Engine Rebuild

Can I use any type of oil (like WD40)?

It really should be motor oil, as the point is to seal the rings momentarily to increase the compression. WD40 is way too light. What actually happens is that the rings wear on the outside where they scrape the cylinder, so they get thinner, creating a larger gap at the back of the ring-groove in the cylinder, plus the gap in the rings grows wider. The oil won't do much with the actual gap in the rings, but it helps fill in the extra space behind the rings in the ring grooves, and seals the contact between the rings and the groove itself -- the bottom of the groove and bottom of the ring particularly as the piston move up for the compression test.

Using new rings will help fill the grooves in the piston, but not completely as the grooves actually widen slightly from the rings pounding against the upper and lower sides of the groove as the piston moves up and down, so the fix isn't total on old pistons. And to compound it, the cylinder will be worn too (from the rings scraping on them), so the piston becomes a sloppy fit and more gases can squeeze down the sides; plus the fact that the rings are pushing out against a slightly larger (worn) cylinder, so the gap in the rings is bigger than it should be.

All this means that new rings in old cylinders/pistons will help, but not for very long, and the compression still won't be as good as fitting new cylinders/pistons.

The VW engine is great for this job though. In most cars, you have to get the cylinders in the block machined to an oversize, then fit oversize pistons and oversize rings to match. With the easily replaceable cylinders/pistons in the VW, you save a lot of time -- which equals money if you have to have it done at a shop; and you CAN do it yourself because no machining tools are needed. Bonus either way.

Don't underestimate the amount of work involved in doing this job. You have to take the engine out, remove a heap of tinware (the cooling shrouds etc), the inlet manifold, the heads themselves, the cylinders, the pistons, then start the process in reverse, making sure each piece is clean and fits right. And maybe your heads will need work or replacing you won’t know for sure until you remove and inspect them. It's straightforward, but it DOES take time, so you can't just say, "I'll do it next weekend" and expect the car to be back on the road on Monday. As a first time effort -- there will ALWAYS be something that bogs you down (a part you hadn't thought of, or the heads needing work for example). But if you are prepared to take your time, and go carefully at it, and be prepared for the inevitable frustrations it will bring, it can be done by anyone with a small amount of mechanical knowledge, and who has a few essential tools, such as a good set of ring spanners (I forget what you call them in the US), a torque wrench (absolutely essential), and various screw drivers, pliers etc.

And read the relevant parts of Bentley too.

He also said he'd give me a rebuild engine "long block" "head to head", whatever those mean, for $550 exchange with the old engine. What do you think?

Interesting proposition. A "long block" usually means a bare engine which is complete -- including the heads.

You then install the tinware, inlet manifold, distributor, fuel pump and exhaust from the old engine. So there would still be some work in doing the engine swap (but not at all difficult), and $550 sounds like quite good value, since it would include reground crankshaft, new main bearings, conrod bearings, oil seals, valves and so on (which your engine won't have if you only do cylinder/pistons).

Plenty of work to do there -- but quite straight forward "bolt it on" stuff -- nothing which needs an engineering degree to figure out.

One of the basic tenants of VW repairs is "Replace the Exhaust Valves at 50,000 miles or when you take the heads off if sooner".

The exhaust valves are probably the hardest working component of the VW engine, and they are not too pricey to replace. Since a dropped valve can do an awful lot of expensive damage, replacing them when the heads are off is good insurance. The inlet valves don't need it nearly so often -- they run much cooler and so don't stretch/break like the exhausts. Use only high quality exhaust valves -- stainless steel is not necessary, but no JC Whitney stuff here please.

While you've got the heads off I would strongly recommend that you have the valves done, and while you're at it take a close look at the rings.

With the heads off, try wiggling the pistons sideways and up/down. They should move just a fraction inside the cylinder (aluminium expands more than steel so they are a loose fit when cold) but should not be a sloppy fit. If they are, a cylinder/piston set is needed.

Then remove at least one cylinder (maybe #3), carefully remove the top ring from the piston, and insert it in the cylinder. There should be a small gap between the ring ends -- a few thou (I forget the exact amount) but if there is an obvious big gap, or the ring look thin, replace ALL the rings in all cylinders as a minimum. Of course a piston/cylinder set would be better (around $200 US), but ring replacement will get you another 10-15,000 miles or so before the cylinders have really had it (provided the pistons weren't too loose).

A hose clamp of about 3.5-4 inches makes an excellent ring compressor (if you don't have a compressor tool) when reinstalling the cylinders over the pistons.

I am beginning to think my 1600cc engine may be ready to go, it seems I am getting some bearing noise, and now all of a sudden one cylinder has dropped from 127 to 100. The other three are all at 125-127. This engine is also running a little hot on the freeway.

Sounds like it's on the way out - a little early but not too bad, and obviously you don't know it's full history anyway. Compression dropping to 100psi means either rings, or valves. You can check for this by squirting about 10ml of engine oil into the cylinder then quickly doing a compression test again. If the pressure is a little better, the rings are shot (the oil will help seal them for a short time) but if there's no difference, the valves are the problem.

My exhaust tips are quite white....nice and clean combustion....so, is this an advice to change my piston rings?

No - don't change the piston rings on their own - they won't last very long, and will make the worn cylinder wear even more quickly. With the VW engine, you should always replace the cylinders, pistons and rings as a complete set. That way you get maximum mileage for your money.

My suggestion would be - replace the broken exhaust stud without removing the heads if that's possible, and then use expanding push rod tubes to fix the oil leaks. Re-torque the heads before you put the engine back in, to make sure the cylinder-to-head seal is good.

If you have to remove the heads, be very careful cleaning the carbon out so the cylinder seating area is not damaged, and replace the heads on the same side so there is less chance of leaks. If you have to remove the heads, you can use the original push-rod tubes if they are OK - just stretch them a little and use new end-seals.

Can I simply install a new piston-cylinder-ring kit?

If the crankshaft and other internal parts are in really good condition you can just put a new cylinder/piston set in and away you go. My very first "rebuild" was to do this (which also turned my 1500 into a 1600 since I used the 1600 cylinders and pistons - they fit in the heads just the same), but the next time the cylinders were worn out, the whole engine needed a complete rebuild because the internal case parts were also very worn by that time. That engine now has nearly 400,000km, and it was getting very tired again just before the accident which squashed my Bug. He's being very slowly rebuilt, but I think the engine will need another complete rebuild once I get him going again (or a new engine).

I understand quite well all the engine parts and how to change them, the only part that I don't know is that crankshaft. I mean, the crankshaft bearings and what to do to them in a major overhaul. I know how to change pistons, rings, cylinders, heads, oil pump, carb., dist., but the great doubt is that: those crankshaft bearings.

I understand. I can't help you much on that, since I'm not an expert on full rebuilds (I only ever had that one full rebuild, and I didn't know enough about VWs then to do all of it myself, so I had a rebuilder do the case/crankshaft etc.

Since my engine will need such rebuilt, I'd like to start buying pistons, cylinders, rings, etc. and keep them apart until I really need to do that work. Am I doing well? Is bad to run the engine until it really needs to get fixed, or should I start thinking in doing that the sooner the better?

No, it's OK to keep using it. If it needs a complete rebuild then all the worn parts will be repaired or replaced anyway if they are a little bit worn or very worn.

Another thought - you might just put some money away every week and when you have enough just buy a Mexican-built brand new engine. I believe that they are very good, and this means it's only a day to replace the complete engine, and your bug is back on the road again. Those engines come as carburettor or Fuel Injection models, so you just choose whichever suits your bug.

The cost of a new engine is about the same as a complete rebuild of the old one.

You'll have to take it easy for a few hundred miles - it's not a complete rebuild so a full run-in won't be necessary, but gently on the new bearings is a good idea.

A full run in is needed to harden new cam lobes - at first start go straight up to 2500rpm and hold it there for 15 minutes, then change the oil. Then gentle driving for 500 miles and change the oil again, then it's finished. The high speed first run is supposed to be fine for rings and pistons since the engine is unloaded, but it's essential for the cam or it won't last.

You won't have new cam lobes -- your mechanic said the internals were OK, only the case is being replaced. So that means the cam shaft, P&Cs head etc are all the same, so running them in is not necessary. But the crankshaft bearings will be new, and a little gentle running till they settle in is wise.

Only one oil change should be necessary at 1-200 miles, just to flush out any particles which in there from the internal work that has been done. Then back to normal 3000 mile changes.

That run-in can be on the road - just light on the throttle and don't load the engine hard -- use more rpm and less heavy throttle rather than the other way round.

I'd adviseleaving your valves at 6 thou, since your college-son is less likely to remember to check them as often as you or I, and 6 thou allows for "lazy" maintenance. If he's certain to check them every 3000 miles, then 4 thou will give you a slightly quieter engine.

We talked at some length about run-in - he said it wouldn't be necessary. He put all of the parts together with oil, he said, so a preliminary spin wouldn't be necessary. And he said it wouldn't be necessary to change the oil for 3000 miles. I like your idea of a 200-mile change better.

It's only precautionary, a few hundred miles is enough to dislodge any tiny fragments of metal which are always likely after a rebuild of any sort, no matter how careful you are/he is.

I'd rather flush away a sump full of good oil than risk anything staying in there for 3000 miles.

And a quick check of the valve clearance when you first change the oil to make sure nothing has tightened up and they should be fine then.

I talked to him about the wear on the rear face of the engine case. He said that was due to the crankshaft moving back and forth, and the wear was from the flywheel rubbing on the engine case. The flywheel isn't damaged because it's made of steel and is much harder.

I told him there is (was) oil everywhere, even up into the fan housing. I had to take the cooling vanes out and clean them and the inside of the housing. I cleaned and painted all of the tin today. He said that oil all over the place is typical of this situation - the whole problem, clutch, then main seal -- was due to the bearing failure and the resulting excessive endplay.

As I'm sure you would guess, with the new (rebuilt) engine case we have a new engine number now -- AD 2,059,089R, as opposed to what it used to be - AE 320891. In your "Changes Made to the Beetle" article it says --

• Engine AD 0,000,001 - AD 0,360,022 50bhpDIN 65bhp SAE 1600
• Engine AE 0,000,001 - AE 0,558,000 47bhpDIN 60bhp SAE 1600(USA)

Obviously that DOESN'T mean we have more hp now, since that is determined by the displacement, etc.

I think the main difference was the compression ratio - I've seen references to "dished pistons" (never used in Aus) and think these were used on the "smogged" engines like the AE series to reduce the compression ratio from 7.5:1 back to about 7 or 7.2:1.

I suspect the AE series may originally have had a throttle positioner and been jetted rather lean in the Californian market (they had a 34PICT/4 when everyone else was using a 34PICT/3), but don't know if they were "original equipment" in other parts of the US or just in Cal.

Capacity remains 1600 for both engines.

So if your pistons were dished, then the compression ratio will still be lower than 7.2, but if they were flat, it should be 7.5:1 - whichever case they are used in.

I'm guessing, but that R on the end is probably an added "rebuild" symbol - VW didn't use letters at the end of the number as far as I know.

Strange though - the AD numbers ended with 990,000 in 1973!

I was reading the "rebuilding your engine" book last night, and this aspect was brought home to me - he was talking about reasons for blowing smoke as the engine got tired. Leakage past worn piston rings and the resulting excess oil film in the combustion area of course, (and worn bearings resulting in more oil splash at the back of the pistons which resulted in more oil on the cylinder walls for the worn rings to miss), and then he described the effect of worn valve guides (they wear mainly because the rockers work them at an angle, so side-load the valve stems a little), and once you get worn guides, you tend to get a lot of burnt gases getting into the rocker covers and from there to the sump, and from there to the breather and so you get a lot of oily/burnt air being fed down the carby, so it smokes from there too. In other words, you can’t always pick on any one cause for a smoky exhaust - it could come from several directions. He put that interrelationship into words better than the thoughts I'd had previously about it.

I had a nice phone call from a VW guy in Melbourne this morning -- he's successfully converted a 1300dp into a 1600sp.

You can do it either way. The only difference is two of the cylinder studs (upper centre ones) are shorter for the dp heads, and the inlet manifold and upper cylinder tinware are different. That's it. You can even use the 1300 heads with 1600 cylinders if you don't mind 8.8:1 compression ratio and 98RON (about 95AKI) fuel. You can shim it back to about 8:1 (thicker shims than that would affect the pushrod length/rocker angle too much). Otherwise you get the proper 1600sp heads to get a normal 7.5:1 compression ratio.

The smaller 30 series carburetorss will sit on a dp manifold (on a 30/34 adaptor) but the larger 34 won't sit on the smaller sp manifold, so the carby of choice is usually the 30 series, since it will work OK with 1200/1300/1500/1600 engines (although it's at it's limits with the 1600). The 1600dp really needs the doghouse shroud, but you can get away with the older 1300/1500 shroud with the 1600sp (a few less hp).

It's amazing what a mix-n-match engine the VW has.

Can you tell me if the 1600 cylinders/pistons will fit my 1300 case without machining the case cylinder holes?

Yes -- the 1600 pistons and cylinders will fit straight into the case holes of a 1300 beetle, but if you try to use the 1300 heads the compression ratio will be too high -- about 8.8:1 and the valves are a little small -- so you also need a set of 1600 sp or dp heads (depending on which inlet manifold you have). With that, you have converted the engine to a 1600 with normal 7.5:1 compression ratio, and horsepower will rise from about 44 to about 56hp for the 1600sp or 58-60hp for the 1600dp. You can continue to use the 30 or 31 sized carburettor with the 1600, but you'll need to change the jets to suit the higher airflow. Let me know what carburettor and distributor you have and I can suggest some suitable sizes.

I've heard two stories about using the 1300 heads. It was my belief that they would actually fit on the 1600 cylinders without modification, but others have said "you need to fly-cut the heads". Whether the fly-cutting was to change the combustion chamber volume (re the compression ratio issue) or whether it was because the TOP of the 1600 cylinder is different to the BOTTOM (since the bottom definitely fits into the same case hole), I don't know and the folks saying "fly-cutting is needed" won't say.

In any case as I pointed out the result would be very high compression and replacing the heads with 1600 heads (larger combustion chamber) is a better option.

I'll keep at the 1300/1600 heads thing though -- I want a definite answer myself, and when I get it I will post it here.