What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Bad Valve Guides?

Operator238

Operator238

1/2 ton status
 Premium
Joined
Aug 13, 2023
Posts
251
Reaction score
111
Location
Houston
So I bought this truck and have minimal driving experience with it. I’m restoring it now. I noticed it would smoke on start up and while running; so I attributed it to bad valve seals (easy fix) or carb pouring fuel. I have done warm compression reading tests and they were beautiful across the board.

So I bought some valve seals and a cylinder pressurizer tool. The tool has a valve that I can shut off pressure( I have a small pancake compressor). The cylinder I can hear and see bleed through the intake. The pushrod for the exhaust Cyl 2 had copper on the lifter side. Is this bad guides?




The truck has a crate short 350 and I guess transferred the original 305 heads (801) and intake over.

What are your thoughts?

IMG_2659.jpeg

IMG_2639.jpeg

IMG_2636.jpeg

IMG_2660.jpeg
 
It is possible there might be a bit of carbon between the valve and the seat. Hard to tell, but in your opinion how much air is escaping out the intake, also compare to the air escaping the valve cover, be sure to check/include dip stick
 
Valve cover is off. Cylinders not holding at all but make a good compression when warm/hot
 
There will be leakage, but should be past the rings. If you still have the spring on that valve, remove compressor, give the valve stem a light rap, or 2 with soft face hammer. Be careful not to drive the into top of piston. Then put the air back on and see if leak stopped or changed
 
Valves seat better on a running engine, then this static condition with a little shop air. With the valve spring and retainer installed and with the air pressure in the cylinder, I like to tap the end of the valve with a mallet, as suggested by @Wes Harden, even multiple times. It will make a loud "pop" noise and you can often tell an immediate difference in the leaking sound. As long as it quiets down after a couple of taps, the valve is working fine.

How much pressure are you applying? Have you put air to all of the cylinders to know if they are all about the same? You can make a leak-down tester out of a few basic pneumatic parts and there are guidelines out there for how much pressure drop is acceptable.

I guess your theory is that you have a bad valve guide causing improper seating. There are scientific ways to check for this, but mostly by disassembling the head :frown. The shadetree way is to simply push on all of the valves with springs still attached and see if you can move them at all N, S, E, W.
 
I can try and tap it with a hammer and see if that fixes it but at the end of the day if I’m getting bronze material on the end of the pushrod, why wouldn’t I address that? Additionally, a set of quality heads these days you might as well go to the junkyard and get a 5.3 LS.
 
An LS is a good bit more work than going to the junkyard and picking up an engine and a lot more work than bolting heads on. You're heads appear to be in good shape, why not pull them and send to a machine shop? I'm also not sold on the guides being bad, why would the bonze only be on the tip?
 
Is the fan turning because the engine is rotating? (Once that piston gets BDC, the air pressure won't try to make it turn anymore.)

If the guides are shedding bronze, wouldn't it gather on the valve stems and not the pushrods? Oil comes up the pushrod from the lifter. There are other sources of bronze in the engine besides babbitt - sometimes the speedometer gear or tip of the fuel pump pushrod. You would think that if the guides are shedding, you'd find a lot of that material underneath the valve stem seal.
 
Last edited:
The engine maybe rotating from the air pressure, but with the rockers off it doesn't matter.
Only matters for a leak down test when engine is whole
 
Unless it’s from a moly additive, I’m not sure where it would be from. If the valve seals are bad is it inconceivable to think the bronze material is coming upwards from the guides?
 
looks like and additive since it wipes off. Camera/pictures moves to much to fast for me to get a good study. Nice still of the stuff would be best for me.
 
So do I just put the pushrod back and tighten the rocker down to X ft lbs? Or do I need to measure lash? Etc?
 
there is a procedure for doing valve lash,

I forgot what you decided to do.
Install push rods, small amount of assembly lube on ea end. assembly lube on all valve tips. Set rockers on studs, assembly lube in bowl around stud, put in pivots balls, start nuts. new nuts are advised. with a 6-8" long 3/8 drive ratchet a deep 5/8" socket and 3-6" extension. With you dominant hand begin tightening all the rockers, while other hand is jiggling the push rod up and down. when up and down is no more stop and move on to next one. when all the rocker are at this spot. Rotate the crank by hand until #1 is at top dead center compression stroke. Both #1 valve will be close, push rods should be even, or very close to even. If some of the rocker get lose or tight that's ok, we're going to do the fine adjustment.
With #1 at TDC compression adjust these valves exhaust 1 3 4 8 , intake 1 2 5 7 . Check for up/down on the push rod, using the same tool tighten till just no movement. Once the push rod won't move go another 1/2 turn and stop. Move on to next.
once those 8 are done, turn the crank 360°, #6 should be a TDC compression. Adjust Exhaust 2 5 6 7, Intake 3 4 6 8, same way as above. That's it, you can turn the engine over a couple time and watch all the valve go up and down, look for spring coil bind, all the valves should move the same amount.
 
Like Wes comments.... Remember seeing them set while running....tighten rocker till it pumps up and stops chattering.... Back off 1/4 turn
 
messy to do when running, my ocd won't let me do it like that. I even have the plugs for the rockers.
 

Looks like the exhaust valves didn’t have any seals. These are 801 heads (305ci) on a 5.7.

The intake has some BOK seals that had a clamp around the guide bosses.

Did I do this right ? I using the same umbrella seals (FelPro SS10058) and valve stem seals (Felpro SS5112) on both intake and the exhaust valves.

Here is a picture of what it looked like when the springs were removed

IMG_0334.jpeg
 
Last edited:
Alright, I got the passenger side done.

Just replaced the intake positive stop seals and O rings. I added umbrellas to the exhaust valve and new O rings.


Upon further inspection, these are 601 heads. The block is a 5.7L block. I’m tempted to put a better intake manifold and put some new rocker arms to get just a little bit more lift but not sure it’s worth it.
 
I suppose it's good news in a way it's such a simple fix, but such a glaring error makes you wonder what other surprises are in store. Valves feel tight in the guides, so no longer suspecting them?
 
You must log in or register to reply here.

Latest Posts

Top Bottom