Before I decided to convert to an LS1, I was planning to use:

stock 914 torsion bars
100 lb. rear springs
stock sway bars
Bilsteins all around.

The car is steel flared and will have a proper 5-bolt conversion running 16x8 up front and either 16x8 or 16x9 in the back.

This will be a street-only car. Should I put stiffer springs in the back? If so, how much stiffer?

How does the wt of the LS1 compare to a 6? I am by no means a LS1 conversion expert (always wanted to do the LS3 w/ 930 tran) but I think I remember seeing folks running 180+ lb rear springs on 6 conversions and even heavier on cast iron V8 conversions. I think the weight of the LS1 is not too far from the wt of a big 6 motor.

I agree... 100 will probably be too soft. Why not check with Renegade? They have done a few of these in the past.

I think the LS1 is in the big six territory weight wise. Or just shy of it according to Renegade.

If I have to use 180 or heavier springs in the rear, I guess I should upgrade the torsion bars up front too?

-DB

The method we used on my race car might also work here but unfortunately requires the possibility of more than one spring set. The way we did it was to take the car onto a race track and go through a tight left and tight right corner to see if the inside front wheel lifted and then add spring pressure to force it down so all 4 are on the ground. We ended up with 300# rear springs. For the front we used the 135 MPH to 40 MPH VERY hard braking test such as getting set up for the left turn #3 at CA speedway and went up in front T-bars until the rear wheels did not hop. The stiffer front helps keep the nose dive out of the car's handling but make sure the front and rear brakes are sharing the load equally so one or the other is not locking up. We ended up with 23mm bars I think.

The post about increasing both ends is very true as the car is pretty well balanced and you want to keep it that way.

Street only? I would start out with some 140's. I have 180's right now and they are not harsh by any means, but they are firm, If you have 100's right now and liked it prior to the conversion then 140's should be similar if not a tad bit firmer and better all around.

I had 200# rear springs with the Bilstiens - perfect! I run an LS2.

and stock front torsions?

Dave, unless your at a race track, you dont need anything more than the stock torsion bars. The sway bar could be upgraded, but torsion bars should not be changed..

Ok, that makes me feel better. I'll probably start with 180s in the rear and the stock bar up front and see if I need to go up or down from there. Thanks!

I agree, but it depends also on how you like the car to feel. I am running 21mm torsion bars up front and 140lb springs in the back. The 21mm front sway bar feels like the M030 sport suspension on my 993. I am running a 3.2 six with a 901 gear box. My car is also flaired and I'm running 22mm sway bar up front and a stock sway bar in the rear. My tires are 225 up front and 245 in the rear. My car is 90% street and 10% autocross. If anything my car has a little more understeer than oversteer, but I could adjust it out with the sway bar. My sway bar is all the way tight right now.

Weight of LS Engines.

LS Family Small-Bloc k V-8
Part Number Description Engine Size Weight HP Torque
19165628 LS327/327—Base Assembly 5.3L 433 332 352
19244096 LS327/327 Deluxe 5.3L 332 352 57
17801267 LS1 5.7L—Without ECU and Wire Harness 5.7L 409 350 365
17801268 LS6 5.7L—2004 Corvette Z06 Gen III V-8 5.7L 464 405 400
12611022 L99 6.2L AFM 6.2L TBD TBD 62
19244097 LS3 6.2L—2008 Corvette Gen IV V-8 6.2L 415 429 424
19244549 LS376/480—EFI LS3 Gen IV V-8 6.2L 415 480 475
19171225 LS376/515—Carbureted LS3 Gen IV V-8 6.2L 415 515 469
19211708 LSA 6.2L SC 6.2L 556 551
19201990 LS9 6.2L SC 6.2L 638 604
19211710 LS7 7.0L—2006 Corvette Z06 7.0L 440 505 470

Here's the page on GM parts
LS Specs

Dave - I'm running 911 front torsion bars...I can't offer an opinion regarding 180 or 140 pound springs because all I've had are the 200. With that said, for the street I woudn't want anything less. I've now gone up to 300 rears with coil overs for more aggressive use. I also have a solid Weltmiester front roll bar.

I have 180's in mine. I think this is a good rate for a mostly street car.

Jerry

I am in the same boat with a LS1 and 915. At 409 lbs, street only driving and comfortable ride needed for a bad back, I am going with Bilstein front struts on a Carrera front end with stock sway bar and 140 coils on reinforced control arms in rear.

Talking about LS1's, what engine mount did you use and does it place the trans in its original location?

All of my LS comrades are missing one point...how many owners of LS powered teeners actually end up only on the street? Once you get a glimpse of how the car performs the street is no place to extract even a fraction of its pace - safely. My wife regularly suggests taking the 914 out for a trip - with how prissy she is if it was uncomfortable we would be in her minivan - 100% of the time. On the flip side, I can take it to Road Atlanta and sweep across the back straight kink at 145 mph with confidence. The beauty in this are the choices.

The basis for my suggestion lies with a women's opinion (perceived) and track performance - beat that! (this is not my wife's arse!)

so...ya'll think its really OK to double the rear spring rate while keeping the front stock?
come on guys, THINK!
the car will nose dive, braking will suck and car will be tail happy.

well, at least 911 torsions are 18.8mm

When I had my 914-V8, I was running a stock 911 front end with 180-200# springs, adjustable perches, and Koni Adjustable reds. It was fine for the supension on the street. Did not run a rear sway bar since I was not running a limited slip differential. I also had mininum stress kitting in the key areas. Handled like an old type Corvette - wanting to throw you to the opposite front corner as you were making a left or right turn.

These characteristics were not the problem of the suspension I used but because the engine gave a higher center of gravity that the stock -4 or -6 engines.

I built this cay back when the only kits were very crude from Rod Simpson and the first owners of Renegade Hybrid. Very little information was available at that time.

Subsequently, building a 914-Sixer (Porsche 3.2 Carrera engine with a rebuilt 901 transaxle. Stress kitted the body to the max with Racer Chris' products (I mean everything), seam welded in critical areas, 22mm torsion bars, 21mm sway bar (thru body type), 180-200# springs with the red Koni adjustables and adjustable perches, rebuilt rack and pinion steering, inner and outer long stress kit, etc. Do not run a rear sway bar since it is not limited slip differential.

How does the 914-Sixer handle? Very quick and nervous car. What I have done is eliminate the flex in the car body which is probably needed along with too heavy of suspension. I will have to soften the suspension either through the shock adjustments, sway bar adjustments, or replacing the torsion bars in front.

For the street and based on my experience on the two cars I have built, I would go with a stock 911 front suspension with a 21mm sway bar and 180# springs in the rear. Do some stress strengthening but watch out the type you do so you do not make it a rigid body. You need some flex in both the suspension and the body for the street. The trick is to find out the right amount for both.

I actually like my Sixer and its suspension but it is very nervous and "darty" which a problem I am currently working to solve. Slight move of the steering wheel and it moves very quickly laterally.

I only got long winded since I believe you should take your build in stages for setting the suspension and reinforcement. For now set the rear with 180-200# springs since starting at 140# was a little too light for my tastes. The 140# can be used but they were not for me. Also, I would use the stock 911 front suspension (19mm torsion bars) and an aftermarket through body front sway bar. Brakes should be considered at this time and there are a lot of opinions on this subject. I used 911 (3.5in type) brakes on the front and the 914 brake setup on the rear with 19mm master cylinder.

Believe me you can go all over the ballpark, just set the basis as you see it from receiving all the information; then, start planning the next moves to make the best car possible for your needs. It will become the car you want if you just take your time and evaluate each stage.

I do not like the idea of doubling the rear spring rate without changes to the original stock front end. This does bother me since I really believe you will have a totally unbalanced car even for the street. The 914 front suspension is strong enough including the brakes for a starting point except I would consider increasing the torsion bars from 17mm to 19-21mm. Then again you have to eventually consider shocks and brakes.

Hope this helps.

Steve Hurt

This car essentially a race car built for the street

200# would be about right for the additional weight and power of the LS-1... I use 200# for a 225HP 200+ft/lb torque TypeIV.

For brakes, I'm using PMB restored M calipers and a new 19mm MC on vented rotors front and back. I may go bigger ultimately, but I think I should try these first to see how well they perform.

For stiffening, I have the GT kit and the Engman long kit installed. No plans for anything else yet.


With 914 A-arms the smallest option I've come across is 21mm. So from what I'm hearing, maybe 21 front and 200 rear would be a good combo to start with. And then upgrade to an adjustable front sway bar up front. Sound like a reasonable plan?


@pdlightning: I was planning to use the Renegade setup, which moves the trans back some, I think. I'm using 944 CV's and a rebuilt 901 box with a flipped H.

Yes that sounds like a good combo, but from your first post it sounded like you were going to keep everything else stock... Which is why I suggested 140's....

However I would still say stick with stock A arms and just have the upgraded sway bar up front...

IMO, this is where the fundamental handling issue lies. The high rear CG plays havoc with weight transfer when trying to get the chassis to handle on the track. Rear spring rates need to be pretty high, and a rear sway (given you have LSD) will help settle down the rear. This of course is only part of what's necessary for the track.

The OP is building a street car, so ride comfort would be the preferred goal (if it were me), along with decent stability and balance. His proposed starting point seems reasonable (in post #21). If there's a trait he doesn't like, he can make subsequent changes.

Andys

Initially, I was hoping to keep the stock front to save some $$. But, it sounds like I need to go more aggressive.

Considering the significant added horsepower, weight, and the higher CG, I'm leaning towards the heavier 21/ 200 combo and adjustable sway. I want the ride to be firm and sporty but reasonably comfortable. Of course, comfort is a relative term. For perspective... I'm 33, lean and fairly fit. And let's face it... this car is all about going fast... so if the ride is firm (but not harsh) I'll be very happy.

Thanks for the input guys!

renegade no longer sells heavy duty springs.

they offer something like this now.

http://www.ground-control-store.com/produc...ption.php/II=76

jim

Dave,

If you wish to keep expenses down and use the stock front (with 911 brakes/5 lug/sway), I don't see much issue with this. Now perhaps some may disagree, but the stock torsion bars should be adequate for the street (and give you a better ride)........there's that comfort thing again, but I am twice your age so it figures.

Andys

When I first built my car with the SBC I ran 21 mm torsion bars. 22 mm sway bar and 200 lb springs. When I put the LS1 in,I changed the rear to 180,front back to stock torsion bars. Still have the 22 mm sway in front with a stock bar in back.
This setup works for me for street and the 2 or 3 autox I do a year.

Jerry