Ready Rebuilt Heads

#28

To the OP, you do realize a broken rocker is easy to change w/o removing head, right?

#29

Yes I have heard mixed opinions about the difficulty and best approach and was heading down the path of pulling and refreshing, but as I look at the cost of a refresh I am considering trying just the rocker arm without the head removal. I have seen a few diy on it. If you recommend any to check out or have advice let me know.

#30

It’s one of those jobs that’s not hard if you know how but can be tough to handle the details.

We replaced #3 or 4 intake in 35 minutes on a hot engine at Sebring last year, with two very skilled helpers, but not a job to do alone if you’ve never seen it done. Of course it depends on your own skill level too.

I think we posted the write up last year on this site so try searching for it.

#31

If you’re at the track just replace the one arm. If you’re at home, replace 'em all. I’ve done both scenarios and neither are difficult to do without removing the head.

#32

Can’t you make it super easy by drilling a hole in the firewall to remove the shaft? I’ve never done it, so I don’t know. That’s what I’ve read on the forum before.

#33

That used to be the conventional wisdom, but there’s an easier and less-destructive way.

The idea is to take the shaft out the front, regardless of how far you need to go to reach the rocker.

The hard part about sliding the shaft is that it’s impossible to get all 6 valves off the rocker at the same time.

So, the trick is, before starting to remove the shaft, remove all the retaining clips, figure out what your target crank position is (making sure you are aligned to slide the rocker shaft through one of the holes in the cam gear, is to identify the valves that are going to be “up” when you get to your target position.

So, temporarily, rotate engine to move the troublesome cylinders so the pressure is off the rocker(s), and slide them laterally to “park” them in between the lobes. Then, return the crankshaft to desired orientation, and you should have a shaft that can slide without pressure from any of the cam lobes.

The next thing holding you back will be the amount of varnish/crud built on the shaft, making it resist sliding even though there is no valve pressure. YMMV on that one, for sure. With a clean engine, it’s very easy to slide.

Reinstallation is similar. Make note of which rockers need to be parked, and slide the shaft back in and install the retaining key up front. Align the rockers you can, and install their clips. Then, rotate the engine until you can slide the parked rockers back into place. Be careful you don’t get the parked rockers hung up on one of the lobes. Direction of rotation to unpark can be important.

#34

Off topic again, but I feel compelled to “contribute”. I built a few engines last year before deploying and parts cost was near $2400 on each. That included new pistons, proper rings, coated rod bearings, new OEM rockers, new FEBI cam, valve guides, freeze plugs, M50 windage tray, oil pump, water pump, and all the other typical parts and seals. Add $50, and you can have all new zinc plated hardware. I’m picky about head gasket (Goetze) and rear main seal (Corteco) but use VR for most other seals. Machine work varies considerably from different shops, but I think it’s very difficult to properly build a motor for under $5K.

See you all at Road Atlanta in August!

#35

[quote=“ctbimmer” post=71804]That used to be the conventional wisdom, but there’s an easier and less-destructive way.

The idea is to take the shaft out the front, regardless of how far you need to go to reach the rocker.

The hard part about sliding the shaft is that it’s impossible to get all 6 valves off the rocker at the same time.

So, the trick is, before starting to remove the shaft, remove all the retaining clips, figure out what your target crank position is (making sure you are aligned to slide the rocker shaft through one of the holes in the cam gear, is to identify the valves that are going to be “up” when you get to your target position.

So, temporarily, rotate engine to move the troublesome cylinders so the pressure is off the rocker(s), and slide them laterally to “park” them in between the lobes. Then, return the crankshaft to desired orientation, and you should have a shaft that can slide without pressure from any of the cam lobes.

The next thing holding you back will be the amount of varnish/crud built on the shaft, making it resist sliding even though there is no valve pressure. YMMV on that one, for sure. With a clean engine, it’s very easy to slide.

Reinstallation is similar. Make note of which rockers need to be parked, and slide the shaft back in and install the retaining key up front. Align the rockers you can, and install their clips. Then, rotate the engine until you can slide the parked rockers back into place. Be careful you don’t get the parked rockers hung up on one of the lobes. Direction of rotation to unpark can be important.[/quote]

This is good guidance.

My addition to it would be on how to move the reluctant rocker arm shaft. The trick is to bonk on the end of the shaft so you can coax it forward. By using a pair of vise grips and a handy big bolt or a small socket extension, you should be able to position a “drift” on the other side of the rocker arm shaft. Then bonk on it and move the rocker arm shaft forward.

As the shaft moves forward you need a progressively longer drift so add socket extensions. Just be wary of the odd socket extension that is a little beefier than the others because it can hang up on the holes in the AL head. You’ll feel sheepish if you’ve been whacking on your drift for a while before you realize that instead of pushing the rocker arm shaft all you’ve done is bash up the rocker arm shaft’s AL hole.

That joke would have worked better if the head was made of Arsenic.

#36

I know a GTS2 guy (also M20) who used to break a lot of rockers. He used to keep in his tools a series of wooden dowels of varying lengths, that were sized to fit through the rocker towers in the head. Softer than the metal, of course, but would have to be a quality wood to avoid splintering under gentle prying or tapping.

He would start with a short dowel at the rear, use a long screwdriver or similar to pry it forward a little and switch to the next longer until he was able to get the end of the shaft visible inside the head, where more conventional forms of leverage could be used.

#37

There is alot of help for Jody in the Charlotte area.

As much as this board is helpful…

There will be a weekly NASA SE meeting next Tuesday night 7:00 pm, Iron Thunder in Concord NC.

RP

#38

well it is #5 rocker arm intake side and i have all of the rocker arms tension free (slight tension on the broken one) shaft is even lined up with hole in the cam…but I can not figure out any way to get leverage to drive/push the shaft out the front. ideas? please let me know, very soon I will likely resolve to just pull the head…all ideas welcome.

#39

OP, the ideas on how to drive the shaft forward are in this thread. You need to look at your available implements and probably improvise somehow. Would be a damn shame to pull the head when you’ve accomplished most of the hard work of shaft removal. the firewall is your leverage point, so dtermine what you can use (1/4 sockets/extensions perhaps) to drive forward armed with a small flat crowbar or broad screwdriver.

anything that can make leverage. may be a 3-handed job, so consider looking for a friend to help.

Good Luck!

#40

its moving! thanks for the :slight_smile: encouragement!

#41

Long story short that shaft did not move very far and I was not willing to force it any further. Pulled the head…stripping it now, just the valves springs and he cam left to remove. Then to the machine shop to clean and inspect. Question is this. Other than the camshaft and the good valves, is there anything I should not replace? I have heard to even replace the rocker arm shafts but I really can see no reason for that, but would do so if advised from this forum those aside. The plan is to replace:
Springs both rocker arm and valve
rocker arms probably go with ie hd
Valve guides and seals-green vinton
Spring cups
Spring retainers
Worn valves
Exhaust manifold studs
Valve adjustment eccentric , nut , bolt
Head bolts
Intake and exhaust gaskets
Front camshaft seal

Again Are new shafts really needed?
Is any of this unnecessary?
Finally…

How can I tell if the camshaft is worn enough to warrant replacing

#42

[quote=“bronzite30” post=72148]Long story short that shaft did not move very far and I was not willing to force it any further. Pulled the head…stripping it now, just the valves springs and he cam left to remove. Then to the machine shop to clean and inspect. Question is this. Other than the camshaft and the good valves, is there anything I should not replace? I have heard to even replace the rocker arm shafts but I really can see no reason for that, but would do so if advised from this forum those aside. The plan is to replace:
Springs both rocker arm and valve
rocker arms probably go with ie hd
Valve guides and seals-green vinton
Spring cups
Spring retainers
Worn valves
Exhaust manifold studs
Valve adjustment eccentric , nut , bolt
Head bolts
Intake and exhaust gaskets
Front camshaft seal

Again Are new shafts really needed?
Is any of this unnecessary?
Finally…

How can I tell if the camshaft is worn enough to warrant replacing[/quote]

Re. worn camshaft. Look hard at the leading surfaces of the cam lobes, especially near the top of the lobe. Look for discoloration or a change in surface texture. Most old cams are worn a bit. You might ask the machinist for their opinion of your cam lobes. Also look at the cam’s bearing surfaces for wear, likewise look closely at the cam’s journals (the holes in the head that the cam spins in). Wear to either creates an oil pressure problem. You can find a new cam for <$200, but if the head’s cam journals are worn, that turns the casting into a door stop.

Things you don’t need to replace.
Exhaust studs
Valve springs and cups.
Rocker eccentrics and nut.
Rocker clips. You might have called this a spring but it’s really a clip.
Valves, as long as they are straight and have enough material left for machine shop to grind new surface.
Valve guides as long as they aren’t sloppy loose. A little loose is ok, because race car.
Replacing your rockers is not a “must do”, it’s a “nice to do” so it depends on your budget.

#43

So do you agree new rocker arm shafts are not needed?

#44

[quote=“bronzite30” post=72155]So do you agree new rocker arm shafts are not needed?[/quote]Yes, not needed.

#45

Note I did test valves for leakage using the water test per Bentley manual. There was only a very small seepage so I feel like valves are sealing fairly well and hopefully have enough material for a resurface…Is it recommended to let the machine shop to grind the new valve surface? That looks pretty simple.

#46

The drip test is pretty rough. 160psi air will find a way out that water drips didn’t. Think “surface tension” not the size of the molecules. The drip test won’t show the difference between a terrific seal and an "ok’ seal. Have the machine shop do the valve job. You might emphasize to them that it’s a race engine and that if they need extra $$ for the valves to be handlapped post grind, you’ll be happy to pony up some additional $$.

#47

Machine shop that has the head suggesting to add shims to the valve springs to add about 10 lbs of pressure from 70 to 80 lbs. is this allowable? Concerns? More cam wear etc?