Hi all,
I need some education on valve stem seals. I'm familiar with the Ford umbrella style that moves with the valve. But I'm not familiar with the seal that actually snaps to the head valve guide. Attached is an image of that style of seal. Is this a GM seal? Can you tell in the attached image if the valve guide boss has been machine for this style of seal? It measures .522 inches. How do I buy a new seal with this dimension? Can you advise me a part number? The valves are standard diameter. Please educate me.
Thank you
Cory
Try M-6571-B221. This is a part # off a Ford Motorsport SVO box of 16 pieces. I measure 7.7mm and 12.5mm on the two IDs. 11.7mm and 15.9mm across the two outer compression bands using a vernier caliper with dial. Box is circa 2000. White nylon with silver bands as your photo. Hope this helps.
The pictured seal is an aftermarket unit (Perfect Circle? or ????). You can still opt for the Ford-style umbrella seal if you choose. The machined guide will not alter the effectiveness of the umbrella seal if you go that direction.
Frank
Boss has definitely been machined. I used Crane 99820 but that was almost 40 years ago. Not available at Summit but has the specs you're looking for https://www.summitracing.com/parts/crn-99820-16
Some on EBay https://www.ebay.com/itm/306185233774
Yes definitely, the guide bosses have been machined to something other than as O.E.M.; though the typically practiced dimension is either .500" or .530"/.531" diameter. :-\
The "Teflon" P.C. type seals were popular a period of time ago, but now other material and design types have proven superior and are now more commonly utilized.
Though the machining doesn't preclude the ability to utilize the O.E.M. style "Umbrella" seals, it does effect the functional efficiency due to the reduction in diameter and height of the guide boss, so I wouldn't recommend them. ;)
Scott.
Scott, which PC seals do you recommend incase he decides to go that way?
Roy
Quote from: TA Coupe on June 16, 2025, 06:58:43 PM......... which PC seals do you recommend?
I would suggest that a "Positive displacement" (vs. "deflective"), "Viton" or "fluoroelastomer" material, consisting of a steel skirting (with internal sealing if space permits) and spring tension choker is probably the overall best at the job; but it's just not for every application. :-\
Example: https://www.competitionproducts.com/Howards-Cams-Small-OD-Valve-Seals-11_32-x-531-575-OD-Set-of-16/productinfo/HRC93375/
There are several different examples available each with considerations for specific fitment issues which need to be taken into account. We can sorta make some assumptions based on the photo provided in the O.P.'s opening inquiry; here we assume that we're dealing with an 11/32" valve stem as this being "typical", but of course not the only possibility, but the first most glaring issue is that in the O.P.'s original posting the .522" dimension as this isn't so typical, therefore further investigation, not only of this topic but others, such as guide to valve clearances, seal to retainer height restrictions, spring inside diameter, etc. probably should be investigated before we just leap to an advisement of a singular item. ???
Normally, and please don't anyone be offended as my intent is to only aid, but if one is on a forum asking these sort of questions, for reasons other than just an educational inquiry of curiosity, which I do applaud, and the circumstances for which I provide my response; but if holding a set of 'old' O.E.M. cast iron cylinder heads that are of an unknown history and state of condition, that are intended to be put back into a state of being truly serviceable, and we're stuck on what seals we should be using, we've got a long road ahead of us. This is the "job" of the "capable" machine shop whom 'should' be familiar with this, and other topics concerning these cylinder heads and provide 'proper' advisement post a reasonable "hands-on" inspection. :)
O.K., I know, I didn't answer your question; so with the 'very' limited information that I'm privy to here, . . . . . hmmm . . . . . . "maybe" this "might" work:
https://www.howardscams.com/valve-stem-seals-posi-stop-1132-514-540-howards-cams-93360 8)
Scott.
Quote from: pbf777 on June 17, 2025, 10:30:20 AMbut the first most glaring issue is that in the O.P.'s original posting the .522" dimension as this isn't so typical
100% this ^
FWIW, the Crane teflon seals I installed in 1986 are still functioning flawlessly today. That includes every type of driving from SAAC open track days to just driving around around town.
Hi all,
Thank you for your input. Together we are smarter. I will assure, these heads will be professional checked out and reworked as needed. I would not go alone, but do like to have input from you all. I have been using my machinist for over 34 years. He is a pro. You look up gear head in Wikipedia, and there is a picture of him. (LOL)
Thanks again
Cory
Just dropped the heads off to my guy. When I was there, he was freshen up this engine he had built. Crazy piece.
O.K., seems nobody picked up on this, as I first stated:
Quote from: pbf777 on June 17, 2025, 10:30:20 AM. . . . . a "Positive displacement" (vs. "deflective"), "Viton" or "fluoroelastomer" material, consisting of a steel skirting (with internal sealing if space permits) and spring tension choker is probably the overall best at the job . . . . .
Example: https://www.competitionproducts.com/Howards-Cams-Small-OD-Valve-Seals-11_32-x-531-575-OD-Set-of-16/productinfo/HRC93375/
But then, I suggested:
Quote. . . . . . "maybe" this "might" work:
https://www.howardscams.com/valve-stem-seals-posi-stop-1132-514-540-howards-cams-93360
And these really aren't the same specific design.
The reason that I suggested the later might work better, is because this design provides a better ability to function acceptably with:
First: Greater deviations in the guides' I.D. vs. O.D. as machined centerlines.
Second: Also allotting for greater guide to valve stem clearance and the resultant lateral movement between the two in operation.
Thirdly: The pliable shirting with the spring tension belting allows for greater latitude in the guides O.D. sizing as machined and still grip/seal acceptably. ;)
Just food for thought, for those whom might be interested. 8)
Scott.