When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
These are cylinders #3 and #1 intake in the pictures.
This first one is #3 intake
This is #3 intake and exhaust. Exhaust on the right.
This is #1 intake.
As you can see by the witness marks on the valve stems that the roller runs directly over the center of the valve tip.
Problem is that both #1 and #3 intake valves have what seems to be excessive clearance now. Measured .003" on #3 slop at the top of the valve guide using a dial run-out mic. and then .004" of slop on #1 intake.
I measured several other valves and the rest run from .001" to .0015" of slop at that location.
So what is going on here?
I seem to remember Straub mentioning that the roller wear should favor one side of the valve stem over the other, but don't remember which side. When I assembled them I strived for centered on the stem and minimum width.
If my geometry is bad shouldn't I be seeing similar wear on all the valve guides?
I did notice that both of the intakes with the worn guides had push rods that I could see had been rubbing on the head as they passed though to the lifter. Could this be the problem?
As you can see from the pics I'm using the self centering stamped roller tip rockers. How would you go about establishing the center of rotation for these rockers to get your 90* at mid lift reference point?
Is the wear patch width giving you some clue as to the push rod length being incorrect?
As you can see from the pics I'm using the self centering stamped roller tip rockers. How would you go about establishing the center of rotation for these rockers to get your 90* at mid lift reference point?
Is the wear patch width giving you some clue as to the push rod length being incorrect?
You have a ball instead of a bearing. The pivot point is the center of the ball; if you can imagine that on the side of the rocker, that's your point of reference.
The wear pattern or "sweep" looks wide and the fact that you say you have excessive guide wear tells me your geometry is probably off. It also looks like you've been experiencing some valve float.
Last edited by scott foxwell; 10-19-2014 at 03:38 PM.
Dont really see what your saying. I see a nice wear patch over the center of vlv tip (just love those comp mag rockers). And i believe i can see the vlvs have rotated some also - normal. Theres no way a rocker tip can stay over the center of a vlv tip. Idealy u want the rocker tip to move from one side of vlv tip center when on base circle then cross the center of vlv tip to an equal distance to the other side of vlv tip center when at mid-lift then return back to starting location at full lift. Ideally u want a 90 degree geometry of vlv stem and rocker centerline at some point (sorry i dont recall but its in the Chevy Power Manual somewhere). Reality is close is good enough for a street engine.
I would have to question what your guide clearance was originally? So what brings up this issue in the first place? Smoking oil? Just checking vlv train health there Doc?? Im sure u know if it aint broke dont fix it. Hey its a Chevy.
You have a ball instead of a bearing. The pivot point is the center of the ball; if you can imagine that on the side of the rocker, that's your point of reference.
The wear pattern or "sweep" looks wide and the fact that you say you have excessive guide wear tells me your geometry is probably off. It also looks like you've been experiencing some valve float.
Ok Scott I like the video you made and it seems like a really good way to get the geometry right.
That being said it does not work with these rockers. I got right down on that head, rocked that rocker back and forth to establish the center of roatation, marked it drew a line and followed your directions to the "t". 3/8 studs .o42" per turn .549 lift total half that .2745" which is 6.5 turns on the nut from 90* on the rocker.
That barely engages the locking nut onto the stud.
But ok moving on. Adjusted the adjustable push rod to meet the ball socket on the rocker.
Have installed checker springs so as to not compress the springs in the lifters.
Using your method the rocker tip runs off the end of the valve stem on the exhaust side. Waayy too long. Came up with 7.350" push rods.
Currently I am running 7.050" push rods with 1/2 turn preload.
So I decided to just start at 7.100 " and work my way up to see what gave the best results.
My current set up gives a .075" swath on the rocker tip.
At 7.100" I got .075" again
Tried 7.150". I then got .065" wide patch but it is now moving toward the exhuast side of the head.
Tried 7.200" and got the narrowest patch. .050"
But now definately towards the exhaust side of the head.
Current 7.050" on the right. 7.100" on the left
7.150" pushrod with .065 patch.
7.200" push rod with .050" patch.
So should I be favoring the exhaust side of the head in order to get the narrowest patch or centered and accept a wider patch?
Dont really see what your saying. I see a nice wear patch over the center of vlv tip (just love those comp mag rockers). And i believe i can see the vlvs have rotated some also - normal. Theres no way a rocker tip can stay over the center of a vlv tip. Idealy u want the rocker tip to move from one side of vlv tip center when on base circle then cross the center of vlv tip to an equal distance to the other side of vlv tip center when at mid-lift then return back to starting location at full lift. Ideally u want a 90 degree geometry of vlv stem and rocker centerline at some point (sorry i dont recall but its in the Chevy Power Manual somewhere). Reality is close is good enough for a street engine.
I would have to question what your guide clearance was originally? So what brings up this issue in the first place? Smoking oil? Just checking vlv train health there Doc?? Im sure u know if it aint broke dont fix it. Hey its a Chevy.
You don't miss a trick do you Cardo
Yep what started me down this road is a little bit of smoke out the left side pipe at idle.
Rings and compression good so moved to valve guide seals. Seal on #3 and #1 intake were worn and I had a couple extra so replaced them, but that is not the root cause.
I didn't check the slop of the valve guide at install but from a comparison of other valve guides on the engine I can comfortably say that these ones are excessive.
So why???
Bad geometry is the first thing that comes to mind. Thought I had that figured out, but maybe I missed something.
So that's where I'm at now. Trying to figure out why.
I remember reading that if geometry is poor that you will also not get full lift on the valve.
So decided to recheck that. I measured .561" of lift .549 is the advertised for the cam with 1.6RR. So I guess that is good unless excessive lift indicates poor geometry as well.
My guess is that it is hard to be exact on that measurement once installed or maybe rocker ratio isn't exactly 1.6 or the cam specs are not perfect.
Ok Scott I like the video you made and it seems like a really good way to get the geometry right.
That being said it does not work with these rockers. I got right down on that head, rocked that rocker back and forth to establish the center of roatation, marked it drew a line and followed your directions to the "t". 3/8 studs .o42" per turn .549 lift total half that .2745" which is 6.5 turns on the nut from 90* on the rocker.
That barely engages the locking nut onto the stud.
But ok moving on. Adjusted the adjustable push rod to meet the ball socket on the rocker.
Have installed checker springs so as to not compress the springs in the lifters.
Using your method the rocker tip runs off the end of the valve stem on the exhaust side. Waayy too long. Came up with 7.350" push rods.
Currently I am running 7.050" push rods with 1/2 turn preload.
So I decided to just start at 7.100 " and work my way up to see what gave the best results.
My current set up gives a .075" swath on the rocker tip.
At 7.100" I got .075" again
Tried 7.150". I then got .065" wide patch but it is now moving toward the exhuast side of the head.
Tried 7.200" and got the narrowest patch. .050"
But now definately towards the exhaust side of the head.
Current 7.050" on the right. 7.100" on the left
7.150" pushrod with .065 patch.
7.200" push rod with .050" patch.
So should I be favoring the exhaust side of the head in order to get the narrowest patch or centered and accept a wider patch?
Yes...narrowest sweep pattern is what you're after regardless of location on the valve tip (within reason of course). It's not uncommon for the sweep to be on the ex side of the valve tip. Your last picture looks very good.
Yes...narrowest sweep pattern is what you're after regardless of location on the valve tip (within reason of course). It's not uncommon for the sweep to be on the ex side of the valve tip. Your last picture looks very good.
That is very interesting. It flies in the face of most everything I've read. Why is this not more commonly known?
That is very interesting. It flies in the face of most everything I've read. Why is this not more commonly known?
Good question and not one I have an answer for except to say that if something is repeated often enough it becomes truth, no matter how wrong it is. It's one of the reasons we did the video.
Proper geometry (rocker 90* to the valve at mid lift) will yield minimum sweep, or minimum sweep will yield proper geometry. One is a direct result of the other.
Good question and not one I have an answer for except to say that if something is repeated often enough it becomes truth, no matter how wrong it is. It's one of the reasons we did the video.
Proper geometry (rocker 90* to the valve at mid lift) will yield minimum sweep, or minimum sweep will yield proper geometry. One is a direct result of the other.
Even the published materials I have state centered sweep.
I'll give 7.200" rods a shot, apparently what I have now is not optimum for wear. I'll have to check lift with that length see how it does.
So how can you tell valves have floated? Is it the slight galling seen on the tip? I suspect the same after seeing the valve spring shims.
Maybe time for beehive springs or a lower max RPM.
Even the published materials I have state centered sweep.
I'll give 7.200" rods a shot, apparently what I have now is not optimum for wear. I'll have to check lift with that length see how it does.
So how can you tell valves have floated? Is it the slight galling seen on the tip? I suspect the same after seeing the valve spring shims.
Maybe time for beehive springs or a lower max RPM.
The patterns on some of your valve tips show signs of unusual wear. It may just be due to the valve train issues. Anytime you see a bow tie or star looking pattern, its a sign of excessive movement and instability.
Let me ask...is this a hyd. cam or solid?
I'm not a fan of beehive springs. If you ever break one you'll drop the valve into the cylinder. With a single/damper or dual spring, at least you have something that will hold the valve up.
I think we have similar combos. Comp cams 224-230 hyd roller 1.6 roller rockers lift is .535 .544. My push rod length is 7.266.
I am also experiencing smoke at idle out of the passenger side. I'm hoping its do to a intake change gasket issue .
I switched to victor Jr and 650 dp
I did have sealing issues with the first intake as well think it was on and off 4 times in the first week. The gasket seems to always sit too low after its torqued. Felpro 1205.
The patterns on some of your valve tips show signs of unusual wear. It may just be due to the valve train issues. Anytime you see a bow tie or star looking pattern, its a sign of excessive movement and instability.
Let me ask...is this a hyd. cam or solid?
I'm not a fan of beehive springs. If you ever break one you'll drop the valve into the cylinder. With a single/damper or dual spring, at least you have something that will hold the valve up.
Good point on the valve springs. This is a hydraulic roller cam. Howard's roller lifters, claim that they are good to 6500 rpm. Heads are shaved .030" so I expected to be on the shorter end of push rod length.
I gave my specs to Dart. Tech says should be good to 6000 rpm. I don't exceed that.
Could it be I'm getting some bad harmonics at certain rpm's?
Good point on the valve springs. This is a hydraulic roller cam. Howard's roller lifters, claim that they are good to 6500 rpm. Heads are shaved .030" so I expected to be on the shorter end of push rod length.
I gave my specs to Dart. Tech says should be good to 6000 rpm. I don't exceed that.
Could it be I'm getting some bad harmonics at certain rpm's?
Bad geometry can cause all sorts of harmonic issues. Get that fixed and see how it runs. May be a whole new ball game.
Be sure to add .05" to your pushrod length to allow for lifter preload.
Bad geometry can cause all sorts of harmonic issues. Get that fixed and see how it runs. May be a whole new ball game.
Be sure to add .05" to your pushrod length to allow for lifter preload.
When I check the sweep I have tightened the nut as I would when running. Pushrods contact plus 1/2 turn. This would account for the preload wouldn't it ? Or are you saying add .050 to the 7.200" even with the 1/2 turn added?
Think I may need some new .015 valve spring shims. These ones are really beat up now.
When I check the sweep I have tightened the nut as I would when running. Pushrods contact plus 1/2 turn. This would account for the preload wouldn't it ? Or are you saying add .050 to the 7.200" even with the 1/2 turn added?
If you're sure you're not collapsing your lifter now when you check your pattern, then whatever pushrod length you're coming up with you need to add .050" for the preload. How ever many turns you're at now the pattern looks good.
If you want to give me a call tomorrow I can go over this with you in person...maybe clear up some of the confusion and make sure you're getting this right. 423 391 7774. Best to only do this once and I'm sure its a little difficult trying to follow this in writing.
If you're sure you're not collapsing your lifter now when you check your pattern, then whatever pushrod length you're coming up with you need to add .050" for the preload. How ever many turns you're at now the pattern looks good.
If you want to give me a call tomorrow I can go over this with you in person...maybe clear up some of the confusion and make sure you're getting this right. 423 391 7774. Best to only do this once and I'm sure its a little difficult trying to follow this in writing.
Latest results with valve sweep no pre-load and checker springs
Using 7.250 length. .060" wide sweep.
7.300 length. .050" sweep
7.350 length. .050 sweep
I think .050' is the min sweep. 7.350 is only .080" from the exhaust side of the valve tip at the end of it's movement and the 7.300 is .090" from the edge at the end of it's sweep.
So 7.300 seems to fit the bill for min sweep. 7.250 however is .110" from edge of the valve and has a .060" sweep.
10-19-2014, 10:32 AM
Valve train geometry problem or something else??
