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Author Topic: Disassembling veggie block w/ piston slap- rod length?  (Read 2663 times)

March 22, 2023, 08:22:59 pm

oblique

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Disassembling veggie block w/ piston slap- rod length?
« on: March 22, 2023, 08:22:59 pm »
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?



















 
« Last Edit: March 22, 2023, 10:36:11 pm by ORCoaster »



Reply #1March 22, 2023, 10:37:38 pm

ORCoaster

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #1 on: March 22, 2023, 10:37:38 pm »
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. 

Reply #2March 22, 2023, 11:02:31 pm

oblique

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #2 on: March 22, 2023, 11:02:31 pm »
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.

Reply #3March 22, 2023, 11:57:01 pm

fatmobile

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #3 on: March 22, 2023, 11:57:01 pm »
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.
Tornado red, '91 Golf 4 door,
with a re-ringed, '84 quantum, turbo diesel, MD block

Reply #4March 23, 2023, 01:41:59 pm

oblique

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #4 on: March 23, 2023, 01:41:59 pm »
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!

Reply #5March 23, 2023, 11:36:31 pm

oblique

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #5 on: March 23, 2023, 11:36:31 pm »
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.












Reply #6March 23, 2023, 11:56:46 pm

fatmobile

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #6 on: March 23, 2023, 11:56:46 pm »
 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.
Tornado red, '91 Golf 4 door,
with a re-ringed, '84 quantum, turbo diesel, MD block

Reply #7March 24, 2023, 01:06:31 pm

oblique

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #7 on: March 24, 2023, 01:06:31 pm »
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?

Reply #8March 24, 2023, 01:33:45 pm

fatmobile

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #8 on: March 24, 2023, 01:33:45 pm »
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?
Tornado red, '91 Golf 4 door,
with a re-ringed, '84 quantum, turbo diesel, MD block

Reply #9March 27, 2023, 12:11:48 am

oblique

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #9 on: March 27, 2023, 12:11:48 am »
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!








It has the riveted hole just like the rest.

« Last Edit: March 27, 2023, 07:37:41 am by oblique »

Reply #10March 30, 2023, 11:31:23 am

libbydiesel

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #10 on: March 30, 2023, 11:31:23 am »
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. 

Reply #11March 31, 2023, 06:31:23 pm

RustyCaddy

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #11 on: March 31, 2023, 06:31:23 pm »
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?

Reply #12April 01, 2023, 08:01:12 pm

fatmobile

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #12 on: April 01, 2023, 08:01:12 pm »
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.
Tornado red, '91 Golf 4 door,
with a re-ringed, '84 quantum, turbo diesel, MD block

Reply #13April 01, 2023, 10:39:05 pm

RustyCaddy

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #13 on: April 01, 2023, 10:39:05 pm »
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.

Reply #14April 02, 2023, 12:56:43 pm

fatmobile

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Re: Disassembling veggie block w/ piston slap- rod length?
« Reply #14 on: April 02, 2023, 12:56:43 pm »
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.
Tornado red, '91 Golf 4 door,
with a re-ringed, '84 quantum, turbo diesel, MD block