Jump to content
Sign in to follow this  
2one8

Best coil-over option for '76 620

Recommended Posts

I have a '76 620 LWB that I'm going to be doing some extensive work to, and I'm looking some swap options for suspension. This truck will be primarily street driven, but it will see some road course track time from time to time, but nothing competitive, just casual club run track days or whooping on V8's at Powercruise USA. Powerplant will be a 515rwhp/509ft lbs VQ35 swap from my G35, so I need the rear end to be strong enough to support the power and torque.

 

At first I was looking at using a Toyota 8inch rear with a 4-link, but after reading more about 4-link setups they don't handle well. After further digging I found some threads about guys using the S13 subframes, and even found a thread about swapping the rear subframe in as well. I know the S13 rear diff and axles aren't going to like the power so I'd be upgrading diffs and axles. Are there any other swaps that would be a good option to look into? I'm not sure how I feel about a rear sub-frame swap because I'm then cutting into the bed to fit towers, and I want to be able to put the motorcycle in the bed.

 

 Everything I've ever worked on and built has been uni-body and independent suspension, so this is a new realm for me. And yes, I'm well aware of the work that this will take. This is one of those "once in a lifetime" builds. I'm bored with just doing bolt-on work on modern cars, time to get out of my comfort zone and build something that fits me and my character.

Share this post


Link to post

Why don't you think an S13 R200 diff won't take a measly 500 hp ?

I know of many 700+ cars with that size diff in them, and they don't break.

 

Just don't use one with the Viscous diff, they don't work for anything....Good idea, that just never worked right from day one.

They barely hold 150 hp when they are at the right temp.

Too cold, they don't hold, and too hot they don't hold.

 

And all you have to do to put 1000 hp through one is to install an S15 helical, as it has the larger 30 spline output shafts.

Plus it being a helical, there is nothing else out there as good for road racing.

 

The IRS is worlds above in handling over any solid axle set-up.

  • Like 1

Share this post


Link to post

Exactly how much space do you think the strut towers would take up to keep you from loading a bike into it?

 

Also, Project Car Magazine did a full front and rear s13 suspension swap years back into a 620. The builder managed to build towers off the rear frame that fit under the wheel tubs. Invisible from outside no sheet metal work at all.

Share this post


Link to post

I would read this thread if I were you, and before people start talking about strength, this is a race truck that a well known driver other than the owner and son drove and he said it was the best balanced race truck he had ever driven.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwig8sfVqobYAhVR_oMKHWKbDNUQFggpMAA&url=http%3A%2F%2Fcommunity.ratsun.net%2Ftopic%2F7446-project-mx520-top-secret%2F&usg=AOvVaw1_18Gx_Q5EcnmUQqgPZt7b

MX5201sttrackday.jpg

 

I could see the photo above find when I copied it, Photolame sucks, we should stand out in front of the CEOs house with signs telling the world it is this guy that did this.

Share this post


Link to post

Too bad all you can do is read the story...

But Miata rear end won't take the engine 2one8 is talking about.

Pretty sure his big power idea won't work, due to it being a real miss match, and very unbalanced.

Hell, even the old GTP cars only ran at about 600HP, even though the engines were god for twice that.

They relied on state of the art suspension, and aero to go fast.

Big engines mounted over the front axle, in a pick up isn't there.

Maybe a drag truck, but not something meant for a road course.

Share this post


Link to post

Make it a mid engine.

  • Like 1

Share this post


Link to post

Exactly how much space do you think the strut towers would take up to keep you from loading a bike into it?

 

Also, Project Car Magazine did a full front and rear s13 suspension swap years back into a 620. The builder managed to build towers off the rear frame that fit under the wheel tubs. Invisible from outside no sheet metal work at all.

 

With a rear sub-frame swap I'd want to run a strut bar from tower to tower which would prevent me from loading the bike. Granted I can remove the bar if need be. However I may have to run the radiator in the bed, so I may be SOL as far as loading the bike anyways.

 

Too bad all you can do is read the story...

But Miata rear end won't take the engine 2one8 is talking about.

Pretty sure his big power idea won't work, due to it being a real miss match, and very unbalanced.

Hell, even the old GTP cars only ran at about 600HP, even though the engines were god for twice that.

They relied on state of the art suspension, and aero to go fast.

Big engines mounted over the front axle, in a pick up isn't there.

Maybe a drag truck, but not something meant for a road course.

 

Yeah these HP levels in a light truck aren't ideal, but I can run multiple maps and with proper tuning I can down-tune to manageable power. Chances are I'll tune down to 450ish for daily, can get down to 350ish on low boost but she will be sluggish low end due to lower compression. Either way, I'm fully aware this thing will be tail happy.

 

Make it a mid engine.

 

This is already going to test my fabrication skills lol

 

Share this post


Link to post

Anyone have a link to or copy of the Project Car Mag article I can look at? Google didn't come up with anything and I cant find it for digital purchase anymore.

Share this post


Link to post

You shouldn't need to run a radiator in the bed. The vq shouldn't be THAT deep of a motor. Fairly sure the vq fits 510 engine bays with a radiator.

 

I will check over the next couple of days to find my collection of project car mags. I'm only missing 2 which bums me out. I want them all.

 

And you can always use pins to lock the rear bar in place when you need it or disconnect it quickly when you use the truck to haul.

Share this post


Link to post

You shouldn't need to run a radiator in the bed. The vq shouldn't be THAT deep of a motor. Fairly sure the vq fits 510 engine bays with a radiator.

 

I will check over the next couple of days to find my collection of project car mags. I'm only missing 2 which bums me out. I want them all.

 

And you can always use pins to lock the rear bar in place when you need it or disconnect it quickly when you use the truck to haul.

 

Radiator in the rear will depend on intercooler fitting. My current intercooler is 12x31x4. I've been looking at some of the SR20 swaps and it looks tight even with smaller intercoolers.

Share this post


Link to post

Wallrocket just posted this setup recently. His build is in the projects section.

 

Inter cooler was pretty simple. I just had this Honda FMIC laying around in the shop. It had 3 12mm bolt size holes on top to bolt it to something, I just drilled the holes out on the Datsun radiator support and called it good. Its very sturdy, and i am happy with it. To help others with this inter cooler, i think its for a Honda, has 3 bolts top and 3 bolts on bottom, inlet is 2.25 and outlet is 2.25. I will get the length and what not later for you guys.

uY6YDu.jpg

 

Share this post


Link to post

If you try to put strut towers where the rear tires belong, you'll run out of room for the tires you'll need to hook up 500hp.  

If they go inside the rear wheel wells, you won't be using space you need for a bike, although you have to get creative with strut tower braces.  

 

Personally, I'd build a 9" and run a 4 link with a custom Watts linkage setup so you can turn corners.  Or build a quick-change for fine tuning later.  Make your suspension loading adjustable for up to a 45/55 weight balance so the back end stays in back.  

  • Like 1

Share this post


Link to post

If you try to put strut towers where the rear tires belong, you'll run out of room for the tires you'll need to hook up 500hp.  

If they go inside the rear wheel wells, you won't be using space you need for a bike, although you have to get creative with strut tower braces.  

 

Personally, I'd build a 9" and run a 4 link with a custom Watts linkage setup so you can turn corners.  Or build a quick-change for fine tuning later.  Make your suspension loading adjustable for up to a 45/55 weight balance so the back end stays in back.  

 

I've been looking through Chad Copelands build and how he did his rear suspension (I would post a link, but my computer wont paste anything). He cut the rear tubs to make room for the suspension. Take away the rear strut bar and there looks to still be plenty of room for the bike. While I'm hauling the bike I likely wont need the strut bar as long as the rest of the suspension is solid. If I'm hauling the bike its probably just to BIR for a track day(I see youre from MN), or to a show where its just going to sit in a parking lot. I'm also planning to go wide wheels and flare out the wheel wells, so I can make up some lost wheel size that way. This is just one option I've been looing into.

I'll look into the Watts setup for sure. Solid axle suspension is a whole new world for me. I already have a Toyota 8inch that I'm told by a local shop should be plenty for this, but I'm not opposed to running something else.

Share this post


Link to post

A 9" is overkill for your power...

The Toyota 8" damn near is also.

The stock H190 is fine, if you want to go 4-link, and their are pleanty of gear ratio sets available.

LSDs can be had. If you can't find one, let me know, I get them in the 29 spline for the truck on a regular basis.

 

I did my 4-link, and kept the stock fuel tank & spare location, and run a Watts Link.

 

DSC08381.jpg

 

But an IRS will still out handle a solid axle any day.

 

Oh, and you don't need a strut bar on an IRS system like an S13, where you have upper & lower control arms.

Strut bars only help if you have struts....

Damn kids sticking strut bars on things like Supras, that don't have struts, is retarded.

All it does is add 'bling'.

  • Like 1

Share this post


Link to post

Ummm.... putting wider rear wheel wells in the truck's box isn't going to do anything for you unless you narrow the frame.  That's quite an undertaking without a frame table.  It CAN be done, but it'll be 50 hours of extra work and you'll need a fuel cell mounted somewhere else, as well as likely having to re-route all plumbing.  

 

The Toyota is a good potion, but it likely is too wide.  53 1/2" is your goal drum to drum, or narrower, to fit wheels inside the fenders.  What's the Toy measure - 59?  A 10-bolt 2WD S10 measures 54 1/2" but a truck axle can't use c-clip eliminators or a lot of the other goodies unless you're big on doing your own machining.   Then brakes become an issue - custom brackets.  

 

Where in MN are you?  

Share this post


Link to post

Ummm.... putting wider rear wheel wells in the truck's box isn't going to do anything for you unless you narrow the frame.  That's quite an undertaking without a frame table.  It CAN be done, but it'll be 50 hours of extra work and you'll need a fuel cell mounted somewhere else, as well as likely having to re-route all plumbing.  

 

The Toyota is a good potion, but it likely is too wide.  53 1/2" is your goal drum to drum, or narrower, to fit wheels inside the fenders.  What's the Toy measure - 59?  A 10-bolt 2WD S10 measures 54 1/2" but a truck axle can't use c-clip eliminators or a lot of the other goodies unless you're big on doing your own machining.   Then brakes become an issue - custom brackets.  

 

Where in MN are you?  

 

Flaring the rear, not tubbing it, so trimming the body for wider wheels and running a flare.

 

I'm leaning more towards IRS and swapping an S13 rear sub-frame in. I've been looking at different ways others have don't IRS and have some ideas. I like the way it was done in this photo, it looks like most of that would fit in the wheel well, or at least in place of the wheel well and shouldn't affect any central bed space. I would like to see if I could notch the frame vs moving it, but in this case the upper control arm would cause an issue but I've seen it done differently in a couple other posts, so I might be able to come up with something that will work. I'm not concerned about moving frame if need be, but avoiding it or keeping it minimal is ideal.

 

And I'm in Brainerd.

 

scontent-a-sjc.xx.fbcdn.net-16874-138976

Share this post


Link to post

Did you read that MX520 thread, did you see this photo of how Bob did his rear suspension?

This is a winning race truck in it's class, some pro driver from the past that has drove race cars all his life said this was the best handling truck he had ever drove.

mx52012-7-08007.jpg

This truck still has the stock uncut box as far as I know, you will have to hack the shit out of your box to do what is in the last photo you posted.

If this photo disappears let me know and I will replace it with one that doesn't disappear.

  • Like 1

Share this post


Link to post

Nice.

What subframe is that ?

Share this post


Link to post

Wayno all I'm getting is photobucket warning.

Share this post


Link to post

Wayno all I'm getting is photobucket warning.

Postimage will not upload anything right now, it says something about maintenance(I just tried again), I have the photo saved to my computer, I just need Postimage to work, when it starts working I will fix the photo.

I looked at the properties and it says it's hosted at Photolame, at first I could not see that part in the text, I had to expand the box to see who hosted it. :(

Share this post


Link to post

Nice.

What subframe is that ?

 

That is the Miata IRS as far as I know but is a custom install, that is the MX520 truck/project, although it is not a project anymore, it is a race truck, and I suspect a licensed legal driver for the roads also.

Share this post


Link to post

Too bad, those Miata diffs are as small as an R160, and won't really stand up to much abuse.

Unless he is using a small engine.

 

I've got a picture somewhere of a 510 rear suspension installed in a pickup, and although I have a couple of the 510 subframes around here, never considered it a viable option for me.

Share this post


Link to post

Too bad, those Miata diffs are as small as an R160, and won't really stand up to much abuse.

Unless he is using a small engine.

 

I've got a picture somewhere of a 510 rear suspension installed in a pickup, and although I have a couple of the 510 subframes around here, never considered it a viable option for me.

Are you kidding, this is a race truck, a winning race truck, he gets 2 wheels in the air sometimes when cornering, I have not heard about him going thru rear diffs ever.

He is using the complete Miata drive train from front to rear as far as I know, and this is the second one he has built, the other one is a 411 wagon, a race car that is only a race car as far as I know.

http://community.ratsun.net/topic/52056-misinformation-look-here-to-get-the-411/

 

11891171_843492932372998_113763271699017

Share this post


Link to post

A torque arm or properly set up 3 link rear would handle very well. A torque arm would fit quite nicely. Watts link and you could a tunable neautral handling rear that you could dial a decent amount of anti squat into to handle the hp you have.

 

I have measured it up and widening the chassis 4-6in on a 620 would open up a world of options in suspension, rack and pinion, wider track width while keeping wider rims with less scrub radius than large offset rims would. Also could fit a wider diff without the need to shorten axles.

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×

Important Information

By using this site, you agree to our Terms of Use.