500$ for studs!!!. ARP is making a killing. That is nuts. You can by the same steel and make them for alot less then that. I know where to get the steel for those.

Hey Dave. Have you looked into drilling out the 6.9 block for 1/2 " studs? I have an old block. I may mess around with it and see.

 

How do you plan on "making them"? If you got the correct alloy, how are you going to make the threads? If you cut the threads on a lathe or use a die, then you have messed up already. Cut threads are really weak compared to the rolled threads that a bolt manufacturer uses. They actually are compressing the metal when they make the threads, making it much much stronger.

 

The metal isn't hard to get. If you know where to look. The only reason I know is my brother is a knife and tool maker on the side.

I fool around with some machine work and tools myself and you would be suprised at how easy stuff like this can be made. There are tool and die makers all over if you look. Alot of the shops will help people with little stuff like this just to break the normal boring day. Just have to ask around.

 

The threads are cold forged, and the studs are re-usable, unlike the OEM bolts, and ofcourse the ARPs are much stronger. Overall clamping force is about double compared to stock, partly because more torque is going into actually going to clamping the head instead of defeating friction of the bolt.

As an update, some of the parts arived today (overnight, not bad), but the ARPs could take a week to get in, can't wait to start the assembly, I really miss that diesel sound.

 

Just for fun I tapped a piece of steel to 7/16 x 14 then tried tapping it to 1/2 x 13.

The threads in the steel were so weak the threads pulled out of the steel before almost any torque was applied.


ARP recommends you install to torque and then remove the head studs four times before you do the final assembly.
This removes any imperfections in the nut or stud threads so the torque is clamping force, not resistance of the nut to stud threads.
I also used moly assembly lube very sparingly so I did not contaminate the head gasket with oil.
Wipe all mating surfaces down with acetone to remove any oil contamination before you start.
The night I did my head install, that is all I got done.
I did mine in four steps each way, that is a lot of studs to install five times and remove four times in four steps each way.
My right arm was a bit tired the next day for some reason.

 

You actually have to torque them down and remove them 4 times when installing them for the first time?

The problem with tapping 1/2" in a 7/16" hole is that there is a space conflict between the two sizes, 1/2" is not big enough to be cutting into completely new steel, if the original hole were something like 3/8", then that would be a different story.

 

Yes, you will have a tired arm.

As an average I gained about 1 full turn on each stud nut by the fifth install.

 

1 full turn? OK, definately worth following the book then, glad the engine is out of the truck.

 

Update.........After the studs arrived the machinist figured it was not safe to use the heads that they had drilled out, the washers were too small on the bolts.

Now I have another question.

The failed fire rings in the head gaskets caused some erosion on the head in that area. Block has some as well, but not as bad as the head. They are going to send the heads out to be resurfaced, which has me a little concerned, but he told me that they will only take off about 5 tho off the surface. The info I have about the 6.9 says that there is about 9 tho of clearance between the valve and the piston. Do you think this is safe?

While looking up pistons from his suppliers, he came across pistons that were shorter than the stock size for this very purpose. Since I changed my mind on reboring, I'll need different pistons anyway.

 

I have the minimum head thickness service limits somewhere.
Now if I can just find them.


Found a post by Pete that had the service limits faster than I could find them on my computer.
Thanks Pete (PLC7.3).

There is a minimum head thickness regarding the milling of heads..... in most cases the heads are less than 5 thou over the minimum from first assy.

Minimum head thickness (from "deck" to valve cover surface): 4.7950"
If you need more let me know.


Also if you can, use 7.3 exhaust valves and all 7.3 rockers.
Better stuff than the 6.9 stuff was.

How much less is the pin to crown distance?

 

Well hopefully it will still be enough. I don't remember what the difference in size was between the stock height pistons and the shaved ones (more than 5 thou though), but for the same price, I might be able to get lower compression for more boost (might).

I take it you haven't heard of these before?

Not sure if I'll go with 7.3 valves and rockers, this build is getting more expencive every day it would seem.

EDIT: I remember one source that stated a crearence for the 6.9 to be 9 thou from factory, not sure if its true.

 

The clearance between the head and piston crown is the thickness of the head gasket with stock configuration pistons.
Stock height pistons are flush with the block deck at TDC.

When I was shopping for pistons, I did run into three different pin to crown piston heights.

I used stock height Sealed Power hypereutectic pistons, then milled them .040 which left me with a 20.25 to 1 compression ratio.

But milling the crown would do nothing to change the depth of the valve reliefs, so that would not help you any.
Where I think you will run into problems if you go below the service limit is the valves will open farther, and the valve reliefs will not be deep enough.
And my next concern is the pistons with shorter pin to crown dimensions may also have shallower reliefs.

One of the Reviva 7.3 engines I tore down must have had the block decks surfaced, the piston crowns were above the deck about 10 thousandths at TDC.
That engine did run rather well, but the piston to head clearance had to be almost nothing.
I never did run those numbers to see what the compression ratio would have been, but I bet it was up there.
That would have been a very bad engine to crank the boost up on.

 

I'm not sure I follow you here, the valves point strait down at the piston, so milling the pistons down should increase the clearance. I remember one of the pistons I pulled out of my engine had a valve imprint on it, and it was a nice little semi-circle right on the highest surface of the piston, not the cast prechamber zone.

 

The pistons protrude 30 thou above the block face .....

 

Mahle makes the pistons in .010 shorter tops for surfacing and such. I have them in my engine. There may be others also. My pistons are at 23 thou or so out which is less than stock and I am running 13 lbs of boost with arp 7 inch studs, they dont make a kit for a 7.3 so I got off the shelf ones and they are fine so far.