# Head Bolt Check



## PontiacJim (Dec 29, 2012)

Things not thought about when rebuilding the engine.

There are options when choosing head bolts when the time comes.

Prior to installing your head bolts, it is very important that you have clean threads on both the block and the head bolts. Dirty, deformed or damaged threads can cause problems when it comes to tightening head bolts. You may think you’ve applied the proper amount of torque, but the bolt may be exerting much less clamping force than normal depending on how much friction is in the threads. Dirty threads can reduce the clamping force up to 50 percent.

First, clean up all the threads in the block with a thread-cleaning _chaser_, NOT a regular tap. Thread chasers are designed so that they do not remove material from threads but merely remove debris and corrosion. Make sure you go all the way to the end of the threads in the bottom of the hole - thread chasers for head bolts are generally flat bottom also know as a "bottoming tap" so it will get to the end of the threads.(I recently rented one of these thread chasing flat bottom tap kits for engine rebuilding from O'Reiley's.) Clean out all the holes in the block with brake or carburetor cleaner to remove all the debris. I would also suggest using an air gun to make sure you blow out all the debris and ensure that the bolt hole is dry. You don't want any liquid or excessive oil in the hole as the bolt/stud can trap it in there and when it heats up, it wants to expand and with no place to go, the pressure could build up enough to crack the block.

Pontiac engines use "blind holes" in the block for head bolts. This means that none of the head bolts go through the water jacket like some other makes. So no sealer is needed on the threaded ends. 

You can typically re-use the stock head bolts and I have never heard or read of any problems associated with re-using them as long as the engine has not been torn down a couple times in the past - then it might be risky to re-use them and better to install a new set. They also have the accessory mounting studs needed on some builds that other bolt kits do not. Wire brush all bolt threads, carefully inspect each one, and replace any that are nicked, deformed, or worn. If a bolt doesn’t thread into a hole smoothly with finger force alone, there is a problem with either the bolt hole or the bolt. If you want to purchase a new bolt kit with the accessory studs, they can be had. Butler offers them, Inline Tube has them, Jegs has them, and I have seen them on Ebay as well.

The threads on the bolts typically need to be oiled for installation. It is recommended to use a 10w-30 or 30 weight oil. How much oil? My machinist says to put oil on the threads and then wipe off with a rag so just a light coating covers the threads - never wet or dripping. Put a light coat of oil under the bolt head as well. Then torque to factory specs. You can use other lubricants, but this can change the torque requirements and unless you know what that is, stick to the oil and factory specs. 

An upgrade from stock head bolts are the ARP brand of head bolts. They are stronger. They have a radius that can be seen under the bolt head going to the bolt shank and requires the matching ARP hardened washer which has a chamfer that the bolt radius seats into. They typically have a slightly different torque spec and requires their supplied ARP Ultra-Torque lube to properly torque them down. Instructions are supplied along with torque values.

Next up is the stud, also made by ARP. The studs are threaded on each end. Studs provide a more even clamping load than bolts and won’t wear out the threads in the block if the heads have to be removed repeatedly for tear downs and inspections. They also provide a much more accurate and consistent torque loading. This is why they are used in most racing engines. The "top" side of the stud has a hex broached into it so an allen head wrench can be used to ease installation - it is NOT used to tighten or torque the stud down. Cylinder head studs are installed only hand tight. It is extremely important to ensure that the studs are fully bottomed out in the hole in the block and not hung up on damaged or corroded threads in the block preventing the stud from being fully seated and is why a thread-chaser/bottoming tap should be used. If the stud threads extend past the blocks deck surface, it often indicates that the stud did not fully seat. This indicator may not apply if the block has been milled to "zero deck" it - no personal knowledge on decking a block and using studs so I am not sure?

The studs should be first test fitted into the block. ARP notes that it is generally easier to remove the studs, put the head gasket and head on the block and then install the studs. This will reduce the possibility of damaging the upper threads of the stud and scraping the cylinder mounting holes. You can use a light coating of the ARP Ultra-Torque lube on the threads that go into the block or you can use the blue Loctite on the stud end that goes into the block. You can use one or the other, but never use both. Do NOT use Loctite on the nuts used to secure the head to the head studs. When using the Loctite, make sure you assemble/torque the heads to the block before the Loctite cures.

On a street engine, or in a situation where the heads would be difficult or impossible to remove with the engine in place, studs may not be the best choice from a cylinder head service standpoint. For example, if a master cylinder or other component prevents a cylinder head from being removed or installed with the engine mounted in the vehicle, bolts may be a better choice simply in terms of practicality.

If the block has been decked or resurfaced to get it straight, make sure the head bolt holes in the block have been chamfered so the uppermost threads won’t pull above the deck surface when the bolts are tightened. 

Decking of the block, resurfacing a cylinder head, and even a thinner head gasket can decrease the overall height of the cylinder head. This could cause a head bolt to bottom out, so be sure to check bolt lengths to make sure they won’t bottom out in the blind holes. If a bolt bottoms out, it will apply little or no clamping force on the head, which may allow the gasket to leak or even crack the block when torqued down to spec. If one or all of the head bolts are dangerously close to, or do happen to bottom out, the problem can be corrected by using hardened steel washers under the bolts to raise them up the amount needed.

This is from the SD Performance site:

"ARP produces some of if not the best fasteners on the market, but we have run into an issue from time to time especially with cast iron heads that some of the lengths are too long, most commonly the medium length bolts under the valve cover on the ends of the heads. This issue can also be caused by decking of the block and heads so checking to make sure there is adequate room to stretch the fastener is critical.

When using ARP head bolts we recommend to do a trial run on each one without the washers installed to make sure the head of the bolt contacts the cylinder head. By doing this you can be assured that there is adequate room to stretch the fastener once they are installed with the washers. If you find the bolt head doesn't contact the cylinder head before bottoming out, an easy solution is to add a second hardened washer (must be a hardened washer!!!) which are available from ARP as well as other manufacturers. Shortening the bolt/s is another solution but we prefer the additional hardened washer. Be sure to use ARP Moly lube on the threads and under the bolt heads for proper stretch/clamping. "

My personal experience with having a head bolt too long was when I mistakenly ordered the ARP Ram Air IV head bolts instead of the standard ARP D-head bolt kit. The Ram Air heads, due to their design, used a couple longer head bolts to secure the head. Rather than buy a new head bolt kit, I simply added another ARP hardened washer under the bolts that were too long - which the machinist I used at the time suggested. The extra hardened washer did the job and I never had any issues. Lesson learned - order the correct head bolt kit for your application and head. :thumbsup:


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## geeteeohguy (Feb 2, 2008)

On the 'other' forum, several gentlemen have experienced head gasket failure using ARP bolts that were manufactured slightly too long. They bottomed out in the block, failing to clamp down the head. Used factory stuff for me, when it comes to head bolts. Not saying ARP are bad, just some were too long. I would measure them prior to use! Also, be very careful what type of rag you use if you are tempted to wipe down internal engine parts. Lint can accumulate in the strangest places and block oil passages. Great post, Jim!


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## Shake-N-Bake (Jun 16, 2015)

Thanks for the tip about chasing taps for rent. I hadn't thought of that but after reading your post I went down to AutoZone and sure enough they had a set. Going through my block now. Will wash it when done and then I need to spend a few days with micrometers and a notepad. Hopefully the machine shop has everything within tolerances.


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## RMTZ67 (Mar 12, 2011)

*Head studs*



PontiacJim said:


> Things not thought about when rebuilding the engine.
> 
> There are options when choosing head bolts when the time comes.
> 
> ...


Wow, you are correct in saying its a easily overlooked part of a build. I decked my 400 somewhat and a slight mill on the heads. I did not see no obvious issues when torquing but worth a look. Thanks for the post.


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## BearGFR (Aug 25, 2008)

There's also such thing as having head bolts too short. D-port heads use different length bolts from Round Port heads, which use different which bolts from aftermarket heads. Getting this wrong is dangerous too, especially if you go to torque down a head bolt that's too short, so short that it doesn't engage more than a few threads in the bolt hole. It can rip those threads right out of the block.

Bear


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## tiretread (Sep 28, 2015)

Good thread. Just about to put 093 heads on my 389. Spent this past weekend cleaning the threads.


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## 69_Custom_S (Jan 17, 2018)

This past spring I put together my 400 with original head bolts and I ran into water in the oil on the first startup from the head gasket not sealing properly. After checking and rechecking I figured out that the head bolts were just barely bottoming out. I ordered and installed ARP head studs and new head gaskets and it solved the issue. Since the threads on the studs are longer they were able to reach and provide the correct torque. A lot of posts on the forum say reusing the original head bolts is fine and I agree BUT if you decide to reuse original head bolts I would recommend measuring each bolt threaded all the way in and then measure the head and head gasket to make sure they will be short enough to clamp down to the proper torque reading without bottoming out, this is likely more critical in motors with decked blocks/ milled heads/ thin head gasket.


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## 11th Indian (Feb 15, 2018)

Used some old head bolts to make a thread chaser, compressed air and a shop vac to prepare my LS7 project for a heads / cam last year.


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