beetle engine problems...
Discussion
I've recently rebuilt a VW type 1 1300cc engine with a number of simple tuning modifications and ALL components, other than the crank case, are new (combination of GSF, SSP & BBT suppliers).
Currently, the engine is out of the car, for the third time.
The engine was in the process of being run in - it had done around 200 miles ish when it went bang!
Apparently the car began to fill with smoke then slowed making horrific noises as it was coasted onto the hard shoulder.
It still ran but with a heavy knocking.
Upon removal of the engine I found:
1. all pistons had evidence of contacting the combustion chambers
2. number 1 & 4 main bearings look like they've done a million miles - all copper coloured and scored
3. number 1 & 4 crank journals are badly scored (the lovely new crank)
4. all conrods exhibit excessive sideways movement (new bearings etc)
5. number 3 main bearing (the split one) looks like its edges have been peined over and is scored etc etc.
This all points to oil starvation - so what good was fitting the new, high pressure Shadek oil pump?
All oil galleries were cleaned out.
Cleanliness upon rebuild was observed.
The pressure relef pistons are new.
The thermostat bellow could be seen to open when the engine got warm.
Apparently, the oil pressure light did not come on through any of this.
Question: what the chuff has happened and why?!
Currently, the engine is out of the car, for the third time.
The engine was in the process of being run in - it had done around 200 miles ish when it went bang!
Apparently the car began to fill with smoke then slowed making horrific noises as it was coasted onto the hard shoulder.
It still ran but with a heavy knocking.
Upon removal of the engine I found:
1. all pistons had evidence of contacting the combustion chambers
2. number 1 & 4 main bearings look like they've done a million miles - all copper coloured and scored
3. number 1 & 4 crank journals are badly scored (the lovely new crank)
4. all conrods exhibit excessive sideways movement (new bearings etc)
5. number 3 main bearing (the split one) looks like its edges have been peined over and is scored etc etc.
This all points to oil starvation - so what good was fitting the new, high pressure Shadek oil pump?
All oil galleries were cleaned out.
Cleanliness upon rebuild was observed.
The pressure relef pistons are new.
The thermostat bellow could be seen to open when the engine got warm.
Apparently, the oil pressure light did not come on through any of this.
Question: what the chuff has happened and why?!
Does the low oil pressure warning light work?
Was the engine turned over without plugs in to get oil pressure up before any attempt at starting?
Has oil pump output been verified with a pressure gauge, even if just plumbed in temporarily?
Don't see why oil starvation would cause piston/head contact - are the engine clearance calcs and resultant compression ratio correct?
Was the engine turned over without plugs in to get oil pressure up before any attempt at starting?
Has oil pump output been verified with a pressure gauge, even if just plumbed in temporarily?
Don't see why oil starvation would cause piston/head contact - are the engine clearance calcs and resultant compression ratio correct?
Aye: pressure lamp woked - sender checked etc. I understand that as and when these come on the engine is dead by then anyway! Apparently they operate at about 20 psi...
Pump not verified by gauge - just assumed.
Yes engine cranked without plugs in until battery started to die.
Have quizzed a bloke from SSP - he suggests that either the timing was / is too advanced and / or the mixture is too weak - hence high temps.
Even this wouldn't really cause a complete lack of pressure.
Pump not verified by gauge - just assumed.
Yes engine cranked without plugs in until battery started to die.
Have quizzed a bloke from SSP - he suggests that either the timing was / is too advanced and / or the mixture is too weak - hence high temps.
Even this wouldn't really cause a complete lack of pressure.
Was the crank case line bored for oversize main bearings?
The mains are trapped between the halves of the case and the case can wear allowing the bearings to move. This is also a source for loss of pressure.
The reason you see contact of piston to head is that the combination of big end and main bearing failure allowed just that little extra travel of the piston.
A post mortem like this unfortunately may still not answer the questions.
Recover as many bits as you can and start over.
Good luck.
Steve
The mains are trapped between the halves of the case and the case can wear allowing the bearings to move. This is also a source for loss of pressure.
The reason you see contact of piston to head is that the combination of big end and main bearing failure allowed just that little extra travel of the piston.
A post mortem like this unfortunately may still not answer the questions.
Recover as many bits as you can and start over.
Good luck.
Steve
re using a pounded out crankcase is also a bad idea.. even line boring doesnt help much.
what 'mods' had you done to the engine?
what were the heads?
was you using a stock pump, full flow or filter pump.
were the relief pistons OEM or bugpack/other
what oil was you using.
had you blocked off the cooler and used a remote kit
what carb(s) were you using, what main jet?
what 'mods' had you done to the engine?
what were the heads?
was you using a stock pump, full flow or filter pump.
were the relief pistons OEM or bugpack/other
what oil was you using.
had you blocked off the cooler and used a remote kit
what carb(s) were you using, what main jet?
The case has not been line bored - a rough check is to look for a ridge on the main bearing "caps" in the case. This is caused by the bearing outer diameter hammering the case - in my case, there was a ridge but so small that I ignored it.
If this is the problem, how much pressure could be lost - surely not enough to cause massive failure?
Modifications:
Original heads - ported & gas flowed + 3 angle valves & seats
Engle W100 camshaft
Shadek 30mm oil pump
Lightened flywheel - balanced when attached to crank
Electronic ignition module
Weber 38DGAS twin choke carb on bespoke tubular inlet manifold - the carb and timing has been set up and jetted at RE Performence, Bury. (The carb was a new spare for a Reliant Scimitar)
Pressure relief pistons Bugpack / other.
"Hotter" spark plugs
Oil used: Duckhams classic
If this is the problem, how much pressure could be lost - surely not enough to cause massive failure?
Modifications:
Original heads - ported & gas flowed + 3 angle valves & seats
Engle W100 camshaft
Shadek 30mm oil pump
Lightened flywheel - balanced when attached to crank
Electronic ignition module
Weber 38DGAS twin choke carb on bespoke tubular inlet manifold - the carb and timing has been set up and jetted at RE Performence, Bury. (The carb was a new spare for a Reliant Scimitar)
Pressure relief pistons Bugpack / other.
"Hotter" spark plugs
Oil used: Duckhams classic
hotter spark plugs? surely you should be running a set of colder bosch W5AC plugs.
other plugs will not run well in this engine. hotter plugs will only increase your problems
put the original relief pistons back in... throw the bugpack ones away, but use the bugpack springs
shadek pump.. who? the stock pump is fine, just use a late 30mm one, or a berg blueprinted one
15w40 mineral oil will be fine, even a semi syntheic will be ok.
what colour was the metal of the cylinder barrels? was it a goldy colour?
other plugs will not run well in this engine. hotter plugs will only increase your problems
put the original relief pistons back in... throw the bugpack ones away, but use the bugpack springs
shadek pump.. who? the stock pump is fine, just use a late 30mm one, or a berg blueprinted one
15w40 mineral oil will be fine, even a semi syntheic will be ok.
what colour was the metal of the cylinder barrels? was it a goldy colour?
no they're not. vw aircooled heads have chambers and flat top pistons
if the cylinder barrel has discoloured to a goldy tinge, then it is a sure sign of overheating.
also check the heads between the valve seats and spark plug.. a crack here = scrap head
who built the engine by the way?
if the cylinder barrel has discoloured to a goldy tinge, then it is a sure sign of overheating.
also check the heads between the valve seats and spark plug.. a crack here = scrap head
who built the engine by the way?
I see what you mean now. I am very familliar with VW engines and have built many, would have worded this as signs of pistons hitting the cylinder head. I agree with DrDeAtH about the oil pump and the oil pressure relief valves. It is a good tip about looking for cracked heads too.
It sounds too me like the main bearing have been pinched by the cases when the engine was assembled, the mains fit onto small dowels inside one half of the case when putting the two halves together the bearings can be accidentally moved. To give myself an easy way of checking this hasn't happened I fit the bearings into the case before fitting them onto the crank and draw a pencil line on the flat of the bearing carrier in the case. Just before finally pushing the case together that last inch you can look inside with atorch and ensure the pencil mark is still aligned, as you tighten the case make sure the crank doesn't nip up.
Might be teaching you to suck eggs but hope that helps.
It sounds too me like the main bearing have been pinched by the cases when the engine was assembled, the mains fit onto small dowels inside one half of the case when putting the two halves together the bearings can be accidentally moved. To give myself an easy way of checking this hasn't happened I fit the bearings into the case before fitting them onto the crank and draw a pencil line on the flat of the bearing carrier in the case. Just before finally pushing the case together that last inch you can look inside with atorch and ensure the pencil mark is still aligned, as you tighten the case make sure the crank doesn't nip up.
Might be teaching you to suck eggs but hope that helps.
Shadek pump - from Big Boys Toys.
Cylinder walls are a normal silcery grey colour and at their top ends they are slightly blackened - the engine was running rich at the time it went bang.
Using hotter plugs is a simple performance tuning tweak - should have worked well in any engine, or so I'd thought.
The cylinder heads are fine - the offside head however does have the beginnings of a crack adjacent to the spark plug hole.
I built the engine, and this isn't the first!
How can the bearings move easily if they are dowelled into place? Yes, there is a small amount of rotational movement due to the dowels being smaller than the hole in the bearing, but if they are out of alignment, the case cannot be bolted together.
OK, so we suspect overheating - what, then, was the cause? What should I look out for when I come to re- rebuild it?
Cheers
Cylinder walls are a normal silcery grey colour and at their top ends they are slightly blackened - the engine was running rich at the time it went bang.
Using hotter plugs is a simple performance tuning tweak - should have worked well in any engine, or so I'd thought.
The cylinder heads are fine - the offside head however does have the beginnings of a crack adjacent to the spark plug hole.
I built the engine, and this isn't the first!
How can the bearings move easily if they are dowelled into place? Yes, there is a small amount of rotational movement due to the dowels being smaller than the hole in the bearing, but if they are out of alignment, the case cannot be bolted together.
OK, so we suspect overheating - what, then, was the cause? What should I look out for when I come to re- rebuild it?
Cheers
lotisi said:
It sounds too me like the main bearing have been pinched by the cases when the engine was assembled, the mains fit onto small dowels inside one half of the case when putting the two halves together the bearings can be accidentally moved.
Don't know the VW beetle engine, but presumably if the main bearings get pinched out of location when torquing up then the crank would be very hard to turn over by hand, telling you that something is wrong?
nel said:
lotisi said:
It sounds too me like the main bearing have been pinched by the cases when the engine was assembled, the mains fit onto small dowels inside one half of the case when putting the two halves together the bearings can be accidentally moved.
Don't know the VW beetle engine, but presumably if the main bearings get pinched out of location when torquing up then the crank would be very hard to turn over by hand, telling you that something is wrong?
It's not like a normall engine where you are just bolting in the crank, you are feedin the crank/rod assembly into the case and aligning the gears on the crank with the gears on the cam to set the cam timing and sanwiching the whole lot into the crankcase. The dowel is very small and I have known some new beetle engine builders not even notice they are there ( they only locate in the bearings by about a mm) and because there is a depression in the bearing you can nip it up and the crank still turn.
Here's some pictures of beetle engine building if anyone wants to see:
www.funkenblitz.com/engines.shtml
www.funkenblitz.com/engines.shtml
to be honest... some of the big boys toys engine parts are total shite...
best to stick with proven name branded stuff. but also use OEM parts where cruicial.. ie: bearings, seals and relief valves.
hotter plugs.. what were the make and range? nobody in their right might fits a plug that runs hotter than stock. always cooler.
as i said earlier you should be using bosch W5AC plugs. nowt else... they will run with nitrous too. i know they work... 12's on the track is proof enough.
if the mains ave been crimped by the dowel, ther may be a line on the crank where the bearing started to burn. though you would have found the crank hard to turn after bolting the case up...
some pics would be helpful.
best to stick with proven name branded stuff. but also use OEM parts where cruicial.. ie: bearings, seals and relief valves.
hotter plugs.. what were the make and range? nobody in their right might fits a plug that runs hotter than stock. always cooler.
as i said earlier you should be using bosch W5AC plugs. nowt else... they will run with nitrous too. i know they work... 12's on the track is proof enough.
if the mains ave been crimped by the dowel, ther may be a line on the crank where the bearing started to burn. though you would have found the crank hard to turn after bolting the case up...
some pics would be helpful.
DrDeAtH said:
to be honest... some of the big boys toys engine parts are total shite...
best to stick with proven name branded stuff. but also use OEM parts where cruicial.. ie: bearings, seals and relief valves.
hotter plugs.. what were the make and range? nobody in their right might fits a plug that runs hotter than stock. always cooler.
as i said earlier you should be using bosch W5AC plugs. nowt else... they will run with nitrous too. i know they work... 12's on the track is proof enough.
if the mains ave been crimped by the dowel, ther may be a line on the crank where the bearing started to burn. though you would have found the crank hard to turn after bolting the case up...
some pics would be helpful.
best to stick with proven name branded stuff. but also use OEM parts where cruicial.. ie: bearings, seals and relief valves.
hotter plugs.. what were the make and range? nobody in their right might fits a plug that runs hotter than stock. always cooler.
as i said earlier you should be using bosch W5AC plugs. nowt else... they will run with nitrous too. i know they work... 12's on the track is proof enough.
if the mains ave been crimped by the dowel, ther may be a line on the crank where the bearing started to burn. though you would have found the crank hard to turn after bolting the case up...
some pics would be helpful.
All true. I would like to see some pics too.
I'll try with some photos asap.
Apologies - error number 1 = I mentioned hotter plugs; I've got this the wrong way round. Yes, I do mean cooler.
I've been to see a bloke at Manchester Aircooled and he suggests that the failure is due to oil starvation caused by worn / knackered crank case rear journal.
This is the opposite from any idea from others I'd consulted - that the knackered crank case rear journal was caused by oil starvation. The plot thickens!
Apparently even the tiniest of gaps in the tolerance of the bearing fit will cause massive pressure loss.
So; next thing is I need new or line bored case, new crank & bearings, new camshaft & bearings and new big end bearings.
Ho hum.
Apologies - error number 1 = I mentioned hotter plugs; I've got this the wrong way round. Yes, I do mean cooler.
I've been to see a bloke at Manchester Aircooled and he suggests that the failure is due to oil starvation caused by worn / knackered crank case rear journal.
This is the opposite from any idea from others I'd consulted - that the knackered crank case rear journal was caused by oil starvation. The plot thickens!
Apparently even the tiniest of gaps in the tolerance of the bearing fit will cause massive pressure loss.
So; next thing is I need new or line bored case, new crank & bearings, new camshaft & bearings and new big end bearings.
Ho hum.
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