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Looking to raise stance evenly on my 71 350


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#1 G71

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Posted 11 July 2018 - 03:46 PM

My objective is to evenly raise the stance on my 71 350 with ac.
ideally I would not like any part of the tire to be hidden within the wheel well.
I will be using 225/70 or 235/70 on 15x7 FW rims all around.
I am not concerned about originality, BUT I DON'T WANT TO SACRIFICE RIDE QUALITY.

I have asked and read about this topic extensively so here is my summary for opinion before I make my decision.

FRONT
I have been advised by many not to use big block springs as the car will ride like a rock. What will be the best choice to rise the front and keep the ride quality intact.
I called moog and they advised spring #6330 for a big block without air or a 350 with air or spring #5536 for a big block with air.
Any advice?

REAR
moog standard #5379
Moog HD standard #5413
Moog variable rate cargo coil #cc501
(Might the HD or cargo coils make the ride rough?)

Other considerations are the air bag system or spacers.

So ultimately I ask what choice of all the afforenentioned might achieve my objective of evenly raising the stance without giving up the smooth comfortable ride.

Thank you all for your opinions

#2 snomobeelr

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Posted 11 July 2018 - 04:40 PM

 No matter what spring you get you don't know how it will actually sit until the spring is installed. You can not adjust coil springs and  they will settle after time. Last front springs I was told they would work for my setup. Well they didn't and there sitting on my shelf.  Viking adjustable shocks or bags if you are particular about how you want the car to sit.  I have the viking shocks on all 4 adjust ability is great. 



#3 Rock

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Posted 11 July 2018 - 05:48 PM

I 2nd the Vikings. Not only can you tailor the ride height you can adjust the drivability by a couple of quick adjustment knobs.
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Nothing special about this Monte. No SS, no rare options just a super sweet car to drive and take me back to the good old days!

#4 Rock

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Posted 11 July 2018 - 05:48 PM

I 2nd the Vikings. Not only can you tailor the ride height you can adjust the drivability by a couple of quick adjustment knobs.
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Nothing special about this Monte. No SS, no rare options just a super sweet car to drive and take me back to the good old days!

#5 G71

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Posted 11 July 2018 - 10:10 PM

Thanks to all for the tips

Will the Vikings all around compromise the ride quality?

#6 Rock

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Posted 12 July 2018 - 04:54 AM

Compromise? It will improve the ride quality. You can adjust it to ride like a Cadillac or as aggressive as a Porsche. You can buy an A body kit for about $1200. Expensive but worth every penny
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Nothing special about this Monte. No SS, no rare options just a super sweet car to drive and take me back to the good old days!

#7 Rock

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Posted 12 July 2018 - 04:54 AM

Dp
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Nothing special about this Monte. No SS, no rare options just a super sweet car to drive and take me back to the good old days!

#8 502ci

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Posted 12 July 2018 - 09:24 AM

Anyone looking to adjust their ride height and want an end result exactly to their specific desires will only be happy getting a full coil over system. It just will cost alot more but you will have the look you are after...also later on it can be adjusted up or down if you so desire.

Bill

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#9 MCfan

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Posted 12 July 2018 - 11:34 PM

G71,

 

What you are hoping to do with replacement coil springs may be a tall order (especially with a 28" tire) because a high stance and a soft ride are somewhat conflicting objectives (IMO), However, you being an engineer, would know that there is no voo doo magic associated with compression coil springs.  They are simple mechanical devices that produce linear force proportional to compressed distance because they are just a torsion bar shaped into a circular coil.  There are several important variables that make them unique, however, free height and deflection rate are the most important specifications so that's where one must focus to achieve the results you want (if that is even possible).

 

If you want a higher than stock "stance" you must have a greater than stock working force holding the vehicle up at rest.  Since the working height of 11.7" was determined when our Montes were designed, the difference between 11.7" and the free height of any spring times its deflection rate will give you the working force when installed in your car.  However, you also want to maintain a comfortable ride quality so that says the deflection rate of any spring you pick must be relatively low, close to the stock 250 or 275 pounds per inch in the front and 130 pounds per inch in the rear (see attached tables of stock front and rear spring choices).  The only way to get a greater working force (higher stance) with a low (comfortable) deflection rate is to choose a spring with a relatively tall free height and mild deflection rate.  BTW, the greater the free height of a front coil, the more difficult (and dangerous) it is to install.

 

You are quite correct that HD and cargo springs will not give you the comfortable ride you are looking for so just rule them out to start with.  Also, since there are many ways to increase the height of the rear of your car (including changing springs, of course) your biggest challenge is to find a front spring that gives you both height and comfort.  Certainly the adjustable coil overs are a great solution if they are within your budget, especially since you don't care that much about originality.  But, there are also a lot of coil spring choices out there if you know what you are looking for. Unfortunately, your choices will be quickly narrowed by needing both a high working force (tall free height) and a mild deflection rate. Your initial research and advice from Moog is interesting but you may want to spend some time scanning the specifications of hundreds of other Moog springs at this site: Moog Universal Coil Springs

 

I am running the Moog 6330 and 5379 springs on my '70 SS and you can see the resulting stance in the photo below.  My SS was built with the GQ front spring, heaviest of 10 used by GM (see attached table of front springs), which had a working force of 1760 lbs and a deflection rate of 275 lbs/in.  The Moog 6330 has a slightly lower working force of 1700 lbs and a slightly higher deflection rate of 293 lbs/in so my SS now sits slightly lower in front (as I prefer) but still rides very well. On the rear, I replaced the stock BM coil with a working force of 530 lbs and a deflection rate of 130 lbs/in with the Moog 5379 that has a greater working force (@ 9") of 702 lbs and a slightly softer spring rate of 122 lbs/in so my SS now sits slightly higher in the back (as I prefer) but still rides very well.

 

Frankly the only way I see you satisfying your two conflicting objectives is to select the tallest free height spring that has an acceptably mild deflection rate and even then, you may have to add spacers under the taller front coils or between the coils because they will increase the working force and front end height without changing the spring's deflection rate.  Obviously, the only springs you can select from must be constructed properly with one end squared and the other tangential and the correct inner diameter of 3.68". For example, the Moog 5384 has a working force of 1885 lbs and a deflection rate of 294 lbs/in but its coil diameter of 4.09" rules it out.  Maybe you should talk to the Moog staff again and emphasize your conflicting objectives to see if they can come up with a "special application" spring recommendation.  You already have their standard answers and the heavy duty alternatives will give you the rough ride you don't want.

 

BTW, one of our members, Patrick Sheean, achieved a pretty aggressive higher stance on his '71 by installing new springs he got from Leo Konick (I believe) but I have no idea what their ride quality is.  You might want to send Patrick a PM to find out.

 

If you continue your research with Moog and other coil spring suppliers, I suggest you ask for a properly constructed front coil with a free height of 18.7" to 19" and a deflection rate close to 250 lbs/in which is what your stock spring rate undoubtedly is right now.  Frankly, I'm not very hopeful that you will find that but you may be able to augment the height with a spacer.  Good luck.

 

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Dennis

 

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