Machining for guideplates
Thread Starter
Drifting
Joined: Mar 2001
Posts: 1,396
Likes: 7
From: Indiana
Machining for guideplates
I will be removing my heads during my cam swap today in order to replace Permaseal head gasket with steel shim type for added compression. While I'm at it, I will be installing some guideplates. Does anyone happen to know the angle of the rocker stud boss pad in realtion to the bottom surface of the head? I can probably get it close with a protractor, but thought I could save time if someone already knows this. How about the push rod slot angle?
Tom
Tom
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 279
From: Olmsted Falls, Ohio
Re: Machining for guideplates (tsw71)
Any compentent machine shop will machine the tops of the rocker pedestal down for guideplates for about $50. All you need to take off is the thickness of the guildeplate (maybe 1/8"). Unless you are going to 1.6 ratio rockers you should not have to worry about the pushrod slot. If you are using push-in rocker studs, you should have the pedestals drilled and tapped for screw-in studs.
Thread Starter
Drifting
Joined: Mar 2001
Posts: 1,396
Likes: 7
From: Indiana
Re: Machining for guideplates (KenSny)
Yeah, I had considered just taking them somewhere for this, but as a tool and die maker, I just can't bring myself to pay someone to do what I can easily do myself. I have access to one hell of a set of tools and machines, and thought it would be fun to do myself.
As far as the pushrod slots go, I bolted the plates on to see if it would work without opening up the holes, but unfortunatley, it will cause binding unless I open up the existing puchrod slots.
As far as the pushrod slots go, I bolted the plates on to see if it would work without opening up the holes, but unfortunatley, it will cause binding unless I open up the existing puchrod slots.
Burning Brakes
Joined: Jan 2001
Posts: 1,004
Likes: 16
From: Gainesville, Florida
Re: Machining for guideplates (KenSny)
I dug out the old "How to Hot Rod Small-block Chevys" book (1976) because I remembered seeing some side view schematics of the various SB heads and thought maybe it would provide some info on the stud bosses. Unfortunately, it didn't.
But in the Screw-In Rocker Arm section, it says "...pull the old studs out of the heads and then have the stud bosses milled .250 for Chevy studs w/o guideplates; .320 for production studs w/guideplates; or .410 inch for Mr. Gasket studs without guideplates. Be sure to mill the sud bosses BEFORE tapping the existing holes to 7/16-14 NC ....".
So I guess .320 is the magic number for the amount to remove. As to the angle, can you setup the angle of milling machine/drill press (if using a spot facer) to match the same angle as the stud? That should give you the proper guideplate surface angle.
Mark
But in the Screw-In Rocker Arm section, it says "...pull the old studs out of the heads and then have the stud bosses milled .250 for Chevy studs w/o guideplates; .320 for production studs w/guideplates; or .410 inch for Mr. Gasket studs without guideplates. Be sure to mill the sud bosses BEFORE tapping the existing holes to 7/16-14 NC ....".
So I guess .320 is the magic number for the amount to remove. As to the angle, can you setup the angle of milling machine/drill press (if using a spot facer) to match the same angle as the stud? That should give you the proper guideplate surface angle.
Mark
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 279
From: Olmsted Falls, Ohio
Re: Machining for guideplates (mdsmith)
.320 seems like a good number if you currently have press-in studs. You need to take into account the thickness of the guideplate and the extra height the hex-head will add in this case.
If you already have hex-head studs installed then you don't need to mill off as much.
If you already have hex-head studs installed then you don't need to mill off as much.
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 279
From: Olmsted Falls, Ohio
Re: Machining for guideplates (mdsmith)
.320 seems like a good number if you currently have press-in studs. Because you need to take into account the thickness of the guideplate and the extra height the hex-head will add in this case.
If you already have hex-head studs installed then you don't need to mill off as much.
If you already have hex-head studs installed then you don't need to mill off as much.
Burning Brakes
Joined: Mar 2001
Posts: 1,211
Likes: 5
From: Nashville TN
Re: Machining for guideplates (tsw71)
Keep in mind that while your heads are off you might want to have the valves cut, and most importantly the heads inspected for cracks. Spend the money on the correct valve springs for your cam.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
5 Best & 5 Worst Corvette Daily Drivers
Joe Kucinski
The Headlights of Every Corvette Generation Explained
Joe Kucinski
5 Best & 5 Most Overrated Corvette Track Packages of All Time!
Joe Kucinski
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
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
Thread Starter
Drifting
Joined: Mar 2001
Posts: 1,396
Likes: 7
From: Indiana
Re: Machining for guideplates (dman535)
Sorry guys :bb I should have included my sig or mentioned that these are 1 year old S/R torquers with hex style screw in studs. I will only need to mill off the thickness of the guideplates from the bosses.
MdSmith, I know what you mean about those sketches. I have a couple old Chevy Power books that have incredibly detailed drawings of factory heads including dimensions for porting and other mods, BUT not a single angle in called out on any of them. I guess it must be top secret stuff or they were too cheap to have someone throw in the extra dimensions.
It shouldn't be too bad finding the correct angle. The mill I will be using can do any angle up to 45 deg. Of course, if I go that far, I will need to add a welder to my shops inventory :D
dman535, I am planning on using the springs that are currently installed. These are only 1 year old and the pressure specs match my cam perfectly, and will also allow up to .560" lift just in case this .495" lift cam isn't enough to make it run good.
Thanks for the help guys, Tom
MdSmith, I know what you mean about those sketches. I have a couple old Chevy Power books that have incredibly detailed drawings of factory heads including dimensions for porting and other mods, BUT not a single angle in called out on any of them. I guess it must be top secret stuff or they were too cheap to have someone throw in the extra dimensions.
It shouldn't be too bad finding the correct angle. The mill I will be using can do any angle up to 45 deg. Of course, if I go that far, I will need to add a welder to my shops inventory :Ddman535, I am planning on using the springs that are currently installed. These are only 1 year old and the pressure specs match my cam perfectly, and will also allow up to .560" lift just in case this .495" lift cam isn't enough to make it run good.
Thanks for the help guys, Tom
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 279
From: Olmsted Falls, Ohio
Re: Machining for guideplates (tsw71)
I've got a set of Torquers setting on the bench now that I'm rebuilding, I just got them back from bead blasting. I was thinking of guideplates also, but if you look at where the guideplate would be compared to the pushrod slots in the head, you can see that these slots are taking the place of guideplates. In fact, the slots are pretty close to the stock pushrod diameter. All I'm going to do is use hardened pushrods forget about the guideplates. Yes, I know that the L82 used guideplates, but the pushrod slots are different and therefore at high rpms you might have some pushrod flex that could be corrected with guidplates.
Another thing. It's not "super" critical to get the exact angle of the rocker pedestal when milling it down. Think about how the rocker fulcrum (sp?) acts on the stud and you can see a slight "mis-angle" will be taken up when you adjust the rockers...
Have fun.
Another thing. It's not "super" critical to get the exact angle of the rocker pedestal when milling it down. Think about how the rocker fulcrum (sp?) acts on the stud and you can see a slight "mis-angle" will be taken up when you adjust the rockers...
Have fun.
Thread Starter
Drifting
Joined: Mar 2001
Posts: 1,396
Likes: 7
From: Indiana
Re: Machining for guideplates (KenSny)
I agree that the guideplates are usually not needed, but a few of my slots have been getting wider. When I installed my heads last year, I used stock type pushrods. These soft pusrods were flexing slighly and began widening the pushrod hole in the head. This caused one of the rockers to slide off of the valvestem :eek: and also caused the rocker to begin sawing through the rocker stud. I have since replaced puahrods with hardened chrome moly type to solve the problem and get me by until I put on the guideplates. What's even stranger is that this little problem was happening with the other heads that were on before these. In fact, that is why I finally decided to get new heads intead of modifing my old fuelies that the Torquers replaced.It seems very unusual to be seeing this again with these fairly new heads.
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 279
From: Olmsted Falls, Ohio
Re: Machining for guideplates (tsw71)
Ouch! Sounds like something went wrong and is just migrating to the new heads. Have you looked at that lifter or camshaft lobe to see if it is damaged?
For the small difference in price I always use hardened pushrods, even without guideplates, better wear and probably less flex.
I'm going to install 1.52 roller tip rockers on mine along with the hardened pushrods. Since these heads are used I'm going to replace the springs since I don't know what kind of life they have had and one seems to be shorter (maybe gone flat?) than the others. But I agree that the World springs if new, have very good specs.
New Cam, Heads, Intake, & Carb is this winter's project for me.....
For the small difference in price I always use hardened pushrods, even without guideplates, better wear and probably less flex.
I'm going to install 1.52 roller tip rockers on mine along with the hardened pushrods. Since these heads are used I'm going to replace the springs since I don't know what kind of life they have had and one seems to be shorter (maybe gone flat?) than the others. But I agree that the World springs if new, have very good specs.
New Cam, Heads, Intake, & Carb is this winter's project for me.....
Thread Starter
Drifting
Joined: Mar 2001
Posts: 1,396
Likes: 7
From: Indiana
Re: Machining for guideplates (KenSny)
I'm heading over to my shop now to machine the bosses down. The cam that I pulled out yesterday does look a little suspect as do the lifters. I will mic the cam to see if it is as bad as it appears to be. I'm not sure if you saw my post last week regarding my disappointing dyno run, but things appear to be adding up now. I will post my results later. This should make a good example of what happens to new cams with slightly used lifters installed (it's a long story :bb )
It certainly sounds like you are going about it the right way. I would like to add those 1.52 rockers too, but I have spent enough for this month already. I will try to talk my brother in law into letting me "borrow" ;) his new set that is just sitting in a box waiting for a engine . As to the pushrods, I agree. I am running the comp cams 1.52 roller tip rockers with the hard pushrods without guiedplates in my streetrod. They have worked pefectly for many years.
I have always use nothing but the best in my streerod, but shamefully have done thing the cheap way with my Vette in the past. Not anymore. As always, ya get whatcha pay for.
It certainly sounds like you are going about it the right way. I would like to add those 1.52 rockers too, but I have spent enough for this month already. I will try to talk my brother in law into letting me "borrow" ;) his new set that is just sitting in a box waiting for a engine . As to the pushrods, I agree. I am running the comp cams 1.52 roller tip rockers with the hard pushrods without guiedplates in my streetrod. They have worked pefectly for many years.
I have always use nothing but the best in my streerod, but shamefully have done thing the cheap way with my Vette in the past. Not anymore. As always, ya get whatcha pay for.
Le Mans Master
Joined: Mar 1999
Posts: 6,744
Likes: 1
From: delmont pa
Cruise-In I Veteran
Cruise-In II Veteran
Re: Machining for guideplates (tsw71)
if you install the guide plates you must also enlarge the stock pushrod slots with a 7/16 dia reamer for clearance or you will have a bind on the pushrods. :chevy
Thread Starter
Drifting
Joined: Mar 2001
Posts: 1,396
Likes: 7
From: Indiana
Re: Machining for guideplates (clem zahrobsky)
Thanks for all of the help guys. I did this all earlier today. I sure stayed pretty busy for what was supposed to be a holiday. The machining went pretty quickly, but the time to disassemble, clean, and re-assemble turned it into a 3 hour job. I simply milled the pushrod slots to make each pair into one large 1/2" horizontal slot. There should be plenty of room for just about any lift or rocker ratio I decide to use in the future.
And in case anyone is curious what the angle was..... it was 11 deg.
I can't begin to tell you how much it does come in handy. After the heads were done, I turned my attention to my wiggly distibutor. It turns out that the lower bushing wall was almost gone and the shaft was badly worn and about to be worn into the aluminum housing. Fortunately , the end where the gear is pressed onto is a bit smaller allowing me to grind the bearing surface down to the same diameter. Then I only needed to make a bronze bushing to match the new shaft diameter.
All in a days work :cheers: :cheers: :cheers:
And in case anyone is curious what the angle was..... it was 11 deg.
Lucky you, I wish I still had access to a milling machine and a big lathe.....
All in a days work :cheers: :cheers: :cheers:
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Re: Machining for guideplates (tsw71)
The 11 degree figure is published by GM in their "Chevrolet Power Service Manual". I suspect the reason why it is so elusive is because most "Automotive" machine shops do not rely on a milling machine for this task... they use cutters which use the stud centerline as a reference. This is what I use... they are inexpensive and accurate enough for the task at hand- as long as the user has some skill. A milling machine is awesome, but not really necessary for this operation (but sure makes the job easier!). Also, be aware that it is possible to run across a set of heads that have been "angle milled"... that is, the gasket surface has been milled at a slight angle to the original face. In this case, the 11 degree figure goes out the window.