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Gon fix it with me hammer
 
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valve stem seals / valve spring preload

Howdie folks, best wishes for 2005


started reassembling my engine last week , thought i'de start with the valve heads, seemed straightforward...

but turned out less straight forward

them white teflon valve stem seals , are a PITA

please correct me if i'm wrong, but they are supposed to go completely over the valve guide , right?

if so , how do you guys do it? that sucker is so tight, the only way i can get it over the valve guide, is with serious brute force

and then the seal looks just like that : seriously brutalized, what am i doing wrong here? is there a trick to get them on?



also , the valve spring preload, is this a very critical thing ? i mean
yes i can measure the valve compressed height
book says 35.5 mm for the intake , 34.5mm for the exhaust
.03 mm tolerance
but the way to measure this is very inaccurate

- measure the depth of the dish
- install the spring
- measure the height of the spring on top of the dish where the springs sit in (add depth of the dish)

then add washers as required

the problem is the inaccuracy of my measuring , 2 measurements, neither are very precise ( anything in between a mm is guess work )

to me it feels like that 0.3 mm tolerance, is not going to be achieved this way

any ideas?
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Old 01-03-2005, 12:48 AM
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bump?

common guys , i have the parts laying on my cofee table, just waiting to assemble them... first stage of actually getting my engine back in one piece...them valve stem seals just frustrate me , don't dare to hammer them in to place, cause they looks violated that way , rather put on the ones from the gasket kit , even though they might not be as good
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Old 01-03-2005, 08:23 AM
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for the seals, I used a 1/4 drive deep socket which was just the right size to fit over the rubber part and sit on the brass part, then tapped it down.

Not sure I have the white teflon valve stem seals but it worked for what I had.


no ideas on the valve spring height, I just put back what I had, I am not refreshing the valves this go around....next year if I have troubles, it is a race motor after all.

Jim
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Old 01-03-2005, 10:17 AM
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Lightly tap the Teflon seal into place with a suitable socket be careful not to over do it it probably goes down about 8mm or so. Usually there is a piece of formed plastic in the Gasket kit that goes over the valve to protect the seal on the valve stem from being damaged in the process.
In regards to the Springs, Porsche makes a tool that one would use in conjunction with the top retainer and the bottom pearch to arrive at the preload. If you do not have such a tool you can resort to what many Performance Engine Builders do, and that is to set the Tension at Full lift a given distance away from the spring bottoming. This clearance is generally 1.25mm. To do this install one Top Retainer together with the Keepers on one valve, pull the retainer into the intalled position and measure to the bottom of the head without the spring seat installed. This measurement should be done with a Venier Caliper as square as possible to the Valve Axis. Repeat for the opposite valve and record.
This will provide the measurement of the Installed Height. Now for preload you will need cam lift and if you don't have that measure (subtract) the small side from the tall side of the cam lobe and multiply it by rocker ratio I think 1.425 will do. With your Cam lift figure in hand go to a Vise and compress the Spring to your Installed Height (first measurement) also use your same Caliper and Subtract your Cam Lift (your second measuremnt) by compressing the Vise remember you absolutley must have 1.25 for clearance before the spring coils touch and the rest should be made up of shims for your preload. This should be as good as it gets since all compression springs are design to a given Clearance before the coils touch and in the case of the Porsche 1.25mm is a proven safety margin and the spring rate is what it is by the material and size of wire and it will not change, but this installation will affect the seat and nose pressures in acoordance with your shim pack
This can be done with simple tools but does not provide information in regards to the spring rate and or the condition of the springs.

Kindest regards
Old 01-03-2005, 01:37 PM
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thanks Jim , i'll try that

Racing97 , ehm i'll have to read that a couple of times more , it's to early in the morning, need some cafeine first
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Old 01-04-2005, 12:59 AM
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I understand,
There will be quite a bit of standing and staring at the parts until it makes sense. I am not usually that informative as it is easier for some people to be more descriptive and clear. Anyway good luck
Old 01-04-2005, 08:03 AM
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This is the way to measure the installed height for the springs. Every once in a while one pops up on ebay.

http://www.goodson.com/instr/MVS-130.pdf
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Old 01-04-2005, 11:00 AM
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Quote:
Originally posted by BK911
This is the way to measure the installed height for the springs. Every once in a while one pops up on ebay.

http://www.goodson.com/instr/MVS-130.pdf
well , i tried it again yesterday , with one of these things
(don't know the name in english ) , used the long end to measure



and yes , i can measure with it, but i'm not convinced that it's accurate enough... the scale only goes in mm's , so anything in between is guesswork, the readings also vary depending on how i position the thing, and what i base my reading on...

because i'm measuring twice per valve ( valve seat depth + compressed height between edge of seat and retainer) , i think the total tolerance is to big ( could be anything from 0.4 to 0.6 mm off )

maybe i'm taking taking this part of the rebuild to serious , don't know, it's a first for me too, but if i'm gonna spend that much money for new P&C's , cams, case machine work... then i might as well look around to find me the 80 buck tool to do the springs right... especially since it's not simple to re-do after the heads and camhousing is glued

thanks everybody for the tips ..
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Last edited by svandamme; 01-06-2005 at 06:09 AM..
Old 01-06-2005, 06:07 AM
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If you have a spare retainer you can machine a notch out of it for the Caliper to travel down to the head square to the axis. This proess works in a pinch but the spring hieght mike is the best tool for the job.

Good luck
Old 01-06-2005, 08:33 AM
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Vandamme,

When I installed my seals I put some shrink tubing over the top of the valve and used motor oil as a lubricant. They went on super easy. Then I just cut the shrink tubing of when I was done. Worked like a charm!

Norm
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Old 01-06-2005, 10:47 AM
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The notched retainer is a smart suggestion. Stijn, I believe to have some I can use for that purpose
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Old 01-06-2005, 12:42 PM
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Quote:
Originally posted by svandamme
i can measure with it, but i'm not convinced that it's accurate enough... the scale only goes in mm's , so anything in between is guesswork, . . .
If its a venier caliper there should be some additional markings that allow you to accurately determine the readings that are less than the primary scale.

There should be some addtional markings along the measurement axis that line up for each tenth of the smallest division.

As far as your springs go, I would recommend taking them to a machine shop along with your preload and open specs so they can check your spring pressures for you. That way they can determine if any need to be replaced or require additional shims.
Old 01-06-2005, 02:23 PM
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i looked at it again , and figured out the smaller scaling , but it's still open to interpretation (depending on how you look , how straight you put the caliper, where you put it on top of the spring, ... )

have somebody looking for the specific tool , if he finds one , i'll use that, if not, then i guess i'll just have to live with it...

that shrink tubing for the valve stem seal , think i'll try that, although i'm not sure if it there's enough room to get it in between valve guide and valve stem seal , it's allready tight as it is...

i read something on a mustang forum , about taking off some material from the top of the valve guide, so the valve stem seal fits better , anyone heard of this??

sounds weird to me , the thight fit seems required, so the thing doesn't move , and actually seals well , > less oil wasted.
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Last edited by svandamme; 01-07-2005 at 12:24 AM..
Old 01-07-2005, 12:21 AM
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correction , it was a chevy thing

http://chevyhiperformance.com/techarticles/148_0307_heads/

Most heads will require machining the valveguide to mount the seals. A machine shop can do this, or you can purchase the cutters directly from the cam companies.

the mustang article was nice as well, explained what's necessary to do a head rebuild, discusses coil bind and some other thingies

http://www.mustang50magazine.com/howto/24453/
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Old 01-07-2005, 12:30 AM
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little bump ...

found out why i had such problems measuring with the vernier caliper :

last weekend , i sat down , and went for it : turns out that when
my heads where machined , and received new valve guides
at the edge of the guide ,where the guide exits the head

there was some sort of resin or maybe solder residu

although very little of it... it did have an impact

the valve seat went around it , but the metal plates used to correct the preload weren't... so they wiggled

last time i didn't notice , because i measured with the springs on

now i measured without the spring ( used the valve stem to compare against valve seat +47.5 mm metal tube ) and it became very clear that there was a problem with that resin like stuff



BTW , i did get that tool from Goodson , the MVC-150 , but unfortunately that turned out to be useless for the 911 heads... because it didn't fit in the hole ...it was to wide in diameter
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Old 02-28-2005, 05:12 AM
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The resin like stuff is probably something like locktite they used on the guide when it was pressed into the head.
Old 02-28-2005, 02:50 PM
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yeah , i figured that much ... brownish ... hard stuff... looked a lot like what you got coming out of solder when it melts...

to think what a headache this stuff gave me ... the chimmy was wiggling on one side... and my vernier caliper was giving a variating readout ... plus or minus 1 mm...

thought it 'de be a good idea to post , in case someone else has this..
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Old 03-01-2005, 12:06 AM
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