I've been putting this off for a long time, but I need to get it done because it's likely fouling out my plugs and O2 sensor. I ordered the Lisle valve holder for my air compressor since it seems to get the best reviews. I'm a bit confused though since many people say to put the piston at TDC, yet some say when you put the air to it that it pushes the piston down to the bottom. Is this an issue with 305/350s? If so what's the best way to keep it from happening?

 

Yes. That way, when the valve doesn't get held up by the air pressure, which it pretty much never does, it can't fall all the way into the cyl where you can't retrieve it. It can't fall all the way out, but it can sometimes fall in far enough that the tip of the stem is down into the guide. Real PITA to pull it back up. Sometimes the piston can push it back up but not always. Best to just keep it from happening to begin with.

Of course. That's how the engine produces power in the first place: pressure in the cyls pushes the pistons down. If you're real lucky, and get the piston to EXACTLY TDC with no error whatsoever, it works OK enough; that's harder to do than it seems though.

Absolutely. Same as any other internal combustion engine in that regard.

Don't bother with the air thing. It doesn't work, even if you somehow manage to get a hose to hook up to the chuck on all 8 cyls. You'll see. Instead, use rope. Just stuff the cyl full of rope with the piston at TDC, change the seals, pull the rope back out, turn the engine 90°, do the next cyl in the firing order. Some 5/16" or 3/8" rope works great. You'll only need a couple of feet.

 

Now see that's a little different than what I've read. I've seen where people put the piston at BDC, put in the rope, and then raise the piston to compress the rope. I've seen one report here where someone got the rope stuck, I'm assuming wrapped around the valve somehow. I'm guessing that's extremely rare though.

I did read on a Corvette forum (C4/L98) if the piston is truly at TDC then the valve can only fall about an inch.

 

That isn't how I've typically done it; but it should work fine as well.

Yes, an inch, or maybe a little less, is about as far as the valve can go with the piston at TDC.

 

I like the harbor freight valve spring removal tool, works great. I just rotate motor over while sticking a screwdriver or any other tool into the cylinder I'm working on, till the piston comes up to its highest point,then just leave the screwdriver in there while I remove the spring,valve will drop just a tiny bit, change the seal, then just lift the valve with the screwdriver, place the tool with compressed spring on the valve stem, insert keepers and done. So easy. Best 5$ ever spent.

 

I've done it this way and it worked good with piston at TDC. None of the valves "fell" down. I had to push the valve fairly hard to get it to drop. I pulled it back up and it stayed. I did have 2 times that the air pushed the piston down. If that happens it will be as soon as you put air to it.

 

I used the rope method.

Piston down, nylon rope in, piston up.
No problems with valves falling in.

 

I've watched a few YouTube videos and recall one saying that when reinstalling the rockers, to tighten them just until they don't wiggle, and then 3/4 turn more with a wrench. Does that sound correct?

 

Yes, IFF (mathematical shorthand for IF AND ONLY IF) you can be CERTAIN when doing that, that each and every one is on its true base circle. Otherwise you'll end up with a mess. If you are CERTAIN that the instance of TDC for each cyl is the one that's firing, NOT the one that's the changeover from exhaust stroke to intake stroke, it's probably "good enough", for a stock cam.

 

well I'm certain of anything since I've never done this before. Is there a safer method? Maybe not do the extra 3/4 turn?

 

• Search IOEC
• Intake opening exhaust closing

 

I've done the rope method. Works great. Really no way for the valve to accidentally fall into the cylinder if done correctly. Run piston down to BTC, insert rope, move piston up until it compresses rope, R&R valve springs/seals, drop piston down and remove rope. Make sure to pull all of the spark plugs first so it's easy to turn the crank by hand.

 

It's EOIC.

Exhaust opening, intake closing.

You adjust the intake as the exhaust is just barely beginning to open, and the exhaust as the intake has just finished closing. It's not absolutely "exact", but it's PLENTY close enough for almost any situation. For any stock cam, for sure. It will certainly work here.

Another way to do it, which IS "exact" for ANY and EVERY cam and situation, is to adjust a valve when the engine is turned to the spot where the same valve on the cyl 4 cyls away in the firing order, is at peak lift. Since the cam turns at half the crank speed, it makes ½ revolution for every full rev of the crank; which means that whatever one cyl is doing, the one 4 cyls away from it in the firing order, i.e. one full crank rev, i.e. ½ cam rev, is doing the EXACT opposite. When I say "exact", I mean "EXACT" down to the absolute last fraction of a degree, within the production tolerances on the cam. Therefore when #1 intake is at full lift, #6 intake is on the base circle; etc. Once you spot 1 valve of whichever kind nearing full opening as you turn the crank, then you can keep turning it until that valve's full lift is reached, then adjust as described. Once you find the first one, you can simply turn the crank exactly 90° from there, and the next cyl in the FO will be ready to adjust. Then when you do all 8 of one kind of valve, turn slowly and watch for whichever of the other kind is on its opening ramp, and repeat for all 8 of those. If you use the EOIC method you can also use the 90° rule from one valve to the next. I would recommend doing all 8 EOs and adjust the intakes, then do all 8 ICs and adjust the exhausts.

Easiest way to do this, in the context of a valve guide seal replacement, is to go all the way around the engine and do all 16 seals; then turn it slightly, and watch for whichever telltale you choose; and do the adjustment; rather than adjusting at the same time as spring installation.

I'd also suggest using less than ¾ turn of preload. ½ turn is enough. ¾ is for people who aren't precise enough and want to make sure none are left loose. You can do better than that though, with either of the 2 above methods; you don't need to half-a$$ flat-rate it.

 

I was close

 

It's OK, we all get a brain cramp now and then. Getting the letters out of order isn't SO bad. Like, I don't know if you knew the dyslexic agnostic insomniac... he laid awake nights wondering if there really is a dog.

 

One thing that is a bit freaky, is the lifters are hydraulic. So when you make your turn, they are pushing down a bit, gotta trust yourself when you make that final turn and just stop. If you remove the intake, its also a good time to pull out the lifters and see if they are in good shape and maybe even soak them in some kerosene and then an oil soak, and then make sure to put them back in the same exact hole you find them. removing the intake gives you a chance to really clean up a lot of stuff under it, also can be a can of worms if something goes wrong like breaking a TPI bolt.Be sure not to over torque your valve covers, just enough if just right! When I did this job, I tore the top half of the engine off, kept heads on. Made the job much more accessible and gave me a chance to flush the engine by hand, the valley had a bunch of sludge from sitting for 25 years - for storage, I had filled up the block with oil so everything was lubed. It took me a week to clean it to perfection and looking like a block fresh from the factory. Now when I change oil, its as clean as the day I put it in.

 

Finally got the valve covers off. What a PITA! I finally had to just bend that AIRS tube back some with a pipe wrench to get clearance. 7 and 8 look like they'll be fun trying to get that spring compressor tool onto.

I notice the driver side rockers are a lot dirtier than the passenger side. Is this because the PCV is on that side or a sign of something else?

 

I did all 16 valve seals in my garage with a tiny air compressor and some homemade air tools. No valves were dropped and car went back together fine. Some of the springs back by the firewall are no fun and I don't even have an AIR system on my car to fight with. It's a good time to put in new valve cover seals and check out PCV hoses and valves. I don't remember one side being more dirty than the other.

 

I just did this... very slowly (I only had X amount of time to work on it each day) I had the whole top end off though cause I was doing a ton of other things....



It was a pain, but the air system worked fine,... but my compressor worked kinda hard to keep up air pressure. I think I kept the PSI at about 90. Valves were pretty solid.... I heard a bunch of air moving about in the engine on some cylinders though... so I wonder if i have bad rings or something


no issues with the valves falling with the air though...... I tried the rope method, but for whatever reason i felt that didn't work well. be sure to use a good water separator... I guess mine was bad so a lot of moisture got in and rusted some thngs up... it took me several months to complete this job cause I was busy with other projects, work.....travel,, lost interest in working after work etc.....so I guess whatever moisture got in there seized things up a little....luckily I broke it loose with some nice PB blaster down the cylinder.. be sure to tap the valves with a rubber mallet to free them up from the spring though.



Well worth it though... no longer have that puff of smoke!

 

Well it's taken me about 5 hours today just to get to valve covers off and the plugs removed (with a couple of breaks). This is going to be a several week job for me since I can't spend a ton of time on it everyday. Overall though I don't think my spark plugs looked too bad. Had to remove the O2 just to get the #5 plug out.

 

Did your pistons try to move to the bottom when you turned on the air? I got the hose today, and I also have some 3/8 rope, so I'm not sure which I'll try. Both look like they'll be difficult to get into the spark plug holes.

 

they did on a couple cylinders, but I still ran the air. I THINK I was actually running it at 120 PSI for those though.... it kept my compressor running the whole time so i tried to do it fast / i took a break in between valves to let my compressor have a rest. I did a cylinder a day before I took my long months break lol

For a couple I clamped the belt onto the pulley with vice grips and jury rigged something so the crank wouldn't move much though...I recall jamming a bar into the balancer or something and putting a floor jack under it so it wouldn;t turn...it didnt work for all though because of angles / the way the balancer was positioned at times for some of the cylinders.....,,,,,, im thinking it would have been fine without though cause i did at least one with the piston down and i didnt do anyhing about it....... but you take a HUGE risk if the valve ever falls / your compressor craps out / power fails etc.... .

The valves gave me no issues at all falling wise.....but you do need a good compressor id say.


When I think about it, i think the valves felt like they would move more with the rope method, so I only did one with rope. I recall seeing the valves fall a bit and it scared me a lot.... i might not have used enough rope or something but I felt like I put a ton in there.

 

I did mine with a little pancake compressor with out any problems. I had 2 cylinders roll over on me as soon as I put air to them. I marked the front of the crankshaft pulley starting at the timing mark and marked it every 90*. Lined up the marks with the timing mark on the timing cover. I turned the crankshaft every 90* and followed the timing sequence order per cylinder.

 

Was the compressor constantly running?


Im thinking i have maybe bad rings or bad seats or somethng... if I turned off the compressor the air pressure would drop fast.

 

Part of why rope is better.

 

I'll try it again next time... hopefully many many many years from now lol

 

My compressor did not run constantly. It ran very little.

 

You were lucky.

Every situation is different.

Now granted, I am a TOTAL JERK; butt I personally know someone who was skydiving one day (don't ask), and their parachute failed. I think they started out at 10,000 feet. (3000 meters more or less for those of you that work in that realm)

They survived.

Now: should I go get on every skydiving forum I can find, and tell all the n00bz, "you don't need a parachute, I know blah blah blah blah blah" because ONE person endured it and lived to tell about it? (they didn't "walk away"; they were more like a blob of jelly that somehow the doctors were able to get some bones to regrow, and their various internal organs that ruptured, were able to be sewn back together enough that they didn't bleed out on the spot)

That's why I use rope. SURE, I've done it with air and it worked; maybe 2, 3 times; butt I've also tried air about 15 times as many times, and it CRASHED AND BURNED. Rope has worked WITHOUT FAIL, every single time; DOZENS. Maybe hundreds, I couldn't say; just, LOTS.

Beware the curse of the small sample size. Especially when the sample size is just ONE.

Incidentally, the compressor in my garage is a 2-cyl 5 HP 60-gallon upright, and I usually set the tank/motor to 150 psi and the regulator to whatever the tool needs (usually anywhere from 50 to 120 psi); and THAT has failed on me for doing valve springs with the air chuck, MORE THAN ONCE. (I'm a glutton for punishment) The rope method has NEVER failed, even when I didn't have any air AT ALL.

 

Been contemplating doing this job as well since I get that initial puff of smoke when starting the engine but I see engine swap in the near or distant future...if the latter might as well just do it!!! Anyhoo...all good points taken. What is everyone doing for valve seals nowadays??? Felpro seems to be the go to for everything but are there other offerings that people have gotten better results???

 

Not really. Those are fine.

Use the "positive" type; they have a clamp around them, and fit down tight over the guide. NOT the "umbrella" type (which stay on the valve and go up and down with it, and do exactly what their name implies). NOT the O-rings that go down into the top of the retainer and below the keepers. Get 2 sets, use em on both intake and exhaust.

 

Just curious, have any of you tried using an endoscope camera with a light to see if the piston is at TDC? I know I'd still need to use some rope, but I could see when it's close.

 

I came here to say exactly this. Also, I second using intake seals on the exhaust valves. The umbrella seals are kinda worthless.

I used soft fluid transfer hose in lieu of rope, much easier to feed into the spark plug hole.

You’ll know what I mean once you’ve pulled the first one.

 

Well the rope thing seems to be working, and I got cylinders 1 and 3 done. When I started on #5 my cheap harbor freight spring compressor started messing up, so I'm done for today. I'm going to try one of those pry bar style ones and see if I have more luck.

My intake valves already had positive style seals to my surprise, and they didn't look all that bad. They're black instead of blue like the new Fel-pro ones. Exhaust valves had nothing, and the o-rings on both sides fell apart.

 

Pics made threads better ;D

 

I got all of the seals done on the driver side. The old o-rings pretty much just crumbled apart so I vacuumed the pieces out with my shop vac. I've read where a few of you say to use the positive seals on both intake and exhaust, but I had already bought the umbrella seals for the exhaust valves so I used them. Returning stuff to Rock Auto is a pain.

All in all, for a 164k mile engine, I think it looks pretty clean. None of the oil passageways are clogged, and I can see right through the holes in my pushrods.

 

Interesting reading here....
https://garage.grumpysperformance.co...20/#post-49771

I wonder if it would be worth it to add a magnet next to each drain back hole while I already have the covers off.

 

I dont think Id want to put anyhing there is possible.. plus it's been working fine for this whole time right?

 

I got all the seals done and the rockers put back on. Still need to adjust the lash though, and it'll be a couple of days before my new valve cover gaskets come in. I could probably reuse those orange ones since they still seem pliable, but don't want to take a chance. I went ahead and repainted my valve covers too.

I can see now why shops won't mess with this job, it's time consuming for sure. The spring compressor I rented from Oreillys definitely worked better than that Harbor Freight POS.

 

I finally got around to adjusting the valves today using the instructions in this video...


After adjusting all of them I went back and added an extra 1/6 turn (about 12:00 to 2:00 with the ratchet), since he used 1/2 and others have recommended 3/4 to one full turn. Anyone think there will be any issues with that? I'm hoping to start putting everything back together tomorrow.

 

Probably not.

Adjusting them with less preload favors high RPM usage but they make more noise and may need adjustment more often. More preload tends to make them "pump up" at high RPMs especially if there's valve float (valves bouncing off the seat when they're supposed to close, NOT "toss" over the nose of the lobe), make less noise, and stay within tolerance longer.

The factory used a full turn. Racers will set them to as little as 1/16 turn. A typical "hot street" or "street strip" setting is ¼ to ½ turn. Typical "Chilton's" type instructions is ¾ turn. Take your pick.

 

Got all of my plugs put back in today, and when I got down to the last wire, the little prong in it broke. I ordered a new set from Rock Auto, they have some clearance air filters for $2 so I threw one of those in too.

It'll be another week I guess.

 

I hate when that happens!!

 

I got it all buttoned back up today. No issues and smoke seems to be gone. I do notice my cold idle seems to be a little lower than before, but I did replace some old vacuum hoses so maybe that's it.

 

job well done!