ONE FOR THE ENGINE BUILDERS

[RICH-I-AM]

Right then,need a little bit of help with my engine.
I stripped my engine down to bare block basicly to stop the leaks and give it a freshen up.
Honed and cleaned the cylinders today to fit tomorrow.
Between the cylinder and block there should be a paper gasget,Right?
Well on strip down the gasget paper was there as was a metal gasget/shim? same size as paper gasget.
Its the same on all 4 cylinders.
The(Haynes)manual doesnt mention the metal gasget.
Looks like on a previous build it wasnt done very well and its dificult to tell which way it all goes back together.

Is it Cylinder,Metal ring,Paper gasget,Block?
or
Is it Cylinder,Paper gasget,Metal ring,Block?

The vehicle is a 70 Bay with 1600cc Single port. Engine Code B

Thanks for any help
Rich :mrgreen:

 

[noddy]

Hi

The metal ring is used to lower compression in bus engines.
Original bus pistons had a recessed crown to lower compression, but these are no longer available so to get over the problem on higher compression (hotter running bus engine) a metal shim is fitted at the base of the barrels.

If there good reuse them (metal shim), not sure if you also need the paper gasket, last engine I stripped down was a while ago and I cant remember if it had paper gaskets as well.

Hope this helps.

Ian

 

[Bay-low71]

Rich

The paper gaskets are no longer required so long as you use a good sealant, I purchased my sealant from John Mahle racing. http://www.johnmaherracing.co.uk/jmrshop/index.htm" onclick="window.open(this.href);return false;

As for the rings, my engine had no rings, however it won't hurt for you to check the deck height with and without the rings fitted, this is the gap between the top of the barrel to the top of the piston, whilst at TDC. It is this measurement that relates to compression it is the clearance between the piston and the heads and valves. Can't remember the actual gap but its somewhere between 1mm to 2mm (0.040" to 0.080"). I'll confirm when I have another read up in the VW Bible.

Hold or even bolt the barrel onto crankcase without the heads, if you have removed the rings from the piston all the better just hold down on case, place a straight edge accross the top and measure the gap between piston and straight edge using feeler gauges whilst piston is at top dead centre (top of stroke)

If you were to change the B & P's I'm sure the rings will no longer be required.

Hope this helps......Ben (I'll get back to with what it mentions in the book about deck height)

 

[noddy]

The barrel shims are required all new pistons are bug pistons (flat topped),bus pistons (dished top) are no longer available to my knowledge.
If you don,t shim the barrel your engine will run at a higher compression than was intended for a bus, more strain on crank and bearings etc, another side affect of running higher compression on a standard engine is you are going to get a hotter engine and more chance of detonation.

Buses with standard engines already run hotter than bugs, so putting a bug style engine in a bus will just make the problem worse.

In a B code engine number 3 cylinder will already be hot anyway so I would avoid increasing you compression ration any further.

As for the paper gasket I just took a look at my B code engine, the paper seal goes between the case and the shim.

 

[RICH-I-AM]

Cheers for your replies chaps.
Cylinders not being fitted till nxt week now.Took the valves out today(both heads) and need all exhaust valves, all valve guides and at least one valve seat.Off to the engineers monday for valves(all 8),guides and seats :evil:

Anymore input regarding B engine piston,valve type things feel free.

Cheers Rich :mrgreen:

 

[RICH-I-AM]

:mrgreen: :roll: :mrgreen:

 

[bigsid]

Personally I wouldn't bother with the shims on rebuild. I'm sure most of us have engines without dished pistons and no barrel shim (almost all recon's are that way anyway)

The compression ratio even with the non dished pistons is very low and its one of the reasons that VW's were so popular in parts of the world that had really crappy fuel.

On modern petrol all the slight increase in compression ratio will mean is a little more efficiency from the engine. (the thin base shim will probably only account for .1 or .2 more on your CR say 7.6 to 7.8 )

As for getting hot, what really makes a difference is being paranoid about all the cooling tin and engine bay seals, as well as getting the ignition timing right.

Do that and you should get another 50,000 out of a freshen up.

 

[noddy]

I beg to differ Bigsid, remtec still fit shims to bus engines.

I agree with what you say about engine tin, engine bay seal and timing, these are more important that having the shims in.

Just another point of interest, just put the thermostatic system back in to my engine and its made a big difference to how it runs, over not having it fitted. Stumbles less when pulling off seem to have more pull going up hills.

Hooser this book is well worth getting "how to rebuild your volkswagen air-cooled engine" by tom wilson ISBN: 978-0-89586-225-9.

last couple of engines I've rebuilt I found this a great help, loads of information you dont get in the bentley or haynes manual, what signs of wear to look for, part interchangeability etc.

If your fitting a new oil pump in your B code engine, be aware the oil inlet and out let ports in the B case are smaller that the later universal case, I had to do some hunting to get the right pump. If you fit the later style pumps (bigger ports) it will leak around the edges of the pump, I think the pump for your case starts with a 311 part number.

 

[alikat]

Suggest you work out your Compression Ratio without the shim, and then see what shim is required (if any) to get it to where you want it. This is NOT a 'just fling on a thin (how thin is thin?) shim fix, they are available in a huge range of thicknesses to get the CR spot on. I would also suggest you look into purchasing a Bentley VW factory manual for your bus -
VW p/n LPV 997 288 , ISBN 0-8376-0094-4, which covers most things in great detail.
As your engine is now over 30 years old, it would be rash to assume that everything is as it left the factory. Flycutting the head seating surface will increase the CR, and hemi-cutting the chamber will reduce it. Have these been done in the past?? Working out the CR will tell you.
And NO paper gasket. Why they are still supplied in the kits from Brazil is beyond me. A good RTV or case sealant should be fine. You may need to freshen up the seating surface on the case if it shows signs of wear, and in the head if there has been blow-by. If you are splitting the case, check the crank for straightness - mine was 0.012" out, and had to be straightened and ground 10 under to correct it. The PO thought it OK to run without most of the tinwear!

Good luck!

Al

 

[RICH-I-AM]

Heads at the engineers.
1.Collets eaten through a couple of valve ends
2.valve guids megga worn
3.Valve seats falling out(literally)

Split case today
1.Cam bearings warn(heavily)
2.Cam lobes pitted(heavily)
3.crank bearings scored
Checking big ends tomorrow

Why do i bother!!!!!!!!!!

 

[RICH-I-AM]

Another quicky
When you bolt your 2 halfs of the block together whats the best sealer to use?
Silicone(general stuff) Hermatite or is there something else?
Cheers again :mrgreen:

 

[Araon]

NEVER, NEVER, NEVER let silicon sealant close to your motor, when it deteriorates at the spill over and works its way through the engine it clogs..... Apart from that its too thick.....

I've always used Hylomar blue personally.....

 

[noddy]

I use this stuff:

http://www.frost.co.uk/item_Detail.asp?productID=9215&frostProductName=High+Temperature+Gasket+Sealer+(85gm+tube" onclick="window.open(this.href);return false&catID=56&subCatID=&FrostCat=Gaskets&Sealers&FrostSubcat=

Don't apply too much to the matting face of the case the last thing you want is a blob of sealant dropping off the inside of the case and blocking an oil way.

vwheritage sell engine assembly paste to cover all those new contact surfaces to stop dry start.

Just a tip, first time you get the rebuilt engine ready to start, run it up without the plugs in to get oil round the bearings.

 

[alikat]

Aviation permatex - read this http://www.geneberg.com/advanced_search_result.php?keywords=9010" onclick="window.open(this.href);return false;

Al