Unibody? ? ?

[BigBore240]

I was talking to a buddy of mine the other day and we came to the point where i started to talk about how i was planning on putting a 350 small block in my 89 240. He looked at me and said "you're a dumbass, you put that thing in there and you'll kill yourself. The 240 is a unibody so the frame only goes back past the driver seat. Might as well put wheels on the top of the car too!" My instant reaction was "you're full of ****!". However, before i go and by another new motor for my car (I already got a DE and after that decided to try to get a 350), i figured it wouldn't hurt to ask you guys to give it to me straight up. If it is a unibody, i'm not going to waste my time with a 350 and just have a decent 240 that can slide me into a corner or two here and there.

[TheOne]

what? unibody? i believe the frame goes past the driver's seat.

and people have allready put 350 small blocks in a 240sx, Aries is 1 of'em here in nico, also do a search there's other threads with such info.

[BigBore240]

I know it sounds retarded but the guy usually knows a thing or two about a thing or two, that's why I'm asking you guys. Also I have been trying to find out if Aries and everyone else who did that swap have had to strengthen their frame but no one over gets back to me about it. I've found out about mounts, diffs, radiator problems, all sorts of stuff from old links, but no info on the frame. If I do put a small block in my old man has a **** ton of performance parts for it so i NEED to know if the frame is really good, decent, or unibodied. HELP!

[frapjap]

Lets evaluate this real quick...

N/A Small Block ~300hp...

Sr20~ can be built to 2-300(and more hp) with no frame/structural problems.

People who really build these cars dont do much for the frames except some sway and stut bars.

Take this a little further, when they build this high horsepower SR, they intend (usually) to take it to the track to drift. Now...this usually puts a big strain on the chassis, but seldom, if ever, have I seen any 240sx have its frame twisted for reasons other than an collision.

These cars hold up to literally beating on them daily, (whether or not its a unibody) then honestly, your buddy doesn't know and intake manifold from a header to make a comment about your Nissan not holding up to installing a SBC into it. So long as you've researched (and it seems you have)and realized that you need some custom work, I say all systems go and make that v8 work!

[Veriest1]

Sure they hold up. But that doesn't mean they don't flex. And flex is bad for any type of performance.

You will need to do some form of chassis bracing. People even need to do this when they upgrade suspension. See nissanperformancemag.com and take note of the chassis flex they noticed with just an upgraded supsension and hard driving.

SPL sells a few different underbody braces. Fenderbraces will probably be a good investment as well as a basic cage.

[BigBore240]

Thanks for the tips guys, I'll look into it and post any additional info that I can put together. It will probably take me a while to find a stick 350 (probably out of an early 90's camaro unless someone has another suggestion), but as soon as I have it I'll take pics and write up some steps or something for everyone. Thanks again.

[Ubernoober]

Everything is Unibody these days except the truly large SUV's and trucks. So whats the big deal? What does he think a Corvette is?

The problem is that you MUST NOT compromise the structure of the unibody when you place that engine in the car. If you do, you should re-inforce with a tubular subframe.

[Veriest1]

What does he think a Corvette is?

Lol, good point. I didn't even think of that but it's true. For example, in '96 (Or whichever year the Pathies got the rounded headlights for the first time.) Nissan switched to a unibody frame for the Pathfinder because it was stronger and lighter.

[Fenvy]

I'll be the first to ask: what's a unibody?

[MinisterofDOOM]

Lol, good point. I didn't even think of that but it's true. For example, in '96 (Or whichever year the Pathies got the rounded headlights for the first time.) Nissan switched to a unibody frame for the Pathfinder because it was stronger and lighter.

Actually, that is not why they did it. The reason was they wanted to give a more car like ride. Then they got smart and realized that unibodies SUCK for trucks, and went to the modified F-Alpha fully boxed ladder frame this year.And yes, it was 96.

I'll be the first to ask: what's a unibody?

It's a chassis/frame setup in which the body and frame are integrated. Use of trusses means the structure is lighter but more rigid. It's especially helpful in the roof and roof pillars, which is why so many passenger cars use it.But for a truck, which needs chassis flex for offroad use, a unibody is a bad choice. A fully boxed frame truck chassis allows for torsional flex while mainting strength and payload capacity.

This Saab uses a unibody (also referred to as "monocoque") frame.The color in the image shows strength--darker red is stronger, lighter yellow weaker.

=====================================================

"Fully boxed" vs "boxed" vs standard ladder frame

This and this are pictures of Nissan's F-Alpha platform, which underpins the Titan (and Armada, QX56; as well as the Frontier and Xterra in "shrunken" guise--but these particular shots are of a Titan F-Alpha ladder frame). The fully boxed frame rails are painted red (or orange--these cheap LCD monitors we have at the office suck).

the individual frame rails are what set the three styles apart.

I would have used ASCII art...but it won't work in this software.

A fully boxed frame cross section is fou sided ( [] but without gaps)

a boxed frame is three sided ([ but extend the top and bottom--sometimes they face downward rather than sideways) And a standard ladder uses L-shaped frames. Very obsolete.
Modified by MinisterofDOOM at 4:54 AM 7/15/2005

[Veriest1]

Actually, that is not why they did it. The reason was they wanted to give a more car like ride. Then they got smart and realized that unibodies SUCK for trucks, and went to the modified F-Alpha fully boxed ladder frame this year.And yes, it was 96.

It's a chassis/frame setup in which the body and frame are integrated. Use of trusses means the structure is lighter but more rigid. It's especially helpful in the roof and roof pillars, which is why so many passenger cars use it.But for a truck, which needs chassis flex for offroad use, a unibody is a bad choice. A fully boxed frame truck chassis allows for torsional flex while mainting strength and payload capacity.

Well, you pretty much said it. It's more rigid. And since Nissan was converting the Pathfinder over to more of a soccer-mom-pleasing-gracery-getting-kid-hauler the stiffer unibody was the way to go.

This is the information I was going off of. It's in the "New Car Test Drive" link.http://autotrader.com/fyc/revi...dptop