IP Upgrades
Junior User
Joined: Feb 2007
Posts: 55
Likes: 0
From: Loveland, Co
Hey guys, just want to say what a great site this is!!! I was just wondering how low of a compression ratio i could run and be reliable on my 94 IDI turbo diesel?? I was thinking of doing a cummins swap but after thinking about it i like the challege of making decent numbers out of a rig that you don't see everyday!! so any advice would be great thanks guys!!!
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
Find a good never been bored 86 or 87 6.9 engine is a good start.
Living in Loveland is going to limit how low you can go on compression if you want to start the engine in the winter though unless you can plug in everywhere you go.
I know because I used to ski there back in the early 80's.
Living in Loveland is going to limit how low you can go on compression if you want to start the engine in the winter though unless you can plug in everywhere you go.
I know because I used to ski there back in the early 80's.
Junior User
Joined: Feb 2007
Posts: 55
Likes: 0
From: Loveland, Co
Well good news is i just moved to grand junction so the weather is a little warmer all year round and there is an international and cummins dealer here in town! One thing the bothers me is all the cummins running around showing off, i want to be able to keep up and show them what ford power is all about!! so you think i should go with an older 6.9?? isn't the compression higher on that then my 7.3? the after market is limited enough isnt it worse for the 6.9?
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
6.9 compression is higher than 7.3 compression, 22.5 to 1 versus 21.5 to 1.
Anything that will bolt to a 7.3 will bolt to a 6.9.
Heads are the only big ticket parts that are not swapable, and there are some other parts that go from the 7.3 to the 6.9 that can not be swapped the other way.
Anything that will bolt to a 7.3 will bolt to a 6.9.
Heads are the only big ticket parts that are not swapable, and there are some other parts that go from the 7.3 to the 6.9 that can not be swapped the other way.
Elder User
Joined: Apr 2006
Posts: 894
Likes: 0
From: South Dakota
I have one question Dave, if taking .020 off the top of the pistons on the 6.9 drop the compression to around 20.25 to 1, would taking .010 off the top of the stock pistons on the 7.3 bring the compression ratio to about the same? I'm looking at getting into my own rebuild here soon and I want to get everything planned ahead... Thanks
-Dave
-Dave
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
Have to figure that one out, all my calculations are for a 6.9.
Bore and precombustion chamber size are different on a 7.3.
Off the top of my head, the lower 7.3 compression ratio is just from the precombustion chamber size difference.
Bore and precombustion chamber size are different on a 7.3.
Off the top of my head, the lower 7.3 compression ratio is just from the precombustion chamber size difference.
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