I got my new used engine installed and it isnt running quite right, so I did a compression check. all cylinders except 6 and 8 are at 130. SO I then pump air into the cylinder, and notice air in 6 is coming out of 8. Air in 8 is coming out of 6. SO I pull the head on the right bank. I fill the intake runners, and they all hold gas except 6 and 8, which are leaking pretty bad. The engine sat since 08. SO I took the valves out cleaned up the runners ect, they where pretty carboned up in these 2 cylinders. same with piston in 6 cylinder. I now filled the runners up, and they are holding with an occasional drip. To me there shouldnt be any drip, so What is normal or expected. I dont want to send um out unless I have to.... The engine is a 1987 350 nothin special. Rebuilt Jasper engine, looks like it is already 40 over.
Sounds like 2 issues. #1 Sounds like a head gasket blown between 6 & 8 #2 Sounds like carboned up valves, or valves that need to be ground. I would lap those valves for sure or have a valve job done before reassembly. A little leak when sitting is always amplified by RPM.
Head gaskets are fine. I have intake valve issue's that is it. rest is fine. I am gonna go to the machine shop tomorrow. The one valve is to far gone.
Back from the machine shop; The #6 and #8 intake valves are bad. They where being pulled into the head dishing them. its hard to believe this happening with around 10000 miles on a bone stock engine. It is another example of cheap chinese metal used in the mass engine rebuilding arena. This time it was Jasper. #2 and #4 werent far behind so the whole right bank will be getting new valves, and over the winter I will do the left bank. valve springs have 85 lbs seat preassure. Stock is 65 and good street application is 110. SO these are in the ball park, or a happy medium, but by no means enough to pull the valves into the head.
I ran a set of heads, that came off a race motor, from a friend. I put a lot of miles on them, and they started ticking. Not long after, one of the rocker studs snapped off. When I pulled the heads, I couldn't get the socket down over a head bolt. I dug in the oil with my fingers to find big chunks of metal. When I pulled the heads, most of the valves were sucked up, into the heads, and the valve seats were destroyed (the chunk of metal that I found). I still don't know how it didn't get sucked up into the pump and trash the engine. I had to break down and buy some re-built heads from a local city motor place down town. After selling the truck to my cousin, I had heard that like 6 months later, he had to pull the motor due to compression loss with those new heads. Guess you just never know what you are going to get sometimes. Haven't really talked to my cousin much since then.. I'm sure he thinks I sold him a lemon motor, and tried to screw him over. But I think he got rid of the truck anyways..
Me neither.. I had a tiny screw lock up an oil pump once, and it sheered off the shaft, and I was lucky to see the oil pressure fall to zero, while driving.. Yet, I found huge chunks of what looked like the valve seat, on top of the head, in the oil. It had gathered in the valley where the head bolt was, and I had to dig it out to get a socket over the bolt, to pull the heads. The machine shop told me the heads had too strong of springs for the street, and had pulled the valves up into the heads.
Your head gaskets were not fine. If they were, air would not go in 6 and come out 8 unless there was a gapping crack between the intake valves. If you dont have the deck and heads checked for flatness there is a good chance it will do it again.
Head gaskets where fine..... Like I said both 6 and 8 where leaking and the intake valves are right next to each other so with both intake leaking the air went up into the intake and right back down the other cylinder and out the valve. Very common on cylinders next to each other Heads are getting double checked but no rust or water leaching, and all looked OK they will get magnafluxed before reasselmbly
You are trying to tell us the air went up the cylinder head runner into the giant plenum of the intake and then took a 180 degree turn and went back down the # 8 intake runner passed through the leaky valve and back into the #8 cylinder !!! Wow >>>>.
Shit, we forgot those 80's chevys had the high pressure intake check valves preventing compressed air from leaving the carburetor thus forcing back around the intake valves in weak adjacent cylinders. He's right.
Mustang6147, nope, I aint buying it. Check again. And who told you this? The machine shop? Put a straight edge on both the head & block surface. Also let us see the head gasket (both sides). Not being mean, but your statement about cylinders next to each other, makes no sense. John
I sure am glad none of the other cylinders had intake valves that were open. (OK, maybe the rocker arms were backed off) And on the intake seat in the oil, how does a valve seat get into the oil. I can see it blowing back into the intake and moving around or going through the exhaust port, but under a valve cover? Larry T
Yep, could have been bad for sure. Seriously, mustang6147, not sure where you got that idea, but it is just not right. [hint] We're trying to help here....been there and done that.
I know, I know Larry T... If I didn't pull the heads myself.. I'd say I was full of shit.. but there was tons of chunks in there. Never knew what it was, but the seats were gone, and the pieces looked just like 'em. It was before the days of digital cameras, and I was a poor Air Force family man, so I have nothing but my word to back it up..
No pictures, it didn't happen. (JUST KIDDING) Who knows, I've seen some pretty strange stuff that I couldn't explain on engines I've pulled apart too. Larry T
Well heres the deal.... When I pumped air into the #6 it came out the number 8 so I figured a bad head. I called up a buddy who works at a parts store, who used to work at an older store which had a machine shop. He is a knowledgeable old timer, I called up to see how much he could get refurbished heads, we BSed for a bit then he asked for the symtoms. As soon as I told him, he said the intake valves where bad. Who am I to question. I can build an engine. I drag race. built many engines, but I was in disbelief so I took the heads to a machine shop who builds my buddies dragster engines. He is a hell of a machinist, who happened to be between jobs. When I told him, what all I did. He looked puzzled and dis-assembled the heads, and found no cracks. He did find the valves where dished, like cheap metal was used to make them. He is magnafluxing them, and if all OK then reassemble with new intake valves. Everything I have said is true, I just need to get the heads back and roll at this point. I am happy that I am not the only one who hasnt heard of this, I thought I was nuts.
The one pic is with a LED flash light in the intake runner and the valve closed with before taking them out. Spring pressure is 85lbs at seat and that much light is coming out. The other pics are right after I took the head off. No sign of bad head gasket.
sounds like air was traveling through intake .did you have carb on motor ? if so butteryflies were keeping air pressure in intake so it was coming through other cylinder.more than likely you would have felt air on other cylinders also.i wouldnt waste my money on having heads repaired i would find used set for fraction of cost and replace both heads.
Id have them pressure tested , fixed , fluxed and decked call me crazy but a very slight warp will start to blow a head gasket the minute you start it .
If you look between the two cylinders in the picture there looks to be carbon buildup between the cylinders. I also dont see a nice clear ring around the cylinders you should see if it was sealed well. This is a sign of a blown head gasket. The gasket does not have to have a hole to be blown. Definately, got valve problems too....overreved and bent valves?...looks like a wreck all together. I guess with a 1/16th inch gap on one valve and the other one open you might get some air flow, but it would be howling in the intake if it was taking that route.... If it was mine and had that much problem I would pull it out and check everything. If all is good you are just out time and gaskets.
you have leaking head gaskets, depending how long it has been like this it might fire slot the block and head. when you fill a cylinder with pressure it will help seal the valves, and then push the air threw the gasket where its been leaking. From that picture those look like some proline or engine quest stock replacement heads, they either had junk valves or to strong of springs to mushroom the valves.
In the engine world I just assume that everybody does things in the same manner. When trying to find problems like you had the norm would have been to do the leakdown test. 1-remove all sparkplugs, 2 remove all pushrods, 3 inject air into each cylinder, 4 listen at exhaust,intake,and crankcase for the air leakage. In the way that you posted this it would lead you straight to the blown head gasket theory as in I inject air into #6 and it comes out in #8. What you failed to post was that the air was raizing hell and trying to blow out the carb too. So as long as you left the carb butterflies shut the air was actually passing through the intake runners and back into the adjoining cylinder. My mistake for not asking enough questions before posting. Like I said I just assumed everybody did things the same way that I do >>>>.
I agree with turbo s10 thats a blown head gasket. People have mentioned checking the mating surfaces of the block and heads. Have you done that? Without these surfaces perfectly flat, you will blow another head gasket long before its time. Its obvious that the valves are bad,so fix them but if it were me I would deck the block and heads before reassembly to avoid a tear down in 6 months when the head gasket gives up again. Besides when milled down you increase the comp ratio increasing the power out put. Thats my 2 cents
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