30hp engine failure - strip down and evaluation

[Mike1973]

Right, I'm an engine numpty here, so could do with some help working out why my faithful old 30hp gave out on me recently, so that -
a - I can fix it back up
b - I don't do the same thing again

It was in the Kombi when I got it in 2004. The Kombi had been stood since 1990. I just did a top end overhaul, changed the oil, plugs, etc... adjusted the valves, statically timed it with a test light off the coil to 7.5˚btdc.

The motor had a little endfloat, and used oil, so I knew it would need rebuilding sooner rather than later, but I got nearly 30mpg and it ran strong. Also, I've done 11,000 miles since getting it back on the road, a lot of them on the motorway at 45-55mph.

Lost power suddenly on motorway at 50mph, pulled over a mile later and died on the hard shoulder. Loss of compression seemed likely, and on inspection once the motor was out No1 had no compression at all. (but only tested by sticking a finger in the sparkplug hole... )

No1 barrel smooth? I thought it would be really scuffed up?

Heavy scoring to the edge of No1 cylinder. All the rings in place, but the piston rings are really bedded in and flush with the piston. Oil ring is still free.

I'm using this manual to help with the rebuild. I do have a Bentley but for later model splits.

Cheers, Mike.
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Editor - Split Screen Scene, the Journal of the SSVC.
My flickr http://www.flickr.com/photos/29051501@N08/

[keifernet]

Looks like it was running lean and hot and the top of that piston started to burn and once that started it was all over...

Might have been a vaccum leak or jetting... Or you could have used the wrong mark when you set timing only static and did not check distributor and how well it was advancing and what the total degrees of advance was with a light.

[miniman82]

Detonation!


Time for new P+C's, and I would check that head too. Having a look at that cylinder's rod bearing might not be a bad idea either, detonation can pound the crap out of bearings.
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Build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=212747

[DarthWeber]

Yikes! Was that piston starting to melt or is the white color from something else?

[SRP1]

Lean mixture for sure, the question is what caused it to go lean? Vacuum leak, insufficient fuel supply, or a change of parts used on the engine.
Unless you made a change to the engine just prior to this happening I would say a vacuum leak is the culprit. Generally speaking on an engine with as many miles as appears to be on this one, a lean mixture problem would have come into play a long time ago, so that rules jetting out.
Other things follow a lean mixture like detonation, and high cylinder temps, but you should be able to hear detonation severe enough to have caused this.

[hoghead5150]

how do the rest of the pistons look? is #1 the only one that is like that? might help narrow it down. i agree with detonation causing this, but if all pistons are pretty much the same i would suspect lean conditions or timing. if only #1 is like this, i would suspect vacuum leak.

[The Noof]

[miniman82]

Oh, really? Same exact thing happened to my old roomate's split window on the way back from Pomona, and it most definitely was a vacuum leak.
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Build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=212747

[The Noof]

[SRP1]

[keifernet]

It could be a combination of all... what ever it is I have seen it enough times, and so have you guy's to recognize... it ain't pretty... and arguing about EXACTLY what it was is not going to help

But he needs to check for evidence of a vac leak at the intake and make sure the timing is set correct on the rebuild... lest we see him post again in a few thousand miles.

[The Noof]

[miniman82]

[Mike1973]

Cheers for you expertese fellas, it is much appreciated.

I'm still stripping the motor down, but here are some pics so far.

Pistons 2 and 1. No2 is covered in oil, but No1 is dry in comparrison. I guess it failing would burn the oil off?

And with the head off the other side, 3 and 4.

I removed the manifold 12 months ago to help change the dynamo/fan. Refitted with new gaskets. Not done anything major since. I'm still running the exhaust the bus came with though, which is a bit of a frankenstien affair, with 30hp pipes mated onto a later zorst Might be a candidate for pulling the inlet manifold out of true, making a leak at the heads?

Anyway, because of the endfloat, I want to totally strip the block down, and go through all the bearings. And yes miniman82, the rod for No1 does flap about a bit now

I've been given a set of clean heads that need new valve guides. And I was hoping to get away with just replacing piston rings on the other pistons... whats the score with this? Can you replace just one barrel and piston on a rebuild or is this a no-no? Or do all these barrels and pistons all look worn out? Again, unknown territory for me so forgive my ignorance...
_________________
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Editor - Split Screen Scene, the Journal of the SSVC.
My flickr http://www.flickr.com/photos/29051501@N08/

[DarthWeber]

You've got it pulled down that far, might as well go all the way. Just think how much your motor will appreciate new bearings and some TLC!

[hoghead5150]

change all pistons and barrels. no since in taking it down that far and just changing one. looking at the pics of the 3&4 pistons, i would say that the problem was a vacuum leak on the 1&2 side. most likely intake gaskets causing the #1 piston to go real lean and #2 looked a little lean also.

[krusher]

Some words of warning as its a 30hp rebuild.

Simple parts arnt as easy to get as a 1600.

A set of barrels and pistons is going to be expensive.

The heads arnt semi hemi cut thats whats 30hp combustion chambers look like stock.

Dont have the case line bored or the crank ground until you have the bearing in your hand that are the size your going to go to. If your case is going to its first line bore and the crank to its first grind then those are the hardest bearing sizes to find as that what most people need, and 30hp stuff isnt falling off the shelves like 1600 stuff does.

I would expect you will have to shop online outside the uk to find parts.

You may be able in the Uk to pick up a complete 30hp engine for peanuts as no one wants them.
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(06:31:07) RoachGhia: "i drink dick way too fast"

[Mike1973]

Cheers fellas. While I was dragging the bike out of the garage this morning for work I picked the manifold up and had a quick shufti... Holding it up to the light I could see a crack of daylight through the inlet where it fixes to the head, on 1+2 side... I'm hoping it's something that can be repaired....

Krusher is spot about parts supply here in the UK. Difficult to get 25/30hp stuff over here, not much 'off the shelf', and when it is it's usually not cheap I dread to think what a set of new barrels and pistons will cost me, and that will probably knock the rebuild on the head.
I'm always struggling to keep the Kombi on the road as stock as possible, but doing it on a very limited budget. I'd already assumed the best place to get bearings and gaskets would be the States, (from doing the top end rebuild a few years ago) but I'll do the rounds of suppliers and compare prices. KK in the UK and BBT in Belgium are closer suppliers.

Second hand 30hp motors turn up occasionally in the UK, anything from £30 to £250. But then you've got another used, maybe high mileage engine. It may 'run really well', but for how long? I'd love to do my own rebuild and know I've got a solid engine under me. Maybe getting a set of good used barrels and pistons is an option?
_________________
Gaffa Tape Tourist - Touring Europe at 45mph
Editor - Split Screen Scene, the Journal of the SSVC.
My flickr http://www.flickr.com/photos/29051501@N08/

[krusher]

Your a brave man to keep on the 30hp road, I used to use my barndoor with a stock 30hp, was great fun on country lanes and pushed the bus along happily at 50mph, but I never took it on the motorway, did not want a lorry smashing into the back of me as i did 30mph up a hill.

Maybe you should look into a vintage performance rebuild for a bit more power.

I was going down that route, even have ported heads on the shelf, but was in search of more power int he end and ditched vintage speed.

These might get you started

http://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=111198057
http://www.wolfsburgwest.com/wolfsburg_new/engine/25-36_hp_engine.cfm
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(06:31:07) RoachGhia: "i drink dick way too fast"

[cal63look]

In your last picture you posted, It looks like the left sparkplug isnt seated all they way? It looks like 3 or so threads left, that could def create some heat. Are those the correct lenght sparkplugs?

Just thowrin that out there