I just did a compression test

[woodman]

The results are:
Cyl #1 dry/wet 117/127
Cyl #2 dry/wet 105/115
Cyl #3 dry/wet 115/125
Cyl#4 dry/wet 35/55

I tested #4 twice. Same read. I could hear/feel alot of air bypassing the cyl through the open intake port when it was cranking.

I was really jazzed up until the last one. Does this mean a bad ring? or valve? if so, can one ring/valve be replace without disrupting the rest?

[Zeke]

Most likely an intake valve if you hear the air at the intake port. Do the heads on both sides. Take them to Rimco in Santa Ana for a stock valve job. You can also take your cylinders there for honing or boring. They must be at least honed for new rings.

[Kevin@ojai.net]

I would, just for grins, adjust #4's valves (I'll bet they are tight). Then I would re-do that comp. check on #4. If it gets better I would just monitor and neglect... in other words, keep an eye on it...

-Kevin

[norustscott]

I am with Kevin adjust the valves on 4...better yet. back the adjust way off and do the test....eliminate the valve train from the equation...Then adjust and redo the test.

[Dave at Pelican Parts]

Small problem--if the intake valve doesn't open, the air can't get in.

I'd suggest adjusting the valves to spec and tre-trying the test. If the readings don't change, I'd say that you have an intake valve problem.

--DD

[Potter]

I have a similar situation. I like the idea of addressing it in the least intrusive fashion and then get more complex (read $$) as necessary.

How difficult is it to adjust valves? I am a novice. I replaced the starter.......removed and cleaned the injectors.......cleaned the FI points in the distributor.........all of which was OK, but I was fairly nervous. On a scale of 1 - 10 (1=simple), how would you rate the skills and effort necessary to adjust valves??

[Dave at Pelican Parts]

I'd say about a 5. It can be tough getting to the valves, and there is some "feel" to how tight the rocker should be on the feeler gauge. If you've got a buddy in your area who works on cars, you might have them check one for you. You can then see how the feeler gauge feels on that one and use it for reference.

My first valve adjust, on an old Honda Accord, I set the valves way too loose. A friend of mine stopped by and said, "Yup, they're way too loose. Here, let me do this one." And that's how I learned.

--DD

[Loan Dog]

Adjusting 914 valves is a very easy job. On a 1 to 10, probably a 2 to 3. The most important part is making sure you start with your #1 piston at TDC (Top Dead Center) Print the tech article at the Pelican site and read it twice before you start. Then when you go to your car, it will all make sence a lot easier.

[norustscott]

I should have specified "way off" dave is right. When I was trouble shooting a valve seat problem I set them @ .010 for the test and got good numbers. 150psi

[woodman]

OK. I'll make the adjustment tonight. I too need to re-read the article. I havent adjusted valves before. But I hope it's easier since the motor is out. I did not see any TDC marks, so I'll try the follow up method inserted at the end of the article.

[Kevin@ojai.net]

If this is your first adjustment I would recommend using the size up and down of .06 to check your work. The .07 would be tight, the .05 would be loose (DUH), and the .06 would be just right... That would probably help give you a feeling of what the correct adjustment is...

If an adjustment shows that the valves were tight I would re-adjust/check them in a couple hundred miles to make sure they didn't get tight again...

Also remember when adjusting; that although too loose can be problem, a little loose is better then a little (or alot) tight...

-Kevin

[Zeke]

And now we get back to the old why is the valve tight issue. (If in fact the valve lash is what is causing the low readings on #4).
It has been said that if you have one tight valve and all the rest are in adjustment, that there may be an indication that the valve is stretching or the seat is moving, both bad signs. Let's not put this gentleman back on the road so soon if he may have a big failure comming.

I stand by my first advice. Motor is out of the car. Do the heads. A simple valve job is not expensive. And you know everything is good to go.

[Jake Raby]

If teh valve is tight, it may be starting to stretch on its way to dropping......especially if its the exhaust.

[woodman]

Rookie question: what is done in a complete quality valve job?
With a higher mileage motor, I don't want to risk fatal damage. And what a good price be for both heads?

[Rot 911]

I'm with the other guys speculating that you have an out of adjustment valve. The first time I did a valve adjustment on my 911 I ended up with zero compression on one cylinder! I had adjusted both intake and exhaust valves too tight and neither was closing all the way. Made for some cool backfiring thru the MFI stacks though.

[tryan]

double / triple check every thing. you might have a chunk of popo holding the intake open.

where you driving the car before? did it feel like it was running on 3 out of 4 cylinders?if so drop the motor and fix it.

the go no go method is the best way to learn the drag of a correct adjustment. ( kevins isn't that the three bears story? ha ) .

if you do have a problem , it is way better to fix it now ( a few hundred vs thousands if the valve drops, zekes therory)

yes , i have dropped a seat before. an ugly sight.

[pbanders]

One more perspective on valve adjustments. I don't remember where I got them, but I have two feeler gauges, a 0.006 and a 0.008, that are about a foot long. The long gauge makes it very easy to do the adjustment. I set them so that there is very light drag on the gauge when I pull it out. With the gauge inserted, I also grab the rocker and push and tug on it a bit, to make certain that everything is in contact. If it isn't, you can feel the slop. Tighten the lock nut, re-check, re-set if it's too tight or loose.

[Jake Raby]

Concerning a correct valve job:

These engines are old now,and even if they have been rebuilt recently doing a valve job is a tricky thing.

I refuse to do valve jobs anymore, as I have set myself up for disaster too many times. It is very easy to blow a bottom end of an engine by tightening up the top end with some new rings and valve work......
Do it all the way or not at all in my opinion,plus if the engine is in decent shape itsonly gonna cost a few more bucks to split the case and do it right.......

Most engines I see have cams that are hating life so bad that alone they call for a complete teardown. Once long ago valve jobs weren't so risky,but that was before crappy parts and chevy mechanics had a chance to destroy the internal workings of our simple but complex engines..

[johnboy914]

I will second Jake's assertion (I know he doesn't need seconding) but I had a motor that was getting tired, low compression. So, I thought the best thing to do was to fix the symptom. Redo the top end. The problem with that is that you are now putting fresh motor compression stress on the main and rod bearings that had just as many miles on them as my tired heads did. Result = end of #3 rod sticking through top of case in the middle of Iowa. It took less than 500 miles after the top end rebuild for that to happen.

Of course, check, recheck your valve adjustment on #4. If your motor is out of the car, this is cake.

good luck.

vroom.

[Jake Raby]

Johnboy,
I appreciate your back up there, as you have experienced it as well. The way you worded it was spot on!

Sorry that you had to be a statistic to realize the fact as well,a good education in this world costs thousands in exploded parts. I'm still paying my tuition!!!LOL