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OLD VW NUT
Samba Member
Joined: February 23, 2011
Posts: 2776
Location: High Desert of Washington 98823
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 Posted: Sun May 27, 2012 10:03 pm Post subject: |
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| whirlpool wrote: |
okay! I think I am in trouble.
Compressed air hisses our from the right upper part of the head on cylinder4 and also out of the bottom of 2.
1 and 3 seem to be airtight.
I removed everything on cylinder 3 and 4 side and I could not find anything wrong. I replaced and re-torqued to 7 ft/lbs and 4 was still hissing from the same general area. The head looked okay and cylinder too.
OH...and nobody said "hey dummy! the engine will rotate when compressed air hits it"  @ noob |
Did you take the rocker arms off before you did this? If not at least put each cylinder at top dead center firing before you hit it with air. This also makes it less likely that the motor will spin.
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71 Ghia Coupe - stock body - no rust! Powered by a 2110 W/Dual HPMX 44's - Rancho Pro Street Transaxle - A/C by Gilmore
Other car - 2013 VW Golf TDI |
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SRP1
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Joined: January 06, 2007
Posts: 4340
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| Posted: Mon May 28, 2012 12:29 am Post subject: |
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Did you use shims under the cylinder to set deck height?
If you did are the shims of equal thickness? The shims must be equal, which means you must measure the shim thickness prior to installing them to verify they are correct for your set up, and matching.
Last thing to check prior to installing the head is to make sure the cylinders when seated are level with one another. |
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whirlpool
Samba Member
Joined: June 20, 2010
Posts: 84
Location: Keller
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| Posted: Mon May 28, 2012 5:00 am Post subject: |
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Initially I did not remove the rocker assembly. As I still heard the hiss I thought that maybe I was not finding TDC on 2 and 4 so I removed them. I did not use shims as my deck height varied but all cylinders were well within spec.
I will check the cylinder wall height today with a straight edge to see they are level.
another noob question. When the engine is turned over with everything torqued and spark plugs in, where does the trapped air go? does it escape or does it just remain compressed until the cylinder moves again. |
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whirlpool
Samba Member
Joined: June 20, 2010
Posts: 84
Location: Keller
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| Posted: Sun Jul 08, 2012 9:24 am Post subject: |
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| modok wrote: |
| ok, then what you can do is set the cylinders in the case and see if they are level across and then do the same with the heads If one or the other is not right you should be able to find it |
Life is not kind as it is too darned busy! I picked up this job a few times and each time with the same results 2 and 4 leak and 1 and 3 okay. I tried moving cylinders around (keeping the pistons with each) no joy on 2 and 4.
As suggested I have tried to see where the air leak was leaking, using prussian blue ink and it appears to be across the majority of the surface of 2 and 4, no matter which cylinders. I am not using any shims.
When using a straight edge against the cylinders they are not level as the straight edge rocks a fraction of a mm, and it appears as if they are not square on the engine case rather than just different heights. So it is either engine case or cylinder! I just cannot see whatever is causing them to be at different angles.
Any thoughts on how to check this properly and get the cylinders level? |
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hill
Samba Member
Joined: September 24, 2011
Posts: 442
Location: PNW
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| Posted: Tue Jan 08, 2013 1:59 pm Post subject: |
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Was your case machined to fit the cylinders and/or establish the deck height?
Or are you using a new Brazil made magnesium case? Some of them come with all sorts of inaccuracies and might need a machine shop to make the way it should be.
Take the heads off and make sure that the head bolts are able to pass freely through the cylinders. If not you may need to relieve the bolt passages in each cylinder so that there's no chance that they might get caught and stuck slightly off when going in to their deck seating.
Something's not right yet.
The cylinders should be equal in length. If the set you have has variations in height and you don't have a way to turn them to equal length at least try to put long ones and shorter ones into the same head. You want to minimize any differences to a point where the squish of copper head shims (like a gasket) can absorb and equalize the differences (if very small differences).
I lapped each cylinder into it's location in it's head using some 500 grit lapping compound. The fine side of the little Clover can of valve grinding compound will work about the same. This would be most important if you aren't using the copper shims there. Don't think that you could grind cylinders to the same length with compound - you'll be a grandpa before it's finished.
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