Justin WAS running 110ft lbs using the same 8740 Chromoly Studs on his 6.9, not only Justin but many other IDIers started to see Head Gaskets failing in their 6.9Ls, I was talking with Justin at the time along with Muddy74Ford and Justin had found that what was happening is the Head Studs were stretching over time and weas leading to the gasket failure because they were allowing the Heads to lift with higher cylinder pressures. So Myself and Muddy74Ford both contacted ARB and asked them at the same time Justin did (without either of us knowing the other was talking to ARP) and got about the same information from ARP that we were all putting the ARP 8740 Cromoly Studs past their yield points by torquing them to the 100 ft lbs over ther 80ft lbs suggested by ARP.

We talked with ARP and came to the conclusion (at that time Justin had also come to the same conclusion) that the +625 Material was the best bet to use given the application. Justin has gone another route to find a more affordable material and Stud to use since ARP's Price Tag was pretty high even with a Group buy. Justin is currently trying his own 9/16" studs for his 6.9L and I've decided I'm going to just purchase the +625 Studs to try a different route and since my engine was already built around the 6.9L studs.

Nothing against Justin, just going another route.



The Bronco and Pickup in the F100-F250 Variants were the same Frame/Perch widths (Excluding the F250 Highboys from 1967-1977 early) in the rear as well as the front. The F250 had a leaf front and a slightly different shape on the Front Horn than the Bronco/F100-250 but past that the frame width was the same on the 2wd Frames from 1973-1979 and 1977.5-1979, the 2wd was a different frame arch towards the cab as the 4wd truck however, but that is another topic.

Now as for the F350 Chassis Cab Frame they were significantly different even from a 70s Truck Chassis. they actually narrow to an almost Highboy width after the Cab and use a Highboy Style 2" Spring as opposed to the 3" Bronco/F100/F250 rear spring (Again, excluding Highboys of course) so they have a much narrower perch (a lot like the F Series 3" Perch in 2") and a narrower Perch separation from rail to rail. the Shock mounts for the 1979 F350 are just clamped on with U bolts for the Dana 70.

Also to my knowledge the Dana 70 SRW was the only axle used in the 1979 F350 and the Dana 70 SRW and DRW was the only one used in the F350 Chassis Cabs, the Sterling was not used until later with another Chassis.

So I would not say the 10.25 is a direct swap at all and the Perches would need to be modified in order to work. I also have a 1979 F350 I am currently swapping a 7.3L IDI into here and explored the Dana 70 F350 option.

 

Robert thanks for the update. I have been curious what has been going on with your build since I have been on deployment. I do thing the ARP 625 is the best route even though they are expensive. I will probably do the same with my build once I am back... Have you decided on what you are doing as far as turbos go?

 

I agree with Robert on this one... and the 10.25 Sterling wasn't even used in a Ford Truck until 1985... How are you getting that it came in the 1979 F350 exactly??? Did someone swap a Sterling into your f350??? I'm just a bit confused because the Dana 70 was a 10.5" not 10.25"

http://en.wikipedia.org/wiki/Sterling_10.5_axle

 

Justin did not measure any permanent stretch until 130 ft/lbs, with 110 being in the safe zone. I am guessing 80 ft/lbs is ARP's conservative rating. I don't know how much you have invested in your 6.9 block and heads, or what your 625 alloy stud quote is, but one of my local machine shops quoted me $1,250 to sleeve a 7.3L block down to a 4.00" 6.9L bore... just sayin'... That might be a more cost effective option to achieve the head fastener strength you want. Here is the post from Justin's head stud tech thread on the ARP stuff...

 

F834, theyre saying the stretch was over time.

Ill have to re-read what i wrote, because apparently you guys are mis interpreting what i meant to say. I am putting a 10.25 in my 79 because the D60 rear that was factory, went **** up. Granted by my guesstimations its got around 400k on it, but when i put the IDI in it started growling. Now if you get on it hard it jumps teeth... not pretty. Also, inboard drums are seriously the gayest thing since the rainbow parade. The only F350 dents ive seen with 70s are 2wd, ive only seen one other f350 upclose that was 4x4 and it was a D60 rear also, with some help i came to the conclusion it has something to do with gvwr, aka regular F350 vs F350 super camper special for instance. Im not saying this as fact, just what i have found and believe to be accurate.

 

If you talk to Justin he will confirm that the Studs did stretch and that the Fastener is the issue... Both me and Robert here have both worked closely with Justin since the beginning, and the Fastener was at fault...

As for the Sleeved 7.3 Block this Block has already been build and is already done, it's a minimal investment to have the Studs installed, Sleeving and building a 7.3L Block is a whole new endeavor and will be starting all over...

 

Are you kidding I have 8k in just the motor, there is no way I am starting over! and dumping all the machining, finding and buying a 7.3 the rebuilding again.. I think I will stick with the ARP studs.

 

I even got a little confused on that post, sorry about that if it sounded like I was jumping on you, not my intent...

I have seen some of the Standard Fleet Issue F350s with D60s but really the better option was the D70 Single Rear Wheel due to the larger ring gear and Carrier Bearings.

I don't know how common the D60 was in F350s or if it was even Factory Available over someone twinning D60s.

A good solution would be the Sterling in that case if a D70 is out of the question,myself I'm more with Robert on the keeping it Period correct which some people dont care so much about, but I always find it interesting to get 1970s stuff to work.

As for jumping teeth I'm curious to know if the D60 maybe had an aftermarket ring gear in it or was possibly abused prior... I've put some D60s through serious abuse with no issues, and I've had IDIs in front of Ford 9" axles and not had any issue either.

I know Robert here was going to address the issues with modern Ring gears being too soft (Cheap Chinese steel just isn't as good as the old stuff was) but I'll let him address that.

With that Sterling Swap you can swap to it but the Perch Size may need to be changed if you have 2" Width springs and you will definetly have to change where the perches sit. IDK if that answers your question or not?

 

Great Googly Moogly those rockers are trick! I'm just glad you can install them after the head is already bolted up, or else I would be laying up an extra few dollars now for "While it's all apart anyway" expenses.

I may have missed it if you made one already, but could you lay out an itemized list of what your individual machine shop costs were (I.E. magnafluxing, balancing, line bore, etc.)




As for a D60, the handful I've seen blow up were spinning 38" tires or bigger under trail trucks that barely qualified as "trucks" anymore. At 400k, I'd guess that just bearing wear alone could make a tooth have bad contact under load.

 

I have not broke out all the pricing on the build yet. I am still buying stuff. once I get this all done I will post all the pricing. if you look back at page 5 I listed what was done on the engine so far. except the new tear down replace the studs and rebuild.


The rockers are more of a safety and to see if there is a difference, a lot of people say many different opinions only time will tell.

Currently I have the drivetrain in the shop. I am having Yukon bearing (Timken) and seal kit, 35 Spline Yukon axles, bore out the tubes to fit 35 spline, Dana 410 gears, ARB Air Locker, and Rear Disc brakes. The Dana 44 Yukon bearing (Timken) and seal kit, 30 Spline RCV Axles, Dana 410 gears, ARB Air Locker, Convert to 8 lug outters.

 

Thanks for posting it here and keep updating your blog!

What turned you off to some of the other machine shops before you found the right one?

 

That is a great post by justin. So we could basically go in and safely retorque our original head bolts to say, 105lbs for those of us running stock head setups? If so, then this could add some significant clamping force to mild turbo builds without doing studs.

 

The Studs don't stretch over time, they just simply aren't strong enough, even at 110Ft/lbs to hold the heads down when big combustion pressures are happening.


You have to think of the fastener like a super stiff spring, and the 7/16 studs simply don't have the cross-sectional area to pull the loads necessary to hold the heads down.


ARP specs the torque at 60% of yield for CYA purposes, I was basically told that by the phone tech when I was talking to him about overtorquing them, and what I was getting out of them. Generally that is sufficient for any automotive fastener requirement. However, being that the head fasteners were undersized on the 6.9 in the beginning, and we are trying to pull a lot more out of the parts than originally asked, the only way is to get the preload closer to yield, which is why we go to 100-110. That being said, Im under the opinion that even if we took them to 120, which is 90+% of yield, we still wouldn't have the clamp load necessary with 7/16 8740 studs, to take full advantage of cylinder pressures. The 7.3 doesn't seem to have any issue holding pretty good cylinder pressures, because you can clamp the **** out of the studs.


The 625's should do just fine, there is more preload out of them for a given torque rating because of the material. That being said, If they were mine, I would take the 625's to 130ft/lbs heat cycle them a few times, do a retorque, and run the **** out of them. If that doesn't hold up, than your only other option is a 7.3 block.

 

Thank you Justin for the post.. Happy Thanksgiving to all

 

Seems like the threads would pull out of the block. No problem with that you think?