Motor building questions.

[Pleky]

I'm getting set to build up a 3.2 and I had a few questions.

First, I was thinking I could bore the thing out an extra millimeter or two. Anyone know how much is too much for the block to handle?

Second, I figured that I could bump the compression up a smidge to 10.1:1 and be happy. I'm lying to myself. If I decided later that I wanted a bit more power, could I safely boost it? We're talking 5lbs or less (I don't want to start going through transmissions like they are wear parts).

Thanks, and sorry if this was answered elsewhere because I can't find it.

 

[K-Dawg]

Stock 3.2 head gaskets can only handle a 93mm (I think that's right) bore. Any bigger and you need custom gaskets.

Stock compression is 9.8:1; 10.1:1 should be fine for low boost.

www.shonutperformance.com

 

[93rev2sev]

I would pass on the boring if there are ANY plans for boost. You will get more of a return by going up 1 or 2 PSI than having a slightly larger bore. Also, it will cost over a grand for pistons/rings/etc.. if you change the bore.

A stock SHO engine can handle plenty of boost. Upgrade the fuel delivery(regulator, pump and injectors) and you can safely run 10+PSI with a decent tune(which you would need anyway).

I've seen 9PSI with stock injectors, regulator, pump on my 140,000 mile engine and haven't burned anything up *YET*...It's only a matter of time if I decide to keep it at 9PSI. I think 6PSI is the limit for stock fuel delivery....and even that's pushing it.

My advise (since you only plan on MILD boost) would be to "pretty up" a $300 engine with all new seals and some rebuilt heads and rod bearings and concentrate on fuel/air delivery and a tune.

 

[Pleky]

Hmmm, I imagine I could get custom gaskets from cometic but I haven't gotten a response from them yet :/ there is a company in texas that does custom copper gaskets too, but I forgot their name at the moment.

I know that a stock motor can take the boost, and that its more cost effective but I decided that since I'm going to tear it down I might as well build it up stronger. Its a nice 80k mile block. There is supposedly a guy out here that does really good motor work so why not just bore it a bit when I get new pistons?

I'm pretty ocd sometimes, so I'll probably replace most everything I can just because.

 

[rubydist]

If its a typical SHO motor w/ 80k miles, you will still see the honing cross-hatching on the cylinder walls, which means all you need to do is take the rings off the pistons and clean them up, and you can use the same parts - no need for pistons, rings, or boring. There are plenty of other places to spend your money that will gain you much more.

 

[92ShoOff]

Yeah 93mm is the max based on the 3.2L head gaskets. I bored mine out to 93mm with custom Diamond Racing forged aluminum pistons and it cost a bit but the internals were balanced also, and the engine makes GREAT, smooth power.