MTFCA Forum

Went to torque @50lb the headbolts on my 26 today and the rear center bolt pulled out. Had used a torque wrench on all the others and used a ford sparkplug wrench on this one cause it was under the dash. I compared that bolt with an original and the repop was about 1/8" shorter. I was lucky and had some long v8 studs that were 1/4" longer, turned the large part down and screwed in in after pushing the firewall back a little. I tightened it very carefully and it held. bottom line is check those pretty repop domed bolts for length!

or check the block for good threads.

...And check your torque wrench for accuracy on a regular basis. Many are way off, and get way off suddenly... Many times the torque wrench is to be blamed for stripped threads, stretched bolts, and split nuts.

and make sure the holes are cleaned out.

Jim is right on with his warning. Did a short block for someone and he installed new dome bolts with a Z head . Stripped out bolt holes in block. Bolts were short like Jim says. Dan

For the record: Block was just cleaned in the machine shop. Head was Z. Had had this engine down many times over the years with the same combination. None of bolts tightened with torque wrench failed. Bolt that failed was rear one on a 27 and was against the firewall where a torque wrench would not fit and was tightened with a ford spark plug wrench.

your arm is too strong! An (at least for me) way to judge torque for those bolts is to tighten one of the other bolts with a torque wrench just a couple ft lbs loose and then take the Ford or other wrench and on the bolt which was torqued just a little loose and with the Ford wrench pull it just enough that it moves slightly. Then judge the amount of torque to pull the one the torque wrench will not fit.
Norm

If you don't use the same torque wrench and setup (length of extension) on all of the bolts (capscrews if you want to be technically correct) they are not all torqued to the same value.

I use a torque wrench extension which is similar to a crow foot wrench to get the two bolts under the firewall, I purchased it from McMaster-Carr.

I’m not trying to be a troll, actually congrats on gettin-er-done, just a word of caution...

You guys do realize that if the difference between “no bite” and “bite” is adding an 8th or a QTR to the head bolt length, then all your torque is being held by but 1 to 3 threads?

Since the original blocks only had 8 or 9 active threads to begin with, that’s sort of pushing it?

Just offering it up for further future thought...

The reproduction bolts are or were short. My customer’s problem was two fold, bolts were short and his AL head was about .100 thicker than any other Al head in my shop, one head was brand new. This lead to a major problem.
Also, in Lang,s catalog, I think it says NOT to use these bolts with an AL head. And only tighten to 45 ft lb.

It's better to not use reproduction anything unless you can trust the source, and even then you may not be able to rely on the product. I would like to see our parts suppliers use their products on their own cars before offering them to their customers!

With the head and gasket setting on the block, drop a bolt in the hole and there should be a minimum of 6/10 of a inch of bolt shaft above the head. That will equate to a thread engagement of about 8 and a half threads. And to compound the situation your dealing with 100 year old cast and possibly under size diameter bolts. If the bolts are 1/8 short you lose a fraction over a full thread of engagement. I’ve run in to this before and it sucks.

Z head fitting is somewhat of a gamble due to a number of things. The bolt length problem arises because of inconsistencies in the actual height of the head, the use of a washer under the bolt head, and now slightly shorter bolts. All this before the head gasket is placed where it will not be in contact with the piston. Much to look out for.

I replace standard head bolts with those from a 6 cylinder GM Holden. These have an 11/16 head rather than 5/8, but their true value is in the length. With cleaned out bolt holes in the block, these bolts go almost to the bottom of the hole, for maximum thread engagement. Perhaps there is a US equivalent to these.

Allan from down under.

Just finishing a customer built motor with 15 domed nickle plated bolts in a Z head. It lost a head gasket seal with 3 striped and 4 soft torqued at 30 lbs, that's almost half of the 15. I used Keen Serts as there wasn't any good thread for the first 3/8 of an inch.
Helicoils might have work, but I didn't want to take any chances. I have used them In aluminum racing blocks with as much as 15.7 : 1 compression.
[The pictures show the KeenSert and my setup to install them on center and square to the block

Hello Bill, Where do you get the Keen inserts. I have a flathead va that needs some.

Jim, I get them from McMaster Carr.

They are great Inserts.

Keenserts are a good product. However, if you are of the opinion that Helicoils are a risk, then you are mistaken. Helicoils are in fact, ideal for this job as they remove the least material in an area which is prone to break-through, and the head itself can and should be used as the drill pilot for location and squareness.

For those that will undoubtedly and repeatedly swear that helicoils are inferior, my experience with their use is on the Space Shuttle, guidance systems on spacecraft and satellites, and the navigation/pointing system on the M119A Howitzer. I know of no Keenserts on those products, but plenty of Helicoils...none of which have I ever seen fail. That said, I do not underestimate the abilities of a bad mechanic to ruin or mis-use a tool.

As applied to a T engine, at the very minimum, Helicoils are far stronger than the parent material cast iron in a T block.

Only problem with Keen type I have found is they make too big a hole. Sometimes the wall of T block is too thin a casting. Look into Loc N Stitch Full Torque inserts. They have blind inserts that will seal water jackets too. I have used them where a large part of insert was in water jacket and still held at double the torque valve of bolt. Not cheap, but is a new block and rebuild cheaper? Dan

Scott, Helicoils are not inferior, I had to use the KeenSert for that hole as the customer had tried to use a self tapping Insert and It pulled out because of a poor quality thread in the block. I have used Helicoils for more than 40 years on jobs for Kodak, Xerox and IBM and never had a reject. Yes KeenSerts are expensive but they have there place. I tend to use Helicoils If I can to save a torn thread and when prepping very high compression race engines and to save the customer money as KeenSert's are expensive and time consuming to Install.

Bill

sounds like you did a good job of saving a spoiled repair. I tend to find that folks that have experience with Helicoils beyond buying the $20 kit off eBay and then botching the job, tend to understand their utility in industry...you are obviously one of those folks with industrial professional experience. Having to deal with what you did, I am pretty sure I'd have done exactly what you did, too.

Dan also gave good advice with the locknstitch sealed-bottom insert. I have never used them but can definitely see where they would have great value in some certain circumstances.

Another alternative is a Keysert. These are available in more than one thickness, to cater for different states of repair. The neat thing about them is the hole into which they are threaded is a standard size, so the expense of a special tap is sidestepped. Once installed, the little tangs are driven down to lock them in place.
Allan from down under.

Never heard of Keysert...just learned something...looks like the Keensert patent may have expired

Scott, if I could get my damn phone to talk nicely to the forum, I could post a picture. I have a problem understanding how to download photos,and when I try to post on the forum from my phone it keeps asking me for my user name and password, and then tells me they are already in use!!!!!

Allan from down under.

End result: I bought a set of grade 8 bolts from RK which are 1/2" longer than the repop bolts. Checked depth of each hole, installed new bolts one at at time removing the repop, torqued to 45lb then to 50. Satisfactory job done.

I pulled the head off of my '27 a few years back. When inspecting the headbolts, there were a couple that I didn't like. I bought two repops from Lang's which looked better in every way then the originals. The length was correct. Maybe they are using a different vendpor now? I would think that modern bolts would be stronger then the originals if they are decently made.

I’ve repaired plenty of helicoils in T blocks...

The problem with helicoils is always that the last guy that attempted to install it botched the job.

On a T block, you typically find that the previous repairman didn’t take into account the first 4 or so turns of lead on the helicoil tap. The installed helicoil threads are generally 2 or 3 turns deeper than it should be and the head bolt bottoms or binds against the tapering helicoil threads instead of torquing against the head. This is generally what “happened” in cases where people say a helicoil moved or won’t stay put. (If you form 9 turns of thread with the helicoil tap and the tap has 4 turns of lead, then you can only install 5 turns of helicoil, because the bolt needs to go further into the block than the lead of the helicoil will allow.

Unfortunately, the instructions don’t cover “everything you can do wrong and why”.

https://www.grainger.com/category/faste ... Google+PPC


Granger has the Keenserts and a really nice chart about them.

Adam

I agree with you. I'm going to guess that you have modified a Helicoil tap or something like this, like I do: https://www.fastenal.com/products/details/3297121

Your point is a very important one which I have failed to mention in the past. Personally, I just modified a standard Helicoil tap to become a bottoming tap rather than spend the money for a factory made one. Your point is the difference between someone who knows wha they are doing and someone who simply has access to eBay. Your warning, I think, also applies to anyone who is installing any kind of insert into a blind hole. If you don't know what you're doing and botch the job, that doesn't make the product defective.

Thanks for the pointer.

I recently purchased a set of domed headbolts for my 27 project. I checked them against one original I had and they are indeed too short by a couple threads. Doesn't seem like much but the Ricardo head I am using is taller than a stock Ford high head. Combined with the shorted head bolts, there is just not enough threads going into the block to satisfy me. I purchased 20 grade eight shanked 7/16" by 14 tpi , 3 1/2" long from McMaster Carr. I almost have room for a 3 3/4" bolt. Only problem I see is the shanked section is not thinner like Ford headbolts, but its easy to turn them down if I need to.