zero compression in #1 cylinder 1981 3.8l

[trooper1822]

Ok so after rebuilding this engine with new gaskets and everything I finally got it back together today and tried a compression test. All of the cylinders were good with the exception of the #1, it showed zero. As I posted previously I got this boat used and am fixing it up. You can get the back story from the other threads if need be. When I had the engine torn down I found no cracks anywhere on the block or the cyl walls. No water in oil The #1 did have rust on the valves and I cleaned it up as best I could. I am starting to wonder if maybe the valves are not seating properly and I need to pull the head again and have the valves redone. I know it could be rings but I would think even with a leak I should get something to read on the gauge. At a loss here. Any help would be greatly appreciated.

 

[Speak]

Re: zero compression in #1 cylinder 1981 3.8l

Might want to check for cracks on the valve seats when and if u pull the head Check that area of the head carefully. But first bring the piston upto top dead center then put 50psi into the cylinder thru the spark plug hole and listen carefully. If u have a hissing in the exhaust then u know the leak is getting past the exhaust valve or on the intake valve if hissing us heard they the carb/intake manifold.

Stuart

 

[trooper1822]

Re: zero compression in #1 cylinder 1981 3.8l

I will do this. Going to try and pull the head again this weekend. I know I will have to buy another head gasket but can I reuse the exhaust and intake manifold gaskets or will I have to buy another new set?

 

[Howard Sterndrive]

Re: zero compression in #1 cylinder 1981 3.8l

before buying more gaskets.
just slide the port side exh manifold off and take the valve cover off and check the valves/rockers on #1 by cranking it over. Maybe a valve is stuck or a rocker nut just cranked down too tight.
( I always set rockers with a compression gauge anyways- not much oil flying around cranking it with valve cover off)

you definitely need new head gasket and intake manifold gaskets if that stuff coming off - can probably reuse exh manifold gasket.

 

[trooper1822]

Re: zero compression in #1 cylinder 1981 3.8l

Thank for the advice. I think the first thing I will try is squirting some oil into the cylinder and see if it raises the compression. If so then I know it's the rings. If not then I will try the rockers and see if maybre it is torque too tight. What should they be torque to or should I just go by trial and error? Thanks

 

[Bondo]

Re: zero compression in #1 cylinder 1981 3.8l

Thank for the advice. I think the first thing I will try is squirting some oil into the cylinder and see if it raises the compression. If so then I know it's the rings. If not then I will try the rockers and see if maybre it is torque too tight. What should they be torque to or should I just go by trial and error? Thanks

Ayuh,.... Rockers aren't torqued on yer motor,...
They're adjusted for 0 lash at the valve tips...

How'd you do the original adjustin' of the valves,..??

 

[wcasey5]

Re: zero compression in #1 cylinder 1981 3.8l

If your valve are not seating, you can lap them yourself with grinding compound and a valve suction cup. If ou have the head off, lay it so the combustion chambers are pointing up and fill them with gas. If the gas leaks out, your valves are not sealing. Kinda red neck, but if you have zero compression it won't be something marginal.

 

[Silvertip]

Re: zero compression in #1 cylinder 1981 3.8l

If you have no idea how to adjust the valves, you have probably already bent one or more or bent a pushrod or two. Best read the manual.

 

[trooper1822]

Re: zero compression in #1 cylinder 1981 3.8l

Ayuh,.... Rockers aren't torqued on yer motor,...
They're adjusted for 0 lash at the valve tips...

How'd you do the original adjustin' of the valves,..??

I never adjusted the valves after I took the heads off. Just left them alone.

 

[trooper1822]

Re: zero compression in #1 cylinder 1981 3.8l

So I tried putting some oil into the cyl and tried doing another compression test and it still showed zero. Did not budge at all. Tested the other cylinders and the gauge does work. So I am starting to lean towards its the valves not seating. So I am guessing I should pull the head again and go from there. Also considering maybe buying a new head or just having the valves on this one replaced? So many ways I can go with this.

 

[trooper1822]

Re: zero compression in #1 cylinder 1981 3.8l

just out of curiosity does anyone know where I can buy new valves, springs and other parts just in case I do have to redo the valves? Will be pulling the head tomorrow and going to take a very hard look at it. But first I am going to make sure the rockers are adjusted properly and try a comp check one more time.

 

[Silvertip]

Re: zero compression in #1 cylinder 1981 3.8l

If you didn't put the push rods in the same position they came from and didn't put the same rocker arms in the same position then you need to adjust the valves. You also replaced head gaskets which changes the geometry of the valve train so you need to adjust the valves. You can remove the valve cover and measure the valve movement on that cylinder and compare it to one that is working. **** you check the condition of the valves and seats when you had the head off. For all you know you have some burned/bent valves.

 

[Howard Sterndrive]

Re: zero compression in #1 cylinder 1981 3.8l

I never adjusted the valves after I took the heads off. Just left them alone.

that's a new one. Never heard of someone assembling the top end of an engine without adjusting valves before.
Did you put sealant on the head bolts? Are you just winging this?
Do you know how to time the distributor properly? Your 229 is different from any other chevrolet engine in that regard.
A lot of parts can get damaged if proper processes aren't followed.

I would recommend this book, although it is for Chevy V8's - your 229 V6 is virtually identical in assembly process. Every process in this book must be done properly and well for your engine to ever work reliably.
Rebuild Small Block Chevy by David Vizard 1987, Paperback | eBay

 

[trooper1822]

Re: zero compression in #1 cylinder 1981 3.8l

that's a new one. Never heard of someone assembling the top end of an engine without adjusting valves before.
Did you put sealant on the head bolts? Are you just winging this?
Do you know how to time the distributor properly? Your 229 is different from any other chevrolet engine in that regard.
A lot of parts can get damaged if proper processes aren't followed.

I would recommend this book, although it is for Chevy V8's - your 229 V6 is virtually identical in assembly process. Every process in this book must be done properly and well for your engine to ever work reliably.
Rebuild Small Block Chevy by David Vizard 1987, Paperback | eBay

Thanks for the reply, yes I did use sealant on the head bolts before I resembled. I do have a free manual that I found online for the engine and have been reading a lot on the rebuild process but I will admit I did not know I should have rechecked and adjusted the valves. when I took the engine apart I labeled everything so they would go back where they came from So I tore apart the engine again on the side that has no compression in the #1 and decided to try and see if the valves are leaking. Upon visual inspection everything looked fine. So I tried the water method of putting water on each valve and seeing if they leaked. What do you know, the #1 valves leaked. The exhaust valve did not leak any water but the intake valve was leaking fairly well. It took about 15 sec for most of the water to drain out. So I tried again using acetone and it pretty much flowed right out. The other two held water with no issue So It looks like there is my issue. Now I am trying to decide if I should replace the valves as there is some pitting on the valve surfaces but not that bad or if I should get lapping compound and try lapping the valves. Will need to find somewhere that sells the correct valves if I decide to replace them.

 

[bruceb58]

Re: zero compression in #1 cylinder 1981 3.8l

Why not just take it to a machine shop and let someone who knows what they are doing do it. While you are at it, take the other head to them as well.

 

[Silvertip]

Re: zero compression in #1 cylinder 1981 3.8l

You do realize there are specifications for valve seat sealing width and in some cases multiple angle valve jobs are required. Simply lapping the valves does not make it right and cause other issues. If the seat is pitted, you need a lot of lapping to remove the pit. You are apparently trying to get by on a budget but you may actually shoot yourself in the foot in the process. This is one area of the engine that needs proper repair. You keep mentioning rebuilding this engine. If you don't do head work, you didn't rebuild the engine. So what did you do?

 

[Bondo]

Re: zero compression in #1 cylinder 1981 3.8l

Thanks for the reply, yes I did use sealant on the head bolts before I resembled. I do have a free manual that I found online for the engine and have been reading a lot on the rebuild process but I will admit I did not know I should have rechecked and adjusted the valves. when I took the engine apart I labeled everything so they would go back where they came from So I tore apart the engine again on the side that has no compression in the #1 and decided to try and see if the valves are leaking. Upon visual inspection everything looked fine. So I tried the water method of putting water on each valve and seeing if they leaked. What do you know, the #1 valves leaked. The exhaust valve did not leak any water but the intake valve was leaking fairly well. It took about 15 sec for most of the water to drain out. So I tried again using acetone and it pretty much flowed right out. The other two held water with no issue So It looks like there is my issue. Now I am trying to decide if I should replace the valves as there is some pitting on the valve surfaces but not that bad or if I should get lapping compound and try lapping the valves. Will need to find somewhere that sells the correct valves if I decide to replace them.

Ayuh,.... No matter how bad the valve is leakin', the 1 You say, "Upon visual inspection everything looked fine."

You wouldn't get a Zer0 compression test....

Unless you hadn't adjusted the valves, 'n the valves were actually Wide Open...

I'm sorry,...
but ya can Not pull the heads off a motor, 'n put 'em back on, 'n expect the valves to be Properly Adjusted...

If yer gonna play a Mechanic, ya gotta follow All the rules found in shop manuals...
When ya Don't,.... Well, you can see the results....

No disrespect intended, just tryin' to be Honest.....

Yer spinnin' yer wheels,... bring the heads to a Machine Shop, 'n get 'em rebuilt....

 

[trooper1822]

Re: zero compression in #1 cylinder 1981 3.8l

Ayuh,.... No matter how bad the valve is leakin', the 1 You say, "Upon visual inspection everything looked fine."

You wouldn't get a Zer0 compression test....

Unless you hadn't adjusted the valves, 'n the valves were actually Wide Open...

I'm sorry,...
but ya can Not pull the heads off a motor, 'n put 'em back on, 'n expect the valves to be Properly Adjusted...

If yer gonna play a Mechanic, ya gotta follow All the rules found in shop manuals...
When ya Don't,.... Well, you can see the results....

No disrespect intended, just tryin' to be Honest.....

Yer spinnin' yer wheels,... bring the heads to a Machine Shop, 'n get 'em rebuilt....

No disrespect taken, I have been in the Army for 8 years and have learned to take all criticism both good and bad. I joined this forum to learn and I am. You are correct I am taking this as a learning experience and I am sure I will have a ton more questions in the future and appreciate everyone's answers. I have been studying the shop manual and am learning a lot. I contacted a few local machine shops as I realize the heads are not a area I want to tackle as far as trying to rebuild. But I have decided I am going to buy a set of re-manufactured heads that I found. Both heads have been jet cleaned, magnafluxed, and had the valves and seats reground and were assembled with new valve seals and have been resurfaced .010. After calling the shop and getting rough estimates, it would be cheaper for me to buy new heads. The set I found are less than 220 so this seems to be the smarter route and they come with a 90 day money back guarantee. I read on how to properly adjust my valves once the new heads are in so I will do it properly. I will have to read up on how to set the timing as I have not done that since I was about 15 lol. So I guess now I am going to work on some other areas while I wait for the new heads to arrive. Question I do have for you all is your opinions on reusing head bolts? Most places I have read suggest just replacing them as they are under a lot of stress and once removed may not torque back to the proper spec. I have found the bolts for about 20 a set but can only find them for the 4.3l and if I remember correctly they should work on the 3.8l?

 

[wcasey5]

Re: zero compression in #1 cylinder 1981 3.8l

sound's like you have a great plan. I haven't dealt with a 3.8, but usually the non re-usable head bolts are the torque to yield bolts, and that should be in the manual. If you can find a set of bolts for around $20 then it's a no brainer, get them.

 

[Bondo]

Re: zero compression in #1 cylinder 1981 3.8l

Most places I have read suggest just replacing them as they are under a lot of stress and once removed may not torque back to the proper spec.

Ayuh,.... You do Not have torque to yield bolts,... No reason to buy new 1s, unless they've rusted, 'n disappeared....

Yer head bolts are Much Stronger than the cast iron they screw into....