V8 rear suspension

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speedbug78
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V8 rear suspension

Post by speedbug78 » Mon Jun 17, 2019 12:38 pm

We've been discussing the front suspension here: viewtopic.php?f=3&t=31942
And we've begun to talk about the rear as well. I was hoping to do that in more detail here.

Summary = I have done a low budget 302/T5 engine swap in my SRL311

My experience so far shows that despite moving as much torque as possible away from the bottom end (headers, single plane intake, decent flowing heads, large carb, reasonable big cam) it is still pretty easy to spin the tires, at least in the lower gears. I have not experienced any hint of wheel hop. The anti-torque bar (is that what you guys call it?) seems to be doing it's job well. I have not tried anything resembling a sticky tire yet either.

- My goal is to have a capable street/strip car
- Don't want to run faster than 11.50.
- Shooting for ~300hp at the wheels.

I have been told by several people that the rear end will hold this power (R180?). I haven't seen much in the way of parts support though, but I haven't searched extensively.

If I use slicks on the strip I will be required to use aftermarket axle shafts. Are these available? Will the rear hold up to this?

I do have a 9" sitting in my shop, and some have recommended adding rear weight to my car. I'm not sure how much weight this would add, especially if I use an aluminum third member, aluminum center housing and disk brakes?

I'm interested in cost/benefit of both rear ends.
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Alvin
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Re: V8 rear suspension

Post by Alvin » Mon Jun 17, 2019 1:37 pm

Make some passes with the sticky tires. If you break anything, do the 9".
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FergO2k
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Re: V8 rear suspension

Post by FergO2k » Mon Jun 17, 2019 2:09 pm

RCMike can weigh in, as he has had "a bit" more experience with turning a tire than myself in his SR20 powered swap.
He has twin torque bars on the rear, so going partway towards the "3 or 4 bar link" rear end. A 2L will have a 3.7 geared rear end, which most swap to the 3.9 from a 1600 the same time as the swap.
With sticky tires and a 3.7, you could transmit some serious torqueing action up the line, something is gonna eventually break!
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Re: V8 rear suspension

Post by JT68 » Mon Jun 17, 2019 4:48 pm

The stock rear is a good unit, but I doubt it will hold up to drag racing with even a mild 302 for long. I'd hate to see you grenade an original roadster LS, so I'd go with the 9" or Rx7 rear certainly.

Also, roadster axles have a nasty habit of coming out under racing conditions, so thats another good reason for floating aftermarket axles. (Hate to see anyone get hurt) That has caused some pretty spectacular crashes over the years.
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speedbug78
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Re: V8 rear suspension

Post by speedbug78 » Tue Jun 18, 2019 9:52 am

Another related question. At some point I'm going to want more rear tire. There isn't much room back there. Would you guys recommend back-halving the car, running flared fenders, or something else?
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notoptoy
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Re: V8 rear suspension

Post by notoptoy » Tue Jun 18, 2019 10:13 am

Choices I have seen wider flares/chopped fenders. With stock leaf spring suspension you are limited, if you modify the suspension you could have other options.
"When all else fails, force prevails!" Ummm, we're gonna need a bigger hammer here.

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Pjackb
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Re: V8 rear suspension

Post by Pjackb » Tue Jun 18, 2019 10:40 am

Some good read
Alvin wrote:
Sun Nov 09, 2014 4:22 pm
Yes

FD3S RX-7:
http://www.311s.org/phpBB3/viewtopic.ph ... &hilit=rx7" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

Others:
http://www.311s.org/phpBB3/viewtopic.ph ... &hilit=irs" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

http://www.311s.org/phpBB3/viewtopic.ph ... &hilit=irs" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

http://www.311s.org/phpBB3/viewtopic.ph ... &hilit=irs" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

http://www.311s.org/phpBB3/viewtopic.ph ... &hilit=irs" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

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Re: V8 rear suspension

Post by jhayden » Tue Jun 18, 2019 1:08 pm

Speedbug,

Many on this forum can give you expert, experienced advice on autocrossing and road racing these cars, but there is precious little discussion of drag racing and related topics such as wheel hop, hook up and weight transfer. Not that the discussion is unwelcome, it’s simply an activity that very few members here choose to do.

At this point, Alvin’s suggestion of making test runs (1/8 mile tracks in this area will allow runs w/o a roll bar, but that's for hard top cars) with sticky tires seems spot on, and you can tell us how it goes. Everyone here will be interested in your results, and some will have experience to offer informed recommendations. (Members Spyder and Will reportedly have some experience in breaking things and finding good ways to fix them.)

Suggest picking up a copy of the Clymer handbook/service manual for our cars (cheap on eBay). It contains a reprint of the factory manual which includes all the weight and dimensional specs you will need.

If you’re not already a member of drag racing and 302 forums, there are lots of good ones available, and you now have some real, bona fide weight distribution numbers both for your build (that few would have believed, and apparently some still can't accept) and stock that you can make available to help inform the discussion.

It would be a welcome surprise if you find someone on those forums who have any familiarity with our cars!

Jon

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Alvin
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Re: V8 rear suspension

Post by Alvin » Tue Jun 18, 2019 11:49 pm

jhayden wrote:
Tue Jun 18, 2019 1:08 pm
Many on this forum can give you expert, experienced advice on autocrossing and road racing these cars, but there is precious little discussion of drag racing and related topics such as wheel hop, hook up and weight transfer. Not that the discussion is unwelcome, it’s simply an activity that very few members here choose to do.
Jon
Me Me Me oooh I can discuss drag racing!!! :lol:
Image
Image
Sticky tires and weight transfer :mrgreen:
Image

jhayden wrote:
Tue Jun 18, 2019 1:08 pm
At this point, Alvin’s suggestion of making test runs (1/8 mile tracks in this area will allow runs w/o a roll bar, but that's for hard top cars) with sticky tires seems spot on, and you can tell us how it goes.
Jon
Speedbug,
As JT mentioned, I agree that the stock rear end won't hold up to slicks and 302-supplied torque. Road racers brake axles frequently so you'd be on borrowed time. But it might be a fun experiment to see just how sturdy your stock rear end is, while you prep a proper 9" setup. You mentioned your roadster is a "low-budget" build, so take note that factory limited-slip units for the stock rear-end are around $1200.
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speedbug78
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Re: V8 rear suspension

Post by speedbug78 » Tue Jun 18, 2019 11:59 pm

Nice to meet you Alvin!!
"Low budget" is kind of relative but it means that I buy speedmaster heads instead of AFRs, stuff like that. Price for stock rear parts are definitely part of the consideration. A good 9" setup won't be cheap either. Ring and pinion, lsd, bearings, seals axles, disk brakes, and maybe carrier and housing parts. If I want to run 4.56 and a spool then I have a bunch of the parts, but I don't consider that very fun on the street.

Edit:. Guess I already "met" you with your first post. I just didn't realize who the advice was coming from.
Last edited by speedbug78 on Wed Jun 19, 2019 12:11 am, edited 1 time in total.
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Alvin
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Re: V8 rear suspension

Post by Alvin » Wed Jun 19, 2019 12:07 am

speedbug78 wrote:
Tue Jun 18, 2019 9:52 am
Another related question. At some point I'm going to want more rear tire. There isn't much room back there. Would you guys recommend back-halving the car, running flared fenders, or something else?
ps...I wouldn't do anything until you put in some solid runs as is with a M/T E.T. or similar tire. You can fit a 245-width tire using the right size wheel back there. Just shy of the magic 10" :D
https://www.jegs.com/i/Mickey-Thompson/ ... 0/10002/-1

If you still need a wider tire after testing...the only limit is your imagination, skills, funds and personal aesthetic :D
Oh, and your racing group guidelines :lol:
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speedbug78
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Re: V8 rear suspension

Post by speedbug78 » Wed Jun 19, 2019 12:13 am

I have a couple of 32x14 take offs from our small block alcohol dragster. How big of tubs can you fit in a roadster? 😁. Actually I have those earmarked for my fed.
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speedbug78
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Re: V8 rear suspension

Post by speedbug78 » Wed Jun 19, 2019 12:16 am

Seriously though 245s aren't bad at all. It doesn't look like there is that much room, but a 10" tire should hold this engine easy, so a little under might be fine. Thanks for the info!
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Re: V8 rear suspension

Post by Alvin » Wed Jun 19, 2019 12:22 am

Here is an example of what you can do with the rear end to support a 350v8:
viewtopic.php?f=15&t=27727&p=264196#p251098
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This member is "back-halfing" hisi chassis, to fit 325/50/15 tires:
viewtopic.php?f=27&t=11228&hilit=projec ... =15#p97180
Image
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Eric's 302-powered roadster:
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speedbug78
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Re: V8 rear suspension

Post by speedbug78 » Wed Jun 19, 2019 11:30 am

Thanks for sharing. I haven't browsed the member's garage area much yet, so hadn't seen the first two. The last one I've seen :)
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