Can I tackle valve seals?

[phlegm]

Watching youtube vids it appears to be a slow methodical process, reading up it seems the rope method is the safest way to keep me from doing a top end rebuild

So anyway, I have an original 350 66k miles, blowing some smoke and oil out exhaust. it stops when its warm, I am thinking seals to get me through for a while and eventually I will have to tackle the top end. I have read through the threads and it looks like some people just change O rings at the top and some do that and the guides, why would I not do both? It looks like its just another $16.00. Also I see 2 kinds of tools, one is the crank tool the other is a prybar. Which is easier for these trucks? I have an AC Cab and just put a booster on.

Finally, given I am 3 shades away from being a shadetree mech. scale of 1-10 how hard is this?

[sick472]

Should you choose to tackle this job, consider buying this tool...

Summit Racing® Valve Spring Compressors SUM-906784...

https://www.summitracing.com/parts/sum-906784

I just did this on a Pontiac 400 and this tool was much easier than the prybar method and much cheaper than the screw down tools. MAKE SURE YOU HAVE 3/8 or 7/16 rocker stud threads before buying this tool...forgive me but I do not know what 350's have.

I also used something like this for keeping the valves up while performing the job...

Air Hold Adapters

https://www.summitracing.com/parts/w...CABEgJ1mvD_BwE

They work great and are much faster and cleaner than rope, but rope will work...You just have to turn the engine alot to press the rope up to the valve so that it stays all the way up. MAKE SURE YOU you get the correct threaded Hold Adapter that matches your plugs....forgive me but I do not know what 350 spark plug threads are and the above link may not be correct for your engine.

The job is not hard, but you need to take your time and not be in a hurry. Knowing where to position the cam so that the springs are fully extended before removal is the trickiest part so do your research well on that aspect. I just did the Pontiac motor and found a write up that described that process and was able to do all 16 valves and I only had to turn the motor twice. Other times, I would turn the motor for each valve and watch the rocker so that I knew the valve was all the way up...it works, but that's alot of turning of the crank.

[Willys_MB]

If you're a little handy, I just welded a plate that looks like our lock retainer clips to a C-clamp I had laying around and used that to compress the valve springs.

This is a really easy job to do, I did it myself and I had little to no experience working on engine internals.

[phlegm]

Thanks guys. Appreciate the advice on the tool for the springs. Also I have seen the air hoses for the valves to stay up and I get a little nervous because my compressor is older and not as reliable as it used to be. No matter how messy it is if the rope is a more sure fire way than I think that's the direction I will take. It's a 48 year old truck I'm going to get dirty either way

[jocko]

Things get easier with the heads off the truck - and odds are it could use new guides and hardened seats. If you want to move one shade closer to being a full blown shade tree mechanic, yank the heads, run em down to the machine shop for a 3 angle valve job w/new guides, etc - and you can either have them reassemble with new seals or you can do that yourself if you'd like to try it and save a couple bucks (I also recommend an appropriate valve spring tool). Personally, whenever I've had machine work done on heads, I also have the stud bosses machined so I could install screw-in rocker studs - in order to prevent the one thing I seem to have happen more than any other problem with Chevy heads (in fact, it's the ONLY problem I've ever had with Chevy heads) - press-in studs backing out. When you're done, it will have been a little bit more expensive, but you'll be pretty happy knowing the top end is 100% fresh and ready for another 66K, and probably much more than that.

[phlegm]

Thanks, I thin for a few reasons I am going to tackle the seals for now and save the heads for later, if it doesn't clean up the exhaust I will have only wasted time.

So is it best to just change the o rings? Or go-to umbrellas, or do I somehow replace the caps and use both?

[KQQL IT]

Unless you're concerned about numbers matching. I'd buy some dart 170cc iron heads.
All new and better ports.

[HO455]

Originally Posted by phlegm

Thanks, I thin for a few reasons I am going to tackle the seals for now and save the heads for later, if it doesn't clean up the exhaust I will have only wasted time.

So is it best to just change the o rings? Or go-to umbrellas, or do I somehow replace the caps and use both?

O-rings and umbrellas is what I do. It is likely you will find only O-rings, real hard flat O-rings. This is an easy task. Using air to hold the valves closed makes the job much faster than using rope. If I was in your shoes I it would be worth it to me to rent a small compressor and cut the time to do this down to half a day. (Non A/C truck) Including readjusting the valves.

[phlegm]

Originally Posted by HO455

O-rings and umbrellas is what I do. It is likely you will find only O-rings, real hard flat O-rings. This is an easy task. Using air to hold the valves closed makes the job much faster than using rope. If I was in your shoes I it would be worth it to me to rent a small compressor and cut the time to do this down to half a day. (Non A/C truck) Including readjusting the valves.

Ok, good advice.... so the umbrellas just replace the caps on the springs and then the Lid goes through them same way. Ring on the underside. Right?

Thx

[Minkota]

Originally Posted by HO455

Using air to hold the valves closed makes the job much faster than using rope. If I was in your shoes I it would be worth it to me to rent a small compressor and cut the time to do this down to half a day. (Non A/C truck) Including readjusting the valves.

back when I was a kid we just used a length of rope as we did not have the luxury of an air compressor.

[randy500]

To elaborate on the rope method.
Use soft tightly wound cord, about a little less than 1/4” diameter, with piston near tdc, feed rope into spark plug hole, raise piston up to tightly push rope against the valves.

[Lemield]

I used the rope method on my 454 in my 70 truck. It took about 6 hours total but was fairly easy and straightforward.

One thing I found, especially on a big block is that it took a lot more rope than I thought.....just my 2 cents worth.

Oh, and I used the pry bar type compressor and it worked great.

[WorkinLonghorn]

Ok, first thing I did when I had your issue (smoke at start-up and after going down a hill in gear) was I checked the compression to see if I needed to do further checking like a leak-down test. Compression was good so I did the seals using the rope and pry tool. I also checked the valve to guide clearance by wiggling the valve to see if the guides were worn beyond spec. which is .0010-.0027. This is not much play so if you see them wiggle more than just very slightly then your seal job my not totally fix the problem. You could also check the springs to see if they are within spec too.

[phlegm]

This is a great thread, great advice. Thanks all, I think part of my question got lost on the the umbrellas...

so the rubber umbrellas just replace the brass caps on the springs and then the Lid goes through them same way. Ring on the underside. is that right?

[underliner6]

+1 on using air. It really made life easy when I did Valve seals.

[WorkinLonghorn]

Originally Posted by phlegm

This is a great thread, great advice. Thanks all, I think part of my question got lost on the the umbrellas...

so the rubber umbrellas just replace the brass caps on the springs and then the Lid goes through them same way. Ring on the underside. is that right?

It's been 25 years but I believe the umbrellas just slide down the valve stem to the area of the protruding guide. They don't replace anything. Just reassemble everything with both seals in place. I think i just used the o-rings, I really can't remember.

[kidatheart]

Originally Posted by WorkinLonghorn

It's been 25 years but I believe the umbrellas just slide down the valve stem to the area of the protruding guide. They don't replace anything. Just reassemble everything with both seals in place. I think i just used the o-rings, I really can't remember.

That is how I did it. I slid the umbrellas to the bottom then installed the O rings, and then put it back together opposite of how I took it apart. When installing the keepers, make sure they are completely seated in the groove in the valve before releasing the valve spring. Then I tap on the top of valve to make sure it stays together properly(keep your head off to the side in case it comes apart!) but keep in mind that I am not a mechanic.....

[HO455]

Originally Posted by phlegm

Ok, good advice.... so the umbrellas just replace the caps on the springs and then the Lid goes through them same way. Ring on the underside. Right?

Thx

I'm not 100% sure as to what you are referring to but this drawing may help figure it out. The part in red is the O-ring. The part labeled as Valve Stem Seal is commonly called an umbrella seal. Some years of Chevrolets did not have the lower umbrella seal. GM cheaped out and paid the price with recalls to retrofit seals.
The lower photo shows different styles of seals used over the years.
Putting some grease on the Valve Locks when reinstalling helps keep them in place until the spring is released and they are seated in the retainer. A small Neo magnet on a rod will help with removing the Valve Lock/Keeper and not dropping them.

[rockyrivermark]

I did this job on my ‘70 350 2 years ago. Very easy. a buddy for company, 12 pack of beer, and open an evening.

What I did was set engine for firing position of first cylinder TDC.
Both valves will be closed.
Use fitting tool that has small piece of rubber hose and threads into spark plug socket.
Connect to compressed air. Can’t remember lbs. 70 should do.
Then compress spring and replace seals. Umbrella seals just slide down. Don’t think you have to hammer them on
Install keeper and release spring compress tool.

Then I rotated engine to next cylinder to the next firing cylinder.
Again both valves close and just follow firing order.
Doing it this way protects you from dropping a valve into the cylinder. If for some reason the air in cylinder failed the valve would drop and stop at the top of the piston so you wouldn’t loose it.

Here’s what I did to set the lash on the valves. This method doesn’t need engine running so no oil mess. Worked really well and super easy
See picture.

[rockyrivermark]

sorry forgot to add picture in my last post.
Here is the valve lash instruction pic. I know there are many many ways to do this but this worked well for me. easy and not messy.
get engine to TDC firing #1 piston. Then adjust the valves notated. Rotate the engine 2 revolutions to #6 firing piston and do the rest.
Some guys say to put your finger over the spark plug hole and the compression will be felt.
The only thing I personally did different was spin the pushrod and slowly tighten the rocker bolt until i feel slight resistance, then half turn on the nut.
Mark

[phlegm]

Originally Posted by HO455

I'm not 100% sure as to what you are referring to but this drawing may help figure it out. The part in red is the O-ring. The part labeled as Valve Stem Seal is commonly called an umbrella seal. Some years of Chevrolets did not have the lower umbrella seal. GM cheaped out and paid the price with recalls to retrofit seals.
The lower photo shows different styles of seals used over the years.
Putting some grease on the Valve Locks when reinstalling helps keep them in place until the spring is released and they are seated in the retainer. A small Neo magnet on a rod will help with removing the Valve Lock/Keeper and not dropping them.

Perfect! This is what I needed, l really wanted to know where I was headed first from you guys,the older I get the more i figured out that youtube lies

All good advice guys I will order parts and let you know how it goes.

[bigsnookmaster]

Do the umbrella and O-ring seals. The umbrella seals slide over the valve and sit over the stud boss. I also would tap the spring retainer gently with a brass hammer before disassembly to break them loose after years of being seated in place. It is a pretty straightforward easy task. Good luck

[hjewell2]

Originally Posted by rockyrivermark

sorry forgot to add picture in my last post.
Here is the valve lash instruction pic. I know there are many many ways to do this but this worked well for me. easy and not messy.
get engine to TDC firing #1 piston. Then adjust the valves notated. Rotate the engine 2 revolutions to #6 firing piston and do the rest.
Some guys say to put your finger over the spark plug hole and the compression will be felt.
The only thing I personally did different was spin the pushrod and slowly tighten the rocker bolt until i feel slight resistance, then half turn on the nut.
Mark