasket.
They will fit through that.
There is also the expensive option to use a special custom-made gasket that has holes big enough for the pistons but without the extra oil drain hole.
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Thank you, wish i had thought of that. The local machinist said he couldn't bore the block out that far, now i understand that he was probably thinking ahead and taking the head gasket into account.
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Nah, he probably just thought the walls were too thin.
He can bore it out that far and use a custom gasket.
I have a block I'd like to do that to also but a $200 gasket is a little high.
Maybe we could get a discount for 2 of them.
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i will talk with the machinist again. He has done a ton of work on VW diesel engines but hasn't ventured much into modifications outside of stock. He can get prickly about being questioned which i understand. His timeline would probably be 8 weeks if he agreed and after that i could get some numbers on the piston protrusion. So will pm you when i learn more and do some back of the napkin math of what this might run. Right now it might be pushing $600 (with a custom head gasket included) so have to think it over some more.
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Did you try getting pistons from Spareto? I got a couple sets a few months ago for fairly cheap. I just checked and they have them readily available.
Mr. RustyCaddy alerted me to a lcoal ebay auction for +1 KS pistons...I ended up buying all four sets...bought a lottery ticket too.
Speaking to Maggie at PP, they have used their Taiwan (Arco?) pistons in 200+ builds for over a decade and have had no issues...even with the rings, apparently. I'm quite certain that Hans sells the very same ones...so that's an option...especially for AAZ kits which are stupid pricey.
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You mean you bought four pistons right?
Not sets of pistons, right?
How much over, they weren't standard size right?
What kind of deal did you get?
How $much$ for 4 KS pistons with rings?
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No I bought 4 sets of +1mm KS pistons in sealed boxes....16 pistons total :D
I bought 2 sets initially then just ended up buying everything...i spent $1kCDN
Thank you RustyCaddy!! I owe you sir, literally lmk what I can do for you.
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That's a super deal.
For something that's getting hard to find over on this side of the pond.
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Oblique-Glad that you are preserving so many IDI motors and that the piston sets help :)
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It's been pretty interesting learning about the details of these motors. I am about to reassemble the first block I had machined.
Couple of questions regarding piston protrusion.
My understanding is that the name brand oversize pistons are shorter - that the pin sits higher relative to the top/crown to account for planing the deck.
I did not measure piston height on either of the blocks I'm working on before disassembly. Both were stock bores and pistons.
I did take one of the old pistons so they can compare measurements but without pre-teardown measurements how much do I tell them to take off the deck? 0.1mm?
The other question was regarding rod bushings...do these typically wear? When I press in the new pins should there be any play? Is there are allowance at all? This veg block had pretty significant piston-valve contact. I'm assuming replacement bushings, if replaceable, are not easy to find.
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I think the bushings are pretty easy to find.
But I haven't looked lately.
I do have them replaced when putting new pistons in.
They also need to be reamed to fit the pins.
Some folks have put the engine together and had a tick that doesn't go away when the ignition is turned off,
when they didn't change the bushings.
As far as the pistons protruding above the block surface.
I usually install the pistons and check to see how high they are.
Sometimes swap to different holes.
Sometimes one piston will sit higher than others.
Sometimes the block needs ground at a slight angle,.. only talking thousandths.
Shortest piston at one end and work up to the tallest at the other.
It's not a given that the new pistons will be shorter, or that the block will need ground.
I just have to install them and see,.. kinda like finding out what valve clearance shims are needed.
Or if a valve might need a little ground off the top to make room for a big enough shim.
I don't put the valve seals in until I've put it together and seen that a valve isn't going to need removed to grind the top