Worstenemy453
Full Access Member
Im most likely going to re-do the 6.9 and focus money on a D60 and ZF 5-6 speed and i was wondering if i could drill and tap the heads and block to use 7.3 studs or bolts ?
Machine Work On 6.9 Block ?
- Thread starter Worstenemy453
- Start date
FordGuy100
Registered User
Nope, difference between 6.9 and 7.3 is 1/16" of an inch, which isnt enough to drill and tap, wont give the threads enough meat. 9/16" is the way to go, but nobody has attempted it....
Worstenemy453
Full Access Member
Where could i get 9/16"s bolts or studs that would effectively hold the heads down. Grade 8's from Fastenal or maybe the 9's ?
FordGuy100
Registered User
Now I was just throwing the idea of 9/16" studs, nobody has attempted it and as far as we know, it might not work. I would call ARP for 7" 9/16" studs if you went that route.
Best and easiest route for a 6.9 is ARP studs, I'm holding 15+psi for the last 5000 miles.
Best and easiest route for a 6.9 is ARP studs, I'm holding 15+psi for the last 5000 miles.
The ZF6 speed bellhousing will not work with the IDI's or 1st generation 7.3 PSD's. Plus, there is no real reason to go to all the trouble to modifiy everything to make it work. The only thing you gain from the ZF6 is a granny gear. It is basically like having a ZF5 with a low crawer gear. IIRC, the gear knob says L (for low), 1, 2, 3, 4, 5, and OD.
Heath
Worstenemy453
Full Access Member
someone else on here is going to do one. I was thinking doing the ZF-6 and NP 271 set-up but i havnt looked to see what they go for.
On a side note, can i use an 87 pedal assembly in an 86 or do i need an 80-86 set-up.
The only guy to do it in the past was a member by the name of Jaybee. He sold that truck about 2 years ago. It was big project. Not only do you need to make mods to get the tranny to bolt up, but you also must have a custom flywheel and clutch made.
The 87 pedal assmemby will work fine.
Heath
the 87 pedals wont work. i tired.
also the way u listed the zf6 speed heath was a 7 speed. lol
it goes L-1-2-3-4-OD
4 speed with a low hole and overdrive.
also the way u listed the zf6 speed heath was a 7 speed. lol
it goes L-1-2-3-4-OD
4 speed with a low hole and overdrive.
bike-maker
Full Access Member
When I traded my C6 for the ZF5, I was going to try and modify the pedal assembly out of my 89 parts truck to fit: no worky. Ended up snagging one out of the local JY for $20.
Knuckledragger
blowing chunks and grabbing porcelain
Wrong. 7/16 is 1/64 of an inch larger than the drill size for 1/2-13 threads. All you would lose is about .007 (two pieces of paper) per side at the root of the thread, giving you about 95% of thread surface compared to a ****** hole. If you want complete threads, tap the block for 1/2-20 threads, which use 29/64 drill size. Much stronger, with a larger root diameter.
The bigger problem is getting the holes drilled and tapped straight. If you have a machine shop, not a problem. An easier solution with less work is to install the 7.3 heads with slightly thicker washers on the studs to reach over the 1/2 inch holes.
There is no good reason to attempt using 9/16 thread studs. Try finding that size in any hardware store, it is not common. It may in fact be a disaster, since there is little material on the lower bolt bosses on the block. I have not compared a 6.9 and 7.3 block, so do not know if the larger head bolts got more material in the block.
bike-maker
Full Access Member
I'm thinking you would be ahead just getting a set of ARP studs for a 6.9. With the studs being so strong, the weak link probably becomes the threads in the block: drilling and tapping the block and leaving less material could possibly result in a weaker head gasket seal than just using the 6.9 hardware.
We all know that one of the weak links in the 6.9 is the head gaskets, but has anyone experienced any failures when running studs?
Used to build alot of big block chevy's: they were notorious for the head bolt threads pulling out of the block during assembly when using bolts. Repaired alot of them with heli-coils. The point is, I never saw a head gasket fail on one running ARP head studs: even the blown alcohol motors with 13:1 compression and about 20 to 25 pounds of boost.
We all know that one of the weak links in the 6.9 is the head gaskets, but has anyone experienced any failures when running studs?
Used to build alot of big block chevy's: they were notorious for the head bolt threads pulling out of the block during assembly when using bolts. Repaired alot of them with heli-coils. The point is, I never saw a head gasket fail on one running ARP head studs: even the blown alcohol motors with 13:1 compression and about 20 to 25 pounds of boost.
Uh, did everyone one forget the thread where a user who had stated that he infact did the exact same thing and mounted 7.3 heads to his 6.9 block??????? It can be done, look at the thread, there are even the BOOB required pics to prove that he did in fact do it and is running it.
bike-maker
Full Access Member
Wouldn't that require running the 6.9 bolts through the bigger holes in the 7.3 heads?
redneckaggie
rebel w/o a cause
The guy had a 6.9(7/16) head drilled to fit a 7.3(1/2) bolt. He did not drill and re tap the block because the engine was a 7.3, not saying it isnt possible though.
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