Valve stem seal OD problem.
Thread Starter
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Valve stem seal OD problem.
I have run into what looks to be a potential hassle on a regular basis with my Dart SHP heads.
This spring I discovered a spring resonance problem along with an installed height error on Darts part and a valve train geometry mistake or at least misunderstanding on my part. Fixed those issues with locators and more spring pressure. Along with that the roller tip magnum rockers were bluing at the pivot so I went full roller rocker.
I thought that should fix all the problems with these heads.
Well not quite.
The valve stem seals are still getting rubbed by the inner spring (dual spring roller cam head) and eventually dislodges the seal from the valve guide. Then you get smoke out the exhaust and have to take the springs off to replace the valve stem seal. These are umbrella style seals. With a brief search I see that I am not the only one with this issue.
I have what I believe to be a fix for the problem but am unsure as weather is is a good one.
The current umbrella style seal is .674" on the OD of the seal and pushes onto the guide with a viton rubber to guide contact to keep it on. This is the seal here.
http://www.summitracing.com/parts/drt-26000021
The replacement I want to use has a metal to valve guide interface but a reduced OD to .575".
http://www.jegs.com/i/COMP-Cams/249/518-16/10002/-1
http://www.summitracing.com/parts/cca-518-16
I figure I'll have to replace the seals at some point. Is the metal to metal (bronze guides) going to cause a problem with removal when that time comes?
Anyone else have this problem and solved it with different seals?
I didn't see any evidence of spring control on the locator seats when I had the springs off, so my best guess is that this is a clearance problem.
Called Dart and their tech's admitted that I am not the only one with this problem, but had no suggestions as how to fix the problem.
This spring I discovered a spring resonance problem along with an installed height error on Darts part and a valve train geometry mistake or at least misunderstanding on my part. Fixed those issues with locators and more spring pressure. Along with that the roller tip magnum rockers were bluing at the pivot so I went full roller rocker.
I thought that should fix all the problems with these heads.
Well not quite.
The valve stem seals are still getting rubbed by the inner spring (dual spring roller cam head) and eventually dislodges the seal from the valve guide. Then you get smoke out the exhaust and have to take the springs off to replace the valve stem seal. These are umbrella style seals. With a brief search I see that I am not the only one with this issue.
I have what I believe to be a fix for the problem but am unsure as weather is is a good one.
The current umbrella style seal is .674" on the OD of the seal and pushes onto the guide with a viton rubber to guide contact to keep it on. This is the seal here.
http://www.summitracing.com/parts/drt-26000021
The replacement I want to use has a metal to valve guide interface but a reduced OD to .575".
http://www.jegs.com/i/COMP-Cams/249/518-16/10002/-1
http://www.summitracing.com/parts/cca-518-16
I figure I'll have to replace the seals at some point. Is the metal to metal (bronze guides) going to cause a problem with removal when that time comes?
Anyone else have this problem and solved it with different seals?
I didn't see any evidence of spring control on the locator seats when I had the springs off, so my best guess is that this is a clearance problem.
Called Dart and their tech's admitted that I am not the only one with this problem, but had no suggestions as how to fix the problem.
Thread Starter
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Safety Car
Joined: Apr 2005
Posts: 3,624
Likes: 431
From: Dale City VA
The "metal to metal" of the seal and guide will not cause any problems. The seals are actually "metal clad" and there is a inner rubber coating that grips on the guide.
Your better off with the metal clad Viton seals. They are usually smaller OD so more clearance with the inner springs and they are just better constructed... most all modern OEM valve seals are metal clad Viton.
As for your problem with the Dart supplied seals hitting the inner spring.... it's actually pretty common with off the shelf parts.
Will
Your better off with the metal clad Viton seals. They are usually smaller OD so more clearance with the inner springs and they are just better constructed... most all modern OEM valve seals are metal clad Viton.
As for your problem with the Dart supplied seals hitting the inner spring.... it's actually pretty common with off the shelf parts.
Will
Thread Starter
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
The "metal to metal" of the seal and guide will not cause any problems. The seals are actually "metal clad" and there is a inner rubber coating that grips on the guide.
Your better off with the metal clad Viton seals. They are usually smaller OD so more clearance with the inner springs and they are just better constructed... most all modern OEM valve seals are metal clad Viton.
As for your problem with the Dart supplied seals hitting the inner spring.... it's actually pretty common with off the shelf parts.
Will
Your better off with the metal clad Viton seals. They are usually smaller OD so more clearance with the inner springs and they are just better constructed... most all modern OEM valve seals are metal clad Viton.
As for your problem with the Dart supplied seals hitting the inner spring.... it's actually pretty common with off the shelf parts.
Will
