Head rebuild help

[cywagoneer]

I posted about a week ago about my rough idling engine. Had a compression check done today and the #7 cyl is dead. So, if I rebuild the head, do I need to do both heads or just the bad one? Also, how much should I expect to pay for this? This is a used engine I just put in to get my by until I can afford a new one. Is it even worth it to have the heads done on an engine with 130K? I did check the main bearings and rebuilt the oil pump before installing. Oil pressure is good at 70 cold, 60 warm, 40 warm at idle.

BTW, Is there anyway to 'unstick' a valve or is that wishful thinking.

[gsmikie]

if you do all the valves you will most likley blow the rings out of the bottom end i would just pull the one head and do the cyl with the bad valve

[Stolen76]

with that mileage, I'll 2nd the good advice given in the previous post !

[OBX-AUTOMOTIVE]

MAY BE A USED HEAD IS AN IDEA!!! smile.gif PULL THE HEAD AND TAKE A LOOK! :eek: :rolleyes:

[Crazy_Jeepman]

<blockquote>quote:</font><hr>MAY BE A USED HEAD IS AN IDEA!!! PULL THE HEAD AND TAKE A LOOK!<hr></blockquote>

Be what I would do. 130,000 mile engine you want to do it all or as little as possible. ;)

[Ernzo]

Hmmmm. Without Knowing what caused the compression failure, is it valves or rings?

IF you have a 'bad' valve, it is possible, I have done it, to take out the head and re-seat the one valve, or replace it. Of course, this is a temp. fix. But, depending on about 1000 other variables, this may be a long or short 'temp' fix!

THis ought to bnot cost more than a couple of hun, and many mechanix will not do it, as it is likely that other problems will develop and the whole deal can go to pieces.

You will have to find a moonlighter or backyard/cob wrench. Not a problem, really.

[Crazy_Jeepman]

If the reading is ZERO I hardly doubt it is rings. A hole in the piston would do this as well, however blow-by would be unbelievable. So it really leaves it to the Valves. When you say the #7 cyl is dead how dead is dead? Do you get a reading at all? If so squirt a bit of oil in #7 and then take the compression test again. If it reads higher it is rings, if no change it will be a valve. If a BIG ZERO, it will be a bad valve or a hole in the piston. ;)

[cywagoneer]

I should have mentioned it before. The reading for #7 was 15lbs, according to the mechanic. I didn't get a list of the other readings, which I should have, but the were okay, again, according to the mechanic. If I were just to address the #7 cylinder, can I change out the valves without any special tools/knowledge? Sorry, this is new territory for me.

So when a valve goes bad, what does that usally mean? Is it frozen in the guide, bent or damaged, all of the above? I am planning on pulling the head and taking a look but need to know what I should be looking for/expecting.

[RichCal]

The general health - and anticipation of longevity - of an engine is: oil pressure and compression. Good oil pressure means minimal wear & tear of bearing surfaces. Yours is excellent. Good compression means rings and valves are good and seating well.
Bad compression in one cylinder means a ring or valve is shot. If its the ring - needs a complete ring job. One valve problem means one head need to come off and repaired. However its wise to do have both done at once just to keep things evened out.
An engine poorly maintained (i.e. few oil changes)and ridden hard can be shot at 100,000 mi. One which is been well maintained and not pounded on can maintain good oil pressure and compression up to 200,000 mi.
However, a valve or valve spring can "go" prematurely at any time due to latent defect. With your oil pressure and assuming the compression is good on the remaining cylinders, I wouldn't think twice about getting the head repaired.
Getting a valve job done does not "cause" the rings to blow out thereafter. However when valves, guides, and springs are so generally worn so as to warrant a valve job, it usually means the rings are worn too and too far behind. But if a head needs repair due to a specific defect, I'd say go for it.
Finally, I wouldn't accept a mechanic's word for it that compression is "good". If he's a good mechanic and up front, he'll hand you a list of numbers... or at least remember the range of pressures he found long enough to be able to tell you. Others' opinions may differ, but I think of anything higher than 135 psi as acceptable.

[PhilSine]

You will need a valve spring compressor, tork wrench, a strong magnet (makes removing the keepers easier), and 2 types of grinding compound to reseat the valves (your local auto parts store will have all of these and even recommend the grinding compounds needed).

[ironroad29]

i woiuld have both heads done your not gonna blow anything and if the engine craps the bed well then all you need is a good short block because your already (no pun intended)ahead of the game .so you would be able to spring for a few more goddies for the bottm end of your new engine,because you've already had the heads done. get a 3 angle valve job while there in the shop it works ask anyone whos had one

[andy d]

i revived a datsun motor once that overheated. it detonated a hole in a piston and warped the head. i bought a parts truck and used the head and a #1 piston/rod. i re-used the original rod bearing inserts. i put the engine back together and got another 50k out of it. i also did this with a bug engine that swallowed #3 exhaust valve. the key is a good diagnosis. make sure it isnt a worn out cam lobe and take it from there. i would start by pulling the left valve cvr and eye balling the valve train with the engine at an idle. good luck

[cywagoneer]

Thanks guys. The mechanic did rattle of the other compression numbers to me over the phone but I neglected to write them down, I'll call and get the specifics. I think I'll just take a chance, have the heads redone and if the rings go, it's time to send the block to the machine shop. I did find a used head for $100, which includes shipping from OR to IA. Does that seem reasonable? I got the info from junkyarddog.com. If he would give a 30 day warranty I might even try that.