Boring out a 6.7

chuggins10

chuggins10

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May 10, 2007
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I have a block that has some scratches in the cylinders and will need to be bored out .20 to smooth them out. I have a goal of max 1200hp on the set up for next year. We will be running a 400/500 compound set up and a large set of injectors to help keep timing down. My worry with going .20 over is how much will that weaken the block? Or should we bore it out and install press in sleeves to come back to standard bore and have the material on there?
 
Custom billet sleeves would be a better option .. I was told Fleece is doing a lot of that 6.7 non deckplate stuff ..
 
Sleeve it. .020" on the 6.7 is no bueno unless its at low power. MANY instances or wrecked crap with a .020 cut.
 
A lot of places are sleeving them back for the high performance stuff. As mentioned the fleece "6.4" is 4.88 stroke and sleeved back to 4.125".
 
Sleeves, if I'm not mistaken the Revmax shop truck was bored and they cracked a cylinder recently. Just something to weigh in
 
Thats the most recent example of it. There have been many instances of this over the years.
 
So for a high HP application, do you take a 6.7 block and sleeve it to a 5.9 bore and add a deckplate?
 
There are a few ways to sleeve it. You can go to a smaller bore, you can stay at the stock bore, and we have even seen 4.250 bores. All that with a deck plate.
 
So what's the consensus on maximum torque/HP on a regular wet block standard bore 6.7 before a cylinder wall lets go?

What about a wet 5.9?

Our new race truck is a wet block .040" over 5.9 but it lives at high RPM to keep torque down, and hopefully make it live. Since filming this video, HP has gone up substantially with the bigger injectors, like several hundred horsepower, so it will be interesting to see if it holds up at the drag strip.

[ame="http://www.youtube.com/watch?v=7Zrx362yze8"]http://www.youtube.com/watch?v=7Zrx362yze8[/ame]
 
cumins01 said:
So for a high HP application, do you take a 6.7 block and sleeve it to a 5.9 bore and add a deckplate?
Click to expand...

Most commonly boring a 6.7 to accept a 4.125 sleeve with a deck plate, netting 391 ci. Some guys sleeve them back to a 5.9, some go as much as 4.250.
 
One of the highest hp 2.6" engines in the country is a wet 5.9L block with a cast cam. Even though it can be done with apparent reliability, I can't say I would recommend it. Common sense would lead to a 4.125" ductile iron sleeve in a 6.7L block filled/non filled depending on the application.
 
Nyes auto did the machine work on my 6.7 .20 over block. Currently just over 30k miles on the engine running a GTX4508R with no issues. 1034Hp & 1900Tq.

Hoping to get at least another 30k out of it.......
 
Count yourself lucky, there are a lot more
bad experience with going that way.
 
I have a 6.7 that was recently bored .0020 over but the pistons/rods have not been installed yet.

I have already bought the 0.020 over pistons and my goals are (as reliable as possible) 800 hp daily driver. Should I pay the 10% restocking fee at cummins and eat the cost of the boring and resleve?
 
EverydayDiesel said:
I have a 6.7 that was recently bored .0020 over but the pistons/rods have not been installed yet.

I have already bought the 0.020 over pistons and my goals are (as reliable as possible) 800 hp daily driver. Should I pay the 10% restocking fee at cummins and eat the cost of the boring and resleve?
Click to expand...

.020" is fine, we've built countless non deckplate setups +.020" without issue.
 
Somewhat related; How important do you guys feel coating the skirts is on a stock bore 6.7 with industrial open bowl pistons?


Also related; I've been told piston clearance should be on the looser end considering I'm running cast pistons in a slightly worked up 6.7. I haven't measured piston clearance yet but it should be slightly more than normal due to getting a light hone on the cylinders. Any ideas on this topic?

And does everyone feel arp mains are mandatory for a 4,500 RPM street motor? Crank has been balanced but was very close to begin with.
 
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