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Old 09-20-2010, 05:02 AM
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Vortec head screw in stud length?

Hi
I'm going to switch from pressed- to screw in studs on my Vortec heads.

I've decided to go the self aligning rockers route, so it will be studs with no provision for guide plates.
After pulled the original studs, I will thread the holes to 7/16"-14 for screw in studs.

Then my question: I see there are lots of different rocker stud lengths to choose from. Should I just pull one of the studs, measure the lenght and order screw in studs not shorter than this?
Or do I need longer than standard studs when I later will change to roller rockers?

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Old 09-20-2010, 06:17 AM
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Quote:
Originally Posted by staleg
Hi
I'm going to switch from pressed- to screw in studs on my Vortec heads.

I've decided to go the self aligning rockers route, so it will be studs with no provision for guide plates.
After pulled the original studs, I will thread the holes to 7/16"-14 for screw in studs.

Then my question: I see there are lots of different rocker stud lengths to choose from. Should I just pull one of the studs, measure the lenght and order screw in studs not shorter than this?
Or do I need longer than standard studs when I later will change to roller rockers?
Click HERE for the dimensions ARP recommends.

It's necessary in most cases to spot face the boss, but if you are going to use studs w/o the hex, you can omit this. But you may be cutting down the boss for higher lift, anyway.

You want longer than stock studs for roller rockers or longer yet if using stud girdles.
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Old 09-20-2010, 08:10 AM
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Thank you for your answer.

But I don't understand this:
Quote:
Originally Posted by cobalt327
But you may be cutting down the boss for higher lift, anyway.
That I may cut down the VALVE stem boss to achive higher lift, is logical to me, but cutting down the ROCKER stud boss for higher lift?
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Old 09-20-2010, 09:05 AM
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If you use the studs with a hex head on them and guideplates you'll need to cut down the rocker arm stud boss to correct the geometry, otherwise your rocker will sit too high. Some people measure the thickness of the guideplate and hex head, others just wack off .320-.350". There's really not much need to be more precise than that.

I like to use the non-shouldered studs with self aligning rockers- it'll save you some money though some people worry about the side loading on the valve stem...
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Old 09-20-2010, 10:41 AM
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Quote:
Originally Posted by staleg
Thank you for your answer.

But I don't understand this:


That I may cut down the VALVE stem boss to achive higher lift, is logical to me, but cutting down the ROCKER stud boss for higher lift?
Thanks for bringing this to my attention. Let me try to clarify, if I may:

First, I should have said "smaller base circle", not "higher lift", although one usually goes w/the other.

Unless you're going to use guide plates and/or hex'ed studs, it's hopefully not going to be an issue. But I would still mock up the valve train to see if there's a problem w/the clearance of the trunnion of the rocker arm to the top of the stud boss, with the correct length p-rod. What you don't want:

It's hard to see, but the clearance is insufficient- even though the geometry is good.

You can make an adjustable p-rod for this, or there available from Comp, and I believe Manley too, possibly others.




Also, if you were to use G-plates and/or studs w/a hex on the stud the stud boss would need to be spot-faced at least, possibly cut more than just that to allow for the thickness of the plates and the hex- as turbolover said above.

Sorry for the confusion, in any event.

Don't forget to check/correct the pushrod length- don't take for granted a stock length p-rod will provide you w/the correct geometry.
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Old 09-20-2010, 11:09 AM
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If I understand you correct, the bottom of the rocker arm might get i contact with the cast iron on top of the rocker arm boss?

And, yes, I'm planning on using the studs without hex head. No guide plates.
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Old 09-20-2010, 11:21 AM
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Quote:
Originally Posted by staleg
If I understand you correct, the bottom of the rocker arm might get i contact with the cast iron on top of the rocker arm boss?

And, yes, I'm planning on using the studs without hex head. No guide plates.

If that is the case, just pull the studs and tap them for your screw in shoulder-less studs, no spot facing required. I've done it many times, and have work out several taps. BTW Harbor Freight will exchange your set of taps for a different one if they become dull- which is REALLY nice when you live a mile away from one.

You can say what you want about the chinese crap (admittedly most of their stuff is substandard) they sell, their warranty service is GREAT!
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Old 09-20-2010, 11:38 AM
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Quote:
Originally Posted by staleg
...the bottom of the rocker arm might [come in] contact with the cast iron on top of the rocker arm boss?
That is one of the things you will be checking for when you do a mock up of the valve train.

Some others:
  • Springs for installed height
  • Coil bind
  • Seal to spring retainer
  • Retainer to rocker
  • Valve to piston (also both before and after TDC on overlap)
  • Push rod to guide slot in head (if used)
  • Rocker to valve tip (by adjusting guide plates if used)
  • Rocker slot for adequate length (if using stamped/cast rockers w/pivot balls)
  • Proper geometry (push rod length)
  • Rocker/polyloc to valve cover or baffle
Probably something I'm missing. But it has to be physically checked, you should not take it on faith or by figuring it out on paper.
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Old 09-20-2010, 12:02 PM
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Thanks for your informative answers. I have done some homework on the subject, but are stricktly on a theoretical level so far.

The possible rocker arm/stud boss interfenece issue was new for me, and one of the things that are wise to do something about before the studs are fastened.
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Old 09-20-2010, 12:09 PM
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Quote:
Originally Posted by turbolover
I've done it many times, and have work out several taps.
Do you have any item number suggestions? Will Mr Gasket 1076 studs fit the Vortec heads with roller rockers?

http://www.summitracing.com/parts/MRG-1076/
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Old 09-20-2010, 01:55 PM
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Quote:
Originally Posted by staleg
Do you have any item number suggestions? Will Mr Gasket 1076 studs fit the Vortec heads with roller rockers?

http://www.summitracing.com/parts/MRG-1076/
What cam/spring pressure will you be running? 3/8" stud or 7/16"?
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Old 09-20-2010, 03:02 PM
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3/8" studs.

I was thinking of this spring:
http://cgi.ebay.com/ebaymotors/ws/eB...=STRK:MEWAX:IT

-1.265" OD
-.880" ID
-130 Lbs @ 1.790" -Valve Closed, Spring Installed Height
-360 Lbs @ .590" lift (1.210")
-Max lift- .590" w/.250" tip length exh valves or .550 w/ .289" tip length exh valves
-Rate# 358
-Average Coil Bind @ 1.150"

Are told to fit without modifications according to the seller.

And Crane Cams PowerMax hydraulic roller camshaft featured 0.509/0.528-inch intake and exhaust valve lifts combined with 222/230 degrees of duration at 0.050-inch measurements.
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Old 09-20-2010, 03:11 PM
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Quote:
Originally Posted by staleg
3/8" studs.

I was thinking of this spring:
http://cgi.ebay.com/ebaymotors/ws/eB...=STRK:MEWAX:IT

-1.265" OD
-.880" ID
-130 Lbs @ 1.790" -Valve Closed, Spring Installed Height
-360 Lbs @ .590" lift (1.210")
-Max lift- .590" w/.250" tip length exh valves or .550 w/ .289" tip length exh valves
-Rate# 358
-Average Coil Bind @ 1.150"

Are told to fit without modifications according to the seller.

And Crane Cams PowerMax hydraulic roller camshaft featured 0.509/0.528-inch intake and exhaust valve lifts combined with 222/230 degrees of duration at 0.050-inch measurements.
I'm not a fan of mystery springs... You can run those if you want but the is NOTHING special about them. The only unique part is a retainer that is missing the bottom .060". I would just get the springs that are recommended for your cam or the next closest thing from Competition Products- I use their springs more often than any others and they always have worked well.
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Old 09-22-2010, 02:15 AM
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What I find special about them is the fact that they are said to fit the Vortec heads without modification, AND allow lift up to .550"...

Why did Crane cams make the special tool to grind down the diameter on the Vortec head valve boss, if we could achieve the same by using an ordinary spring without the modification?

But I agree with you about "mystery" springs. If this is just an ordinary spring, how do I find the Crane or Comp version of it?
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Old 09-22-2010, 07:18 AM
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Quote:
Originally Posted by staleg
What I find special about them is the fact that they are said to fit the Vortec heads without modification, AND allow lift up to .550"...

Why did Crane cams make the special tool to grind down the diameter on the Vortec head valve boss, if we could achieve the same by using an ordinary spring without the modification?

But I agree with you about "mystery" springs. If this is just an ordinary spring, how do I find the Crane or Comp version of it?
The spring alone will not allow that much lift- it has the potential of that much lift. The boss (or seal) to retainer clearance is still going to be an issue if the OEM retainer and seal is used- regardless of what spring you put in.

The choices are: cutting height from the boss, a change in the retainer, a change in the locks, a change in the seal, a longer valve, or a combination of these options. Along w/a spring change to get the correct specs for the cam being used.
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