TheSamba.com :: View topic - 72 engine tear down/rebuild

Mon Aug 11, 2008 9:03 am

I started tearing down my 1.7 this weekend. This engine was sitting in a field for a few years, hence the weeds and mud all over it. Here are some pics and lots of questions. Thanks for everyones help.

Here is the start (well sort of, I removed some parts last week when I didnt have my camera)

longblock

Cylinders 1 and 2

cylinder head 1 and 2

Cylinders 3 and 4

Cylinder head 3 and 4

questions;
1. Looks like there is a lot of carbon build up on the heads. Other than that, none of the valves look sunk or anything. How do they look to you? How can I tell if they are good/bad?

2. The cylinder walls seem to be in excellent shape. There are no major scores and when I rub them, there doesnt seem to be too much wear as there is hardly any "lip" where the pistons reach TDC. Im thinking of getting new pistons as some of these are scored a little. Can I just get the cylinders machined? Or, do I have to replace the cylinders if I am going to replace the pistons?

3. I cant get the #3 cylinder off. It is stuck. This may be why I couldnt turn over the engine before hand. I have soaked it with PB Blaster. Any other tips on removing the stuck cylinder?

4. The lifters look like they have no wear. The crank wants to turn (it will turn back and forth slightly, but is stuck because of the #3 piston. What are the chances of putting in new pistons/machined cylinders and having it run well?

5. I will be splitting the case when I finally get that damn cylinder removed. What should I measure and check for when the case is split?

6. Is it possible to put in new main/cam bearings and not machine the cam/crank?

Yes, I do have the Tom Wilson book but it is packed away right now. Thanks for all of your help and I will update this thread when I dig further into the case and start the rebuild. The number of parts I have taken off is a little overwelming, but I think Ill be ok.

Mon Aug 11, 2008 9:43 am

Anything is possible. New pistons and cylinders would be the way to go.
I would worry less about scuffing and more about miking them to check for fit. A set of new rings and honing the cylinders would be a good shortcourse solution.
Try beating that cylinder off with a rubber hammer. That pic of 1st head looks like it will need total rebuild as valves are rusted in place.
Try tapping that piston down in cylinder with rubber mallet while cushioning the other rods with cloth. if it moves 1/8 " or more, cylinder will come off.

You're gonna know what to replace once you split the case. If that piston is stuck because of thrown rod; you are going to have to find a replacement crank or regrind. If it is not new bearings, rod and main may get you out of a jam. Hard to tell until you post pic of crank, cam,and pistons.

Mon Aug 11, 2008 10:51 am

new pistons and cylinders for sure and a total head rebuild...if you are staying with 90mm pistons keep the small valve size but if you are going with 93mm pistons for a 1800cc motor go with new 1800 heads with larger valves.

Inside: probably a regrind for the crank, rebuild the rods, align bore the case, as what is the point to cheapo out now? Totallly balance all the spinning parts and you should have the flywheel resurfaced and cleaned up. Check the main oil seal surface!!! lots of flywheel get scored from dirty oil and won't seal.

Thu Aug 21, 2008 8:01 am

How can you tell that the heads need a rebuild? I realize they look nasty, but thats a lot of carbon build up. The valves still look seated.

Thu Aug 21, 2008 9:18 am

most original 1.7 heads now have atleast 100k miles on them, VW heads usually need work after 75k miles as the valve guides wear out caused valve to seat wear. The worst the valve seats to the head the less its able to disapate heat which leads to the valve overheating, ending in a snapped valve.

This is the critical issue with Aircooled engines as the valves and heads depend on working together to cool off via the air.

Cheap out now and it will bite you in the butt later. :cry:

Thu Aug 21, 2008 9:44 am

Trim a short 2x4 down so that it will fit into your number three cylinder and whack it good with a BFH a few times. That should get the piston to pop loose. You will likely find a lot of rust in there, I am surprised by the looks of your heads that any pistons would come loose. That thing must have been sitting in a moist area for a long time.

The heads need to go to someone very familiar with T4's and are going to need a complete going through. The heads need to be checked carefully for cracks and most likely the valves, seats and guides are going to need to be replaced.

Your block needs to be professionally cleaned and you need to replace all the pressed in oil galley plugs with screwed in pipe plugs.

If your pistons and cylinders mike out according to the book you can reuse them by just having them cleaned and installing new rings. I think it is unlikely you will find them reusable though.

Thu Aug 21, 2008 11:24 am

Wildthings wrote:

If your pistons and cylinders mike out according to the book you can reuse them by just having them cleaned and installing new rings. I think it is unlikely you will find them reusable though.

In 25 years of pulling apart type 4's I have found two sets of pistons that were ok and in spec. One was a 1.7l domed set for a 914 and the other a US spec 2.0l 914 set which are in my Westy now.
Plan on a set of pistons/cylinders which AA was selling for about $300.