[DeTomaso] Valve Stem seal and Keeper replacement

[Tomas Gunnarsson]

Asa Jay,

I've done this a couple of times myself when changing springs and/or seals. I never bothered bringing the engine to TDC, instead I let it turn over to BDC which is a stable position. Like you I found my seals very hard though not quite as messed up as yours. Allmost all of the exhaust seals had cracked IIRC, some of the intakes had too. I went with teflon seals that require machining when I had the heads refurbished, it'll be interesting to see how they hold up.

Tomas

----- Original Message ----- 
From: "Asa Jay Laughton" <asajay at asajay.com>
To: <detomaso at realbig.com>
Sent: Sunday, August 09, 2009 2:39 AM
Subject: [DeTomaso] Valve Stem seal and Keeper replacement


> Based on a recommendation from Dan Jones (our favorite 351C engineer 
> type), I purchased some new Comp Cams keepers for the valve stems on my 
> engine.  I plan to run the engine basically stock in the Silver State 
> Classic Challenge.  Dan has told me the stock valve stems and keepers 
> can separate after long use, and possibly at high rpm.  I don't plan on 
> any blazing speeds like Mad Dog but I do plan on triple digits.  So I 
> felt it prudent to take Dan up on his suggestion.  While in there, I 
> figured I'd change valve stem seals too, as I've rebuilt other 351C's 
> and found nothing left of the original seals.
> 
> To do the job, I used a compression tester that had an air hose nipple.  
> After removing the shrader valve from the hose and screwing the hose 
> into the cylinder, I dialed my shop air to about 65 psi.  Before hooking 
> the compression tester hose to shop air, I cranked the engine to TDC on 
> #5 and using a wire, verified the piston was near the top.  The air 
> keeps the valves seated while using a spring compressor to remove the 
> springs.  I discovered higher air pressure spun the engine over, but at 
> 65, the piston stayed put and the valves stayed closed.
> 
> The seals and keepers are replace one valve at a time.  Do everything on 
> one, then do the other.  Then move to the next cylinder.  I started on 
> cylinder number 5, drivers side, front.  Both the intake and exhaust 
> seals were intact and looked rather good, except they were hard as a 
> rock.  I replaced them both with new seals sourced from Napa.  These are 
> stock type seals, not positive lock seals.  I didn't want to mess with 
> machining the guides, especially as the valves are still installed.  
> After installing the new keepers, I moved on.  When I got to number 6, 
> things changed.  I started finding really toasted seals.
> 
> It took a few hours, changing everything on one cylinder, then removing 
> the air, rotating the engine, verifying the cylinder I was at was on 
> TDC, installing air, compressing springs, changing seals and keepers, 
> replacing springs and moving on.  Repeat seven times.
> 
> It was a darn worthwhile job and I'm very glad I did it.  You'll see why 
> when you check out the photos and more comments here:
> http://www.teampanteraracing.com/index.php?option=com_g2bridge&view=gallery&Itemid=57&g2_itemId=2951
> 
> Now I have to clean up the valve covers, do some cleaning and vacuuming 
> in the heads, torque all the rockers back in place and put the valve 
> covers on.  Darn near done.
> 
> Asa Jay
> 
> Asa Jay Laughton, MSgt, USAFR, Retired
> 
> & Shelley Marie
> Spokane, WA
> 
> 1971 Mach I Mustang  [ASA JAY]
> 1973 Pantera L 5533  [ASASCAT]
>    
> ******************************     
> http://www.asajay.com
> http://www.teampanteraracing.com
>  
> 
> 
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