Replacing spring with an iron block motor
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From: Lantana, TX
Replacing front spring with an iron block motor
Has anyone replaced their front springs to handle a heavier motor? What spring did you go with?
I've just replaced my blown motor, going from a stock LS1 to an iron block 5.7 My installer messed up my F45 suspension, which had been working great, and now the shocks are inoperable.
Between the extra weight in front, and my shocks stuck in sponge mode, the car is really bouncy and rides really low in front.
I'm going to try and trace the wiring to see if I can get my F45 working again, so for now I'm not looking for new shocks. Just wondering how strong a spring I need.
Is it a simple math formula such as; my original spring was a 250 lb spring... I've added 100 lbs in weight... so I need a 350 lb spring? Or how do I determine what spring I should get.
I've just replaced my blown motor, going from a stock LS1 to an iron block 5.7 My installer messed up my F45 suspension, which had been working great, and now the shocks are inoperable.
Between the extra weight in front, and my shocks stuck in sponge mode, the car is really bouncy and rides really low in front.
I'm going to try and trace the wiring to see if I can get my F45 working again, so for now I'm not looking for new shocks. Just wondering how strong a spring I need.
Is it a simple math formula such as; my original spring was a 250 lb spring... I've added 100 lbs in weight... so I need a 350 lb spring? Or how do I determine what spring I should get.
Last edited by Vette-Dream; May 30, 2017 at 03:17 PM. Reason: added 'front' to spring
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From: Atlantic Beach FL.
You only have one option for the front and it is the spring that the Z51 (FE-3) and Z06 (FE-4) use. The base (FE-1) stock spring was rated at 440Lb/in and the Z's are rated at 525Lb/in. You can use a C6 front spring from a Z and it has the same part number and are more available. That should cure the problem.
There are some more expensive aftermarket springs with stiffer ratings but I'm not sure who is making them any more.
There are some more expensive aftermarket springs with stiffer ratings but I'm not sure who is making them any more.
Last edited by Rob 02; May 30, 2017 at 11:06 PM.
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One thing to consider is the frequency, bounces per minute for lack of a better explanation. That would be a function of the weight to spring stiffness. The FE-4 front spring would no longer have the characteristics of the FE-4 with added weight. It would be softer.
Another thing to consider is the amount of traction gained in the front from the added weight. This would create more over-steer and stiffening the rear spring would create even more over-steer. Wider rear tires might help. Some people like the rear tires to be a little loose in corners though. These kinds of HP mods are probably more intended for straight line power than cornering.
In this case anyway the FE-4 front setup might be a good match for the FE-1 rear.
It seems to me that the purpose for an iron block is because you intend on making big HP through forced induction. That will add even more weight.
Another thing to consider is the amount of traction gained in the front from the added weight. This would create more over-steer and stiffening the rear spring would create even more over-steer. Wider rear tires might help. Some people like the rear tires to be a little loose in corners though. These kinds of HP mods are probably more intended for straight line power than cornering.
In this case anyway the FE-4 front setup might be a good match for the FE-1 rear.
It seems to me that the purpose for an iron block is because you intend on making big HP through forced induction. That will add even more weight.
Last edited by Rob 02; May 31, 2017 at 01:05 AM.
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Thanks Rob! I appreciate the details in your reply.
I guess I didn't give a lot of information on the car or my driving requirements. It is just a street car, I don't plan to put a roll cage in it (convertible) and so it won't be seeing a track, strip, or autocross event. I am going to be increasing the boost from the 8psi it's had on the stock motor to around 14-15 psi with the new motor. I'm not sure how much extra weight the STS turbo kit adds, but I would guess it's pretty much distributed evenly between the front and rear. In front there is an oil pump and intercooler, in back are the turbos, with piping going the full length between them.
Other than some high speed runs in Mexico or smiling at red lights it won't ever really be pushed hard. I actually like the soft suspension as it is now, sure makes these Utah back roads more enjoyable. But the ride height and front dipping has to be addressed.
I'll start looking for the Z spring (FE-4) that you mentioned, and afterwards I'll see how it feels before I look at changing the shocks out.
I guess I didn't give a lot of information on the car or my driving requirements. It is just a street car, I don't plan to put a roll cage in it (convertible) and so it won't be seeing a track, strip, or autocross event. I am going to be increasing the boost from the 8psi it's had on the stock motor to around 14-15 psi with the new motor. I'm not sure how much extra weight the STS turbo kit adds, but I would guess it's pretty much distributed evenly between the front and rear. In front there is an oil pump and intercooler, in back are the turbos, with piping going the full length between them.
Other than some high speed runs in Mexico or smiling at red lights it won't ever really be pushed hard. I actually like the soft suspension as it is now, sure makes these Utah back roads more enjoyable. But the ride height and front dipping has to be addressed.
I'll start looking for the Z spring (FE-4) that you mentioned, and afterwards I'll see how it feels before I look at changing the shocks out.
Last edited by Vette-Dream; May 31, 2017 at 12:59 PM.
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You can use a FE-3 spring as well. Here is a link to a thread regarding spring rates.https://www.corvetteforum.com/forums...s-97-04-a.html.
This one doesn't look too bad if you make an offer of like $140.http://www.ebay.com/itm/06-13-Corvet...VZDME3&vxp=mtr
Here is an older one for cheep.http://www.ebay.com/itm/Z51-FRONT-LE...pZLGQe&vxp=mtr
And another one.http://www.ebay.com/itm/Z51-CORVETTE...RYY2w6&vxp=mtr
This one doesn't look too bad if you make an offer of like $140.http://www.ebay.com/itm/06-13-Corvet...VZDME3&vxp=mtr
Here is an older one for cheep.http://www.ebay.com/itm/Z51-FRONT-LE...pZLGQe&vxp=mtr
And another one.http://www.ebay.com/itm/Z51-CORVETTE...RYY2w6&vxp=mtr
Last edited by Rob 02; May 31, 2017 at 02:40 PM.
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nice links! The thread with spring rates is great. I saw a few on ebay as well but I didn't see the cheap one.
Just bought it
It may be older, but it has to be newer than my car.
I'll grab new bushings, I'm assuming the slightly increases thickness of the new spring doesn't require any cutting or modifying of my existing setup. Just swap the old with the new right?
Just bought it
It may be older, but it has to be newer than my car.I'll grab new bushings, I'm assuming the slightly increases thickness of the new spring doesn't require any cutting or modifying of my existing setup. Just swap the old with the new right?
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From: Atlantic Beach FL.
The FE-1 spring has substantially more arch and hard to slide out of either side without removing a lower control arm. You could try removing the height adjusters first. Some people just cut the spring. The Z spring should slide in one side.
As far as mounting it once it is in place; The spring seemed to need a little compression for the two the rubber mounting points to fit into where they seat up in the engine cradle. I put a little lithium grease on top of the spring pads and put jacks under both control arms to compress the spring a little. I put blue lock tight (the milder stuff) on the bolts and torqued to speck, tightening each bolt a little at a time.
But to answer your question, yeah, they are a direct swap.
As far as mounting it once it is in place; The spring seemed to need a little compression for the two the rubber mounting points to fit into where they seat up in the engine cradle. I put a little lithium grease on top of the spring pads and put jacks under both control arms to compress the spring a little. I put blue lock tight (the milder stuff) on the bolts and torqued to speck, tightening each bolt a little at a time.
But to answer your question, yeah, they are a direct swap.
Last edited by Rob 02; May 31, 2017 at 04:38 PM.
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Joined: Sep 2003
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From: Lantana, TX
I saw a couple of youtube clips on swapping the front spring, it looks like straight forward as long as I have the harbor freight tool for popping off the lower ball joint.
I haven't seen a picture of the front dropped out like this, though I've heard a lot of people say it's the easier way to pull the motor. Definitely would be the best time to swap the spring!
I haven't seen a picture of the front dropped out like this, though I've heard a lot of people say it's the easier way to pull the motor. Definitely would be the best time to swap the spring!
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You can change the spring by ONLY removing the lower control arm bolts on 1 a-arm and the 4 spring mounting bolts. The instructions having you rip the suspension all apart on both sides are a waste of time. Just mark across all 4 of the eccentric washers on the bolts so you can get them back in the same position and then get an alignment after it's done. You should anyways if you have changed the ride height at all.
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Oh? So disconnect the lower arm from the frame (2 bolts x2) leaving the shock and everything else intact. Remove the 4 mounting bolts under the cradle, and the spring will slide out? Talking about the front spring, correct?
My spring is in transit now, I'd love to see a walkthrough before it gets here. Google time...
My spring is in transit now, I'd love to see a walkthrough before it gets here. Google time...
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Jack the spring through the Y of the lower a-arm and remove the 2 lower a-arm to cradle bolts. Lower the spring while maneuvering the a-arm above the end of the spring. Then, move the jack to the end of the spring and lift it again before removing the spring mounting bolts and lowering the jack to get the spring out.
If you can't get the a-arm around the end of the spring then you may have to remove the sway bar link or the lower shock bolts. It's tight but it can be done if you hold it just right.
Start with the car about 20" off the ground or the jack can hit the floor without releasing the spring.
If you can't get the a-arm around the end of the spring then you may have to remove the sway bar link or the lower shock bolts. It's tight but it can be done if you hold it just right.
Start with the car about 20" off the ground or the jack can hit the floor without releasing the spring.
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^Iron blocks can be purchased for cheep out of a truck. They can handle a ridiculous amount of HP too. I have seen people use them when their car isn't worth putting a new engine in as a budget build. Then there are those that plan on making over 800 HP.
The down side is the weight.
The down side is the weight.
Last edited by Rob 02; Jun 8, 2017 at 07:44 PM.
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From: hamilton ohio
I believe the iron block is 65 lbs heavier . Do all the guy's that put a supercharger on there car change the front spring? I would guess that the supercharger kit would be about the same weight difference . I just don't see the need to change the front spring .
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The LS1/2/6 blocks weigh 106 Lbs
The LS7 block weighs 107 Lbs
The 6.0 iron block weighs 216 Lbs
So the difference is 110 Lbs but there are different Lq motors. I'm not sure what the 5.3L weighs.
The LS7 block weighs 107 Lbs
The 6.0 iron block weighs 216 Lbs
So the difference is 110 Lbs but there are different Lq motors. I'm not sure what the 5.3L weighs.
Last edited by Rob 02; Jun 9, 2017 at 11:13 AM.
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Yes, I went with the 5.3 iron block, bored and set up as a 5.7
My stock motor blew after 60k miles @8lbs of boost and I always told myself that when it finally gave up I would just replace it with something forged and built to handle a lot more power. I plan to keep it around 14-15 lbs of boost, and went with the mighty mouse iron block option from Thompson Motorsports.
I didn't plan on changing the spring, but my first builder messed up my F45 shocks and now they don't register. They're stuck in soft mode and the car scrapes on everything. I just figured since I was putting money in to deleting the F45 it would make sense to swap in a stiffer spring for the extra weight. 100 lbs sitting mostly on the front axle is noticeable, or maybe it's just my soft shocks, either way I have the spring in the garage and once my new transmission arrives I'll tackle shocks, springs, and A4 swap ..... and THEN go back to running in my new motor.
My stock motor blew after 60k miles @8lbs of boost and I always told myself that when it finally gave up I would just replace it with something forged and built to handle a lot more power. I plan to keep it around 14-15 lbs of boost, and went with the mighty mouse iron block option from Thompson Motorsports.
I didn't plan on changing the spring, but my first builder messed up my F45 shocks and now they don't register. They're stuck in soft mode and the car scrapes on everything. I just figured since I was putting money in to deleting the F45 it would make sense to swap in a stiffer spring for the extra weight. 100 lbs sitting mostly on the front axle is noticeable, or maybe it's just my soft shocks, either way I have the spring in the garage and once my new transmission arrives I'll tackle shocks, springs, and A4 swap ..... and THEN go back to running in my new motor.