Contour Enthusiasts Group Archives Forums General Autocross and Open Track Hypothetical: Rebuild 2.5 or swap to 3.0?

As the title says, this is hypothetical. I'm playing "what if" games in case my engine blows. I'm at 70k, which seems to be close to the danger zone for rod knock, but I guess I'm OK so far.

So, anyway, If I had a problem, I could rebuild the 2.5 with the ".040 inch overbore" and other assorted tweaks and remain in STS.

Or, I could upgrade to the 3.0, but that puts me in SM, where I'm suddenly way behind. Hey, let's put in the LSD and lightened flywheel/clutch while we're at it, OK?

Money is an issue, here.

What would you do?
Rebuild the 2.5 and stay in STS
Swap in the 3.0 and run with the big boys

I voted for the three liter and run with the big dogs. My guess is you're competing for the challenge, right? More competition will make you a better driver, IMO.
Good luck!

3L! If you stick with the 2.5, you will still have the oil drain issues because of the heads. The 3L heads have oil drains on both sides so you don't have to worry about spinning a rod bearing in a long, tight, right-hand turn...


I guess it all depends on what you want to do with the car. If you plan on keeping it for a while, i'd say go for the 3l swap. If you don't well, yea, I think you know where i'm going with this.

I don't know.

Before I started AutoXing it was 3L all the way. After I started AutoXing it was run this until it blows up and then decide to either go 2.5L or 3L or get rid of it since the car is already totaled and has 140K on it(I ended up getting rid of it based on the totaled car(red rear bumper like you see in all my AutoX pics) as well as the scrapes down the side (damn GF needs to learn how to back out of her spot) and a few other issues that needed taken care of at the time as well as the high miles.

You should have lots of time since my rod knock did not show up until 143K.


I am currently thinking the same things about my miata.

if the 1.6L goes do I put in the 1.8L and go for CSP? Stay 1.6 for ES/STS2 put in ??? for SM? and I have not come to a decision on that either. I know I am not any help on your decision but I just wanted to let you know that others are out there in the same boat as you are.

3.0 seems to be the best bet.

You would be more pleased with the end result of your car. Better power, and better overall design.

Of course you would be in a more competitive bracket. But the challenge is what makes it fun and its what pushes you to new limits. Plus mucho respect for going against the big dawgs and doing well.

Buck for buck, which would cost less overall?

If you go the cheaper route, you may have $$ left over for that LSD or other goodies. MSDS, cams... whatever.

Good question.

Iâ�?��?�m thinking it would be cheaper to rebuild the 2.5, and thatâ�?��?�s why thereâ�?��?�s a dilemma. It would also allow me to stay in STS, where the LSD, flywheel, and headers are not allowed. I originally went for STS so I could have some fun modding and racing without going overboard. If I go for the 3.0, Iâ�?��?�m going to want to add the flywheel/clutch and LSD â�?��?while weâ�?��?�re in thereâ�?� or else I know Iâ�?��?�ll always regret not doing it, and may never tear the car down again to do it later. And as long as weâ�?��?�re messing with it, isnâ�?��?�t it easier to bolt on those headers while the engine is out of the car?

I donâ�?��?�t see myself doing either job myself. I would be over my head in either case, so Iâ�?��?�m asking TH for a ballpark figure for a â�?��?crateâ�?� 3.0, if the need should arise. So, thereâ�?��?�s about $1200 for the 3.0 motor before Terry touches it.

I guess there are other options, too. I havenâ�?��?�t thought about STX or ESPâ�?�¦

it was cheaper to do a 2.5L rebuild for me, that's why I went for that rather than the 3.0L. For 2.5, all you need are PnP heads ($1000), new bearings ($50), and IF YOU WANT, new pistons ($600). Still cheaper imo than getting a new block prepped and shipped ($2500+installation). I'm not including tuning and chip, since you'll have to get it for both. But for 30-40lbs more torque, I dunno. You'll be at the max level of the NA 2.5L, w/o tranny upgrades and headers.

As for the drains in the heads, etc. I personally feel it's a bearing thing, i haven't heard (or can't remember) anyone throwing a rod with clevite 77 rod bearings on this board.

If you PLAN on tranny fun and headers, then get the 3L for sure.

What do the new pistons give you?

If I replaced the SF rods with regular forged rods, what would I be legal for? (STS, STX, ESP, SM?) [some people think it's a rod thing]

What do you mean by "max level?"

If I did the rebuild, it would be to the max allowed within stock category rules (which is what STS allows). So, actually, my earlier ".040 inch" statement is wrong. Stock only allows .020 inch overbore. Street Prepared allows a bit over .040 as well as port matching and no more than .010 off the deck.

Re the oiling failure/spun bearing risk....

It has been proven by several racers, Chris Reinke, Mirko, Bondrurant, etc. that an Accusump solves the problem on the 2.5..inadequete head drains or not. $300 = cheap insurance. So what class would THAT put you in?