Henny and CTWG60 have a long chat about pistons :)

[Henny 0]

pistons worn? Whuh? :shrug:

 

The rings wear, the bearings wear, the cylinders wear, but not the pistons... The 225K mile pistons that came out of my G60 when it was first rebuilt were in good condition and still within spec... true, the rings were shot and the cylinders worn beyond repair, but the actual pistons were fine... The only ways to screw a piston are to run it mega lean and melt it, or to get contamination in there and physically hit it with something (a valve, swarf or a bolt getting sucked in come to mind as examples from my engines alone! :roll: )

 

If you're replacing the rings, and re-honing the cylinders, it shouldn't matter a hoot which piston goes in which hole as long as the gudgen pins are retained with the correct pistons... (and you put 'em in the correct way around! :lol: )

 

This is why you can get oversize rings to go on the original pistons... means you can have a very slight overbore to resolve any cylinder issues and continue to use the original pistons... damned site cheaper than £350 for a slight rebore and a new set of oversize rings!

 

If you were going to the trouble of new pistons, you may as well go whole hog and take it to 1.9 or further... ;)

 

Sorry to inform you of this Henny but pistons do wear. I've stripped a couple of 100k+ blocks in my time and when I've measured the pistons with digital calipers and compared them to the wear limits they have been out of specification, meaning the pistons have been subject to side wall wear. I'm sure many people wouldn't worry but it depends on how long you want the rebuild to last. This is why many new pistons come with areas of molly coating to the front and rear of the pistons to reduce friction and thus wear!

 

As I say speak to a professional and be sure before going to the trouble and expense of rebuilding it.

 

Talking of pistons being installed backwards. I remember seeing a picture of your engine when you were replacing the head gasket the first time round and your pistons appear to be from a cross flow SEAT engine were the spark plug is located to the rear of the engine rather than the front as in a G60 engine, so effectivly you seem to have more squish area to the front of the engine which will be pushing the mixture away from the spark plug which is not ideal. Maybe this is the root of your headgasket issues!! :shrug:

 

Ahhh...

 

Here we go...a theory that might be worth looking into! :D

 

viewtopic.php?f=11&t=1727&hilit=jdub&start=150

 

Interesting CTWG60, I seem to stand corrected about piston wear... out of interest, were the 100k+ blocks VW (specifically PG) blocks? just wondered if that's why I've never come across wear on the pistons of any of the 4 G60 engines I've stripped/rebuilt...

 

Anywho, another interesting point about the pistons in my car... yes, I believe the pistons ARE out of a SEAT, nicely identified there, although I'm not sure if it's a cross flow or not, I'll look into that... I don't think this is the cause of my problems though, as the head gasket problems have all been caused by a dodgy thread in the block which was caused by a dodgy head gasket letting water seep into the bolt hole before I got the block... this has now been remedied and is no longer a problem... the head gasket has not gone again since, as I've recently discovered after taking the head off again to try and get to the bottom of my running problem and finding it was perfect... That does raise an interesting question as to whether to reverse the piston orientation in my engine though, to get the extra "squish" at the back of the head, rather than the front... I'll have a ponder on that, although, looking at the head and where the spark plug actually is in the cylinder head, I don't think it'll make any difference...

[CTWG60 0]

The blocks were not pg engines but were VAG engines, they weren't out of spec by much but I would imagine VAG engines being generally more undersquare type engines ie. more stoke dimension than bore, then more sidewall pressures will be experienced I know that VR engines suffer a lot of sidewall issues due to the design but yeah. Also most vag engines have very low rod to crank ratios so again your going to get more piston wobble/wear than on a honda for example. I do have a pg in the garage at the moment all stripped down but I haven't checked the pistons yet as it wasn't going to remain standard! :wink: But money, time and a lack of enthusiasm are my enemy lately, I have no idea now many miles it has done!! The worst of them was the 2.0L 3A Audi block which had done about 130k, I guess if pg pistons don't experience quite as much wear it must be down to the rather longish total height of the piston spreading the load and keeping the piston more square in the bore and the shorter crank of 86.4mm, I doubt the rod ratio helps but it is more than than a 144mm rod 2.0L engine.

 

As for your engine that shot you've taken it's rather telling if you look at cylinder number one at TDC you can see that toward the rear right of the crown quench area about 2 o'clock you have a white deposit and also to the front right about 5 o'clock. As apposed to the left side which is mucher darker. So I would say you have a lot of combustion occurring in areas were no combustion should be taking place! ie. In the quench or squish zone! Or at least the piston is suffering higher temperatures in this area, isn't your problem not overheating but losing cylinder 1 & 2 after some minutes of normal running. From what I can see of the other pistons they seem to be fairing a lot better but I'd say number one is suffering lean or hotter conditions which they always do anyway but rotating the pistons 180? would see slower combustion flame travel and lower combustion temperatures and also maybe better mpg due to more efficient burning of the fuel air mixture in my opinion. What have you got to lose it's been sat for 2 years undiagnosed after having 3 head gaskets or else your looking at scrapping the block due to the helicoil not working for you! I'm probaly wrong but I think it's worth a shot. Do you have ARP rod bolts? You wouldn't have to replace them if you did rotate the pistons, could be done in situ with the sump removed.

 

Please bare in mind I am a hobbyist and am no expert I just read alot of books and have an unhealthy interest in what goes on in a internal combustion engine during use. I will say though that VAG always situate a raised area of piston crown (compression lump) opposite to the spark plug, it's sole purpose is to push the F/A mixture toward the spark plug the only exception to this I have come across is the cross flow 8v 2.0 engine fitted to the mk4 golf/Beetle, they had compression lumps on both front and rear possibly due to the cross flow head having the intake situated at the front of the engine and the change in airflow dynamics and squish experienced in the cylinder causing hotter or just combustion at the front of the cylinder in the quench zone. I will also say that these pistons are from an N/A 1.4 engine with very square characteristics and they seem to have very little in the way of quench zone toward the rear of the cylinder when compared to a PG piston which seems to be designed to make sure that all combustion occurs in the centre of the piston, possibly another reason for the longish piston design, or at least compression height of these pistons and thus the shorter rod ratio to accommodate such a piston.

 

OK this is turning into a essay.

 

So basically you have a high compression engine with less quench zone and pistons that are pushing the mixture to the area that is weakest in terms of keeping the walls and head gasket protected from combustion. So please don't take offense, I understand the years of investment in this project but I think you could have a relatively simple and cheap fix for this problem, if I'm right!

 

WAY OFF TOPIC! HA! :lol:

 

EDIT: Wow I just took a closer look at the quench area and without being negative you have about 2mm of quench area between the piston combustion dish valve recess at the side of each cylinder and the head gasket! Eeek! That's gotta hurt the head gasket surely!

[Henny 0]

hmmm... interesting.... I'll PM the mod squad and get them to take this out of this thread and put it in a new thread of its own as this is really interesting stuff. (sorry to those who don't find it interesting... :oops: and sorry to Robster for hi-jacking his thread... :wave: )

 

The pistons I have in my engine are designed to be used in a forced induction SEAT and are well upto the job they're being used for, you'll have to trust me on that one, they're definitely not out of a 1.4 Seat engine! :lol: They've got the heat treatment coating on the crowns and if you've seen the thickness of the crowns, you'd agree they're upto the job! 8)

 

You can pretty much ignore the colour of the pistons, that's just where I've wiped 'em down a bit, there's no deposits on any of the pistons, other than a bit of oil that was spilt when I took the head off, and some carbon build up from it running rich when I was trying to find the fault... all four looked like the middle two until I cleaned up the head gasket (and pistons 1&4 with it!), to make sure there was no obvious signs of damage/leaks before I removed it from the block, so don't read too much into the colours/conditions of the pistons, plugs etc... also, don't forget that I'd done LOTS of tests on this engine before I took the head off, so injectors had been disconnected, plugs removed, plugs left in with no HT lead on, compression tester fitted, etc etc etc...

 

The problem I currently have is definitely not with the pistons... The engine bottom end has done 25K miles since it had those pistons (ok, not those EXACT pistons, I had to replace 'em after a bolt came out of the throttle body, :brickwall: but that's a different story!) and most of that was not exactly taking it easy! :lol: Anyone who has been in one of the two cars this engine has been installed in will testify that it's a nice running engine that goes like stink... :norty: this running problem is a new thing, so is not related to the pistons and any odd inefficiencies that they may be causing...

 

...however, what you say does make a lot of sense, and I may well just swap 'em around anyway while it's in bits (hell, what's a sump gasket and some rod bolts cost?!?) and see if it makes it run better once I find out exactly what the problem is/was... 8) I've changed the pistons with the block in the car before (see problem mentioned before with bolt sucked into engine!) so I know how easy it is to do, and I'm in no real rush to get the car back together yet, so it's not like it's time critical, I do want to get it right when it does go together though... 8) The only stopping point is that the pistons have a cut-out machined into them to clear the oil squirters, and I have a feeling that rotating the pistons would mean that they hit the oil squirters as the cut-out could be in the wrong place I'll have a look at my spare set and see if I'm remembering it wrong or not...

 

I've got a couple of tests underway at the moment which should rule out a few more things it could have been, and if these don't show what it was, then it's time to strip the head to nothing and see if there's something silly like a crack in the chambers of the head (unlikely), inlet manifold (again, unlikely) or something a little more off the wall like broken valve springs.... I do have a feeling though that one of the tests I've got going on will come back as being the problem... and I'll be kicking myself if it does... ;)

 

Thanks for the interest though, and any more comments are more than welcome... 8)

[Henny 0]

Well anything is worth a try to get it sorted. I think these psitons do have enough meat to them but my concern as I've said is the quench zone and the pistons orientation. Here is the source of identification of those pistons.

 

EDIT: I've put these through a compression height calculation and they should have a deck height of just under 1mm (0.95mm) below the block surface.

 

I've added the final post from the pistons thread into this thread as a quote above (I'm not a mod anymore so I can't do it the nice way! :lol: )

[Henny 0]

Blimey, those pistons DO look very much like the ones in my engine... :eek: I'll check the part number on the box (Mahle) that I've got at home tonight and see if it tallies up... I'll be surprised if it does though... Don't suppose you know of a crank that's the same spacing/bearing as a G60 one but has a 89.6mm throw do you? That'd answer the final mystery of my bottom end... :lol:

[CTWG60 0]

Blimey, those pistons DO look very much like the ones in my engine... :eek: I'll check the part number on the box (Mahle) that I've got at home tonight and see if it tallies up... I'll be surprised if it does though... Don't suppose you know of a crank that's the same spacing/bearing as a G60 one but has a 89.6mm throw do you? That'd answer the final mystery of my bottom end... :lol:

 

The only 90 mm crank I know of is a eurospec sport crank. I have a book that mentions a realistic stroker crank (it's an american book) and it mentions a 90.50mm crank. VW never did a 90mm crank! It did not come out of a standard passat!! :D I'm sure of that!

 

The eurospecsport crank has a different rod journal diameter though. Only other 90mm VW crank is the VR6 one and it ain't that! So I'd say if your crank looks very lovley and sporty it's probably aftermarket unless it's some sort of modified early pre mk1 golf crank or something.

 

Oh hang on this book when talking about 1.6 and 1.7 litre engines in a section about differences among crankshafts talks about using the 90.5mm cast crank and 136 mm connecting rods that you will have to clearance the underside of the pistons to allow the counter weights to swing by so I think there are aftermarket cranks for 1.6 and 1.7 litre engines. It mentions that the rod journals on the 1.6 and 1.7 are smaller at 46mm. Also mentions a 91 mm crank!!! :scratch:

 

Yeah has to be aftermarket! Check you rod journal diameter when you turn your pistons around! :)

[robster 0]

Good Lord I have created a MONSTER !!

 

Quote:

 

hmmm... interesting.... I'll PM the mod squad and get them to take this out of this thread and put it in a new thread of its own as this is really interesting stuff. (sorry to those who don't find it interesting... and sorry to Robster for hi-jacking his thread... ) :wave:

 

 

Its ok, interesting readng all the same :notworthy: Do feel free to check in on my post every now and again :grin:

[Henny 0]

The only 90 mm crank I know of is a eurospec sport crank. I have a book that mentions a realistic stroker crank (it's an american book) and it mentions a 90.50mm crank. VW never did a 90mm crank! It did not come out of a standard passat!! :D I'm sure of that!

 

The eurospecsport crank has a different rod journal diameter though. Only other 90mm VW crank is the VR6 one and it ain't that! So I'd say if your crank looks very lovley and sporty it's probably aftermarket unless it's some sort of modified early pre mk1 golf crank or something.

 

Oh hang on this book when talking about 1.6 and 1.7 litre engines in a section about differences among crankshafts talks about using the 90.5mm cast crank and 136 mm connecting rods that you will have to clearance the underside of the pistons to allow the counter weights to swing by so I think there are aftermarket cranks for 1.6 and 1.7 litre engines. It mentions that the rod journals on the 1.6 and 1.7 are smaller at 46mm. Also mentions a 91 mm crank!!! :scratch:

 

Yeah has to be aftermarket! Check you rod journal diameter when you turn your pistons around! :)

 

The crank in my engine has standard G60 rods attached to it, with standard G60 bearings (well, ok, they're actually MKIII TDI bearings as they're harder wearing, but you get the idea! :lol:) sounds like it's still a mystery then! :lol: :shrug: I was told it's a standard VAG crank, but I still am not sure what it's out of... I do know someone who has just had a 1940cc 16V G60 built by the same company though, so the crank is definately not a one off... :shrug:

 

Good Lord I have created a MONSTER !!

 

Its ok, interesting readng all the same :notworthy: Do feel free to check in on my post every now and again :grin:

LOL, sorry... will keep an eye on your thread too... :lol: :lol: :lol:

[Henny 0]

right, now I've found out that my engine problems were all caused by valve springs ( :brickwall: ) I'm going to start a full rebuild on this sucker... I may even base it on the original PG block that came out of the car in the first place to make life a little easier (and cheaper!) if I ever need to do a head gasket again instead of struggling to get 1H head bolts!

 

This means that the block will be fully stripped down, and we may finally get an answer as to exactly WTF this crank is... and I may build another while I'm at it as I've got a spare set of pistons! :lol:

[CTWG60 0]

Oh Ian you have got it bad! An unrelenting addiction to g60 engines that is!

On my iPhone if this post looks a bit weird.

Having a few issues of my own with the new head. Unfunnily enough I had a similiar problem to you with valve closure. Not enough valvee to cam clearance. Hade scratching my head for a day or two no compression on three cylinders whatsoever and a massive 6 bar on cylinder 4!

 

Well I rhnk we will all sleep a bit easier knowing the cause of your issues. So a broken spring on an inlet valve was also screwing with the other cylinder, who could of guessed that one!

 

I now have a head bolt issue on refitting my new head. Two of them felt weird toward the end of the 180 final turn like they went past their yield point so I'm now replacing them for the 2nd time. I now have 60 head bolts in

my garage, why I keep them I just don't know. :cuckoo:

[Yandards 0]

Oh Ian you have got it bad! An unrelenting addiction to g60 engines that is!

On my iPhone if this post looks a bit weird.

Having a few issues of my own with the new head. Unfunnily enough I had a similiar problem to you with valve closure. Not enough valvee to cam clearance. Hade scratching my head for a day or two no compression on three cylinders whatsoever and a massive 6 bar on cylinder 4!

 

Well I rhnk we will all sleep a bit easier knowing the cause of your issues. So a broken spring on an inlet valve was also screwing with the other cylinder, who could of guessed that one!

 

I now have a head bolt issue on refitting my new head. Two of them felt weird toward the end of the 180 final turn like they went past their yield point so I'm now replacing them for the 2nd time. I now have 60 head bolts in

my garage, why I keep them I just don't know. :cuckoo:

 

Interesting stuff, Ian did you get uprated valve springs fitted as part of the head work? Also do you think that the higher redline of your set-up coupled with the larger valves is causing too much inertia in the valve train and overloading the stock springs?

 

CTWG60, maybe you are collecting them to have them melted down into new ones?

[Henny 0]

the red line on my engine was actually LOWER than stock as the power trailed off over 6K, so I got Wayne to set the absolute redline at 6,500 and I never really took it that high anyway...

 

The springs were stock (although new) VAG items... the reason they failed is probably due to being over-compressed by the high-lift cam... The bigger valves are almost exactly the same weight as the stock ones, so I don't think inertia will have had anything to do with it, it was just a case of the wrong springs for the cam... :roll: :epicfail:

[CTWG60 0]

Nope I just bought some ARP's to solve my new problem. Need to find a use for these old bolts though. Suggestions on a post card please to...

 

I have a mental health issue and can't throw out old headbolts!

POBOX 3RE 1QH

[Henny 0]

Need to find a use for these old bolts though. Suggestions on a post card please to...

 

Hang 'em on fishing wire from a set of old pistons to make wind chimes? :D

[CTWG60 0]

Need to find a use for these old bolts though. Suggestions on a post card please to...

 

Hang 'em on fishing wire from a set of old pistons to make wind chimes? :D

 

OOOOoooo, Nice idea! :lol:

 

Maybe I could send them to Rob (dirtytorque and commission him to use his artistic skills and welder to produce me a lovely piece for the wife at Christmas. Kill two birds with one stone there!! :lol:

 

Probably me that would end up dead though! Can't imagine headbolts in any shape or form would be comfortable to remove from ones anus!

[dirtytorque 0]

Need to find a use for these old bolts though. Suggestions on a post card please to...

 

Hang 'em on fishing wire from a set of old pistons to make wind chimes? :D

 

OOOOoooo, Nice idea! :lol:

 

Maybe I could send them to Rob (dirtytorque and commission him to use his artistic skills and welder to produce me a lovely piece for the wife at Christmas. Kill two birds with one stone there!! :lol:

 

Probably me that would end up dead though! Can't imagine headbolts in any shape or form would be comfortable to remove from ones anus!

i really don't need any more head bolts lying around. :lol:

 

I have enough of my own.

[CTWG60 0]

HBHA = Head Bolt Hoarders Anonymous :)

[Henny 0]

I'll keep quiet about the 4 or 5 sets of 1H bolts I've got in my garage..... and the 3 or 4 sets of PG ones too... :roll: :help:

 

 

Hello, my name is Ian and I'm a head-bolt hoarder... :roll: :lol:

[CTWG60 0]

ARPs are the only cure! I don't think they do 1H!!! :D I know we can have a headbolt amnesty day at that stealth RR Day. Bring your old headbolts and cleanse yourself of the nasty habit!

[Henny 0]

I think I'm going to be going PG during my next rebuild... I've had enough trying to get 1H bolts... :brickwall:

[CTWG60 0]

There wasn't any block, injector or dizzy drive gear clearance during your build was there so should be straight forward. Give Impulse a ring linky in my signiture Adrain is a good bloke you won't be disappointed. If there are issues I'm sure he could copy the old block.

 

Or maybe you could find some ARP's to suit?!? :shrug:

 

1H bolts have the same part no. as Diesel 1.9 bolts!! Are you sure they are stretch bolts? Some one told be recently diesel bolts are non stretch!!

 

Scratch that. Diesel Bolts 068 103 384 A, 1H Bolts 037 103 384 B, but both are M12x115!! :shrug: Don't know what the thread pitch is though!

[dragon green 5]

Checked out ARPs catalogue,but couldnt find kit for your engine,but they do a lot for european engines !

might be worth an e-mail

http://www.arp-bolts.com/catalog/Catalog.html

[Henny 0]

I've asked ARP in the past and they don't do 1H bolts... they've got some similar, but won't guarantee them...

 

I can't remember if the block needed machining to clear the new crank... guess I'll find out when I try and put it all back together again! :) :lol:

[CTWG60 0]

With you running standard rods I think the issue will be with the oiljets. If you ran with forged rods.. oh you can't can you, you have your standard rods custom bushed or spaced or something.

 

I think you would be better using diesel bolts or trying the ARP bolts or just getting some more 1H bolts and never taking the head off again! :D

[Toad 0]

The 1H is the Ralleye engine isn't it?