# 455 main stud question



## Bensjammin66 (May 12, 2009)

okay so I am going to call the machine shop tomorrow morning for an official answer from them but it is just making me crazy after looking at this engine I have to ask you guys. When I hand tight all of the main studs into the block just like ARP's instructions say (after having the mains line honed) the nuts show about 4 or so threads in the rearmost cap once tight, the main seal cap. What am I doing wrong?


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## BearGFR (Aug 25, 2008)

I'm not clear on what you're saying. Can you put up photos? 

Honestly though, there's a very good chance that you're doing NOTHING wrong.

What I found trying to use an ARP main stud kit on my '69 was that they (pardon the expresson) suck and don't fit. I had similar problems. When installing them exactly as per instructions, either they were so short that the nuts could just barely start on the stud with the cap and washer in place (if at all), or they were way too long (the two front studs - which would have required me having to severely dimple my brand new oil pan to clear. The studs on the center main were so long that there was about 1/8" of bare, unthreaded stud showing ABOVE the top of the main cap making it impossible to properly tighten down and torque the center main.

So, I wound up using studs only on #2 and #4 mains because they where the ones that had the extensions I needed to mount the Milodon windage tray to. Luckily, they were correct. Everywhere else, I used bolts.

Welcome to to wonderful world of Pontiac. Just because an aftermarket manufacturer claims to have the correct parts, even a "name" like ARP, doesn't mean they do.

Bear


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## Bensjammin66 (May 12, 2009)

Here it is with the stud bottomed out in the block finger tight. Cap tapped down flush with block and the nut finger tight.


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## Bensjammin66 (May 12, 2009)

I just dont get it! Using half studs and half bolts on a fresh bottom end isnt something im prepared to do. I have to be missing something. There are too many studded pontiacs out there for this to be an ongoing issue with ARP selling studs 3/8" too short.. 








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## BearGFR (Aug 25, 2008)

You're not missing anything. Either that stud is too short or the bolt hole in the block is drilled and tapped "too deep". Considering that I'm sure you still have the bolt that was originally there, and I'd bet my last paycheck its the same length as every other 2-bolt rear main cap bolt you'll ever find, which one of those possibilities makes the most sense to you?

Bear


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## Bensjammin66 (May 12, 2009)

BearGFR said:


> You're not missing anything. Either that stud is too short or the bolt hole in the block is drilled and tapped "too deep". Considering that I'm sure you still have the bolt that was originally there, and I'd bet my last paycheck its the same length as every other 2-bolt rear main cap bolt you'll ever find, which one of those possibilities makes the most sense to you?
> 
> Bear


Agreed.. The stud has to be too short.. I pulled some of the others and they are all the same length, the studs that is. Whats more disturbing is how did my machinist line hone the mains with one pair thats too short? One would assume immediatley he f'd up but this guy builds many many race engines in northeast ohio. Hell he had a complete stroker pontiac 461 shrink wrapped for a customer when i picked up my parts.


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## Bensjammin66 (May 12, 2009)

So for any stud to work you need as much or more thread bite on each end as the stud is wide. The bottom threads are about 1 1/4" long and the stud is 1/2" wide. So i THINK you just back out the studs from the block till the nuts sit flush on the tops of the caps so long as the bite in the block and on the nut above is 1/2" or greater per side ( stud diameter ) I will verify with ARP and the machine shop tomorrow. This theory does make a little sense though because the nut pulls and stretches the stud and the stud does not and should not twist or move as you torque the nuts on top.


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## BearGFR (Aug 25, 2008)

Just be SURE it has enough bite into the block. If so I believe I'd use red loctite on that end. I'm not sure I'd use it if any of the bottom threads were visible above the block surface at all.

Bear


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## Bensjammin66 (May 12, 2009)

Bear, 

If I back out the stud enough so the top has plenty of bite i would guess I have a solid 7/8" or more in the block threaded. After speaking to the machine shop he said this is how they assembled it for line hone and how they final assemble them too. I will be placing a call to Cetral Virginia Machine and ARP for two more votes on this method and will let you know. I am certain I am not alone on this as there have to be SOOO many other "studded main" pontiacs out there..


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## Bensjammin66 (May 12, 2009)

Per ARP Tech Support, SD Performance, Virginia Machine and Michaels Racing Engines of Ohio... 

Thread the stud out of the block enough so the threads fully engage the nut with no less than .050 of thread exposed above the nut when tight. Just be sure to measure thread depth vs exposed stud when backing it out of the block. The bare minumum thread bite in the block for the stud to be effective is 1/2", with over 1.25" of thread to work with there is plenty to achieve this. 

I hope this helps an at home builder frantically searching the web for answers as i was late last night.


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## Norms68 (Jul 17, 2013)

Thanks for the info.

I just got my ARP studs for my 461 build.

Good to know.

Norm


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## Bensjammin66 (May 12, 2009)

Norms68 said:


> Thanks for the info.
> 
> I just got my ARP studs for my 461 build.
> 
> ...


Thats what this forum is for; helping each other out and consolidating info into one place! As a side note, per ARP, threads showing above the nut should be AT THE MINIMUM .050 and dont worry it leaves MORE than enough bite in the block. But, like Bear said above, check it anyway.


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## PontiacJim (Dec 29, 2012)

Bensjammin66 said:


> okay so I am going to call the machine shop tomorrow morning for an official answer from them but it is just making me crazy after looking at this engine I have to ask you guys. When I hand tight all of the main studs into the block just like ARP's instructions say (after having the mains line honed) the nuts show about 4 or so threads in the rearmost cap once tight, the main seal cap. What am I doing wrong?


Thanks for the info as I also plan on using the main cap studs. Really wanted to address a concern in that you stated that the mains were align honed. I had this done to my previous 400 which had oil pressure problems from day 1 -60 PSI when cold and running and then as it got warmed up to running temp, it would drop to 40 PSI. It continued to drop over time (got 25,000 miles on it) before it had about 5 PSI at idle hot and 20 PSI above 1,000 RPM. Then one day, 0 PSI and that was that. Have not torn down the engine to see what was wrong as it could be several things to include the oil pump or ? Talked to my "new" machinist who is building my 455CI. He said when you align hone/bore the mains, you do not get the crush needed on the bearings to get the correct oil clearances - remember, things expand when hot. Said this will create oil pressure problems in a Pontiac. The machinist has been building engines, to include Pontiac, and big power race engines, for almost 40 years. Said he is working with a high dollar Ford engine that another machine shop did this to and the guy has oil pressure problems and he has gotten caught in the middle as the other machine shop says they did nothing wrong and the owner of the engine says they did. My machinist said the machine shop is at fault because the mains do not have the proper crush. It may just have been the inexperience of the machine shop who did the initial work -not saying that a quality machine shop doesn't know how to ensure this does not become a problem. I still do not know if this was or was not my problem, but thought I would pass this on so as you don't have any problems with your build in the future.


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## Bensjammin66 (May 12, 2009)

It is not required to line hone going from bolts to studs if you measure out fine , but even then i dont know of many machine shops that will install studs without doing it. Same when installing new rod bolts. My previous motor was a 400, it was in the car 12 years ago when I bought it and had similar oil pressure problems to what you were seeing. New cam bearings, flat tap cam and melling pump and the problem was solved. Idle 20lbs / 60lbs 2500+rpms, hot. But the issue of line honing for new hardware causing oil pressure problems is news to me

I don't want to state the obvious but you use over size bearings in the mains to compensate for what they took out with a line hone. it is required to make the caps and block journals true again with the new clamping force and if someone insisted otherwise I would question it on your new engine..


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## PontiacJim (Dec 29, 2012)

Bensjammin66,

Not sure why the former machinist align honed/bored my mains as I used the factory bolts, so no changes. He ordered the rebuild kit through his shop and I used what he ordered. I also assumed he measured everything and never used any plastigage or anything during assembly - so my fault here as the guy was supposed to be pretty top notch, but have since heard a few shady stories. I am no machinist and no expert in engine building either, but it would make sense that when you align hone/bore the mains that you are opening up the holes and it may change the crush on the bearings in that the clamping force is not as tight as factory -so your journal clearances might be affected? 

Again, not even sure that this was my problem as it could have been something I may have overlooked in assembly, a defective part, or a machinist oversight. I would not have known this if my current machinist had not brought up the oiling problem with the Ford race engine he was diagnosing. I just happened to mention my 400 being align honed/bored and the oiling problems I had. I did a lot of web/blog searching trying to figure out what my problem was and found many similar experiences from other brand engine rebuilds and there was no definitive answers followed up other than the obvious like oil pumps, blocked passages, excessive bearing clearances, add an oil cooler, change oil brands, worn thrust bearing, etc.. So the align hone/boring was a new one on me and my engine had had that done and I did have oil problems from the onset.

Sounds like you are on top of it, as I was not because I may have "assumed" more than I should have. Won't due that again with this build.


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## Bensjammin66 (May 12, 2009)

Yah I gotta say, if done correctly, line honing your mains and installing over size .010 or .020 bearings was not your oil issue. If anything that increased pressure and over all true/roundness of the main bores. Hopefully Bear or someone else more knowledgable than me can chime in with some info. You did use over size bearings afterward right? I have a machineist here in Ohio who we hand our stuff to and get back boxes of matched and machined parts. I know you can achieve results with plastigauge but ill be honest I dont trust myself enough to get it all right. I want the block, crank and rods back machined and ready to go with the proper bearing measurements from him so I just get to do the fun part of bolting it all together. Whether upgrading to 4 bolt billet caps or ARP studs, trust me have it done and let them measure it for oversize bearings and you will have no issues.


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## BearGFR (Aug 25, 2008)

Well, I'm not a machinist (through I'd LOVE to learn!), but the align-honing process involves shaving a small amount of material off the main caps, then using the hone to restore the bores to roundness, the proper dimensions, and straightness. There are several opportunities here to get it wrong, mostly involving not restoring the correct bore diameter, not getting the bores on the same centerline (which is the main reason for performing the operation in the first place), or getting the bore centerline "out of parallel" with the rest of the engine. The one side effect that almost always happens is that the operation slightly reduces the distance between the crank centerline and the cam centerline, which causes more slack in the timing chain. Using a custom "slightly shorter" chain corrects that problem.

_If done correctly and to the proper diameter_, there's no reason that the process should make it so that factory spec bearings can't be used and there's no reason for any oiling problems.

These days, finding a machinist that "cares enough" to do it right can be a challenge.

Bear


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