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Master Fabricator
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Discussion Starter · #1 ·
I was setting up my valvetrain geometry and I wanted to get your opinions.

I think the exhaust is good to go, but the intake side is still to far forward and I only have .008 clearance between the rocker and retainer. I think I am going to need some lash caps.

Exhaust:


Intake:
 

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just gonna throw this out there, but from what i understand, narrow is more important than centered. and those are some wide sweeps, although centered. i made a tool to measure the sweep of the rocker roller throughout different lift points, and i set geometry to what forms the narrowist sweep. dont know if big blocks are different but on my last couple motors i have had the sweep down to about .030. just an opinion though not hard scientific facts.
 

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Master Fabricator
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Discussion Starter · #3 ·
If your valve travel is not centered then you will be loading one side if you valve guides all the time.

I understand what you are saying, but it seems like every company has a different idea of "correct" valvetrain geometry.

For example
Crower:
http://www.crower.com/pdf/08/valvetrain_2.pdf

Comp Cams:
http://compcams.com/Technical/FAQ/ValvetrainGeometry.asp

Lunati:
http://www.lunatipower.com/Tech/Valvetrain/HowToVerifyValvetrainGeometry.aspx

You would think someone could agree on the same thing. Anyone other opinions?
 

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they all make sense in their own way. the thing about the narrow sweep is it has the least wasted motion in my opinion. i was gonna leave u a link to mid-lift but apparantly they are now charging money for their information. but to each his own, and their are a lot of race cars out there with centered sweeps that arent causing problems.
 

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If your valve travel is not centered then you will be loading one side if you valve guides all the time.

I understand what you are saying, but it seems like every company has a different idea of "correct" valvetrain geometry.

For example
Crower:
http://www.crower.com/pdf/08/valvetrain_2.pdf

Comp Cams:
http://compcams.com/Technical/FAQ/ValvetrainGeometry.asp

Lunati:
http://www.lunatipower.com/Tech/Valvetrain/HowToVerifyValvetrainGeometry.aspx

You would think someone could agree on the same thing. Anyone other opinions?
pivot length has a direct relation with lift...anotherwords big lift requires longer rockers...otherwise the geo will never be right.

Of course there are "bandaid" fixes but the valvetrain will never operate at a high rpm for extended periods of time without problems
 

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Master Fabricator
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Discussion Starter · #7 ·
pivot length has a direct relation with lift...anotherwords big lift requires longer rockers...otherwise the geo will never be right.

Of course there are "bandaid" fixes but the valvetrain will never operate at a high rpm for extended periods of time without problems
So can you tell me which you prefer for the correct geometry?
 

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So can you tell me which you prefer for the correct geometry?
the crower pattern..long rockers will keep it narrow, short rockers will make it wider
 

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Master Fabricator
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Discussion Starter · #9 ·
the crower pattern..long rockers will keep it narrow, short rockers will make it wider
I have the stainless rockers from Crower. If they are considered the long ones, beats me.

I already tried that setup, seemed a little too much on the inside by the pattern. I will set it up again and post some photos.
 

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Has anyone ran into the issue, where the rocker tip is tilted at the tip of the valve stem? Even w/ adjustable guide plates? Clearly the rocker studs are drilled incorrectly. Has any one had to fix this problem? anyone.
 

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Has anyone ran into the issue, where the rocker tip is tilted at the tip of the valve stem? Even w/ adjustable guide plates? Clearly the rocker studs are drilled incorrectly. Has any one had to fix this problem? anyone.

I have this issue but i didnt notice till after i have ran it and said
fuck it i have 3 years on the street and many passes at the track at 8000rpm no issues
 

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Best is to get the smallest contact sweep on the tip of valve, where it ends up on valve is less important. That much sweep will kill valve guides and create havoc for valve springs. The comp cams directions are way wrong, dont use em.

If anything look up mid lift tech by Jim Miller
 

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Butch
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Car Nut, I'm going to suggest checking this two ways.

I will assume you have standard height locks.

Lets say your valve lift is .700" lift. Half of that is .350" so this is the number you will want to remember

Now (I use checking springs) you want your valve to be .350" lift, which is half of your total valve lift. Now when Geometry is correct, you will be able to take a straight edge or feeler gauge (.030" as its stiff) and lay on the top of the retainer (which is pretty much the top of the valve stem).

When Geometry is correct the top of the valve stem will be dead center of the fulcrum on the rocker arm at .350" valve lift (half your total valve lift)

Now if your valve tip is too low, adjust the push rod shorter but if its too high adjust the push rod longer.

Now you know your Geometry is correct, you can check the sweep on the end of the valve but don't adjust the push rod bases upon the results of the mark, adjust the push rod based on the Geometry I explained above.

The best way is to take a super thin coating of ARP Moly lube, shows the pattern much better but remember DON'T ADJUST PUSH ROD BASED UPON WEAR PATTERN

If you set up the Geometry the way I said it will be much faster, more accurate and parts will live longer

If you have any questions, post them and if I don't reply PM me
 

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Butch
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Ok, my geometry is perfect, 90* at half lift. But my intake roller rocker tips are tilted at the valve stems. I have adjustable guide plates. there right on. Its clear that the rocker stud bosses were drilled wrong. Has anyone had to fix this problem??? Anyone???
 

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Butch
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Ok, my geometry is perfect, 90* at half lift. But my intake roller rocker tips are tilted at the valve stems. I have adjustable guide plates. there right on. Its clear that the rocker stud bosses were drilled wrong. Has anyone had to fix this problem??? Anyone???
Can you get a pic? Most likely tilted due to push rod angles

Is the rocker sitting on the shank of the stud? You can get different shank lengths
 

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Trmnatr, Dart admitted to drilling the rocker studs wrong. The heads are currently at Dart getting fixed. I tried everything to get the rocker to sit parallel on the stem. It was obious that something else was wrong. Any one who knows how to set up their geometry would have found the same thing. I understand pushrod angles, guide plates and studs. This just was not the case. Tilted rockers at the stem tip are indications that the rocker studs and the valve guides are not in line(parallel).
 

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Butch
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Trmnatr, Dart admitted to drilling the rocker studs wrong. The heads are currently at Dart getting fixed. I tried everything to get the rocker to sit parallel on the stem. It was obious that something else was wrong. Any one who knows how to set up their geometry would have found the same thing. I understand pushrod angles, guide plates and studs. This just was not the case. Tilted rockers at the stem tip are indications that the rocker studs and the valve guides are not in line(parallel).
I would have to see it, The way I posted to get the Geometry is the "correct" way. What your stating is the rocker is sitting at 5 and 11 instead of 6 and 12?????

Dart's do not sit perfectly straight, see pic below. But if yours are off any more than the pic below, it is an issue. These rockers were set up using the method I posted and the wear patterns were PERFECT when checked after the MID LIFT was correct.

PS: Notice how the rockers are titled even tho Geometry is correct, any more tilt and I would agree there is a problem
 

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Butch
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