Washers under valve springs AND head questions

[farleyd]

Hi to all, still discovering new things as i dismantle the engine. Now i am on the heads.

1)
While removing the valves, i noticed there were some washers under the spring seats. Is this what some call shims? To get stiffer springs?
Some had 4 washers, some had 5!
Any clue? Whats the stock config?
Anyhow, ill renew the springs with new ones.

2) Two valve guide bosses are craked. Should i have them welded and repaired (then keeping the original matching heads) OR should i use spare ones i have from the same year?

3) I am going RS specs minus the MFI. My heads are from 911S (35mm intake). RS specs are 36mm intake. How much of a miss is it to keep the intakes at 35mm???? Using E-cams.

Thanks!

[TimT]

if the valve guide support or bosses are, cracked it usually means the valves have kissed the pistons quite hard at some point in the engines life. I dont think you can repair that kind of damage.. welding would be near impossible due to the restriction of the port and lack of room to manipulate the electrode and apply the filler

[ChrisBennet]

Originally posted by farleyd
Hi to all, still discovering new things as i dismantle the engine. Now i am on the heads.

1)
While removing the valves, i noticed there were some washers under the spring seats. Is this what some call shims? To get stiffer springs?
Some had 4 washers, some had 5!
Any clue? Whats the stock config?
Anyhow, ill renew the springs with new ones.

Those are shims. They are used to set the spring height. It's normal for there to be different numbers of shims. Whomever does your heads will set the spring height (changing # shims sometimes) as part of the job.
-Chris

[snowman]

The washers under the valve spring are hardned shims and used to adjust the INSTALLED LENGTH. There is a spec for your heads with theis length. It is measured from the top of the top shim to the bottom of the spring retainer. The shims should not be used to adjust spring pressure, except by tiny ammounts.

If you assemble the head yourself, after the valve work is done you can easily adjust the number of shims yourself to obtain the spec length. You can make your own measuring tool by chopping a length of welding rod and filing it to the exact length required. Then solder or weld a short length of welding rod to the middle at a 45 degree angle for use as a handle. Make two, one with the longest spec length and one with the shortest spec length. That way you insert enough shims to be longer than the short tool and shorter than the long tool. You make the measurement by installing the shims, coil base, if used, and the spring retainer and keepers. Leave out the spring. Simply hold the retainer tight and insert the tool to make the measurement. Add or subtract shims as required.

Don't throw those heads out yet. Take them to a shop that specializes in Porsche heads, like Ollies Machine shop in Santa Ana, CA. ( I have no connection to them but I know that they are good.) Many times things can be welded and then remachined to original and rebuilt. Check prices first as its sometimes less expensive to buy another head than to repair one.

[snowman]

PS always use the book and not what someone told you for correct referances and lengths.

[jgparker]

It should be mentioned that the spring height changes depending on what cam you are using. Since you are probably going from CIS cams to an E or S Cam, the spring height will definitely change. The spring height tool (P10c) is the easy way to do this, but I'm all for creative solutions.

I believe the valve spring height specs are:

2.7 CIS Intake: 35.0mm Exhaust: 35.5mm
Early S Intake: 35.5mm Exhaust: 34.5mm
E-cam Intake: 36.0mm Exhaust: 35.0mm

These numbers are the height of the outer spring, not the height of the springs in the retainer and the base. The shims are 0.5mm, so the specs are +/- 0.3 mm.

I've heard you can lower the spring height to decrease the valve float a little, but I have seen the cause the valves to stretch faster than normal.

[snowman]

When you change cams you are going to have to do a lot more work. For one the springs are probably differen't, you must check for coil bind, valve piston clearence, and so forth. Changing valve height is not an accepted method for making significant differences in valve float.

[farleyd]

Ok guys, my heads are from 2.7 CIS. Will be used with RS p/c?s, Webers and E-cams. What would you suggest? Bruce Anderson book isnt mentionning too much head work for that conversion.
Thanks for clearing things.

[Mr Beau]

Wayne's book shows 34.0 to 36.0mm for all non turbo engines. Haynes doesn't have anything for <2.7L engines and I couldn't find anything in the factory manuals.

How critical is the measurement? For a 2.4E, are Wayne's numbers of 34.0 +/- 0.3 for intake and exhaust correct?

Originally Posted by jgparker

It should be mentioned that the spring height changes depending on what cam you are using. Since you are probably going from CIS cams to an E or S Cam, the spring height will definitely change. The spring height tool (P10c) is the easy way to do this, but I'm all for creative solutions.

I believe the valve spring height specs are:

2.7 CIS Intake: 35.0mm Exhaust: 35.5mm
Early S Intake: 35.5mm Exhaust: 34.5mm
E-cam Intake: 36.0mm Exhaust: 35.0mm

These numbers are the height of the outer spring, not the height of the springs in the retainer and the base. The shims are 0.5mm, so the specs are +/- 0.3 mm.

I've heard you can lower the spring height to decrease the valve float a little, but I have seen the cause the valves to stretch faster than normal.

[Trackrash]

Porsche lists 34.0 + - 0.3 for the 2,4 E. Intake and Exhaust.

Too bad Haynes dropped all the old stuff. Their original Workshop Manual is very good.

How critical? There has been some recent discussion about this.

http://forums.pelicanparts.com/911-engine-rebuilding-forum/991556-diy-refurbishing-cylinder-heads.html

[manbridge 74]

Holy thread necromancy...