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Cleaning Heads, GM 462.

2K views 12 replies 5 participants last post by  cobalt327 
#1 ·
Howdy! I have had my motor apart for some time now, and i am doing stuff a little at a time.

I am basically rebuilding my entire motor, but i need some advice on my cylinder heads.

I had a 327 large journal that my dad gave me. Turns out after about 6 month of fiddling around that the piston rings weren't seating right, and i was getting a lot of blowby. The blowby caused all the intake runners and valve to be very oily.

I am basically wanting to take apart my heads, clean the valves, runners, and for kicks clean all the springs, shims, retainers, etc.

Do all the shims and springs need to go back in the exact same spot? I know that the valves all do but for cleaning purposes do i need to do everything one at a time?

I took one intake valve out just to see how dirty it was and i ran into a few problems:

After i get the valve locks out and remove the springs, the valve doesn't slide out until i de-burr the valve from where the locks dug in ( i used 200 grid sandpaper, i was careful to not go further than 3/4" down the stem). Is this natural???








help appreciated, Josh
 
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#2 ·
Keeper groove pulling is common on an engine that has seen a lot of rpm with stock type valve springs. You will want to check the upper edge of the groove closely and make sure it is square. Not excessively hammered. It is actually best to remove the burrs with a fine file before trying to get valve thru the guide. REPLACE the keepers(locks).

Also remove the seals. They are probably junk if you pulled a burred valve stem thru them on disassembly anyways. Check for guide wear, common on a well used SBC . Also the backsides of the valves show oil deposits. Which suggests stem/guide wear. You should be able to move a clean/dry guide to stem just enuff to feel. Any more is re-do guide time. Real important on the intake side.

If the heads were properly set up in the past. Keep all shims in order. Take an exhaust spring and get it tested. This will give you an idea if the springs are any good. Any automotive machine shop will have a spring tester. I do one or two for free. Test height is usually in the 1.720" area. You want 80 lbs. at the very least. More like 90-110 for high performance hydraulic cam, single spring.

Check your exhaust seats in the head for erosion and the seat must be perfectly round and concentric. Not wide on one side . It is common for the center two exhaust seats to be worn more than outer ones.
 
#3 ·
I also noticed in one picture that the valve locks set in the retainer WAY too low. Some of the lock should show above the retainer. Your pic shows the top down in about .030 or so. This is inviting pull thru and catastropic failure. If those are aluminum retainers THROW THEM AWAY!!!
 
#4 ·
well first off, this motor is a high performance motor. My cam is a solid flat tappet power band 4200-7200. It is hard to tell, but the spring are DUAL with dampener (thanks to f-bird'88). Also, the heads have only 2000 miles on them. The very first valve i took out had burrs on it, but i didn't know. So that ONE intake seal is probably scratched. Otherwise, i use a file and fine grit sandpaper. The two valve i have taken out slide in and out like new. No jiggle at all.

According to the cam card, the springs should be 130lbs open, 325lbs seat.

The oil is from excessive blowby. That is the only reason i have my motor apart this far. I am getting a new short block.

So the keepers should be replace anyways? regardless or how old they are?

all the seat look new (minus the oil deposity) like i said, these heads were rebuilt completely in mid 2009. New stainless steel valve, bronze valve guides, but the old springs were used (to match the cam)
 
#5 ·
Biscuit6447 said:
well first off, this motor is a high performance motor. My cam is a solid flat tappet power band 4200-7200. It is hard to tell, but the spring are DUAL with dampener (thanks to f-bird'88). Also, the heads have only 2000 miles on them. The very first valve i took out had burrs on it, but i didn't know. So that ONE intake seal is probably scratched. Otherwise, i use a file and fine grit sandpaper. The two valve i have taken out slide in and out like new. No jiggle at all.

According to the cam card, the springs should be 130lbs open, 325lbs seat.

The oil is from excessive blowby. That is the only reason i have my motor apart this far. I am getting a new short block.

So the keepers should be replace anyways? regardless or how old they are?

all the seat look new (minus the oil deposity) like i said, these heads were rebuilt completely in mid 2009. New stainless steel valve, bronze valve guides, but the old springs were used (to match the cam)
But how old are the valvesprings?? Were they pressure checked at the time of the redo?? Like Bob said, hammered keeper grooves is a sign of a valvetrain out of control or a bad harmonics situation. Spring specs can also appear to match on paper but cause a problem in use do to harmonic resonance and spring surge.

Running excessive valve lash will also burr the valvestem.
 
#6 ·
the valve spring are several years old, but with only 5000 miles.

Bad harmonics is a big factor, at the time i didn't know about harmonic dampeners, but now that i know... The motor had a "stock" 8" dampener. That is just what the motor came with, not what i put on. But from what i read, those stock dampeners are good for 5500? 6000 tops? I am turning 7000.

My valve lash was set per cam card request, .026 int/ .026 ext HOT. I adjusted them, with the intake just closing, exhaust just opening method.

I had to do a significant amount of filing/sanding to get my valves to come out smooth. Just now i took apart the driver side head. From having no knowledge about this, i can tell just by looking that things don't seam right. Plus... The #5 cylinder inner springs are broken. :( :smash:

So i am basically replacing... springs, retainers, shims, seals, valves.

I have replace... main bearings, rod bearings, pistons, piston rings.
 
#9 ·
I don't believe you mentioned push rods. Besides providing the correct geometry, you prolly know the p-rods need to be stiff enough so that they don't set up harmonics and/or act as a spring (like a pole vaulter's pole) and cause the valve to lose control.

Stock-type or thin walled p-rods won't get the job done- even if the springs are sufficient for the cam and RPM.

I am going to assume the clearances between the components of the valve train were verified, or the new build will have them verified.

Good luck!
 
#10 ·
I have not. I can not tell you if they are stock or not. I don't have a part #. They are 5/16 and have what looks like a ball on the end, they are not smooth from end to end. I would assume they are not stock. I have full roller rockers, and rocker studs longer than stock.

What would you recommend for push rods if my cams power band was 3000-7600?
 
#11 ·
For the pushrods, something in chrome-moly, at least .065" wall and better yet .080" wall.

My mention of harmonics had nothing to do with the harmonic damper. I was referring to bad harmonics in just the valvetrain, as witnessed by all the damage you have. Something has overstressed the springs, could be age and some sitting adjusted and fully compressed for 5 years on a stand, maybe the wrong spring rate for the job(too low), maybe fatigue from previous use, maybe set up at the wrong seat height -- something was wrong obviously.

I know you had another thread asking about heads for this engine because you felt the 462 casting were holding back your top end power. You have just discovered your loss of power - the valvetrain is a mess. It is the smoking gun.
 
#12 ·
ericnova72 said:
For the pushrods, something in chrome-moly, at least .065" wall and better yet .080" wall.

My mention of harmonics had nothing to do with the harmonic damper. I was referring to bad harmonics in just the valvetrain, as witnessed by all the damage you have. Something has overstressed the springs, could be age and some sitting adjusted and fully compressed for 5 years on a stand, maybe the wrong spring rate for the job(too low), maybe fatigue from previous use, maybe set up at the wrong seat height -- something was wrong obviously.

I know you had another thread asking about heads for this engine because you felt the 462 casting were holding back your top end power. You have just discovered your loss of power - the valvetrain is a mess. It is the smoking gun.
Agree with ericnova on this one. Get some good chome-moly .080 wall pushrods (one piece type). Make sure you check and get the correct length pushrods for your setup. I would also recommend a stud girdle if you are running an excessive lift of cam. The valvetrain has to be setup correctly and rigid enough to stand up to 7000 rpm's.
 
#13 ·
Biscuit6447 said:
I have not. I can not tell you if they are stock or not. I don't have a part #. They are 5/16 and have what looks like a ball on the end, they are not smooth from end to end. I would assume they are not stock. I have full roller rockers, and rocker studs longer than stock.

What would you recommend for push rods if my cams power band was 3000-7600?
5/16" is the stock diameter. You might have hardened but the diameter should be larger if possible (there are considerations with the opening in the head or guide plate width)- a 3/8" p-rod will be stiffer at 0.055", say, than a 5/16" p-rod at 0.090" wall thickness.

There are a lot of choices. Besides straight wall there are tapered, at least 3 diameters that could be easily used, 4 or 5 wall thicknesses and several good manufacturers.

You couldn't go wrong with a set of 11/32" dia. .118" chrome moly alloy pushrods from Manton, other than the expense (~$8/ea.). May be overkill for a 2.02" valve @ 7600 RPM, but you will not flex them enough to matter, and that's the point.

In any event, research them carefully- good p-rods are not cheap, but can go a long ways towards giving the needed valve train stability that you are now lacking.
 
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