K1ng0011

So my 1985 v6 2.8L camaro over heated and cracked and melted a valve on the passenger's side cylinder head. I bought a new cylinder head to replace the cracked one and had the other one machined. And I put it all back together. Now I have a problem with cylinder #1. The spark plug is always black so oil is getting in the cylinder or something else is happening. When I tested the compression I got about 60psi and it fell pretty fast. The other cylinders have good compression. Before I replaced the cylinder head cylinder #1 was reading about 135psi. The spark plug was a normal color with the 135psi. I torqued the cylinder head bolts after driving it some too. The car is pretty hard to start but once I get it started I can gas it for a little bit and it will keep running then once I drive it around a block once or twice it seems to run fine. And it will start pretty easy after turning it off after I have been driving it. But when it sits for a while it becomes hard to start again. Does anyone have any idea what would be causing this? Like maybe I tightened the rocker arms down to much and the valves are always open?

bwiencek

I'm assuming that it's a mulit-port EFI 2.8L - and I'm going to guess that the black plug is not oil but it's raw fuel being dumped into that cylinder - either you've got a bad injector (stuck open and pouring fuel in - causing the hard start and rough running initially) or it's a fuel pressure regulator that has a ruptured diaphram and the raw fuel is being sucked into the intake and that's the closest runner for it to be sucked down causing the same issue. To check - pull the vacuum hose off the regulator right after running it - if it's wet with fuel inside or smells of raw fuel replace the regulator - if it's clean and dry then pull the injectors and have them flow tested/cleaned.

K1ng0011

That sounds like it is possible but the cylinder definitely is not holding the compression that it should. That is my main concern at the moment. Do you think I tightened the rocker arms too much? The fuel system was working properly before I took the cylinder heads off. Do you think a part just randomly decided to go bad?

FRMULA88

let me guess the low compression is on #1 (the cylinder which had the cracked & melted valve)

A black, wet, oily, spark plug means it's oil fouled.

A dry black sooty appearance would indicate rich mixture

neither is a syptom of bad fuel injector nor would that explain low compression as you tested.

Low compression points to issues with the valves, the piston, the piston rings, all three or any combination of these 3.

Think about the valves:

Worn valves would not introduce oil into the chamber / cylinder but could explain low compression however, you just had the heads rebuilt. So I would toss that idea.

That leaves worn valve stem seals or valve guides.. but you just had the heads rebuilt.

Think about the piston and or rings:
a hole in the piston, damaged ring lands, or damaged rings would give a low compression test reading.. and would also let oil into the chamber.


You probably have a damaged piston / rings.

Why you ask? perhaps when you overheated the engine you did more damage than just a melt a valve.... plus I do not know the circumstances which led to the overheating but my guess this is a tired old motor, overheating it just started the chain reaction.

refurbishing the heads was a good idea but not addressing a worn-out, high mileage, overheated short block usually ends with poor results.
Did you in fact melt a valve or the piston?! To melt a steel valve you would have hole in the piston because aluminum melts at a much lower temperature than steel. I would suspect that cylinder has been glazed with aluminum, the rings are not sealing, or something to that effect.






If I were you I would stop throwing good money on a bad engine... build a 350 and move on.

K1ng0011

Thanks for the detailed explanation. It was cylinder #3 that had the melted valve and the crack in the cylinder head. When I took the heads off the pistions were fine there was no problems with them holes, cracks, malformed, etc. The walls also looked fine no visible problems. The cylinder head had no problems in cylinder #1 that I or the machinist could find. After I melted the valve and cracked the cylinder head on cylinder 3 I did a compression test. Cylinder 5 had 150psi, cylinder 3 had zero, and cylinder 1 had 135psi. After I bought and put the brand new cylinder head on now the cylinder only holds 60 psi and it drops way faster than it should on the compression tester. This leads me to believe it was the valves are not adjusted properly. I have re-torqued the cylinder head bolts just to make sure.

I would love to have a 350 in it but it would take a lot of money, space, time tools. Right now I am just trying to get the car running so I can drive it around and in the very distant future I would like to put a 350 or LS1 in it. But for now I want the car to just run properly if it is possible.

If you need any clarification let me know.

FRMULA88

Did you check the new head before you installed it?:

Are the springs on this new head Ok?
you re-torqued the head, did you double check your valve lash on #1?
If you have too much pre-load you could be hanging the valves open.

If they are too loose the rockers will chatter, but the valves will stay shut. (because the springs keep the valves shut until the rocker arm actuates the valves to open) try loosening the rockers on #1 and check the compression again. if the compression comes up to "normal" then I suspect you had too much pre-load @ #1 rocker arms.

If not I would suspect weak/loose springs, the valves not lapped to the valve seat.. or the head gasket is not sealing..

I would start with the last item make sure the head gasket is sealing.. sometimes when you overheat bad enough you can distort the deck of the engine block.. also are you using new head bolts... the old bolts may have stretched too much and your torque readings are off.. Are you using new head gaskets?

K1ng0011

I dont know enough to know what to look for on the springs but I did not recheck the valve lash. I do think that is the problem. It seems like a good explanation for this issue. It's just a huge pain to get to the valve covers on these engines. You have to take apart a lot of stuff just to get to the valve covers.

FRMULA88

the obvious would be look for broken springs... (pretty easy to see that )

with the valve cover off bump start the engine and watch the valve train actuating. if the rockers are too tight... the spring will stay slightly compresses and this will hang the valves open..

since you have good compression before you replaced the head, I would assume this might be the problem..

K1ng0011

Oh I see. Ok I can do that and that makes sense. I will do that this weekend and hopefully this fixes my problem. I think it will. But all I can do is wait and see. Thanks for your input on this issue. I have never worked on a car until I worked on this camaro. So a lot of the stuff I have done is the first time I have ever done it to a car. I replaced the whole brake system on the car and a whole bunch of other maintenance things.

FRMULA88

We all got started somewhere, have fun and hopefully you learn a few things so next time, next project, it goes, faster / easier.

Alot of this stuff you have to learn by doing, reading a book only gets you so far.

Don't get me wrong I am all for reading and learing all you can but sometimes to really grasp the concept you just have to get your hands dirty.

I am by no means a pro-mechanic but I have been playing with cars since I was 14
and know my f-body inside and out because I took it all apart LOL..

K1ng0011

So what I found out this weekend was the compression for cylinder 1 was lower compared to the rest. I adjusted the vavles and fixed that issue. But it looks like all of the cylinders are only holding 90psi now. When before they were holding 150psi. Does anyone have any idea what would be causing this? I guess I somehow managed to adjust all the valves improperly?