7.1L IDI engine

[schoelta]

Somewhere I remember seeing a 7.1L idi engine. The company I think put 7.3L heads on a 6.9L, or it was the other way around. Anyone know what I am talking about?

 

[6 Nebraska IDIs]

A 7.1L would be a bored out 6.9, heads have nothing to do with it except you'd have to use the 6.9 heads on that 7.1.

 

[6.9poweredscout]

what would a 6.9 bored .020 over be? that's what mine is....

-Jon

 

[Mr_Roboto]

7.1 L would be half of the overbore to make a 7.3. I think the difference is .110, so a .055 overbore would make 7.1L (displacements are all rounded up or down so the exact bore to displacement would have to be calculated by bore and stroke).

The 6.9L and 7.3L blocks have the same water jackets, so any 6.9 can be bored to 7.3L or more barring cavitation perforation.

 

[FordGuy100]

what would a 6.9 bored .020 over be? that's what mine is....

-Jon

Its like 6.96 liters, 424 cubic inches or so. If you round its a 7.0 liter

 

[6.9poweredscout]

Its like 6.96 liters, 424 cubic inches or so. If you round its a 7.0 liter

thanks what i thought! thanks!!

-Jon

 

[k_williams1982]

I had thought about rebuilding my old 6.9 and boring it .060 over and bolting heads from a 7.3 on it. However, the head bolts for a 7.3 are 1/2" and the 6.9 uses 7/16" head bolts. I contacted a couple machine shops and it is possible to have a custom set of head studs made that are 7/16" to thread into the 6.9 head and 1/2" on the top for the 7.3 head to sit on. I'm still debating to do it or not. I figured that only going .060 over would still leave some "meat" on the cylinder walls and still increase my displacement to approx. a 7.1L engine.

 

[david85]

Do the minimum bore possible. Cavatation isn't worth another 0.1 L of displacement.

 

[LCAM-01XA]

How about sleeving a 7.3 to downsize it?

 

[FordGuy100]

I had thought about rebuilding my old 6.9 and boring it .060 over and bolting heads from a 7.3 on it. However, the head bolts for a 7.3 are 1/2" and the 6.9 uses 7/16" head bolts. I contacted a couple machine shops and it is possible to have a custom set of head studs made that are 7/16" to thread into the 6.9 head and 1/2" on the top for the 7.3 head to sit on. I'm still debating to do it or not. I figured that only going .060 over would still leave some "meat" on the cylinder walls and still increase my displacement to approx. a 7.1L engine.

Geez that would get expensive for those studs. If you were going to go that far I say just have the machine shop drill and tap for 9/16" studs in both the head and engine, blowing head gaskets would be a thing of the past

 

[RKOCH]

How about sleeving a 7.3 to downsize it?

No need to down size it. Milodon makes an extra thick HD sleeve for the 7.3L. So you get a cylinder wall thicker than a 6.9L with a 7.3L bore. And is made from a much better material that resist cavition and overall wear.

 

[icanfixall]

Rkoch... Got a part number for the Milodon sleeve????

 

[RKOCH]

I'm sorry Melling not Milodon Melling part #CSL 2274 HP is the 7.3L extra thick sleeve I have used in the past. And they are available.

 

[subway]

i assume you would still need to find a machine shop capable of properly putting in the sleeves then. i have heard stories of Dave Spanogle SP? from the other list having the sleeves drop out on a couple of his remaned engines.

 

[tradergem]

I can't remember who it was that re-sleeved their 7.3L engine awhile back, but they said that they had the machine shop leave a shoulder at the bottom of each bore for the sleeve to sit on. Thus preventing the sleeve from moving down in the bore while running. My understanding is that most machine shops run a straight bore with no shoulder and this allows the sleeves to move which of course ruins the engine.
Jim