I ran across a newly rebuilt 3.1 for a replacement of my current 3.1.... Containing all new internals, rings pistons gaskets and so on and so forth. I got this engine for free so instead of just dropping it in my car when my current 3.1 gives I'm going to port and polish the heads and I'm contemplating on boring it and upping the compression.
If I was to bore how much could i get by with taking off? .40 ???
So I don't search for weeks where can I purchase the over sized pistons at over the net?
What about a crankshaft? I have no idea what kind the 3.1 has but I would love to replace it with a forged one if not applicable to the 3.1 with rods also....
Thanks
RJ
If I was to bore how much could i get by with taking off? .40 ???
The maximum oversize I believe .040", but usually you get such a small increase, you just use overboring to clean up the cylinder if it needs it.
So I don't search for weeks where can I purchase the over sized pistons at over the net?
northernautoparts.com sells hyperutectics in all the available sizes.
What about a crankshaft? I have no idea what kind the 3.1 has but I would love to replace it with a forged one if not applicable to the 3.1 with rods also....
The stock 3.1 crank is cast, yes but it's tougher than you will ever need it to be. It will not break (I've run mine with 400+ wheel HP and it's fine). If you really want, you can take a 3500 crank (it's forged factory), machine the rod throws (they are 2.1" on the 3500) down too 2.0" too fit the 3.1 rods, or you can offset grind it to increase the stroke. Then you need to press off the timing ring on the crank, and machine in the proper grooves for the 3.1 sensor.
Curtis
91' Turbo Z24
http://www.turboz24.com
Boring over .40 won't give you much of an increase in displacement, so if the engine is already rebuilt then I wouldn't touch it. Since Curtis says the stock crank is strong then I'd port and polish it like you want and maybe put a cam in it too. Check with any good performance parts place and tell them what the engine is and what you want to do with it and they should be able to hook you up with parts that will work well together.
If you decide to do a cam
http://www.iskycams.com/ is a good company.
You can't outrun the radio.
yeah my bad I was meaning .04.... But if your saying the only reason boring is so popular is to clean the walls up for scrapes and such then I will just hone it if needed.... Maybe I could just purchase some flat-top pistons and just build my heads up with the idea of high revs and strength....
flat top pistons will yeild you around 12.5:1 compression. it has been done, but isnt very friendly on the street.
if the cylenders are prety good, just get it bored the minimum it needs, throw a set of hyperutectic pistons in that are built for a 3100. if you are realy gonna beat on this motor, install arp rod bolts, beam polish the rods and have the resized, then balance the rotating assembly. its a bit of work, more money, but worth it. as for top end, id honestly use 3400 heads. doing a 3400 top end would be cheaper than having your heads ported.