Datsun 620 sub frame swap

[Kold91]

I want to swap the front and rear subframes from another car into my truck in order to get a much better suspension, disc brakes and be able to run coilovers.

I know one guy did it with a miata into his 520. but I'm wondering if anyone has any experience with a 620?

 

also which would be better, miata subframes or s13 240sx or other? im also going to run the motor and tranny from the donor car

 

 

heres a few pics of my truck. its a 74 with an l18 and a 4 speed

[Skib]

 

 

 

[Suspect]

 

 

 

 

I was just thinking of this truck when I read this post.

[Xander_42]

620 don't have subframes in the way that Camaros and whatnot do, they have frames. People usually talk about subframe swaps when they are talking about American uni-body cars. This means that a you not not just be able to bolt the front half of a different frame onto the cab, and go away. Moving to better suspension and brakes, is going to probably involve a bunch of welding and fab to attach to the 620 frame (or a different frame if you choose to swap to one of those.

 

Additionally in much the same way that 620s don't have frames Miatas and 240s only sorta do. Most Japanese cars do not have front subframes like American uni-bodies, because the Japanese actually understand (or at least learned much earlier) what a "uni-body" car is supposed to be and their cars don't have big half ladder frames under them, the suspension actually attaches to uni-body, except where they use a transverse sub-frame. A transverse subframe is what you have in the front and rear of Miatas and 240s (a term I just made up).

 

Miata rear subframe:

 

It is a subframe bolted to the uni-body that holds all of the suspension except for the shocks and springs.

 

For reference, this is a Camaro subframe:

 

It has a traditional ladder frame shape, and holds all of the suspension, engine, steering, bodywork, etc.

 

I feel like I've left out some of the key information, but I'm tired, so let me know if things were confusing, or whatever.

 

Now I would like to ask you why you want to upgrade to modern suspension and brakes?

 

Here's my personal opinion:

 

You don't need modern suspension. People have been making cars handle with shitty suspension for decades. I guarantee you that a properly sorted 620 with stock style suspension will spank a badly done truck with either Miata or 240 suspension. Taking your time, doing your homework, and keeping a mostly stock system will save you money and be a better truck in the long run.

 

But if you just want to have coilovers so you can say you have coilovers, or if you're just going to stance it and hard park it, or drift it, then I really don't care what you do.

[Kold91]

620 don't have subframes in the way that Camaros and whatnot do, they have frames. People usually talk about subframe swaps when they are talking about American uni-body cars. This means that a you not not just be able to bolt the front half of a different frame onto the cab, and go away. Moving to better suspension and brakes, is going to probably involve a bunch of welding and fab to attach to the 620 frame (or a different frame if you choose to swap to one of those.

 

Additionally in much the same way that 620s don't have frames Miatas and 240s only sorta do. Most Japanese cars do not have front subframes like American uni-bodies, because the Japanese actually understand (or at least learned much earlier) what a "uni-body" car is supposed to be and their cars don't have big half ladder frames under them, the suspension actually attaches to uni-body, except where they use a transverse sub-frame. A transverse subframe is what you have in the front and rear of Miatas and 240s (a term I just made up).

 

Miata rear subframe:

 

It is a subframe bolted to the uni-body that holds all of the suspension except for the shocks and springs.

 

For reference, this is a Camaro subframe:

 

It has a traditional ladder frame shape, and holds all of the suspension, engine, steering, bodywork, etc.

 

I feel like I've left out some of the key information, but I'm tired, so let me know if things were confusing, or whatever.

 

Now I would like to ask you why you want to upgrade to modern suspension and brakes?

 

Here's my personal opinion:

 

You don't need modern suspension. People have been making cars handle with shitty suspension for decades. I guarantee you that a properly sorted 620 with stock style suspension will spank a badly done truck with either Miata or 240 suspension. Taking your time, doing your homework, and keeping a mostly stock system will save you money and be a better truck in the long run.

 

But if you just want to have coilovers so you can say you have coilovers, or if you're just going to stance it and hard park it, or drift it, then I really don't care what you do.

 

Well the main reasons are: I want to go lower (its all the way down with no suspension in the front now) and run 4 lug wheels

[BigBlack620]

Thread grave digging!!! Dude whatever happened to your truck? What did you end up doing? Did you muck it up? Pics

[Cpl620]

a little less grave digging, but bump. i want to know what happened with this and the one that was for sale back in 2011 that had the rear suspension already mocked up.

[Tamungas]

I don't know this thread, but I have a 1972 BulletSide in my garage and what's left of a miata, I all set to start the joining of two souls... If you wanna follow me on this journey friend me up on Facebook. My name is Michael Brewster. And my online name is Tamungas. I'm getting excited.

[datzenmike]

Fuck failbook. Start a build or project thread here where we can see it with lots of pictures..

[AJY]

And I will dig this thread up again... So I had to buy the whole 240 to get the KA24det might as well take the suspension right....?

[teagueauto21]

And I will dig this thread up again... So I had to buy the whole 240 to get the KA24det might as well take the suspension right....?

if your ready for the task. Very few people attempt this and most of them end up either hauling it for scrap or putting it up forsale, but its worth the effort if you see it all the way through.

[AJY]

if your ready for the task. Very few people attempt this and most of them end up either hauling it for scrap or putting it up forsale, but its worth the effort if you see it all the way through.

 

 

Turns out my PO hacked my frame up putting the rotary in so I have a lot of work ahead of me just to go back to stock anyway

[ramen tamer]

Man...I wish this thread had gone on longer and Kold told us what he did to lower the truck.

 

He did, indeed, succeed at lowering it, though.  I know because I recently bought it.  I've been searching around on google to figure out how to undo what he did, because it bottoms out way more than I want it to.  Which is, like, ever.  I never want to bottom out.  

 

Right now, I'm aiming at just getting it back to stock height.  I can get creative, after that.

 

Here's some pictures!

 

See?  Same truck.

 

In all her rusty glory...

 

I reckon those big ass blocks might be part of my problem...

 

And that exhaust there seems to be what drags on the ground.  Right now, at stand still, its about 1" off of the dirt.

 

I guess I just hoist up the ass end of the truck and take those drop blocks out, yeah?  I'll have to look and see what the front is like.  I still haven't checked.

 

The suspension isn't my biggest worry at the moment.  

This sweet ass truck also:

Leaks energy.  I leave the battery plugged in and she won't start in the morning.

Has a vacuum leak/o2 sensor issue/needs a new fuel pump.  The RPMs are all over the place.  Sometimes she just dies for no reason.  This problem is the problem that needs the most immediate addressing.

Has squishy brakes.  This here is priority number 2.  The truck is too damn fast, and my city is far too hilly, for soft, squishy brakes.

 

All in all, I'm extremely pleased with my purchase.  I just got a little bit of work before she's perfect for me.

 

Cheers!

[datzenmike]

Slice those blocks to 2 inch or get new ones. Turn the torsion bars up at the front. For raising the front type 'lowering the 620' and 'indexing the torsion bars' and work backwards. This will give your shock absorbers 2 extra inches of suspension travel to actually have something to work with. While at it, probably has the old blown out shocks, so new are in order.

[ramen tamer]

Awesome!

Thanks, datzenmike!  I'm not much of a mechanic...At all.  So, I'm often at a loss of what I even need to search for.  

 

Getting better, slowly, though!

 

Cheers! 

[orangie]

Keep in mind those rear blocks can also change the pinion angle of the rear differential.  Ideally the angle of the rear diff should match the trans.  To check it, the weight of the truck must be on the tires or similiar weighting points like the rear axle.  It doesn't have to be perfect, but I would try and keep it within 5 degrees of each other.

[]2eDeYe]

Man...I wish this thread had gone on longer and Kold told us what he did to lower the truck.

 

Looks like he just added some drop blocks in the rear and cranked the torsion bars in the front. There is information on adjusting the torsion bars in the FAQ in my signature. 

 

 

In all her rusty glory...

 

 

I reckon those big ass blocks might be part of my problem...

 

Doubling blocks is a bad idea. You can keep the 2" blocks and find some 720 4x4 leafs to get the same or more drop.

When lowering a 620 a bunch in the back it is a good idea to c-notch the frame. 

 

 

It's also sometimes necessary depending on how muc drop in the front to remove the bump stops and even cutting off the bump stop mount if you are real low. 

 

And that exhaust there seems to be what drags on the ground.  Right now, at stand still, its about 1" off of the dirt.

 

A good exhaust guy can route the exhaust above the cross member freeing up some needed ground clearance. 

 

 

I guess I just hoist up the ass end of the truck and take those drop blocks out, yeah?  I'll have to look and see what the front is like.  I still haven't checked.

 

 

 

The suspension isn't my biggest worry at the moment.  

This sweet ass truck also:

Leaks energy.  I leave the battery plugged in and she won't start in the morning.

 

Pull the negative cable and put a test light between the post and the cable. If you have a draw it will light up. Start pulling fuses until the light goes out, this will tell you which circuit has the draw. It's usually pretty easy to troubleshoot what the draw is from there. 

 

Has a vacuum leak/o2 sensor issue/needs a new fuel pump.  The RPMs are all over the place.  Sometimes she just dies for no reason.  This problem is the problem that needs the most immediate addressing.

KA swap correct? Swap in a new fuel pump and use some carb clean to spray around the intake to find your vacuum leak. When you spray the leak the idle will even out. 

 

Has squishy brakes.  This here is priority number 2.  The truck is too damn fast, and my city is far too hilly, for soft, squishy brakes.

 

Disc brake swap or stock drums? 

 

All in all, I'm extremely pleased with my purchase.  I just got a little bit of work before she's perfect for me.

 

Cheers!

 

 

Good looking truck, welcome to ratsun. :)

[ramen tamer]

My plan is to raise it to stock, for now, so I can drive it around and then I can mess with it later if I do want it either higher or lower.  So, I'm just gonna remove the larger of those two blocks back there and re-index those torsion bars up front.  I don't know, precisely, what I'm doing, but I got a redneck friend and you guys for reference and help, so I should be able to get it sorted out.

 

I think I found what's causing my air leak while I was poking around under the hood, this morning.

 

On the air intake, there's a hole for a bolt to mount it onto the engine.  There is no bolt there.  So, I imagine, the whole thing is wiggling like crazy and letting some air in.  I think I might be onto something with this theory, too, because the hose clamp and rubber sleeve that holds the big ol air intake thing onto the other bits (these are the technical terms, I'm sure of it) has moved significantly and looks like it's about to fall off.

 

So, maybe my fuel pump and o2 sensors are fine.  Might change them out, anyways...Just for good measure.

 

I went to Home Despot for a bolt, but I didn't measure anything and ended up buying not the right stuff.  Another trip will be in order.  Maybe tomorrow.

 

As for the energy leak, I've just been unplugging the negative terminal on the battery whenever I get out.  It's a bit annoying, but whatever.  It works for now until I fix it.

 

I'll take more pictures, in a bit, so y'all can see what I'm talking about.

 

Thanks, everybody!

[Stoffregen Motorsports]

Fuck failbook. Start a build or project thread here where we can see it with lots of pictures..

You've got to do both to stay in step. I post build threads on forums and my FB page https://www.facebook.com/StoffregenMotorsports .

 

Two different audiences.

[ramen tamer]

Oops.  I posted all of this in a different topic about the same truck.  I hope it's okay to re-post it here...

 

Okay, so this isn't really an update, since I haven't done any work on the truck.

 

I just figured I show y'all what I think is wrong with the air intake.

 

So!

 

Here's what it looks like under the hood...

 

So pretty.

 

But!  Even though I'm sure you can see it in the other picture, here's a slight close-up.

 

That bolt that holds the air intake onto the engine there, in the middle of the picture, is missing.  I ain't all that mechanically inclined, but I reckon that there is my problem.

 

The hose clamp holding the doohickey to the thingamajig is falling off, too.  Which reinforces this theory.  Here's a picture of that.

 

See where the hose clamp used to be?  See where he's migrated.  I'm sure that's bad.  Also, I can grab the air intake with my hand and wiggle it around with no effort.  I'm sure the bouncing around of the engine also has no problem wiggling the bastard about, either.

 

I'm also fairly certain that's the problem, because when I first got the truck, it was having the weird varying idle issue and occasionally dying on me.  I tightened that clamp and it ran fine for a few days.  Then it started having issues again.  And now it's completely undriveable because of how much the RPMs will vary at any given time.  Also, she's taken to backfiring lately...Which I also think is a problem.  Possibly caused by the same thing.  

 

I gotta get my battery charged, though.  The one in there is from my girlfriend's old car and it's dead.  I could jump it...But with the idle being all out of whack, that isn't gonna happen until I fix that problem.  So, it might be easier to just get the battery fully charged and then try and sort out the vacuum leak.  That way, just in case I'm wrong and this doesn't fix it.  I can continue to work on it and check my progress as I go, without having to get a jump every time I wanna check and see if I sorted it out.

 

Okay...Onto other stuff.

 

Edit: Oops!  Wrong topic.  Same truck, but wrong topic.  I meant to post this in the other topic where I'm talking about this thing.

 

I need to go down to Home Depot and get some of those U-shaped brackets, but shorter, so I can remove those lowering blocks on the rear end.  First, I'm going to need to jack this thing up, which means buying some jacks.  Since I've never worked on any vehicle before, I have zero tools or experience in the matter, but I'm just gonna have to figure it out as I go and try and glean as much info off of here as I can as I progress.

 

 

Keep in mind those rear blocks can also change the pinion angle of the rear differential.  Ideally the angle of the rear diff should match the trans.  To check it, the weight of the truck must be on the tires or similiar weighting points like the rear axle.  It doesn't have to be perfect, but I would try and keep it within 5 degrees of each other.

 

 

Like, I have no clue what this means.  But, I'm certain I'll find out.  

 

Anyways, my next day off is on Monday, but my pinball team is in the playoffs right now, so I don't know if I'll have time on Monday to work on the truck.  Tuesdays is for band practice.  Wednesday, as long as I'm not too hungover from pinball and band practice might be the only time this week I'll be able to accomplish anything.

 

Even if the only thing I accomplish is buying some tools and the proper bolt for mounting the air intake, I'll try to keep all y'all posted.  

[ramen tamer]

Alright, so, I went and bought a new battery.  I bolted down the air intake and I moved the hose clamp and re-tightened it.  At first, the truck was still acting funky.  The RPM needle swinging between 500 and 1000.  

 

Then, I remembered that I have to manually turn the fan on, so I did.  After a little bit, the needle hung out around 750 and stayed there, for the most part.  

 

From that point the truck just puttered a little bit, every now and then, but it stayed pretty steady.  I doubt it was the fan, though, because it hadn't been running long enough to get anywhere near hot.  Is it possible that it just took the computer a minute to figure out not to shoot bursts of air into the engine?  

 

So, maybe, that's fixed.  As long as it keeps up this good work, it sounds pretty drive-able.  Though, I've done something like this before and it went out of whack again pretty quickly.  I hope it stays, this time.  

 

But...I guess my next step is sorting out the suspension.

 

I'm probably gonna go pick up some jacks either tomorrow or Monday morning and remove the lowering blocks.  Then, onto the front.

 

I need to do some reading. 

[ramen tamer]

Okay, so I might be an idiot, because I just don't get it.

 

Torsion bars.  I'm confused.  I've read the Datsun FAQ, I've watched that 521 video and apparently I still don't get it, because once I remove the jack stands from under the truck, the front end is still as low as ever.

 

Like, I can get the bars out...And then I move them a spline and put them back in and the front end is still low as hell.

 

I'm reading everything I can on Google, now, to try and find something I missed, maybe.

 

I dunno.  If anyone has any ideas of what I'm doing wrong, I'm all ears.

 

Edit:

I figured it out.  Now, I feel like an extra idiot.  The problem?  After re-indexing, I wasn't tightening the bolts down nearly hard enough. 

[orangie]

There is a learning curve working on cars.  If nobody gets hurt.  It's a good day.  If something gets broken...well think of it has an expensive credit hour.

[]2eDeYe]

^ that is the truth, working on a vehicle is one of the best hands on mechanical schools there is. 

[ramen tamer]

It's pretty cool, working on this truck.  I've gone from knowing absolutely nothing about cars to being able to raise or lower the suspension of old Datsun trucks in a weekend.

 

If I were to do it again, I probably could sort it out in a few hours or so.  Depending on how stubborn the bolts and torsion bars are on whatever particular truck.

 

I don't have  much more work before the truck becomes my daily driver and I'm getting pretty excited.