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I had something of a similar experience with a machine shop who did some work for me and only did specifically what I asked for. I was asking for the complete job and they did only exactly the one thing I asked them to do when it would be reasonably presumed that any shop would do the whole job and not just one part of the job. I took the heads back and made them do the rest of it and it was on them because I had already paid for "the whole job".
 

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All else being correct, when measuring for correct PR length I've followed the rule, if the "witness mark" is off center and closer to the exhaust side then the PR is too long. Conversely, if biased toward the intake, too short.
 

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Discussion Starter #24
Just guessing that they didn't knock off the tops of the bosses to compensate for the thickness of the guide plates and the hex nutted end of the screw in studs. I have seen .220 quoted but the machine shop should have the exact number. Now comes the question, did they thread the bosses deep enough for your screw in studs after .220 is knocked off the bosses? This starts to sound like a complete do over sort of a thing for the machine shop.
The machine shop did mill the bosses but I suspect they only took into account the guide plates. That makes sense that they did not account for the hex end of the screw in studs. The hex head on the rocker stud measures about 1/4" and would probably be enough to dial in the correct push rod length if milled off the boss. That said, do you think It would be "safe" to tell them to take the bosses down another 5/16"? Even taking off 1/4 makes me nervous. The total thread length in the head is 3/4" (the bosses are threaded all the way through) and the thread length of the rocker stud is 3/4". If I take 1/4" off the boss then i'm only left with 1/2' of thread in the head and 3/4" worth of threads on the rocker stud. I'm not sure but common sense dictates that I may have to back off the torque setting on the rocker studs to account for the shorter thread length in the head.

I had something of a similar experience with a machine shop who did some work for me and only did specifically what I asked for. I was asking for the complete job and they did only exactly the one thing I asked them to do when it would be reasonably presumed that any shop would do the whole job and not just one part of the job. I took the heads back and made them do the rest of it and it was on them because I had already paid for "the whole job".
Definitely will push to get any additional work don at no charge. We'll see, can't hurt to try.
 

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Discussion Starter #25
All else being correct, when measuring for correct PR length I've followed the rule, if the "witness mark" is off center and closer to the exhaust side then the PR is too long. Conversely, if biased toward the intake, too short.
We are definitely on the same page.
 

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Discussion Starter #26
I’m running the same rockers you are, but not with guide plates. I have much more clearance than what you show. I can look back and see what push rods I purchased if that might help.
Thanks for the offer but your push rod length would probably be different from what I need. You have tall valve tips and I have the short valve tips (see pictures in my first post). Thanks for the pictures, good for reference.
 

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Discussion Starter #27
Patrick, Your boss height looks shorter than mine. Disregard the washers in this picture. They match the thickness of the guide plates and I'm using them because my push rod checker wont work with guide plates.
 

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I think I will go down to the shop and look at my 289 heads which are bare but were threaded for studs and the bosses were milled down.
 

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. If I take 1/4" off the boss then i'm only left with 1/2' of thread in the head and 3/4" worth of threads on the rocker stud. I'm not sure but common sense dictates that I may have to back off the torque setting on the rocker studs to account for the shorter thread length in the head........"

".........Definitely will push to get any additional work don at no charge. We'll see, can't hurt to try.

I can't recall what type of heads you have, if they are cast iron then you don't need as deep a threaded hole as if they are aluminum.

You are getting some conflicting advice, if I were in your shoes, I'd take a deep breath and go to another machine shop. Whatever you paid the first place, just write it off. Take your heads to a place that KNOWS vintage Ford Cylinder heads. You need references before you leave your heads and trust blindly, hopeing they they know what they're doing.


Z

PS. I would not under any circumstances tighten the stud any less than the published specifications.
 

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First, I ran and raced these heads for years with ARP hex head screw in studs and guide plates and they ran fine. I will also say that I always install screw in studs with red loctite.



I got a thin, straight, rigid wire and bent a small right angle on the end so I could run it down to the end of the threads inside the boss. I marked the top of the wire at the flat surface of the boss. Using my handy dandy IGauging absolute origin digital dial mic, I get right at .57125 give or take a ten thousandth.


I have not measured a stock head before it has been tapped and milled for studs and guideplates so I don't know how much was taken off to get to that .57125 number.



I would still say to get a machine shop, maybe a different one, to stare at your heads before deciding how much more to mill off.
 

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Discussion Starter #31
I can't recall what type of heads you have, if they are cast iron then you don't need as deep a threaded hole as if they are aluminum.

You are getting some conflicting advice, if I were in your shoes, I'd take a deep breath and go to another machine shop. Whatever you paid the first place, just write it off. Take your heads to a place that KNOWS vintage Ford Cylinder heads. You need references before you leave your heads and trust blindly, hopeing they they know what they're doing.


Z

PS. I would not under any circumstances tighten the stud any less than the published specifications.
I hear ya. The heads are stock cast iron 66 289 heads. To make a long story short this engine was rebuilt by a supposed "Ford Expert". All valve train components replaced. One of the rockers was skewed and chewed into a rocker stud with less than 1000 miles on the rebuild! I would have went back to this guy and got on his case but by the time I got the car back together and on the road 2 years had past. It wasn't until the third year that I discovered the valve train was self destructing. At this point, I posted on this forum looking for machine shop recommendations to rebuild the heads. The guy that rebuilt the heads was recommended so I gave him a shot. Well this is where I'm at now. I'm really frustrated at this point. I can't win.
 

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Discussion Starter #32
First, I ran and raced these heads for years with ARP hex head screw in studs and guide plates and they ran fine. I will also say that I always install screw in studs with red loctite.

I got a thin, straight, rigid wire and bent a small right angle on the end so I could run it down to the end of the threads inside the boss. I marked the top of the wire at the flat surface of the boss. Using my handy dandy IGauging absolute origin digital dial mic, I get right at .57125 give or take a ten thousandth.

I have not measured a stock head before it has been tapped and milled for studs and guideplates so I don't know how much was taken off to get to that .57125 number.

I would still say to get a machine shop, maybe a different one, to stare at your heads before deciding how much more to mill off.
Thanks for checking. That's good information and gives me a good reference. I did the same thing to measure the threads in the boss on my heads but I used a tape measure to check the length on the wire. The actual measurement is probably like 3/4" +/- a smidge.

One thing I noticed and wonder if it is normal that the rocker stud holes on cylinder 1 (I didn't check the others) on my heads go right through into the water jacket? Is this normal? At a minimum I will have to put a sealer on the rocker stud threads that go into the head.
 

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you are getting close, so don't give up.

The heads photos that Patrick posted are a good guide of what yours should look like.

macstang posted a number that sounds right, nearly 0.6" of threads would be plenty. I wish I had thought to record the info threaded depth of the many HiPo heads I've had, which come from Ford with thread-in studs (but no guide plates). I wouldn't be surprised to find out it was a little less than 0.75".

Look, if you have ARP studs, generally considered the industry standard of excellence, which usually have 0.710" or 0.75" bottom threads (depending on whether they are 3/8" or 7/16" top thread spec.) you don't need 0.75" of threads in the head, as the guide plates are spacing up the rocker stud. I would be comfortable with a full 0.5" of threads in a cast iron head. But you may end up with more than that.

So chill out, have a couple of high quality beers, and start looking tomorrow for another machine shop, one with street cred.

Z
 

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Discussion Starter #38
you are getting close, so don't give up.

The heads photos that Patrick posted are a good guide of what yours should look like.

Agreed.

macstang posted a number that sounds right, nearly 0.6" of threads would be plenty. I wish I had thought to record the info threaded depth of the many HiPo heads I've had, which come from Ford with thread-in studs (but no guide plates). I wouldn't be surprised to find out it was a little less than 0.75".

If I have the bosses milled down another .25" and based on my measurements, I'm pretty confident I'll have approximately the same amount of threads left that macstang posted (.57")

Look, if you have ARP studs, generally considered the industry standard of excellence, which usually have 0.710" or 0.75" bottom threads (depending on whether they are 3/8" or 7/16" top thread spec.) you don't need 0.75" of threads in the head, as the guide plates are spacing up the rocker stud. I would be comfortable with a full 0.5" of threads in a cast iron head. But you may end up with more than that.

I'm not sure of the make of the studs but the 7/16 end that screws into the bosses measures .710" (other end is 3/8 fine thread). Good point about the guide plates, I forgot about that. The heads are cast iron so I think I'll be good.

Here's the math for milling down the bosses .25" (1/4"):

.57" usable threads after milling + .125" for guide plate = .659" total length to bottom of threads

.659" total relative thread travel - .710" thread length on stud = -0.015 (6/400") unused threads on stud.

That's just about perfect.

Here's the math for milling down the bosses .3125" (5/16"):

.5075" usable threads after milling + .125" for guide plate = .6325" total length to bottom of threads

.6325" total relative thread travel - .710" thread length on stud = -0.0775 (31/400") unused threads on stud.

That said, since my rockers are currently sitting so low (see my first post), I'm thinking to have the bosses milled down .3125" (5/16"). do you guys think I'm pushing it or should I stick with milling down the bosses .25" (1/4") which would probably work?


So chill out, have a couple of high quality beers, and start looking tomorrow for another machine shop, one with street cred.

Exactly what I did last night!

Z
Mark
 

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Discussion Starter #40
Looking for some advice...

Here's the math for milling down the bosses .25" (1/4"):

.57" usable threads after milling + .125" for guide plate = .659" total length to bottom of threads

.659" total relative thread travel - .710" thread length on stud = -0.015 (6/400") unused threads on stud.

That's just about perfect.

Here's the math for milling down the bosses .3125" (5/16"):

.5075" usable threads after milling + .125" for guide plate = .6325" total length to bottom of threads

.6325" total relative thread travel - .710" thread length on stud = -0.0775 (31/400") unused threads on stud.

That said, since my rockers are currently sitting so low (see my first post), I'm thinking to have the bosses milled down .3125" (5/16"). do you guys think I'm pushing it or should I stick with milling down the bosses .25" (1/4") which would probably work?
 
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