The Stovebolt Site Forums The Shop Area Engine Shop Blown Head Gasket

Found my problem. Head Gasket was blown between #4 & #5 (linked photo). had no compression in 4,5&6. I think #6 had a sticking valve because the intake pushrod popped out from under rocker (got that probable reason from my earlier posts (12v resister coil & 4,5,6 no compression). Ordered new head gasket from napa so I should be back on the road soon. Are the full copper gaskets much better than the copper/fiber gaskets? Thanks for all the answers on my earlier posts-- great site. [url=http://i657.photobucket.com/albums/uu295/Scotter2009_2009/IMG_0717.jpg]

Hi, I suppose opinions of which gasket would go both ways. I would have the head checked for flatness or have it reworked now that it is off.
I would think the fiber type would be better for dealing with any variation in flatness and it would be my choice.
Check those rocker arms for wear,but I spose you already did that.
Dan

Thanks Glasman
I checked it at home with a carpenters square and it looked flat but you may be right a machine shop check is a good idea.
I ran it with the #6 pushrod back in place and it did not pop off again and all the rockers seem to not be sloppy on the shaft or look to be bad.

I think glasman brings up a good point - do we know WHY the head gasket blew?! Blown head gasket is a symptom, not the cause . . .

Engine ever overheat? Run rich? Wrong heat-range plugs?

Would be good to know why it went south.

-Michael

The head must be measured accurately. Allowable warpage is generally only .008 per linear foot. Be sure to check the top of the block also. I have seen them warped a lot. A warped deck will also affect your line bore. I never found it worthwhile to try to true the deck on a warped block. Also, was the head torqued in the proper sequence. GM always recommended retorquing head bolts after run in. This means only trying them for proper torque not backing them off and retorquing them. Unless the engine is very high mileage, there is usually a reason. Especially if you had zero compression on adjacent cylinders.

Thanks Mikestem & Crewelge

I checked the head with a machined straight edge from the shop at work and it is flat. I did not check the block but I will. I never overheated it but it may have been I've only had it a year. #6 six had a stuck valve(I think) and the intake pushrod popped off do you think that could have sent too much fuel to #4 and #5 to make them too rich? alot of carbon on the top sides of all the valves,is that an indication of being too rich? I have not put it back together yet, the valves do not look too worn to me, so I was going to clean them up and put them back in. I really cannot afford to buy new and machine work if I can avoid it. but if I have to I will. I planned on putting as much back on as needed to check the compression before I went all the way. oh ya the head bolts came out pretty easy eccept for one down near the blown end. This stuff is all new to me so I'm learning as I go.

I'm completely new to engines, save for some basics, but ... a LOT of carbon is a very high milage engine, or it's running rich or pulling oil from the crank(y)case. If the valve was an exhaust valve that got stuck, I can see how that could have pushed the gasket to breaking, but that's just thinking of pressure, and I could be quite wrong there.

I looked at the plugs I took out and they are black carboned so I guess it was running rich. also is there a compound I can put on the valves and rotate them in place to help seat the old valves to their old seats? A friend told me he thought therewas something like that to help set the valves. Thanks again to everyone

There is a lapping compound called Clover http://www.newmantools.com/clover.htm I have been using it for 50 years. I am no longer able to get it locally but it can still be bought on the internet. However, care must be taken that you do not get the seats too wide. I have valve grinding equipment and use lapping as a finishing touch. Also, your valve guides should be measured as well as your valve stems. This takes a mike and a small hole gauge. If you know an old timer who still has the equipment, possibly you can get done reasonably. Black sooty plugs can be rich mixture or from oil consumption. A lean mixture is more likely to burn valves than a rich mixture.

Heck, if money is a big issue (when isn't it?!), maybe you're right - just get the valves working ok, clean the plugs, put it back together with a new gasket, then figure out why it was running rich.

IF you get it tuned well and running right, I can't see any huge issues with the existing carbon build-up; maybe engine run-on if it's really severe, but I tend to doubt it.

Guess it depends on your short-term plans for the truck. Long-term, you can ALWAYS take it apart again and get it rebuilt when time and money permit. Maybe fix it and drive it in the mean time?

-Michael

Carbon on the port side of valves often indicates oil leakage around the stem- worn guides or stem seals. Carbon on the spark plugs can result from either oil consumption or rich fuel mixture, depending on whether the carbon is dry and powdery (fuel mixture), or heavy and kind of caked on the plug (oil consumption). If the plugs are the wrong heat range (too cold), you will get the carbon on the plugs. If they are the heat range specified for normal operation, there is more to be discovered. If you can post a picture of the spark plugs, that would help considerably.

Heavy carbon in the combustion chamber usually results from ring leakage, but worn valve guides are a possibility also. At this point, there is more to your story.

Harvester

Youcan buy lapping compound at any parts store. Permatex still makes it. You might take the valves to a machine shop & have them grind the faces & then lap them in to the seats. It is not very expensive. Clean the stems up & you will have a valve job. Be shure to put new seals on. Running it in such poor shape could have carboned up the plugs. Clean them up & check again after you run it a while. If you have the Roch. model B carb, it is real easy to check out while you have it off. Make sure the power valve is working & the float level is correct.

Yep I'm doing an El-Cheapo valve job.
I got my lapping compound, new seals, going to clean the valves and stems and make sure they are not sticky in the guides(all the guides do not seem to have any play in them), new head gasket, make sure carb is working correctly (seperate issue) and not too rich. There was a couple of valves that were very sticky in the guides so maybe I will be good to go. If it all works out I might get a few more good miles out of it and then do a better job of rebuilding it or swap out or something down the road. Hope to post good news by the weekend that I have amazing compression and it runs like a top. Thanks for everyones help Scott

Got it done. cleaned stems & guides, new seals, lapped them, new head gasket, runs really well to me. 120# to 105# of compression on all cylinders. adjusted carb and I'll check the plugs for carbon after a while. hope to be good for a few more miles. Plus it looks good I painted the engine as long as everything was off. Thank for all the input from every one. (What should the compression be if everything is right?)