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Engine rebuild with bigger pistons

visionary613

CEG'er
Joined
Sep 27, 2009
Messages
118
Location
Redmond W.A.
I know alot of the older carborated drag cars have bored out cylinder walls with bigger pistons. Can you do this on a fuel injected car with a ecu? Just reprogram the air/fuel ratio. Or is it more involved?
 
Sure you can do the same thing but you'd need a tune afterward to make sure it was running right. Of course on this platform people just jump to the 3 liter instead of messing with matching rods and pistons with the shop guys.
 
I want to do a fun project. I don't need a motor, so I could take my time boring out a 3l with aluminum forged pistons. What 3l's are the best for 3l 2.5 hybrid.
 
Just wondering if many companies make rings for oversize pistons for the Duratec. You don't hear of many people doing this anymore, but it used to be fairly common. When my SB chevy was done, I had a bunch of companies to pick from. Sorry, just wondering out loud.
 
I think it would be awesome to see what someone could do up with boring out the 3L! And see what other power numbers could be squeezed out.
 
U couldnt bore it out as much as u would think with a 3l without significantly weakening the combustion chambers. I dont think it would be enough bang for the buck. It would be more cost effective to use that time and money on other performance items. And get a bigger gain.
 
years back when I first joined neco there was a guy on the boards. user name was Jjennings he was from Cali. He had his 3L bored out and hit some awesome numbers I have the magazine here somewhere I kept all the 3L cougar project mags
 
years back when I first joined neco there was a guy on the boards. user name was Jjennings he was from Cali. He had his 3L bored out and hit some awesome numbers I have the magazine here somewhere I kept all the 3L cougar project mags

I remember hearing about that also. Please post the mag if you have the chance!

But to take you guys further back....back in 2002 someone actually bored out a 2.5L.... bringing it to a 2.9L or 3.0L. He got the car running....but it never ran right. He did use new pistons and over sized rings also. But he ended up selling it before fixing the issues he had with it.
 
I am picking up a blown 2.5 from bugzuki. I am not sure yet if I'm just going to put in forged pistions, crank, cams etc... Or bore it out first, either way this should be a fun project. I think It really depends on price and avalibilty of the needed parts. Not sure boring is a good idea with the high pressure in the 2.5, but we will just see how much space shaved off the cylinder walls is feesable.:laugh:

I will document the entire build for you guys. I will probley get the engine this week if bugzuki has the time.
 
The price for the bore on the block, just PNP the heads and get some larger valves. Youll be way more satisfied. But if u end up getting the bore let me know how much u shave!
 
Oh geez, Anyone got a crankshaft lying around for a 2.5. Rod bearing 1 and rod bearing 6 took a poopy in the engine. And the crank is cranky from it. Aka the crank is f#%cked.
 
You might do a bit more research before trying to bore a Duratec. There isn't much room. The aluminum block uses cast iron cylinder liners. The combining of the block and cylinder liners cannot be done manually. If you pull the liners out, the block tweeks and becomes scrap. The 2.5 block will not accept the 3.0 cylinder liners. Also there isn't enough meat to bore the 2.5 to the size to become a 3.0.

The only one I remember reading about with an overbore ended up something like 2.7. It is MUCH more cost effective to just get a 3.0 long block and go from there.
 
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