912 Engine Project

[James_Red69]

I thought that I would start a thread dedicated to my engine project. This is a duplicate of a thread on the 912register.co.uk forum - I am just trying to learn from as many as possible.

Back in October I went for a spin which didn't go so well. You can read about it here;

http://www.ddk-online.com/phpBB2/viewto ... 16&t=36448

Following a compression test I decided to pull the engine. I am somewhat a complete beginner to engine work so this thread will be all about trying to extract help and advice along the way so I can learn, learn, learn and get back on the road.

Cyl1 - 145 to 150 PSI (10 bar)
Cyl2 - 145 to 150 PSI (10 bar)
Cyl3 - 70 PSI (5 bar)
Cyl4 - 145 to 150 PSI (10 bar)

My car is a 1969 Cali import;

[James_Red69]

Engine out early December. The motorcycle lift is from ebay and the perfect thing for the job; http://www.ebay.co.uk/itm/New-Motorcycl ... 082wt_1396

[James_Red69]

After advice from various sources to do a leak down test I acquired a leakdown test gauge. It is possible to build one of these, it is a fairly simple device, but I acquired a cheap one on the net.

Results were as follows;

Cyl 1 - 35%
Cyl 2 - 25%
Cyl 3 - 60%
Cyl 4 - 60%

I am less than convinced as to the quality of the tester, it only tests at around 10 PSI which is pretty low.

I found a better way, I just put a rubber glove on each of the exhaust ports and on the intake manifolds, then in turn with each piston at TDC (both valves shut) pressurize the cylinder (I use about 40 PSI). If the valves are good then the gloves should not inflate!

I found;

Cyl 1 - Intake; Slight Leak, Exhaust; No Leak
Cyl 2 - Intake; Slight Leak, Exhaust; No Leak
Cyl 4 - Intake; No Leak, Exhaust; Moderate Leak
Cyl 3 - Intake; No Leak, Exhaust; Massive Leak

The picture below if the exhaust port 'glove' on No 3 with the cylinder pressurized.



So my heads will need to be reworked.

Next steps strip down and heads off.

[James_Red69]

A few photos of the stripdown, its a pretty mucky beast;

[James_Red69]

Heads came off no problem, pictures below.

Rings and pistons look OK, but I am no expert!

Heads look very very messy, is this called cokeing?!

3&4 Head (3 on Right)


No 3


No 4


No 3 (L) and No 4 (R)



1&2 Head (1 on Right)


No 1


No 2




Any and all opinions greatly valued!

[James_Red69]

I now have my pistons removed. First thing I have learnt is that I have the big bore kit fitted :D .

It would appear that the picton on No 3 has damage between the upper two compression rings;



I am not sure what type (make) of pistons these are, anyone got any suggestions? I have some clues from Duane Spensers book (dont have to hand right now).

What are the chances of replacing just one cylinder or will I have to do it as a set?

Also behind the oil scaper ring (lower one of the top three I assume) there is a thin steel band, I cannot find reference to this anywhere in any literature, anyone help?



This band is on all four pistons.

Engine starting to look a little clearner;

[911hillclimber]

Great new thread to watch!
I particularly like the hi-teck compression tester, nice bit of lateral thinking.

Did you notice any 'hissing' from the engine breather at all when pressurising the cylinders? That could indicate probs with bores etc. if that head's valves are good.

I've just done a top-end on my 911 so I know what mess you are going theough. Best to simply go through everything (valve lapping etc) and get the pistons'bores measured-up accuratly.

At least you only have 4 pots to do...

Keep it coming!

Graham.

[hot66]

We all love an engine rebuild thread Look forward to seeing how things progress

[MT]

I agree, especially as this is the part of 911/912 restoration that I am least comfortable with, so to have it described through the eyes of someone in a similar position is excellent. Please cover every step, no matter how seemingly basic, and continue to explain your rationale.

Then quickly move on to a 2.4E 6 cylinder please.......

Agree the glove technique should become a recognised standard test!

I have also made a note of the hydraulic lift given the excitement I had taking the engine out of the 'Doctor's car' using just a standard trolley jack.

Mick

[James_Red69]

Here is a video of my pistons;

http://youtu.be/FKauj27NVPE

After a bit of research I think they are NPR, which is a shame as they are no longer made. I suspect this engine has had a 1990's big bore upgrade.

This is with everything cleaned up;



I have not got into measuring the cylinders or pistons for wear as I am likely going to have to replace as a set.

[James_Red69]

I have spent a small amount of time looking around at options for replacement pistons.

No doubt everyone will be shouting 'Shasta' and there is an unwavering weight of opinion that would say these are the ones to buy. However there is budget to consider.

Before I commit to applying to the Eurozone bailout fund to allow me to up my budget I have been looking at the budget end of the price range and found a set by Quality Specialty Components (QSC) in the USA;

http://qscusa.com/Piston.html

Has anyone had any experience of these sets, the company or any other feedback on their products or service.

I’m not sure why an air cooled Porsche engine piston sets (Mahle, JE, Shasta etc) are sooooo expensive - compare them with a replacement VW set, where’s the £$ difference?!

Thanks

[911hillclimber]

A good question.
The P&B for my 3.2 rebuild looked like £3000 the set.

I was offered a 40k mile set, measured to spec by a competent person to be to nominal and they cost me £500 + a ring set @ £180
In the 3.2's case they are nikasil but £3000?

For most of us a budget is important in a hobby car.

[haasad]

Hi, nice work its so good to do this work oneself and learn as you go. Its clear you are patient and think about each stage. I really like the use of the MC stand. Before you commit to a full set of P&C's it may be worth measuring it all and trying to source a ring set if the bores and pistons will go again. I'm almost sure that some web time would find a supplier for a bespoke set or some that would suit from another application.

That thin ring behind the oil scraper is a spring or tension ring which helps the scraper seat properly.

Just out of interest I made a set of compression rings for an early Norton of some type when I was an apprentice. They were turned on a lathe from a billet of cast iron at full bore diameter then split to get end gaps using a slitting saw. It had three comp rings and no oil control ...must have only revved to about 2000 rpm though. As far as I know the motor was still running last year

PS not suggesting you make rings, just that all possibilities should be explored cos you never know what you will turn up.

EDIT whoops just re read and noted the piston damage, having a piston set made may not be as expensive as you think if the bores are ok or rebore oversize again to match an available piston which suits... definitely some more measuring and research in my view
(but I am a notorious tight wad)
andy

[KS]

Here you go... $200 the full set of NPR 'big-bore' P/Cs

http://www.thesamba.com/vw/classifieds/ ... id=1239308



or alternatively...

http://www.thesamba.com/vw/classifieds/ ... id=1099482

or

http://www.thesamba.com/vw/classifieds/ ... id=1099479

[haasad]

A good afternoons surfing there methinks.....result

andy