rb25 or rb20?

[2face]

ive been thinkin of buyin an rb25 engine, but i noticed that its a little bigger than my stock engine. so i dont know if i should get the rb20 or rb25. im hesitatin on the rb20 because its smaller than my stock engine, even though it has more hp. so which engine would fit better, but still give me more hp?

[madcowvert]

which ever one you put will fit fine i would go rb25

[Eikon]

ive been thinkin of buyin an rb25 engine, but i noticed that its a little bigger than my stock engine. so i dont know if i should get the rb20 or rb25. im hesitatin on the rb20 because its smaller than my stock engine, even though it has more hp. so which engine would fit better, but still give me more hp?

Good question. Sounds like you've done some research already... Nice to hear an educated person looking for opinion rather than a newb looking for info that's already been posted 20 times.

Anyhow... let me ask you a few questions in return...

What's your goal with the 'vert? Daily Driver, Weekend cruiser, autocross, dragstrip, showcar, street racer?????

What's your bank account look like? how much are you looking to spend to get the hp that you want?

What's your level of mechanical expertise? In other words, if you go RB can you fix it if it breaks?

As for your specific question... The RB20 fits better. To install RB20 you need only R32 skyline xmember or McKinney Mounts ($400). To install RB25 you also need a custom driveshaft ($500???) in addition to mounts.

As for which engine is better... The 25 is better. But, is it better per dollar spent??? I didn't think so.. that's why I went RB20.

Heck if you have a good condition KA in your car... the best way to get HP for the least costs is KA-T.

Just a thought..

[ca18datsun510]

ive been thinkin of buyin an rb25 engine, but i noticed that its a little bigger than my stock engine. so i dont know if i should get the rb20 or rb25. im hesitatin on the rb20 because its smaller than my stock engine, even though it has more hp. so which engine would fit better, but still give me more hp?

the rb20 and rb25 are have roughly the same external dimensions. the 20 and 25 size difference is in the cylinders, not the outside.

technically, you dont need a mount kit. you can use the rb20(from an r32 skyline) crossmember and trans with either motor and it will fit. shifter will be a little off, but the driveshaft will fit.

no offense, but with the questions you are asking, you should have a shop do it, or learn a bit more before you attempt to tackle this swap.

[top_secret]

neither of the swaps is as easy as a ka/sr etc... but neither of them is as hard as say a j2z either.

The answers to your questions have all been answered (in fact this same question has been asked dozens of times) on this and other national forums, so you may want to use the search buttons on nico, zilvia, fresh alloy, etc... and read up on the swap so you can make a more educated decision.

The RB20 is a good bit cheaper but parts are very hard to find for it and some people think its poorly designed. The RB25 is more expensive but parts are a bit more available (though not nearly as much as with sr) but its bigger, its 6 cyl, and it usually can produce more torque down low (which is really the only reason to use it since SR can do 600 hp if you build it right).

The worst part about either swap is finding parts, which is hard to do stateside.

btw driveshafts at a driveshaft shop will cost you $200 or so, just make sure your tranmission comes with the driveshaft yoke (most of the time they will torch it off and leave it in the transmission for that purpose).

[madcowvert]

so do they make a drive shaft out of the old one or do they make a new one? i thought the made the whole thing..

[top_secret]

they usually just tig your stock differential yoke to a piece of tubing (new 1 piece shaft) and then tig that to the rb transmission yoke, though I'm sure if you wanted to they could modify the stock shaft to work.

[2face]

im plannin on taking my car to a shop to do the swap cuz i dont want to risk anything if it goes wrong and plus im tryin to learn more about cars so i could start doing the work myself. thanks for the suggestion.

[top_secret]

do it yourself, cheaper, and you learn more, and most importantly you'll know how to fix it when it breaks.

[2face]

true. thing is i dont know much about cars, but im tryin to teach myself. it'd be a great project to work on and like you said i could learn more while doin it. thanks for the suggestion!

[Eikon]

Hey 2face,

It is a great idea to do the swap yourself. But, it can cost something to do that as well. You have to acquire the right tools and account for the chance of breaking something. If you've already got an engine lift, you should be ok.

I wanted to go RB as a learning experience. But, it was also motivated by money. The RB20 is just less expensive than the SR. I am still a bit over my head with the engine, but I'm learning as I go.

My next project is installing a custom front facing intake manifold along with front mount intercooler. Then I want to try to get my head ported/polished and then do a head swap and new head gasket. After that I want to put in a new clutch and flywheel.

that's the fun of working on your own car.. You will learn a ton in the process.

Either way... good luck with it all.

[2face]

money aint a concern for me. as long as i accomplish my project, then im not worried about costs. if i find discounts, though, ill take them. one thing ive been wonderin: whats the difference between the rb and sr? the rb ive noticed is cheaper, but i always thought it had more hp than an sr, or is it the other way around?

[madcowvert]

the rb has more power and is a inline 6rb20 2.0lrb25 2.5l rb26 2.6l twin turbo & awd

the sr20 is a 2.0l

the reasson you can get the rb motor for a cheaper price is do to the fact that most people dont have all the money it takes to buy all the parts to make it work right.. Vs. the sr which drops right in and the only thing you need is the wiring harness

if your going to do the swap you self for the first time i would go with the sr it will be alot easyer to do.