No Compression

[cobra 3.0]

Re: No Compression

The 3.0 runs best on 89 or higher(91). You can adjust the timing to run 87, if 89 is not available.

 

[dick]

Re: No Compression

Man I love this place, no one has heard from Jerry and the topic is now about octane and thread is still going.<br />I'm amazed JB hasn't shut it down.

 

[Bhamil]

Re: No Compression

Maybe JB's a gentleman

 

[dick]

Re: No Compression

Oh , you'll fit in just fine here.

 

[Jerry San Diego]

Re: No Compression

Hello to all that responded to my post- I thank you al verry much for all of the input and suggestions. I pulled my boat out of the water today and put it in my driveway. will be pulling the head off the day after Christmas to see what it looks like in there and will get back to the forum wiht the information on what I found am probably some more questions.I have been burning 87 octane in the engine so I guess that could be some of the problem- It will be interesting to know for sure what happened. The Chrismas season has kept me from the boat bu am dying of curisoity. Thanks again all<br />Jerry

 

[jeff92799]

Re: No Compression

i had a 305 in an old z28 i had do something similiar. <br /><br />we ran a compression test and everything checked out , except the #7 cylinder didnt have anything. <br /><br />turned out to be a broken valve spring. it was stuck open. <br /><br />good luck with whatever you find, go after the smaller stuff first

 

[Jerry San Diego]

Re: No Compression

I have pulled the head off and will be taking it to a machine shop for them to look at it this week. The #4 exhaust valve appears that it could be the problem It is still shinney while all the other valves are covered with black soot. It also looks like it could be a little wavey Also the valve appeard to seat lower that the rest of the valves. this valve is the closest one to the exhaust elbow. Do you think the elbow may have enough restriction to cause a problem in that one valve. This may be the valve that was previously replaced. In adittion when I look into the #4 cylinder with the piston all the way down It look like I can see the rings that are expanded to meet the cylinder wall. Didn't get a chance to look at the other cylinders to see if they are the same way. It started to rain on me- Had to quit. Are the cylinders tapered out at the bottom so the rings may be slightly visible? Thanks again for all the help- I will keep you posted after I have a pro look at the head.<br />Jerry

 

[Walt T]

Re: No Compression

It's shiny because there is no combustion taking place. The raw fuel has cleaned it up. A pro will tell you about the head. You can dribble some water into the intake and exhaust ports and see if they hold water. If water dribbles out then you know it's probably the head. If not it could still be the head.<br />You cant tell anything about rings with them in the hole. If the cylinder looks okay, wait for the head assessment. If the pro says the head is okay, then you get yank an engine. It'll be fun!<br />Oh, the things you'll learn! The words you'll speak! The knuckles you'll break! The divorce you'll endure! But have no fear, we'll all help you out every step of the way. Except for the divorce part, get an attorney for that.

 

[Bhamil]

Re: No Compression

...the divorce part AND the actual pulling of the engine. Every boat owner should have to go through that once just to give you something to talk about at the marina. We'll be with you in spirit, though.

 

[Walt T]

Re: No Compression

Actually pullin engines is the easy part. Ripping it all down is easy too. It's puttin it all back together with only a minimum of leftover parts thats the challenge.

 

[Jerry San Diego]

Re: No Compression

Walt- I put water in all the intake and exhaust ports. Water just ran thru the suspected problem exhaust valve. No water thru the other exhaust valves. Some leakage by all the intake valves but only a little. I will be taking the head in to a machine shop on Wednesday and leave it for repair. Will you know what the shop says. I suspect the previous valve job may not have been a quality job. I will post the results here. Thanks to all who provided help to me. I will surely have more questions before I finish this project.<br />Thanks Again-<br />Jerry

 

[Walt T]

Re: No Compression

Hey great Jerry, You found the problem. Dang, and we were lookng forward to figuratively helping you pull the engine and figuratively messin with your mind.

 

[Jerry San Diego]

Re: No Compression

I took the head into a machine shop yesterday and they tore it apart- The number 4 exhaust valve was pretty warped, but the valve seat was totally destroyed. also one other exhaust valve needs to be replaced. I was told that when the previous valve job was done they did not use hardened seats which should be done on this engine. They told me that the engine was designed to operate on leaded fuel and that running the engine on unleaded fuel creats the heat which destroys the exhasust valves and valve seats. The are replacing all the valve seats with the hardened seats which should prevent this from reoccurring. (I hope so). I don't know if they are correct or not but sounds reasonable to me. When I get the engine back together I will also try to use a higher grade of fuel just incase that may be an issue also. I sure don't want to go thru this process again soon. Will be putting the engine back together within the next week. The only problem I forsee may be adjusting the valve lash. The repair manual I have is confusing to me regarding this process. Any help in this from you will be appreciated. Again I want to thank all of you for your help and advice. I will post again when I get the engine running and do another compression check.<br />Jerry

 

[rodbolt]

Re: No Compression

hello<br /> jerry<br /> look back through the posts I sent to affa. I described the entire procedure and why the procedure is done. I also caution you against the method in the service manual that tells you to do half the valves then rotate the engine and do the other half. I use this method but I have done several thousand chevy valvetrains. it can be confusing.<br /> do the valves one pair at a time and it will work fine.<br /> good luck and keep posting. and for the unleaded thing, Valvetane is a lead subsitute additive that works well.

 

[K Hultgre]

Re: No Compression

I thought the boat was a 1989. Why would the engine require leaded gas?

 

[Walt T]

Re: No Compression

Kevin is exactly right. All engines since 1975 have hardened seats. No way can I believe a machinist installed non hardened seats, I doubt they're even available. The machinist who has your engine now is possibly pulling your leg.

 

[Bhamil]

Re: No Compression

Jerry San Diego; the only time I have disagreed with dieselwalt is over this engine, and I only disagree a little. Please, Jerry, use a better grade of fuel, minimum 89 octane. Chapter 9, page 288 of the OMC manual reads " OMC recommends the use of unleaded or leaded gasoline with a minimum research octane number of 93 or anti-knock index number of 89. Otherwise the timing must be retarded..." and you can retard the timing, but, not enough on that engine; I know of what I speak. Modern electronic ignitions can retard to infinity or advance to tomorrow, but your breaker point system won't cut it. Just use a higher octane than 87 and if your tank now has 87 in it, get an octane booster and follow the directions. BTW, since no one knows when that head was rebuilt or who rebuilt it, it is possible it was done by an automotive mechanic with the wrong parts being used. That size valve has been used in other applications for years and years, and years...

 

[jw454]

Re: No Compression

Its all very simple. Bury the 3.0L, and get a 460.

 

[Jerry San Diego]

Re: No Compression

Again Thanks to all who have helped me- I haven't been able to put the engne together yet. Can you believe all the boat parts places in San Diego have been closed down from Christmas till Monday Jan 5. (Unbelievable)but true. I will be putting it back together this week and will post my final results. Hope it all come out well. Thanks for the help with the valve adujustment I think I hae it figure out now. As far as the hardened seats go I don't know if what the machine shop told me is true or not. Guess I will just have to take their work and see what happens. I know for sure when I looked at the valve seat aftr the valve was removed the seat was completely demolished. The cause of why to me is still a mystery unless it could be the fuel- I will go to a higher octane fuel and will put an octane booster in the full tank of gas I have now. Question- Gasket sealer- Any recommendation on the type of sealer to use on the gaskets when I put it together. The boo says no sealer on the head. But I still have the intake and exhaust and exhaust elbow thermostate housing gaskest- Aslo no sealer on the valve cover gatket? Thanks again <br />Jerry

 

[Walt T]

Re: No Compression

Detonation damage looks like a rock was rattling around in the cylinder. It does not selectively damage valve seats. That seat burned most likely.<br />Your damage was not caused by bad fuel. If it were you would have damage in other cylinders as well.<br />There is no harm in using higher octane fuel, but as I said that's not why you have problems.