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Join Date: May 1999
Location: Burlington, NC
Posts: 273
Rebuilding Heads

I have a '74 2.0L.

Due to a loss of compression on one cylinder, I am going to rebuild/renew the heads.

I am planning to do the following:

1-have machine shop repair damage to what I believe is a burnt valve
2-regrind ALL valve seats
3-replace any damaged valves
4-replace valve guides
5-replace valve springs and keepers with HD springs from PP
6-replace pushrod tubes and seals
7-replace valve cover seals

Are there gaskets between the head and cylinders, or between the cylinders and block? Haven't seen them in PP Catalog.

I'm wondering if shaving the heads to increase compression ratio is advisible and if there is enough material to not compromise the head.

Also, does the Porsche head require a special valve spring tool or will any old valve spring tool be OK?

Like I said, this is what I'm thinking right now. If you have any additions to my list of things to do, let me know. If I forgotten any thing at all, let me know.

Any and all advice is appriciated.

Thanks in advance.

PRITCHARD
Old 11-09-1999, 06:29 AM
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I shouldn't have said repair the valve. I meant repair the damage to the head. I am a little confused about valve seats. I thought that the valve seated directly into the material that the head was made out of. It sounds like there is some sort of insert for the valve to seat itself in. If this is the case, is this a part that I would need to get from PP, or would the machine shop have this part? (keep in mind that over here in the southeast where pickups rule the road, finding a machine shop familiar with Porsche heads is kind of difficult)

About decking the heads, how much material can safely be removed?

As you can tell, I am venturing into unknown lands concerning head work. I appreciate the information. Keep it coming.

Thanks.
PRITCHARD
Old 11-09-1999, 09:10 AM
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Location: Denver, NC
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Pelican Parts offers a machine shop service
that is familiar with Porsche work. Like Brian said it is important to get a shop that has experience with this kind of work.
I would check with Pelican about getting you heads done through them.
Old 11-09-1999, 09:30 AM
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Regarding the "gaskets", there is a paper gasket at the base of the jug, between the jug and the case, and there is a copper ring at the top of the jug, between the jug and the head.

Back when I raced Formula Vee, based on the 1200cc VW type I engine, we needed to squeeze every little bit of horsepower out of those tiny engines, while not violating the formula. One trick was to not use the paper gaskets at the base of the jugs. Instead just use a smear of gasket sealer. The theory was that this gave us that tiny bit more compression in the cylinder. No one ever measured the difference, but everyone who knew about the idea did it.
Old 11-09-1999, 02:09 PM
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How about losing the gasket at the top and lapping the barrels to the head?
Old 11-09-1999, 02:30 PM
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There are different options for gaskets, as well. I have very thin (flimsy) metal "gaskets" between the cylinders and the case. They help keep the oil in, I think... I also have thicker (but not very thick) light-colored-metal (not copper) rings between the cylinders and the heads.

You can evidently leave out the head gaskets entirely. VW issued a service bulletin on this for the VW-badged Type IVs, though it seems Porsche did not for the 914s. This will effectively raise the compression ratio. Measure all the volumes to find out how much! (Write me off-line if you need an Excel spreadsheet to do the math for you.)

Valve seats are hardened steel rings that are pressed into the soft aluminum heads. The aluminum is too soft to last under the beating of the valves, so the steel is used to take the abuse. However, they can and sometimes do fall out of the head! (That may be what happened to you.) This seems to happen most frequently after head-work is done, though it isn't *that* common. If your machine shop *really* knows 2.0 914 heads (with their crack-prone nature), they should be able to tell you to grind the seats or replace them. If you're in doubt, replace them. I've lost three seats so far--it is *no* fun at all digging down into the motor YET AGAIN for the same %$^%!! reason.

I'm not sure on the valve compressing tool.

--DD
Old 11-09-1999, 04:26 PM
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When I did some work on my '73 2.0 heads I just rented a valve spring compressor from my local tool rental place and it worked fine. I don't know if all valve spring compressors will work though.

Also, when I did a "top end rebuild" on my car all the cylinder to case and cylinder to head metal sealing rings appeared to be exactly the same (steel, I believe) and came in the same plastic bag. The old sealing rings were the same as the new ones and were still in place on the motor so I just replaced them with the new ones.

Alpine
Old 11-09-1999, 07:47 PM
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