Need a photo of the place on the head where you check thickness

rich · rich's Garage

I was told there is a boss on our head castings to base line check the thickness to determine whether or not they are in spec. Is this so and if so where is it and how do you check? A pic would be nice.

Some of you know I have a 16V 1980 euro spec "S" engine.

I brought my heads into a head specialty shop. They called me with a dismal report and a price to repair the heads. I asked them if the heads were in spec and could even except another cut. They never checked them and the "Head Specialist" didn't seem to know how to check them.

This has been my experience at every machine shop I have ever used. I am really tired of baby sitting machinists to avoid poor work. Wouldn't you think that if you are a specialist you would start first to see if a head is even rebuildable? Specially when you say things like, " I'm not sure I want to put my name on this work unless we do this added work. I mean don't give me the breeze like your special and then can't answer the first basic question. "are these heads in spec? can they take another cut?" or are we wasting our time?

He called me back and told me he checked them the way he checks 944 heads and they seemed to be below spec already. I'm thinking about picking them up and sending them out for a second opinion.

First can anyone provide a photo of the method of inspecting the thickness of these heads?

And who has had a good experience getting their heads repaired?

And then finally, are thicker head gaskets available?

Who sells them? Any links?

Danglerb · 09-25-2007, 08:15 AM

Maybe talk to Lindsey Racing? http://www.lindseyracing.com/

Unless a shop does a lot of 928 work, best to assume they need some babysitting.

I'm going to be poking around in my workshop manual later on, if I see something on a head spec I'll post it.

rich · rich's Garage

Thanks, I got a responce from the list. Sorry I vented but this is really stressing me out.

jsbc · 09-27-2007, 02:36 AM

as requested head detail and drwg.hope its some help.

jsbc · 09-27-2007, 02:39 AM

try this

rich · rich's Garage

Got it, thanks, after I sent the specialty head shop a copy they were able to confirm my heads were already slightly below spec. They are usable with the Porsche thick gasket but I decided to buy a different set. I have a set of euro spec "S" heads coming from 928 Int. I'll have my original heads repaired later as a backup set or for a spare engine.

Danglerb · 09-27-2007, 11:55 AM

Slightly under spec does what, bump the compression a little?

rich · rich's Garage

Yes and gives cause to be concerned about the possability of a valve hitting a piston.

rhjames · rhjames's Garage

three things that happen when you mill the head to achieve a straight flat surface:

1. the piston to valve clearance is reduced.

2. the camshaft timing is altered.

3. the compression ratio is changed (example: 9:1 can change to 10:1, requiring higher octane fuel)

Heads that are below the recommended spec can be used, but valve to piston clearance must be checked (pistons can be further notched) and the cam timing can be adjusted by using the 32V style cam adjusters kit available from Porken.

Hope this helps------

rich · rich's Garage

I want to meet Porken someday. He's done some strange and wonderful things.

jsbc · 09-29-2007, 09:09 PM

Hi guys just checked out an old site for down loads if you need 928 info go here download while there still active they have been off line a long time dont know if they will be here tomorrow .

http://www.cannell.co.uk/Manuals.htm

Im stripping all i can just in case my next car is a ferrari.etc.etc.etc its so much easier to fix it yourself with a manual

jsbc 928 x2
911t 1970
aston martin dbs
jag mk2
rv. fiat ducato 6 berth
puddle jumper L.R.discovery

Danglerb · 09-29-2007, 10:40 PM

The site is up every month UNTIL it exceeds some bandwidth limit, then its off until the next month.

jsbc · 10-01-2007, 12:38 AM

I have read all the threads about machining this and that. If the amount of material removed from a head to flatten it allows pistons to connect with valves then they have taken off too much and your heads are scrap.If you need that much off then what about camshaft bearings if the heads are warped more than ten thou. then when you straighten the head face the camshaft bearings will be out I would not cut a head unless it was blowing gaskets and i would not cut a head to increase c.r.the gain is not worth it reduce it and blow the motor ,twin turbo or supercharger,thats if you have a spare ten g's and thats worth more than the car.

Danglerb · 10-01-2007, 02:30 AM

Can't the heads be welded or something to build up the height and then decked to new specs?

Euro S heads aren't the sort of thing I think anybody is going to toss in recycle without a struggle.

BTW the valves are a fair amount up in a pocket, so I suspect piston to valve clearance isn't the first or main issue.

rich · rich's Garage

Quote:

Originally Posted by Danglerb

Can't the heads be welded or something to build up the height and then decked to new specs?

Euro S heads aren't the sort of thing I think anybody is going to toss in recycle without a struggle.

BTW the valves are a fair amount up in a pocket, so I suspect piston to valve clearance isn't the first or main issue.

Welding the whole deck is out of the question. Porsche makes a thick gasket that will allow the use of these heads but I decided to just buy another set.

Good point about the cam housing jsbc. I need to checkt that.

Anywho... Heres a thought. How about a set of US spec open chamber heads with porting and big euro valves? May be nice with a blower....

rhjames · rhjames's Garage

jsbc---

the cams are in the towers and not subject to head warpage (as I see it)? the only way I could see them being subjected to head warpage issues is if the mating surface of the cam tower is warped, which can be remedied by the milling of the surface (although I have never heard of this happening).

------------

jsbc · 10-01-2007, 08:24 PM

Here is a naughty fix for stuffed heads take off whatever replace with two gaskets (std)and enough ally to bring back to standard go head, gasket, ally, gasket , block.allow an amount for 2nd gasket, im hoping to twin turbo one of my cars and will do this to reduce c.r. have ally water or laser cut it will stay nice and flat this will fix all but terminal heads.Timing problembs can be sorted by increasing or decreasing the waterpump pulley diameter pump rpm is not important.
(i have a workshop (not auto)and like to play)

rhjames · rhjames's Garage

thought about that 2 gasket thing as well-----then thought better.

we're only taklking about a few thousands of an inch to clean up a head, so putting some sort of spacer with two gaskets is a little much, considering the spacer may warp and blow out under pressure.....

If this was such a great idea, we'd be putting huge spacers in there to build up cubic inches with huge dome/crown pistons to keep the CR up......

try again------

rich · rich's Garage

Yes, were talking a mm or less. Just get the Porsche gasket and lower your compression that way. Used with US heads this could lower the compression for a blower I would think.

jsbc · 10-01-2007, 08:41 PM

Hi RH

If you remove the head and it is not flat then the cam tower area is also not flat if you do not set it up right before machining you can make it worse.The top and bottom of the head are effectively parralellwhen machined by porsche unless tensile stresses are released in the alloy due to overheating (possible) then a bow or whatever in the lower part of the head should be reflected in the top faces. .A twist in the head is earier on the cam than a bow you set the twist so that the best axis is parrallel to the camshaf and lick a little of the high points a bow buggers you up because the center of the camsaft will be either high or low .like i said if it is not blowing gaskets i would tend to pull it down and hope the block pulls it right