A valve seal question
Thread Starter
Drifting
Joined: Apr 2003
Posts: 1,323
Likes: 2
From: Castle Hills Texas
A valve seal question
I am having a reoccuring problem with the valve seals on cylinder #6 on my 350. I had both seals for #6 replaced about 6-8 months ago. Well, the Vette starting doing an intermittent miss after a little 180 mile road trip. I went straight to #6 an pulled the plug and sure enough it is really oil fouled. The boot of the ignition wire was really soft as well and actually ripped when I tried to place it back on the plug. I put a new boot on the wire and replaced the plug for now and I am firing on all eight again. My question is this, is there any correlation to valve seals wearing out faster on #6 since the EGR is right above that cylinder? I realize that I should have been able to get way more than 6-8 months out of the seals. What is a good seal to replace with? I am running AC Delco Rapid Fire platinum #2 plugs all the way around if that info. helps out. The engine is stock with all the emissions crap still on it other than the CAT and I have gone to true duals. Thanks!
Drifting
Joined: Aug 2003
Posts: 1,565
Likes: 2
From: somewhere between heaven and hell WI
Re: A valve seal question (CVT4ME)
I just put new valve seals in the 77 and noticed it only had the small O-rings on it. So I also put the optional rubber boot that covers the bottom of the seal. Not sure if this helps.
If not my guess would be that the head needs to be looked at. That passage must be damaged in some way that it dosent fit the valve properly.
just a guess tho...
If not my guess would be that the head needs to be looked at. That passage must be damaged in some way that it dosent fit the valve properly.
just a guess tho...
Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
Re: A valve seal question (CVT4ME)
It's time to remove the EGR system. (I can tell by now that your fantasy of keeping it more or less stock is fading...thank goodness!)
Tuesday!
Tuesday!
Thread Starter
Drifting
Joined: Apr 2003
Posts: 1,323
Likes: 2
From: Castle Hills Texas
Re: A valve seal question (ffvetteman)
Thanks for the reply ffvetteman. I have had the stem and guide tolerances checked before on this cylinder and all is good. The engine is just now about to turn 43K miles, so I would think the valves and the heads are probably in pretty good shape. I was always under the impression that the little "umbrella" type seals were part of the standard set up. Am I mistaken on this?
Page, I have never really had a "fantasy" of keeping this beast stock...190 horses?....who would? It just costs money to make these changes so I am doing it slowly. I would love to do the head/cam swap at some point but I will have to continue to save my nickels. Hope to be out Tuesday, though it may be in my buddies borrowed Saturn. I have been driving his Saturn while he is on the road with Journey, just to keep it running. The Vette has been getting a long extended break which I am eager to end if the damn rain would ever let up. I feel like I am back in Seattle.
Page, I have never really had a "fantasy" of keeping this beast stock...190 horses?....who would? It just costs money to make these changes so I am doing it slowly. I would love to do the head/cam swap at some point but I will have to continue to save my nickels. Hope to be out Tuesday, though it may be in my buddies borrowed Saturn. I have been driving his Saturn while he is on the road with Journey, just to keep it running. The Vette has been getting a long extended break which I am eager to end if the damn rain would ever let up. I feel like I am back in Seattle.
Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
Re: A valve seal question (CVT4ME)
Umbrella seals are aftermarket. And they are better than the o-ring type seals. This is speculation, but it's possible you have a blocked EGR valve (they have a habit of doing that), which is overheating. Pull that sucker and put a block-off plate on there.
See ya Tuesday, rain or shine, Saturn or Vette!
See ya Tuesday, rain or shine, Saturn or Vette!
Thread Starter
Drifting
Joined: Apr 2003
Posts: 1,323
Likes: 2
From: Castle Hills Texas
Re: A valve seal question (page62)
Hey Page, can I buy a block off plate somewhere or am I going to have to bribe some metal worker with boat loads of alcohol to have one fab'd up?
Melting Slicks
Joined: Oct 2001
Posts: 2,065
Likes: 1,395
From: Halifax, Nova Scotia, Canada
Re: A valve seal question (CVT4ME)
A few years ago I had a friend that had one plug that would foul with oil.
After a few months he finally discovered the problem. It had a 350 with Auto trans. The modulator valve (vacuum controlled) was defective. The engine was "sucking" trans fluid thru the vacuum line.
The vacuum line on the intake is near one cyl. I don't remember which one.
However if you have a 4 speed, disregard this post.
Barry
After a few months he finally discovered the problem. It had a 350 with Auto trans. The modulator valve (vacuum controlled) was defective. The engine was "sucking" trans fluid thru the vacuum line.
The vacuum line on the intake is near one cyl. I don't remember which one.
However if you have a 4 speed, disregard this post.
Barry
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Drifting
Joined: Apr 2003
Posts: 1,323
Likes: 2
From: Castle Hills Texas
Re: A valve seal question (page62)
So, I would assume that you just pop it off, slap on the plate with appropriate gasket and make sure that vacuum is still routed to the necessary places. Is there anything else to keep in mind, like air/fuel ratios or anything of that nature?
Le Mans Master
Joined: Jan 2003
Posts: 6,575
Likes: 1
From: Tuttle OK
Cruise-In VIII Veteran
Re: A valve seal question (CVT4ME)
I suspect your fouling problem may be more than a plugged EGR valve. In effect, a block off plate is the same thing, isn't it? I have mine blocked off and have no problems from it.....
I recently changed heads because because of a loss of compression and found that mine had cracked. The compression loss was a burned valve, but both of the cylinders that were cracked had a lesser compression. They were very small cracks, but enough.
During the process, I discovered that those of us with blue engines have lesser heads, same/similar performance, just lightened up - less iron, quicker to crack. I believe that the engine is about 40 pounds lighter. In any event, although you do not have many miles or much time on your heads, it may be something to check.
I recently changed heads because because of a loss of compression and found that mine had cracked. The compression loss was a burned valve, but both of the cylinders that were cracked had a lesser compression. They were very small cracks, but enough.
During the process, I discovered that those of us with blue engines have lesser heads, same/similar performance, just lightened up - less iron, quicker to crack. I believe that the engine is about 40 pounds lighter. In any event, although you do not have many miles or much time on your heads, it may be something to check.
Thread Starter
Drifting
Joined: Apr 2003
Posts: 1,323
Likes: 2
From: Castle Hills Texas
Re: A valve seal question (Avette4me)
I am sure that the EGR is not the culprit here either, in fact, I think my EGR works as advertised and is not plugged. I would bet money on a valve seal gone wrong...again. The reason that I bring up the EGR query is that it seems that something caused that cylinder (#6) to get wicked hot, enough to weaken the rubber on the ignition wire boot. The boot is not really close enough to the manifolds to be as damaged as this one was. So, I was curious to see if the EGR, with it pumping hot exhaust gases back into the engine, could cause the failure of the seals as it sits right over #6.
The last time the seals were replaced on #6, the guy gave everything a good going over and nothing was visibly wrong with the heads. A compression test was also done at that time as well and all was within spec. Of course, if these heads ever have to be pulled to really be gone through, than a better head will go back on. I have heard the head stories with these stock L-48 engines.
The last time the seals were replaced on #6, the guy gave everything a good going over and nothing was visibly wrong with the heads. A compression test was also done at that time as well and all was within spec. Of course, if these heads ever have to be pulled to really be gone through, than a better head will go back on. I have heard the head stories with these stock L-48 engines.
Le Mans Master
Joined: Jan 2003
Posts: 6,575
Likes: 1
From: Tuttle OK
Cruise-In VIII Veteran
Re: A valve seal question (CVT4ME)
just curious, what kind of compression were ya running.
I love that test, it can tell you which direction to head and it is cheap...
I love that test, it can tell you which direction to head and it is cheap...
Thread Starter
Drifting
Joined: Apr 2003
Posts: 1,323
Likes: 2
From: Castle Hills Texas
Re: A valve seal question (Avette4me)
I want to say that all the cylinders were in the 140ish range...or was it 160ish. I can't really remember. Being that it is a stock L-48, probably 140ish. I remember that they were all very close with none in particular being out of whack in the group.
good compression....
Safety Car
Joined: Jun 2001
Posts: 4,004
Likes: 2
From: Severna Park Md
Re: A valve seal question (Avette4me)
Check out Crane positive seals PN 99819 or if your guides have been replaced with different diameter ones you may need a different number. Bottom line is there are positive locking seals available that lock down over the guide and dont travel with the stem. They have worked great for me. You need to determine you valve guide diameter in order to get the correct ones. On one engine I had, the exhaust valve guides had been replaced but not the intakes. On that engine I needed different PN's for exhausts and intakes. These are not umbrella seals. They are called positive locking seals.
Thread Starter
Drifting
Joined: Apr 2003
Posts: 1,323
Likes: 2
From: Castle Hills Texas
Re: A valve seal question (Jvette73)
Hey Jvette, thanks for the post. I will check out the Crane seals you speak of. If they are white with a metal band around them, then I think I have seen them on the JEGS site. I will double check though.
Does anyone know the stock diameter of the guides for a 1980 L-48 head? I just looked over on the jegs site and they say that the particular part number mentioned is discontinued. The one that is listed says something about needing to machine the valve guide boss for installation. I believe I saw another one that does not require machining that is also a positive stop seal but I don't know the number. I will research further once I get the diameter info.
[Modified by CVT4ME, 9:33 PM 6/28/2004]
Does anyone know the stock diameter of the guides for a 1980 L-48 head? I just looked over on the jegs site and they say that the particular part number mentioned is discontinued. The one that is listed says something about needing to machine the valve guide boss for installation. I believe I saw another one that does not require machining that is also a positive stop seal but I don't know the number. I will research further once I get the diameter info.
[Modified by CVT4ME, 9:33 PM 6/28/2004]
Safety Car
Joined: Jun 2001
Posts: 4,004
Likes: 2
From: Severna Park Md
Re: A valve seal question (CVT4ME)
The beauty of the 99819's was they didnt require machining of the guides to install. They are rubber with a metal ring at both ends to hold them down over the guides and the other ring squeezes the stem. The white ones are good too and ive used them. But the guides may need to be machined in order to accept them depending on what sizes are available. Machining the guide can be done easy. They sell a tool for the job. There are different size tools though so you need to get the right one relative to the size seals you plan to use. The tool fits on a standard drill has a pilot guide that that rides in the guide bore. The cutter then shaves the outside of the guide down to size. Some tools also have a top cutter built in to trim down the hieght of the guide to increase clearence if needed for high lift applications. Its no problem using the tool with the head on car. Just cover up any holes to prevent the shavings from falling in and vacuum them out when done cutting. Hopefully you can find positive seals that fit your guides without cutting. To be positive about your guide diameter you should pull the cover and valve springs and measure. It sounds like a hastle but once you get these positive seals in place your problem should be solved.
Safety Car
Joined: Jun 2001
Posts: 4,004
Likes: 2
From: Severna Park Md
Re: A valve seal question (CVT4ME)
99819 is a Crane # but these rubber seals are most likely made by a different company such as Gulf Rubber or maybe another. i had a few laying around and checked them for #'s. They have printed on them 3013. I did a search and found them being used on a motorcycle application. they,re not made by Crane and im sure they're still out there. Its just a matter of tracking them down. Try a search of rubber valve seals using the #3013. Ill post a pic in a few of what they look like.
[Modified by Jvette73, 6:59 AM 6/29/2004]
[Modified by Jvette73, 6:59 AM 6/29/2004]