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Posted by: Cevan Dec 20 2009, 09:10 AM

What is the normal practice in terms of inspecting the case halves prior to a rebuild? Is this something I can do myself?

All the bearing surfaces looked fine and the connecting rod play was between .008 and .010. Assuming I don't see any visual signs of damage, does it need to be sent to a professional who I assume has an expensive tool that checks the alignbore?

Posted by: DNHunt Dec 20 2009, 09:53 AM

If you have a dial bore gauge you can measure the bore to check for diameter and how round they are. This should be done under torque.

I have seen builders with a lot of experience use a #2 bearing and press it into the saddles as a screen for good cases. It should be pretty tight. I don't have enough experience myself to trust this.

Jake has a trick he uses to check for collapse. Follow this http://forums.aircooledtechnology.com/showthread.php?t=1675 and he mentions it.

You can mock up the build with the crank and bearings and measure bearing clearance with Plastigauge.

Personally, I would get some help if you are not sure. The downside risk with a mistake here are just too great.

Dave

Posted by: Cevan Dec 20 2009, 12:06 PM

There are at least 3 shops in my area that work on aircooled VW's so I'll check with them about doing an inspection of the case. Shipping the case halves somewhere seems like a PITA.

Posted by: hcdmueller Dec 20 2009, 02:44 PM

Make sure you get the registers checked out. I had a local guy check my block but something got lost in the translation. The deck didn't get checked for a collapsed register and now my engine is torn down in my basement waiting for the block to be fixed.

Posted by: HAM Inc Dec 20 2009, 03:54 PM

Less than an hour ago I decked the case that we're using for our next F-Prod race engine. Like EVERY case I have ever decked (and I have decked a lot!), it had at least one spigot that had "sunk" unevenly toward the engine centerline.

This case was actually one of the better ones I have decked as only one spigot (#3) was out. Most cases, especially the later ones, have multiple, if not all spigot collpased. In most cases the point on each spigot that is closest to it's neighbor will be the lowest point, that would 3 o'clock and 9 o'clock.

Many head leaks can be traced to this condition and the problem will increase piston friction as the cylinders are not square to the crank. That friction can lead to lost power and elevated oil temps if bad enough.

The sagging is not always detectable with straight edges, though the classic sag of the 3&9 o'clock areas can be detected with a straight edge.

I should also point out that while the #1&2 spigots had not sagged on my case they weren't level. Both were flat and parrallel to the crank, but #1 was a couple of thousanths higher than #2! I see this a lot as well!
Cases decked on a poorly trammeled mill will not be level, and poor technique will cause issues as well. The same is true with flycutting heads.

Posted by: davep Dec 21 2009, 12:34 PM

Len, In your experience, is the sagging more an issue with the aging of the case after the initial factory build, or does it continue to sag after you have properly decked it? Does the case stabilize at some point, or not? What are the costs to have the case checked & decked?

Posted by: r_towle Dec 21 2009, 01:13 PM

Chris,
For a farmer check...for those of us at home...
This is not intended to replace a machine shop, but allow you to determine if you should bring it to a shop.

Remove head studs (double nut them)
Place case halve flat on a flat surface...a piece of machinist granite is the ultimate way to do this...its honed to a perfectly flat surface.
Choose your flat surface wisely...you are looking for thousandths of an inch.

Once its flat on the surface, use a straight edge on the cylinder registers and measure up from the flat surface to the registers...all the way around. Any variation requires the case to be decked, which is fairly simple. A simple straight edge across the registers will also show you any sunken registers...just see how the straight edge sits....any gap...you need to deck it. That is just having a shop mill it flat..

A second measurement requires you buy inner bore measuring tools...which are cheap (starrett sells them)
It looks like a T.. you stick it in the hole, turn the handle till it touches and then pull it out and meaure it with calipers...
You need to check all your bearings...and you need to see if they are oval...so you do this in several orientations.

If you question any measurements of the farmer test....bring it to a shop and have them check/blueprint the case for you.
They may need to deck the case.
Rarely do these cases need line boring. Question them alot of they say it needs to be line bored...then make sure you can buy the proper bearings BEFORE you allow them to do it...then give them the bearings...

Line boring brings up alot of other issues...
I never really like to hear that the case needs line boring unless they have measured up everything.
Type 4 cases are pretty tough...especially in stock form.
On a stroker, ok...it may need to be bored from abuse...on a stocker its not that common in my limited experience.
If your machine shop wants to line bore it...question if you have chosen the right shop...that is all I am saying.

To baseline the pricing, take a look at Rimco (GIYF) they are a VW machine shop in CA...they list basic (no option) pricing...

Decking is not to hard to setup for...so its not to expensive.
If you do have the case decked, it will change your compression ratio...so you will have to be prepared to do a mock build, measure your new deck height, order shims, disassemble the mock build and install the shims...then measure again.

This is something that you should do anyways...
Rich

Posted by: underthetire Dec 21 2009, 01:30 PM

Now i have not done a type 4 yet, did a T1 years ago. Worked in high school as a automotive machinist ( couldn't stand that dirty loose tolerance stuff ! ) but .008 to .010 sounds like a lot of clearance to me. I would think .002-.004 would be more the norm. Maybe i'm wrong again, i'm used to working on .00001 of an inch stuff now.

Posted by: Cevan Dec 21 2009, 03:06 PM

Accordinging to Tom Wilson's book, .027 is the wear limit for connecting rod side clearance with .004-.016 being within spec.


Hey Rich, the cost of a piece of machinist granite or some other flat surface is probably more than the cost to have a shop measure up the case. Plus, I'd rather not remove the head studs if I don't have to. Of course, finding a shop around where I live that can do this for me is a whole other issue.

Posted by: underthetire Dec 21 2009, 03:10 PM

Oh, sorry. Thought you meant bearing clearance. My bad.

Posted by: HAM Inc Dec 21 2009, 04:10 PM

Dave I don't see to many of the cases I deck later in life. I will say that the race cases I've decked and rechecked later were still straight. The problem could be caused by a combo platter of issues.

The new cases may have internal stresses (pretty much every casting does) that are not relieved until the engine has gone into service. Combine that with detonation, and multiple heat cycles, some involving overheating and you have yourselve a warped case!

I don't want to poo-poo anyones methods of checking the cases for sagging spigots, but I have gone over cases with a straightedge and found no issues, but when decked found that the spigots had sagged n some areas. I have detected sagging in the center areas (3 0'clock-9 o'clock) with a straight edge, but other areas are tough to detect with a straight edge. I have seen spigots that were reasonably level, but not parrallel to the crank. Regardless of the direction they are off they usually clean up with around a maximum of a .005" cut.

If the head studs are removed I charge $150.00 to deck a case. Depending on how they are crated I may charge a fee for re-packaging prior to return shipping. Plastic totes from Lowes are great for shipping cases!

Posted by: ConeDodger Dec 21 2009, 04:42 PM

All three cases that I have checked had sunk at the 3oclock position on the #3 cylinder. The head leaked on the one that I checked after the teardown later.

Posted by: Cevan Dec 21 2009, 06:35 PM

Couple of questions: Do I have to remove the head studs in order for a shop to check the deck registers? Is heat usually required to remove the head studs? When you reinstall them, what keeps them from going all the way into the case as most of them are visible from the inside of the case?

Posted by: Jake Raby Dec 21 2009, 07:23 PM

Yes, studs need to be removed to do the procedure thoroughly.

After almost 4 decades of use most cases require some intervention. Recognizing what needs to be done is primary.. Actually doing it is secondary.

Posted by: r_towle Dec 21 2009, 08:04 PM

Chris,

Contact William Harris via this site.
He used a machine shop twice...great place and they are aircooled guys.
Northshore location, but several guys have used them including a few 911 shops...
they have a great reputation and can do the work.

They are quite experienced with Type 4 motors...ask William.

Rich

Posted by: HAM Inc Dec 22 2009, 09:19 AM

Yes, the studs should come out. Use heat if you have to and the penetrating oil of your choice.

Just screw them in till the last thread enters the case, they'll stay put! You'll probably have to apply oil to the threads just to get them to screw in. Loctite them if they are loose.


Jake is spot on with that observation! These old aircooled engines are great when restored properly, but they do require a good deal of very specific prep work before final assembly can even be dreamed about!
And from what Jake has been telling me lately damn near every new replacement part from bearings to oil pumps to distributors are getting harder to source in quality, ready to install condition. The older these engines get the more of a challenge they are to build properly!