manifold and head gasket

[grantf]

Hi, me again.

So after removing my clogged catalytic converter my car now runs considerably better, but not like it did before my trouble started about a month ago.

I am thinking that I have blown the exhaust manifold again. the car sounds a lot like it did before I replaced it a year ago. First question: could a clogged exhaust cause my new manifold gasket to leak?

Also I have spotted oil seeping from the head gasket. So my second question is should I replace the head gasket. It seems that half of the work to replace the head gasket would already be done because of the work required to replace the manifold gasket.

here is a little more info: compression test results starting with cylinder one are:143,140,145,146,140,139 hot with all plugs removed and WOT. I also replaced my plugs to NGK and did a cold valve adjust.

The valve adjust was after the compression test was made so I do not know if it would effect the results.

car ran a little better also but it is still noisy.

Grant

P.S. I plan to check the valves hot soon, I did the cold adjust just because I have not acheved valve adjustment zenn yet.

[black gold man]

Did you put new cat on or resonator in its place.

[grantf]

Did you put new cat on or resonator in its place.

No Sir. just a straight pipe. The sound though is coming from the engine compartment. Also I have low vacuum and I am running lean, It did improve a little after removing the cat. I had to adjust the AFM to compensate, not something I think is a great idea but I do have the spring tension marked from calibrating it last year so I can return it later. Anyhow I plan on a new exhaust in the near future and I am close to certain that the manifold is leaking.

[siteunseen]

Is the Moto Guzzi running right? Sounds like you'll be putting some miles on it.

[grantf]

Guzzi is running fine. I can change out the manifold gasket in a weekend. should I go ahead and change out the head gasket since I am halfway there anyhow?

What could have caused the manifold gasket to blow?

[siteunseen]

When I bought mine the exhaust was leaking at the last bolt, #6 cylinder, when I took the manifolds off I found my EGR was badly cracked and had rotted out the tunnel under the plentum? on the intake. I almost have the motor ready to put back in 6 months later. The more I took off the more I saw that needed to be replaced. It's a slippery slope that I slid down fast. Put up some pictures of the leaks.

[Walter Moore]

Once I thought that I had oil leaking from the head gasket, but it turned out just to be that the intake/exhaust manifold fasteners were loose. The "Oil" was just unburned fuel and condensation that accumulated near the exhaust leak when the engine was cold.

If you know already that you have an exhaust leak, I would try re-torquing the manifold nuts before I spent the time pulling the head.

[grantf]

Once I thought that I had oil leaking from the head gasket, but it turned out just to be that the intake/exhaust manifold fasteners were loose. The "Oil" was just unburned fuel and condensation that accumulated near the exhaust leak when the engine was cold.

If you know already that you have an exhaust leak, I would try re-torquing the manifold nuts before I spent the time pulling the head.

You make a good point about re-torquing the manifold bolts, but it is evident that the oil leak is coming from the head. I could see "a bubblin crude" coming from the head gasket at idle. Also there is sizable oil leak above the oil filter and forward of it near cylinder one. I am not trying to get better compression by changing out the head gasket just thinking that perhaps since I am most of the way there by removing both manifolds that it may be a good idea to change it out now rather then later in which case I would be removing the manifolds yet again.On the other hand could I do more damage. The head removal looks straightforward as long as I take my time. After removing the manifolds all that really remains is the timing chain, head cover and the bolts themselves. Am I wrong?

Edited July 2, 2012 by grantf

[Wade Nelson]

Clogged catalytic converters and blown head gaskets go hand in hand. Do a compression check, hot.

Nevermind, failed to read your entire post.

Have someone hold a rag up to the tailpipe and you can quickly locate exhaust leaks with the added back pressure.

Who suggested re-calibrating your AFM? It measures the amount of air blowing past it. Reduce back pressure and more will blow past. No re-cal should (have been) required.

Something was wrong to begin with, like running rich or burning oil that caused your cat to clog up. I'd figure what THAT was before doing anything more.

Edited July 3, 2012 by Wade Nelson

[grantf]

Clogged catalytic converters and blown head gaskets go hand in hand. Do a compression check, hot.

Nevermind, failed to read your entire post.

Have someone hold a rag up to the tailpipe and you can quickly locate exhaust leaks with the added back pressure.

Who suggested re-calibrating your AFM? It measures the amount of air blowing past it. Reduce back pressure and more will blow past. No re-cal should (have been) required.

Something was wrong to begin with, like running rich or burning oil that caused your cat to clog up. I'd figure what THAT was before doing anything more.

The P.O.'s hack job suggested the recalibration. A long story but if you would like the read: http://www.classiczcars.com/forums/thread42574.html

My engine sounded really bad a year ago. Another long story but you can read here: http://www.classiczcars.com/forums/thread43150.html

my engine now has the same sound as before.

and I am sure my car has been running lean even before I cut out the cat. My vacuum is lower than 6 months ago with no vacuum hose leaks. believe me I have been searching for vacuum leaks hard for a long time. I am convinced the manifold is leaking and was leaking before I cut out the cat.

oh, and yes I am thinking my previously rich condition did have something to do with the cat failing.

Edited July 3, 2012 by grantf

[grantf]

Update: The manifolds are removed and parts are on the way. It only took me about 2 hours to get this far. The first thing I noticed was all of the shared manifold nuts were loose, way to easy to remove. the exhaust gasket at cylinder 6 was toast. I am going to dive into the head gasket next. So why would all the studs and bolts be so loose? I torqued them to spec last year. Could it be the anti sease I uased? anyhowm new studs and bolts are on the way, I don't think I will be using anti sease in the future for the manifold. and I may do a retorque in the future also.

So it looks like all I need to do now is put the timing at TDC and block the chain.

[grantf]

I pulled the head. No drama. Now it's cleaning time. What a pain in the ars.

I noticed that some of the head bolts are pitted with rust. I am thinking of ordering a new set. Any advice on cleaning the valves? there is a ton of carbon build up on all of them expecialy the exhaust valves, or should I just leave them alone?