What are some opinions on the best NON MODIFIED engine, take price out as a factor. Based on performance alone, top non modified engine.

The new Novarossi LS/LL or RB V12. Btw, what do you mean by non modified? Sleeve only or also no crank mod?

Yep, got to agree with the RB V12

you can add os tz to the list

STS!!! AND the new TZ

Definately!

I believe TZ has sleeve porting then can't be considered as non-modified engine. CMIIW

TZ sleve has no cuts at all. STS D3 does though

RB V12..........Idles like an OS......really wide powerband..easy to tune....lasts longer than 2 gallons.....

Hmm... Maybe it's the Sirio Evo3 that already has porting on the sleeve. Totally forgot

Forget all that. That Mega ZX12 race is the best thing out there. It is a PAIN to tune and the conrod needs to be replaced after a few hours, but that will be resolved shortly. (and even still they're cheap) I'm closing in on Gallon #2 and the sleeve is still great, that engine never had a ton of pinch out of the box, but it still has plenty of compression even when hot. And it's still idling well and really low. I'd gladly choose it over the V12 (which I've run) and the TZ any day. I'm not a Serpent guy and in fact was pretty disappointed with the Mega at first. But now I love it once I really learned to tune it. Now throw in the money factor, which I know you said not to, but for $265 WITH the ideal pipe designed for it (which retails for over $100 ALONE), you can't beat it.

Correct me cause im sure im wrong, but i see no one mentioning the evo 3 or any novarossi engine when i see these are the two engines that won roar and ifmar. These wouldnt be 2 of the best?

All of the motors that many of you mentioned are very good motors. The OS 12tz has a stupid low end power band that will shoot you out of corners like a rocket. The RB V12 is an all-around workhorse with a good balance of low-end and top-end (much like the MT 12). The Picco Mega motors can be ballistic, but you have to have an associates degree to find that tuning balance. But, lets not forget about these motors (even though three have been recently discontinued):

Novarossi NS3 (discontinued)
Mugen X12 (discontinued)
Pixi Black (discontinued)
Max Power 12s3 (the RB v12 on roids)
Rex RER (Nova's Pixi Black)
Nova RR12 (and its cousins including the Rex)
Sirio Evo2 and Evo3 (makes some stupid power under the radar)

You pretty much cannot go wrong with any of these motors. They all have plenty of usable power with some to spare. Most of the above are $250 and under except the Max Power and Mugen X12 motors. So, there you have it. A good range of motors that will fit in whatever niche you have.

You answerd a question i didnt think could be answerd. I see thier is no one best engine? I guess alot of it is prefrence? The only thing i still wonder about is engines that cost 350+ compared to much cheaper engines such as the tz and those pixi black rossi's that seem like they are in the same league. There isnt a huge on road scene here so i cant really ask around about this stuff.

I think it's more like a PhD