SBC Valve seals help!!
Thread Starter
Racer
Joined: Feb 2012
Posts: 261
Likes: 3
From: Clawson Michigan
SBC Valve seals help!!
I have a 1980 Corvette with a 350 gm crate engine that I installed about 5 years ago. It started to smoke at idle and getting worse. I did a compression check and my lowest cyl is 200psi and my highest is 210 psi. The engine has about 1500 miles on it. The engine specs are as follows.
350 cu in
Dart shp 180 heads
Comp Cams hyd roller extream energy 276hr
1.6 scorpion roller rocker arms
Edelbrock performer rpm
Quick fuel 650 double pumper.
Compression is 9.8 to 1
Today I removed 2 valve springs to look at the seals. The seals look good except that the small spring on the seal has rode up and dislodged from the valve seal..any idea why this would happen? The valve ride smooth in the guides as well ..
I will try to post some pics for the experts to look at
https://photos.app.goo.gl/DeNvdcp1w7LdZinJ7
Last edited by Flyinace3; Jun 12, 2018 at 05:02 PM.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
Pull the seals. Get a dial caliper and measure dia and height of surface cut on exterior of guides for the seals. Buy 16 new ones. At least replace the intake seals. Exhausts sometimes dont even get seals. Almost want them to get a little oil.
Last edited by derekderek; Jun 12, 2018 at 08:45 PM.
Drifting
Joined: Dec 2017
Posts: 1,302
Likes: 226
From: PA
I have a 1980 Corvette with a 350 gm crate engine that I installed about 5 years ago. It started to smoke at idle and getting worse. I did a compression check and my lowest cyl is 200psi and my highest is 210 psi. The engine has about 1500 miles on it. The engine specs are as follows.
350 cu in
Dart shp 180 heads
Comp Cams hyd roller extream energy 276hr
1.6 scorpion roller rocker arms
Edelbrock performer rpm
Quick fuel 650 double pumper.
Compression is 9.8 to 1
Today I removed 2 valve springs to look at the seals. The seals look good except that the small spring on the seal has rode up and dislodged from the valve seal..any idea why this would happen? The valve ride smooth in the guides as well ..
I will try to post some pics for the experts to look at
Last edited by vince vette 2; Jun 13, 2018 at 12:12 PM. Reason: Removed photos from OP
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,170
From: Hermosa
I have a set of dart SHP heads that I have since removed from my 350 and am now running AFR heads.
Where to start with those darts?
The valve spring pockets are too shallow. This allows the springs to move around during operation. In my case it dislodged the valve seals on several occasions.
The distance from coil bind when the valve is at full lift is too great. This allows for spring surge and loss of control of the valve and wears on the guides excessively.
The installed height of the assembled heads is all over the place making for inconsistent seat and open pressures.
I would remove all the springs and measure you valve stem deflection at the top of the guide to check for guide wear.
I would also get inside locators for the springs and measure installed height and set them all even or close as possible with a shim set.
If your lucky the guides are not too badly worn yet.
Dart will not admit to an issue with these heads, but it exists.
Where to start with those darts?
The valve spring pockets are too shallow. This allows the springs to move around during operation. In my case it dislodged the valve seals on several occasions.
The distance from coil bind when the valve is at full lift is too great. This allows for spring surge and loss of control of the valve and wears on the guides excessively.
The installed height of the assembled heads is all over the place making for inconsistent seat and open pressures.
I would remove all the springs and measure you valve stem deflection at the top of the guide to check for guide wear.
I would also get inside locators for the springs and measure installed height and set them all even or close as possible with a shim set.
If your lucky the guides are not too badly worn yet.
Dart will not admit to an issue with these heads, but it exists.
Last edited by REELAV8R; Jun 13, 2018 at 12:23 PM.
Thread Starter
Racer
Joined: Feb 2012
Posts: 261
Likes: 3
From: Clawson Michigan
I have a 1980 Corvette with a 350 gm crate engine that I installed about 5 years ago. It started to smoke at idle and getting worse. I did a compression check and my lowest cyl is 200psi and my highest is 210 psi. The engine has about 1500 miles on it. The engine specs are as follows.
350 cu in
Dart shp 180 heads
Comp Cams hyd roller extream energy 276hr
1.6 scorpion roller rocker arms
Edelbrock performer rpm
Quick fuel 650 double pumper.
Compression is 9.8 to 1
Today I removed 2 valve springs to look at the seals. The seals look good except that the small spring on the seal has rode up and dislodged from the valve seal..any idea why this would happen? The valve ride smooth in the guides as well ..
I will try to post some pics for the experts to look at
https://photos.app.goo.gl/DeNvdcp1w7LdZinJ7
As a side note I did change the intake manifold 3 times with 3 different new Edelbrock intakes and about 10 gasket sets later . I used felpro and mr gaskets, gaskets the normal and thick gaskets as well trying to resolve the smoking issue...
Last edited by Flyinace3; Jun 13, 2018 at 12:43 PM.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,170
From: Hermosa
Thanks rev I was hoping you would chime in on this ..I will check the side wear with a dial indicator and the installed spring height... Do the seals I have look the same as what your dart heads had from the factory? I can not tell if the spring is bouncing. I had Steve saanche from total flow set the heads up for me when I bought them. I also ordered a leak down tester and will test each cylinder for the percentage.. I will keep everyone up to date on this... How have the AFR heads been treating you so far?
As a side note I did change the intake manifold 3 times with 3 different new Edelbrock intakes and about 10 gasket sets later . I used felpro and mr gaskets, gaskets the normal and thick gaskets as well trying to resolve the smoking issue...
As a side note I did change the intake manifold 3 times with 3 different new Edelbrock intakes and about 10 gasket sets later . I used felpro and mr gaskets, gaskets the normal and thick gaskets as well trying to resolve the smoking issue...
Night and day difference between the Dart and the AFR heads as far as quality goes. Those advertised 180 Darts are more in the 190+ range.
AFRs dead on 180 cc’s.
darts chamber advertised 64 cc measured closer to 67 cc’s.
Only wish I had bought the AFR first time around. But the Darts did give me the opportunity to learn a bit about porting and practice some. And give me some perspective on middle of the road quality vs good quality manufacturing on heads.
The groove in the shim where the valve spring sits looks to indicate that the spring is moving around a lot.
Last edited by REELAV8R; Jun 13, 2018 at 02:21 PM.
Racer
Joined: Jan 2008
Posts: 295
Likes: 58
From: Arvada Colorado
Your spring dampeners are chewing into the shims. Yes, you more than likely have excessive spring movement. To fix this, I would employ the use of spring locators. These are available from a variety of sources ( Comp Cams, PAC, Manley, etc.). Measure the guide bosses and the spring pockets to find the correct locators. This will fix the valve stem seal issue too.
Thread Starter
Racer
Joined: Feb 2012
Posts: 261
Likes: 3
From: Clawson Michigan
Your spring dampeners are chewing into the shims. Yes, you more than likely have excessive spring movement. To fix this, I would employ the use of spring locators. These are available from a variety of sources ( Comp Cams, PAC, Manley, etc.). Measure the guide bosses and the spring pockets to find the correct locators. This will fix the valve stem seal issue too.
I placed a order for new valve seals and spring locators from summit
COMP Cams 4771-16 - COMP Cams Valve Spring Locators
Dart 26000021 - Dart Valve Stem Seals
Also going to do a leak down test this weekend
Check installed spring height and valve side clearance ..
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Instructor
Joined: Oct 2007
Posts: 124
Likes: 1
From: baltimore ohio
take the springs off of the new seal before you install them, then put them back on
Thread Starter
Racer
Joined: Feb 2012
Posts: 261
Likes: 3
From: Clawson Michigan
My leak down tester came in today ..
I only had enough time to do two cylinders . 4&6 but the results look good to me
Cranking compression is
#4 207 psi
#6 210 psi
Leak down results
#4 8%
#6 10%
I only had enough time to do two cylinders . 4&6 but the results look good to me
Cranking compression is
#4 207 psi
#6 210 psi
Leak down results
#4 8%
#6 10%
Burning Brakes
Joined: Sep 2005
Posts: 1,139
Likes: 109
From: B'ham Alabama
Keep in mind....you can have great compression, (good compression rings), but have a faulty oil ring. In that case, you’d have good compression but could still be burning some oil.
ive seen it several times over the years.
ive seen it several times over the years.
Instructor
Joined: Nov 2008
Posts: 112
Likes: 8
I would guess that the spring came off during assembly. Roll it back in the groove and give it a try. Thats what I'd do. We are talking about a new crate engine. What else could it be?
Last edited by rebel542; Jun 14, 2018 at 11:50 PM. Reason: Add to comment.
Thread Starter
Racer
Joined: Feb 2012
Posts: 261
Likes: 3
From: Clawson Michigan
The smoking issue happened recently. I installed the enengin 5 years ago and I put on about 2000 miles since then. It didn't smoke or use any oil recently.
Thread Starter
Racer
Joined: Feb 2012
Posts: 261
Likes: 3
From: Clawson Michigan
Thread Starter
Racer
Joined: Feb 2012
Posts: 261
Likes: 3
From: Clawson Michigan
almost done with installing valvevspring locators and new seals. This is what I found on about half of them. The leak down test on all the cylinders is between 6 to 10%. I will post more info when I fire her up.
Dr. Detroit
Joined: Mar 2012
Posts: 10,091
Likes: 4,016
From: New Braunfels Texas
Your spring dampeners are chewing into the shims. Yes, you more than likely have excessive spring movement. To fix this, I would employ the use of spring locators. These are available from a variety of sources ( Comp Cams, PAC, Manley, etc.). Measure the guide bosses and the spring pockets to find the correct locators. This will fix the valve stem seal issue too.
Locators are mandatory on just about any head.....or spring locator cups.....
The I.D. locator to me are a better solution for 1.250 and 1.437 springs.......1.550 and 1.625 are fine with a cup as they have a large I.D.
It is crazy how many heads I have pulled apart and they are just using a hardened washer........anyone who would assemble stuff like that needs to be educated because it is just wrong.
Jebby
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,170
From: Hermosa
Shim up the springs so that they are closer to coil bind at full lift as well. This will help prevent spring surge which may also be contributing to unseating those valve guide seals.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,170
From: Hermosa
Yes.....
Locators are mandatory on just about any head.....or spring locator cups.....
The I.D. locator to me are a better solution for 1.250 and 1.437 springs.......1.550 and 1.625 are fine with a cup as they have a large I.D.
It is crazy how many heads I have pulled apart and they are just using a hardened washer........anyone who would assemble stuff like that needs to be educated because it is just wrong.
Jebby
Locators are mandatory on just about any head.....or spring locator cups.....
The I.D. locator to me are a better solution for 1.250 and 1.437 springs.......1.550 and 1.625 are fine with a cup as they have a large I.D.
It is crazy how many heads I have pulled apart and they are just using a hardened washer........anyone who would assemble stuff like that needs to be educated because it is just wrong.
Jebby
You would think that a company that has been around this long would know about such things.
Last edited by REELAV8R; Jun 17, 2018 at 12:55 PM.
Thread Starter
Racer
Joined: Feb 2012
Posts: 261
Likes: 3
From: Clawson Michigan
It's finished so far no smoking which I happy about. This winter I will pull the heads and either get new guides installed or just by afr's and be done with it.
thanks for all the help
thanks for all the help