Groggy 912

[neverbuysaround]

Evening all

I used to be a member but cannot currently log in so have sorted a new username through my wife (hope she doesn't see it).

My 1969 912 about 3 months ago started sounding very noisy on start up and despite throwing £700 at it for tuning/servicing through 2 different garages, it still sounds rough and is returning around 60bhp instead of the 90bhp it should.

It is also not keeping a charge on the battery although I am advised both the alternator/dynamo and battery are fine.

The main issue appears to be compression as one of the cylinders (forgive my naivety, this means nothing to me) has 170 whereas the other 3 only average around 130 and I am told this is likely the problem with the lack of power.

Worst case I am advised a rebuild is around £3k + VAT but is it likely that this could be required as once up to 50-70mph the engine runs well enough but as soon as I put my foot down, it becomes very noisy again?

Any advice much appreciated - as would any 912 specialists in the North West (I think Strasse is the nearest having googled it).

Regards

Rick Keeble

[Barry]

Hi Rick: on the face of it, it looks as though your engine is suffering some sort of mechanical problem: i.e. something that's less likely to be cured via tune-ups or servicing.

Those compression check figures are vital: you may have them the wrong way round? Anyway whatever the figure are, you really want them to be within 5% of each other, or at the very least, not outside of 10% of each other. So if you've got one cylinder that's only reading 70% or so of the others, you've got a problem. In turn this will mean that the poor cylinder(s) can only perform a fraction of the work of the others, which will lead to a rough, uneven sound.

When the speed of the car has built up, and you ease off of the throttle, the uneven-ness will reduce, making it seem happier.

Possible causes?

a) Incorrect valve clearances (hopefully checked already during the service work): if you've got a tight rocker clearance, some of the compression can be bled away.

b) Poor valve seating: burnt edge of valve (weak fuel mixture?), poor valve seating (less likely). Difficult to check for without taking cylinder head off, but worth asking garage for a leak-down test, which is a posh compression check if you like.

c) Blowing cylinder head gasket?

d) Worn piston rings / cylinder barrel (any blue smoke when accelerating?

e) Holed piston (very unlikely because you'd expect to lose all compression.

They're the ones I can think of at the moment. Bottom line, a good garage doing a good compression or leak-down test should be able to take the diagnoses further.

HTH.

BTW, if the bove tests point towards poor piston rings or cylinders, or at least head gaskets, then expect to need some engine work of some sort. If that's the case, see if there's a way of measuring your oil pressure. If it's healthy, you may be able to keep any work confined to the top end of the engine i.e. you may not have to split the two halves of the crankcases, which would hold the costs down a bit.

[hot66]

try Mike @ MB Porsche engineering Nr Kendal

[neverbuysaround]

Thanks chaps, great info and I will try MB in Kendal tomorrow.

Rick

[FraserMurray]

You could always try ninemeister in Warrington, I found them really helpful.

F

[ian c]

i know a guy called hippy , beetle guy but has owned and worked on loadsa 912
will post his number later
if i dont sell my 65 912 project , hes one of 3 possible people to do do my engine rebuild

[Space Ghost]

With regards to the flat battery.... either the generator is not charging it, or there is a battery drain when the car is sitting unused. This can be chacked by taking the + cable off the battery, and putting a test light in there (i.e. + on battery to one terminal on light, other terminal on light to the + cable that was on the battery). If the light glows ever so slightly, then there is a battery drain (this might be the memory for the stereo, which is OK, though)..... simply take the fuses out 1 at a time until the light stops glowing...... you have found where the current drain is occurring and takle it (i.e. look for earthing, errant wires etc). If you do not find the drain, then the generator may not be charging the battery sufficiently to hold the charge... or the battery itself may be duff.

[louis356]

another great thing I have found is if your car is sitting for a long time and the battery is draining try a solar top up

Solar panel drom Mapplins(?) you know who I mean.

Cost me only £10 works like magic . best £10 non Porsche I've spent!

[ian c]

i can vouch for louis on this .
i waited until they had them on special offer , but think i paid £10 too ???
i got one fopr my sisters westy , and one for my 964 .
only problems so far have been 964 one wont work through cig lighter , and it came unstuck from garage window while i was away on a trip ..... luckily it landed on the floor face up , so carried on working
otherwise i would have returned to a flat car that i cannot get out of the garage and i would have real , real trouble getting to the front lid !!

[neverbuysaround]

All

Mike at MB Engineering has now returned my car and it is running much healthier. I drove it the 60+ miles back to my home yesterday and for what he charged me I am very happy.

He states that the carbs need refurbishment though and is sending me some details of a company down south who he states charge around £250 for the pair + P & P.

Does anyone know of anyone in the North West who refurbs carbs and costs? The engine occasionally emits loud bangs and seems to squeek like a mouse a lot, both of which I hope will be cured by refurbed carbs.

Could the bangs and squeeks likely be anything else? Also when I turned the engine off outside my house to move another car off the drive, the car would not start again so I had to push it onto the drive so that too needs sorting - a Maplin solar panel could well be the answer!

Thanks in advance.

Rick

[Timo]

Glad to hear its running better. Did they adjust your valve clearances or anything like that to improve its running? as there is no way a compression problem could have been overcome by adjusting the carbs. Be interesting to see what the compression readings are like now.

[neverbuysaround]

Yeah - the carbs haven't been touched yet, the cylinder head came off and some welding of a crack in there and more work was done. The carbs were more of an advisory from Mike but they need doing due to the squeeks and noises on occasion coming from the back end.

Compression now much better and all 4 cylinders within 10% of each other.