The readings should all be pretty close to each other on a healthy motor. It sounds like it may be time for an overhaul.

 

I don't see how a blown head gasket would mess up a piston or ring.I need more info.
Give me the story of when the gesket blew....temp, overheat? did you drive it like that, how have you tightened the rockers? let me know exactly what you have done....do a comp. on all cyl. take all 6 plugs out and do the check. If it was running fine before I don't see why you would loose comp from the bottom end. How did you tq the head etc. You sure you did everything right? Even if I took that one piston out and laid it on the floor and put it back together that thing will still start......Give as much detail *** possibly b/c I think it is something simple you must have overlooked

 

thanks again for all of your help with this.. it is much apprachiated


here is the full story of what happened when the head gasket blew: recently took a road trip and when car was on the interstate she drove fine.. then when I pulled of to eat and hit a stop light the temprature started to raise but didn't quite hit the red line.. light turned green and I quickly parked the car in first parking spot & looked it over & all seemed OK... had a sit down lunch and after that car was cooled so started to drive home.. she drove home on interstate just fine (no stopping.. got lucky and caught all of the lights after getting of the highway).

Then car sat for a couple of days; then I drove to my wifes office and got about ten miles on the interstate OK with cruise control at about 2300rpm and all of a sudden the temprature started to raise.. I let of the gas and let the car coast (also turned on the fan so I could get a smell of the engine).. temprature then started to drop and I didn't smell anything. so I put lightly back on the throttle and I hear a little rattle and the temprature startted to rasie again (still not in the red) so I imediatley pulled of the highway and called a tow truck... after gettign it home I ran the codes and it was reading P0304 which is a misfire specific to the cylinder # 4 (is the one that now reads low comprssion)... I cleared the codes then cranked her up.. she ran but rough.. kind of like hitting on some cylinders but missing on others.. so I pulled her into the garage and draine dout the oil (had water in it) then statrted into the engine

I shold not that on that last time when I pulled of the highway there was a minimal amount of smoke from under the hood, but not a bunch like you usually see with an overheated car.. thats why I thought just blown head gasket and that was that ( was water in the oil ) but maybee I am not so lucky and there is damge to the lower end???



p.s. when doign the head gakset swap I did everything identical to Chiltons and never meesed with the lower end.. just pulled of cylinder head - took of the old gasket + lighlty cleaned around surface - put in new gasket and then put everythign back on exactly how it was beofre follwing torque patterns etc.,
also I have a picture on file of the gasket I removed if you would like to see it.. gasket is still as one pice a whole but does have a hole by the cylinder that has low compression



thanks again for all of your help with this

 

I redid the compression test...
still only done the cylinders on driver side bc of work.

I ran the compression test 3 times.. first rockers are were tighehted (I tought maybee over tightened and valve stuck open).. second adjust rockers to exact spec... third with rockers loose (made sure the valves were closed).. same results every time:


front cylinder gets about 40 on first stroke then tries to get maybee 45-50 on second and later strokes but never get above 50.
otehr cylinder gets about 150 imdientaley

also did a wet compression test (oil in cylidner.. and ensure valves closed) on the bad cylidner.. got about 45 on first stroke and then same results.. but heres what is weird after I did the wet compression test I took out the compresion tester from the spark plug hole and then turned over the engine with nothing in there.. expecting to see oil come spraying out but it didn't see it spray out so does that say the oil slipped down into the lower end?

 

It's too bad you didn't do a compression test before all this happened. But from the sounds of it, you either have a leak-down past the rings, or a leaking valve that otherwise looks ok to the eye. I have to assume you did a decent eyeball inspection of your head when you had it off.

I recently pulled the driver head on my 2000 3.8 auto. Compression (car has 145k miles) on 5 of 6 cylinders was at 180-190. The one bad was about 90. When I pulled the head, the gasket was fine, and the valves & pistons looked fine. Having the head upside down on the workbench (valves closed, of course) I filled the combustion chamber up with diesel (from the shop heater).

Next day, only 1 was down, and I could tell from looking in the intake & exhaust port which valve was bad since the diesel left it's trail. I would have put this head back on if I did not know to look for a leak...it really appeared to be OK.

BTW, to check the rings (no ring land whatsoever...amazing), I also did the diesel thing with the pistons..they checked out OK.

My defective head has a tiny crack between the intake & exhaust seats that I could only see with a magnifying glass.

So, here's my advice:

(1) Do a professional leakdown to determine if it's valves or rings, or..

(2) do the technique for replacing the oil seals on the valve stems by putting compressed air into each cylinder, then listening to A-the crankcase for hissing indicating rings; B-Intake manifold for a leaking intake valve; C-tail pipe for a leaking exhaust valve.

(3) A more tedious way would be to drain the oil and leave the plug out. Then rotate the motor so that the cylinder in question is at the low point-valves don't matter. Fill the cylinder thru the spark plug hole with kerosene/diesel, etc. and let it sit overnite. At same time, put a can under the oil drain. Next day see if anything filled the can. Also, slowly rotate motor by hand to drive the piston up and watch open spark plug hole for the fluid to come out (if you're lucky). If fluid comes out immediately, chances are that cylinder has good rings.

I have a nice workshop which makes this kind of stuff bearable; if you live in an apartment and you're working on your back in the parking lot on a cold rainy day, well...just endure and good luck. If you do #3, remember to put new oil back in.

This is an open question for any knowledgeable source: The lifters are hydraulic and the rocker arms have no adjustment...or so I assume. However, I do get a very slight ticking sound under load which I suspect is either an ignition miss (but I have new wires) or valve lash. Do these 3.8 motors need a rare shim sometimes for lash adjustment? Even though they are supposed to be self-adjusting lifters? ..Or does the balance shaft make that sound?

 

well sorry but its not sounding good for the lil 3.8

Do what he said....I would pull that head back off and take it to a machine shop....also do what he said with the cylinder, If nothing else your learning sooo check it out

 

thank you all of our help with this it is much apprachaited... will take me a few days before I can work on the car (due to job homework.. aghh) but when I get it done I will post any results I find

thanks again

 

I am having similar problems so let me know what you find out, I would greatly appreciate it.

-Gabriel

 

haven't got it all back together yet (long week at work) but it does look like it was a problem with the valve... will update if I ever get time to finsih the work

 

keep us posted i'm interested to see what it was

 

so the heads came back from the macine shop today and the guy said there was a problem with the valve seats... so he repalced them and did a valve job f(all together $70 ) so that should fix the problem... will verify all is OK or not with the car if I ever get time to work on it and put all of this back together

just another quick question.. Chitons says "repalce every part" but if I was trying to do a bare bones put this back together what is an absoulte must repalce: I know the head gasket must be new and thermostat gasket/seals is most likely essential... but what about some of the upper gaskets (intake etc.,) could I get away with resuing some of them? and what about the head bolts is it essential to repalce them becasue I can't find a set of them avilable anywhere (one place did say could order for $30 something and would arrive in a week)


thanks again fro your help

 

I would reuse the bolts....as far as gaskets..depends on what type and how they look
I have been using the same header gaskets for 7 years.
inspect that piston good....glad to hear it was the valve seat honestly

 

I would replace the heads bolts and all the gaskets. No sense in taking the risk and having to do the job over again.

 

New is always better, but I see no harm in re-using the head bolts. That's assuming you haven't galled them up when they came off. Be sure to clean the threads and under the head of the bolt so they look like new. Then oil the bolts on the threads -or- if they are going into the water passages, use thread sealer (not thread locker). All bolts get oiled under the heads to get proper torque.

I might re-use the valve cover gasket if it was really new, but would spring for new intake. Last Fel-pro head gasket kit I got for a SBC used a tube of silicone for the entire intake valley...before there was a separate rubber gasket for the front & rear valley...it was just where the valley gasket met with the intake manifold gasket that you used a dab of silicone.

 

just wanted to post a quick thank you.. I finally got time this weekend to put her back together and now have full compression on all the cylinders

thanks for all of your help diagonsing this one