<![CDATA[Volkswebbin — replacing piston rings in 74 SB]]> 2010-02-15T03:07:56Z PunBB http://www.volkswebbin.net/topic/86639/replacing-piston-rings-in-74-sb/ <![CDATA[Re: replacing piston rings in 74 SB]]> Yeah if it feeel's low on #1 Pull the head I hand Crank warmed up motor's coupla brisk turn's by hand feel the compression.
  Sure Spark plug is tight < lose Compression obviously ? < check any how
  If feel's low try pullin the head ?
Head's can be both visually inspected and tested for seal .
Quite easy scrape carbon if any off the Combustion chamber being carefull not to remove any metal .
  Look between Spark plug hole and Valve seat's for Crack's < blueing if you need ?
  But pour gasoline in each port !
Exhaust port < check that Exhaust Valve !
Pour in gas watch valve < if valve take's 20 second's or more to become wett < good seal !
  If Gas runn's thru quickly ? Not sealing !
Mark the Badd valve !
  Now if this head was rebuilt ?
  Most likely you can remove the Valve's !
But on a runn in head < Most likely you cant remove the valve's because the Keeper's will mushrooom up the Valve stemm Keeper groove's .
  This Enlarge's the Diameter of the Valve stem and keep's the Stemm from passing thru the Valve Guide < tear's them up !
  So you grind the stemm keeper groooves and replace with new Valve .
  Do not reuse a valve that has been Filed around the Keeper's .
  But if it is the Good Head < supposedly rebuilt that is #1 < badd Cylinder < Gas leak's thru it ?
  Remove valve and hand lapp it in too see if you can get a good seal < might get Lucky Lil suction cupp on a Stick some Valve lapping compound ?
  As to re- Ringing <, Not that hard but understand not all Cylinders and Piston's are good candidate's for re- ringing .
  but test all port's and valves with gas .
Check Cyl to Head matte surface << Head should be smooth not all grooved up from cyl.
  Look for gas mark's or burn mark's indicateing hott escapeing gas .
  If Cyl groove is ?? Lil grooved up  ?
  Post again there's trick's ?
  Do not lapp cyl. intoo head with lapping compound < Usually make's worse !
                                        Sean

]]> http://www.volkswebbin.net/user/3376/ 2010-02-15T03:07:56Z http://www.volkswebbin.net/post/252222/#p252222 <![CDATA[Re: replacing piston rings in 74 SB]]> Ok, low compression on cylinder 1, and it seems like you covered most of the bases. Put a teaspoon of oil into the cylinder 1 sparkplug hole, and redo the compression check. If it makes little or no change in the reading, you have a valve or cylinder head sealing problem (cracked head, leaking head gasket). If the test results come up, like from 115 to 130 for example, then I'd say piston rings. The oil cap bouncing while doing the check on cylinder 1 would tend to support a ring problem: air compressed in the cylinder would escape past the piston rings into the crankcase, which would cause pressure fluctuations at the oil cap while the engine is cranked.

Paul

]]> http://www.volkswebbin.net/user/9721/ 2010-02-15T01:09:25Z http://www.volkswebbin.net/post/252219/#p252219 <![CDATA[Re: replacing piston rings in 74 SB]]> Yancey wrote:

What rods?

                                              Yancey

The pushrods.

]]> http://www.volkswebbin.net/user/10092/ 2010-02-13T23:16:06Z http://www.volkswebbin.net/post/252210/#p252210 <![CDATA[Re: replacing piston rings in 74 SB]]> What rods?

                                              Yancey

]]> http://www.volkswebbin.net/user/7/ 2010-02-13T20:10:38Z http://www.volkswebbin.net/post/252209/#p252209 <![CDATA[Re: replacing piston rings in 74 SB]]> Sean's wrote:

Often a Bad valve adjustment will hold a Valve open < compression will leak thru the open valve .
  You all know Me ?
I dont do compression Test on Bugg's except to Turn them over by hand while observeing the Rotor and at what Cyl. it is pointing too .
  Feel the compression by hand .
  Find a weak Cyl. < back the valves off .
See if it improve's the Compression on that Cyl.
Riddle Me this and Riddle Me that ?
How many threads above the nut are showing on the Valve adjuster's ?
  I highly suspect Bad Valve adjustment Possibly due too the Distributor Drive Being turned from it's Traditional T.D.C. #1 Posistion .
  Even if it has a Badd hole it should runn Ok with a Badd Miss ?
  Find T.D.C. #1 <, Then re-adjust the Valves .
  120 Buck's will buy a new Sett of Jugg's and Piston's .
Ive been re- ringin Piston's for 35+ year's there's considerably more to it than most People would think there is !
  First off you Dont Hone Cyl. too Clean them up of there Ring Groove, and wear .
  You Hone to Cross hatch so that the Ring's will seal .
  If the Cyl. is to worn << you need to Buy new Cylinder's and Piston's .
  How were the Head's Tested ?
  And answer the Adjuster nut Question .
                                                  Sean

OK I checked the valves once again all were at the right specs of .006, then put a new gasket on the intake manifold for 1 and 2, have compression but not the best did a check on all #1 was 115, #2 was 145, and #3 and #4 were 150.  Normally when I pulled the #1 and #2 spark plug wires it would not drop the rpms but this time it did just not much on #1, also checked and there are 2 threads on all adjuster nut's on intake and exhaust on #1 and 2.  Checked to make sure the rods were properly seated also and they were.  The head was rebuild by a VW mechanic in Tampa I am not sure exactly what he does as far as testing.  He replaced 2 or 3 valves as the stems were bent, reseated them and I can't remember what else.  I have the receipt just not readily available at the moment. Did not do a leak down test yet wanted to see what possible cures I had made so far.

]]> http://www.volkswebbin.net/user/10092/ 2010-02-13T19:53:56Z http://www.volkswebbin.net/post/252208/#p252208 <![CDATA[Re: replacing piston rings in 74 SB]]> You don't really need fancy equipment. You can buy an adapter to connect your compression tester hose to an air compressor type fitting.

http://www.type2.com/library/engineg/leaktst.htm

jim

]]> http://www.volkswebbin.net/user/706/ 2010-02-12T22:45:23Z http://www.volkswebbin.net/post/252195/#p252195 <![CDATA[Re: replacing piston rings in 74 SB]]> Often a Bad valve adjustment will hold a Valve open < compression will leak thru the open valve .
  You all know Me ?
I dont do compression Test on Bugg's except to Turn them over by hand while observeing the Rotor and at what Cyl. it is pointing too .
  Feel the compression by hand .
  Find a weak Cyl. < back the valves off .
See if it improve's the Compression on that Cyl.
Riddle Me this and Riddle Me that ?
How many threads above the nut are showing on the Valve adjuster's ?
  I highly suspect Bad Valve adjustment Possibly due too the Distributor Drive Being turned from it's Traditional T.D.C. #1 Posistion .
  Even if it has a Badd hole it should runn Ok with a Badd Miss ?
  Find T.D.C. #1 <, Then re-adjust the Valves .
  120 Buck's will buy a new Sett of Jugg's and Piston's .
Ive been re- ringin Piston's for 35+ year's there's considerably more to it than most People would think there is !
  First off you Dont Hone Cyl. too Clean them up of there Ring Groove, and wear .
  You Hone to Cross hatch so that the Ring's will seal .
  If the Cyl. is to worn << you need to Buy new Cylinder's and Piston's .
  How were the Head's Tested ?
  And answer the Adjuster nut Question .
                                                  Sean

]]> http://www.volkswebbin.net/user/3376/ 2010-02-12T16:33:52Z http://www.volkswebbin.net/post/252189/#p252189 <![CDATA[Re: replacing piston rings in 74 SB]]> burrhead wrote:
jamesdagg wrote:

. You pressurize the cylinders with air at TDC and time how long it takes to leak and you can hear where it's leaking from.jim

Yes you can hear where the air is coming out. thru oil cap = piston/rings, out exhaust = exhaust valve, out thru carb = intake valve
By chance did you measure the depth of the combustion chambers between the 2 heads?

Not exactly what you are talking about "the depth" of the combustion chamber? Please explain in a little more detail.  I have been working on VW's for about 6 years but only on a few mostly beetles and a few busses.

]]> http://www.volkswebbin.net/user/10092/ 2010-02-12T02:42:35Z http://www.volkswebbin.net/post/252186/#p252186 <![CDATA[Re: replacing piston rings in 74 SB]]> jamesdagg wrote:
jilli67013w wrote:
burrhead wrote:

Best to do a leak down test to see where the air is going. if the rings are bad it would oil foul the plug or smoke. Drive it down the road with someone following to see if it smokes. The driver can't notice it sometimes

When the last head was on we did a leak down test and it took about a 10 to 15psi jump which is why I thought it was the rings on #1. Sorry I forgot to mention that.

Miscommunication here. jilli67013w is referring to a wet compression test. Burrhead is suggesting something different. You pressurize the cylinders with air at TDC and time how long it takes to leak and you can hear where it's leaking from.

jim

Yes you are right miscommunication for sure guess I didn't understand thank you for the clarification.  Have never done that type of leak down and not really sure on how to do it if you can guide me I am sure I can do it.
thanks

]]> http://www.volkswebbin.net/user/10092/ 2010-02-12T02:36:48Z http://www.volkswebbin.net/post/252185/#p252185 <![CDATA[Re: replacing piston rings in 74 SB]]> jamesdagg wrote:

. You pressurize the cylinders with air at TDC and time how long it takes to leak and you can hear where it's leaking from.jim

Yes you can hear where the air is coming out. thru oil cap = piston/rings, out exhaust = exhaust valve, out thru carb = intake valve
By chance did you measure the depth of the combustion chambers between the 2 heads?

]]> http://www.volkswebbin.net/user/2281/ 2010-02-12T01:57:36Z http://www.volkswebbin.net/post/252182/#p252182 <![CDATA[Re: replacing piston rings in 74 SB]]> jilli67013w wrote:
burrhead wrote:

Best to do a leak down test to see where the air is going. if the rings are bad it would oil foul the plug or smoke. Drive it down the road with someone following to see if it smokes. The driver can't notice it sometimes

When the last head was on we did a leak down test and it took about a 10 to 15psi jump which is why I thought it was the rings on #1. Sorry I forgot to mention that.

Miscommunication here. jilli67013w is referring to a wet compression test. Burrhead is suggesting something different. You pressurize the cylinders with air at TDC and time how long it takes to leak and you can hear where it's leaking from.

jim

]]> http://www.volkswebbin.net/user/706/ 2010-02-12T01:35:11Z http://www.volkswebbin.net/post/252176/#p252176 <![CDATA[Re: replacing piston rings in 74 SB]]> burrhead wrote:

Best to do a leak down test to see where the air is going. if the rings are bad it would oil foul the plug or smoke. Drive it down the road with someone following to see if it smokes. The driver can't notice it sometimes

When the last head was on we did a leak down test and it took about a 10 to 15psi jump which is why I thought it was the rings on #1. Sorry I forgot to mention that.

]]> http://www.volkswebbin.net/user/10092/ 2010-02-11T20:37:54Z http://www.volkswebbin.net/post/252170/#p252170 <![CDATA[Re: replacing piston rings in 74 SB]]> Best to do a leak down test to see where the air is going. if the rings are bad it would oil foul the plug or smoke. Drive it down the road with someone following to see if it smokes. The driver can't notice it sometimes

]]> http://www.volkswebbin.net/user/2281/ 2010-02-11T13:42:21Z http://www.volkswebbin.net/post/252169/#p252169 <![CDATA[Re: replacing piston rings in 74 SB]]> I did adjust the valves and the head was rebuilt by a VW mechanic that I trust.  When the old head was on there was a similar problem which leads me to believe the rings in that cylinder.  I also made sure all the nuts for the head were torqued in the proper order and to the proper specs. We did not check the other side for compression as it has been running the same every time they have been checked.  The valves were done after the head was in place and torqued.  When the compression test on #1 was done there was movement on the oil filler tube cover.  This was not true with #2.

]]> http://www.volkswebbin.net/user/10092/ 2010-02-10T21:17:22Z http://www.volkswebbin.net/post/252158/#p252158 <![CDATA[Re: replacing piston rings in 74 SB]]> Such a low reading in one cylinder compared to #2 would lead me to suspect something other than rings.  Did you check the compression in 3 and 4 also?  Did the problem occur soon after doing any maintenance on the car?

When you removed the old head, were all the head nuts properly torqued, or were any loose?  Likewise, when bolting up the new used head did you follow the torque sequences (two of them) up to the proper torque?

Where did you source the replacement head - was there any check made to ensure it didn't have issues either?

Possible problems leading to a low reading in the one cylinder include problems with the valve seat, the valve not closing completely, bad valve adjustment, cracked head, broken rings. 

Worn rings or cylinders would be more likely consistent in all cylinders, so checking them all is essential.

I'm not sure that misaligned rings would result in such a dramatic drop.

First thing to check is your valve adjustment.  I must be done when the engine is cold - let it sit overnight where you will do the adjustment.

Intake and exhaust should be adjusted to .006"

Here are a couple articles with step by step instructions, just in case:

http://www.vwtrendsweb.com/tech/0106vwt … index.html
http://www.glenn-ring.com/tech/valve_adjustment.htm

Some engine builders inadvertantly put the distributor drive shaft in backwards, which leads to an engine being "180" out.  What this means is that when you think you have the engine at TDC, it really isn't...so adjusting valves here can lead to some not closing at the right time.  To confirm to yourself that the cam is in the right position for the valves you're adjusting, put your fingers on the rockers of that cylinder and turn the engine a quarter turn in each direction.  If the rockers don't move, you're in the right position.

While checking the adjustment, also check the head nuts with your fingers to make sure none have loosened off.

Let us know what you discover!

]]> http://www.volkswebbin.net/user/5/ 2010-02-10T21:10:55Z http://www.volkswebbin.net/post/252157/#p252157