parrallel measurments of cylinder to cylinder face's

[Gnasha]

I’m rebuilding a type 4 2.0 engine (stock). I have ground all cylinders to a machined deck. The top of each cylinder has been ground into their respective head. When I place a straight edge across no’s 3&4 cylinders and I get a 0.002” feeler gauge under the straight edge at one end.

Is there a tolerance for this dimension?

How flexible are the aluminium heads?


I did two mock up builds but didnt measure the tops of the cylinders, the cases halfs are now sealed together Newbie.............

Read Tom Wilsons book, searched the net and several forums, I came close a few times but no cigar.

[wreck]

I got a similar reading and shimmed out one cylinder to get it flat across the 2 cylinders .
A friend gave me a tip of using ultra grey or sealant of your choice on the cylinder bases , fit the pistons/cylinders , torque the studs , then leave it over night , carefully remove the head and recheck with the straight edge . If a cylinder needs shimmed then it's a bit of work to remove the cylinders clean the sealant and re shim but it will be worth it in the long run to get the heads to seal properly . Once you get the cylinders straight then move on to finishing off the rest of the build.

[GARRICK.CLARK1]

It is really important to get this right , Took me ages to do, had to machine down the bottom of the cylinders many times. The last go ,I was down to machining the cylinders 1 thou, after bolting down each cylinder I finely got the straight edge perfect. Its important N/A even more so under boost. After that you will need to trim the piston crowns to get all 4 piston deck heights the same... that's around the 1 mm mark

[Gnasha]

I’m sorry I may not have explained myself correctly. One of the cylinders i think is at an angle.
So, the straight edge sits across the first cylinder, then touches the first face of the second cylinder, then there is a 0.002” gap at the next face. I think during the machining one of the decks on the case has been machined at an angle.

[GARRICK.CLARK1]

Flip me that's even worse. I think the only way to fix that is to get it decked again by a different machinist.

[Ol'fogasaurus]

Flip me that's even worse. I think the only way to fix that is to get it decked again by a different machinist.

… and locally check the block's deck and bore hole. There are many reasons for the block to change heights most of which I don't know but I have heard it talked about.

Lee

[Gnasha]

GARRICK.CLARK1 Ol'fogasaurus

Thank you for your responses, If im honest, I think I was only delaying the inevitable, (strip down and re-machine) so so annoyed here, but thats life.

When machining the case decks, do you use the crankshaft center line as a datum? torqued together?

The previous "machinist" used the parting faces as a datum.

Thanks again guys..........

[GARRICK.CLARK1]

To be fair Gnasha ,that is a question for a true machinist,I generally leave this type of work to the guys that do AIRCOOLED engine machining DAY IN DAY OUT. They use 1 off tooling for many of the tasks done to VW engine parts. When you have it stripped send it to an AIR COOLED machine shop only ,someone like EUROPEAN MOTOR WORKS will be able to get this done for you . AA sell the base shims to achieve the desired deck height.

[Gnasha]

To be fair Gnasha ,that is a question for a true machinist,I generally leave this type of work to the guys that do AIRCOOLED engine machining DAY IN DAY OUT. They use 1 off tooling for many of the tasks done to VW engine parts. When you have it stripped send it to an AIR COOLED machine shop only ,someone like EUROPEAN MOTOR WORKS will be able to get this done for you . AA sell the base shims to achieve the desired deck height.

Thank you

[Ol'fogasaurus]

To be fair Gnasha ,that is a question for a true machinist,I generally leave this type of work to the guys that do AIRCOOLED engine machining DAY IN DAY OUT. They use 1 off tooling for many of the tasks done to VW engine parts. When you have it stripped send it to an AIR COOLED machine shop only ,someone like EUROPEAN MOTOR WORKS will be able to get this done for you . AA sell the base shims to achieve the desired deck height.

Thank you

Normally I would have said the crank bore but Garrick is correct; everything needs to be checked. I have heard that over tightening the head studs or bolts can cause the deck to end up not flat. Overheating is another possibility but basically, a good machinist, that knows what they are doing, will check everything... and in the proper order too.

Lee

[wreck]

before you strip it , fit just the cylinders in the manner I described and torque the head up . re check it when the sealant has cured . have you tried moving cylinders to verify it is not a cylinder issue instead of the case .

Did you get the case decked ?

[Gnasha]

before you strip it , fit just the cylinders in the manner I described and torque the head up . re check it when the sealant has cured . have you tried moving cylinders to verify it is not a cylinder issue instead of the case .

Did you get the case decked ?

Thank you for your response.

I was getting a 0.006" difference in deck height measuremenst across the top of the gudgeon pin on #4.

I tried the following:
Change piston
Change cylinder
Tried a bran new pison and cylinder
Reversed the rod
All pistons measured from pin to crown.
All cylinders are true and same length

Only the rod reversal made a slight difference and I think it may have been a fluke.

The case decks were all machined.

I will try your suggestion and see what happens

Thanks again.

[GARRICK.CLARK1]

If this was my motor, I'd do this procedure over and over . until you can truly see that the problem is the case .
Slide the cylinder's into the case . NO PISTONS TO BE FITTED AT THIS POINT
Fit sleeves over the head studs, fit washers and nuts to the head studs, lightly tighten down each cylinder. do 1 and 2 side 1st.
NOW , if the 1 and 2 cylinder is EXACTLY the same length,
an engineers flat bar WILL slide across the tops of both 1 and 2 cylinder , the engineers flat bar will NOT rock and will NOT have any day light between the engineers straight edge and the cylinder sealing surface when it is positioned across the total area of the 1 and 2 cylinder sealing edges. Do this horizontally and diagonally across the circumference of the cylinders . You can use a torch for this trick. I did this on mine in a darkened room.

[rwk2]

Have it checked on a surface plate the machinist should have, T1 case shown but principle is the same. I check all case's before they go out. Should read the same all around the perimeter, this is squareness and parallel, or accuracy of the machine it was cut on, on any given side,say 3 &4 this should be " 0" all around, if other side, say 1&2 is different, say .-005, shims can be used, assuming reading is 0 also, otherwise re-decking should be done. don't worry about deck height yet until you KNOW case decks are square and parallel. Crank CL should be determined before case deck is cut to put them equal, its called blueprinting an engine. Pistons,cylinders and rods and crank stroke should all be alike, then deck height is set, if you have difference's, one of these are the problem, usually the one you can't measure accurately,case deck and crank stroke.

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[Clatter]

^^What he said^^

You have to have your case decks cut flat, or all else will follow.

Eye-balling with a straight edge and feeler blades,
If you can find ANY variation in flat across the cylinder tops,
Then something is wrong.