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  1. #1
    Join Date
    Mar 2006
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    Fort Campbell, KY
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    Default Questions on GM A-Body suspension/chassis setup

    I have a 68 GTO and wanted opinions on my setup before I completely commit to it.

    Front:
    ATS AFX tall spindles (have)
    ATS center link (have)
    New pitman arm (have)
    New tie rod ends (have)
    ATS Billet steering arms (have)
    Lee Performance 670 Steering box with Rack and Pinion valve technology (have)
    Rag joint coupler for ATS/Lee Performance 670 Steering box (have)
    Hotchkis adjustable tie rod sleeves (have) (possible for sale)
    UMI Performance tie rod adjusting sleeves (have)
    SC&C SPC adjustable upper control arms (have)
    Howe precision ball joints (have)
    Global west lower control arms with bushing upgrade (have)
    ATS LSX engine plates (have)
    Polyurethane engine mounts from ATS (have)
    Polyurethane transmission mount from ATS (have)
    4L60/4L80 transmission cross member (need)
    Adjustable Hidden Spring Shim:
    TD 3-1/8" - 5-1/4" front (have)
    Tru-Coil™ Front Racing Springs - 5" x 9.5" 650# (have)
    1 1/8" Hotchkis hollow bar sway bar. (have)


    Rear:
    Moser 12 bolt Ford Torino style ends with a 3.70 ratio (have)
    Umi Performance single adj upper & lower control arms #401417 (for sale)
    Umi Performance bolt on lower control arm brackets #4012 (for sale)
    Umi Performance bolt kit #3002 (have) (one set for sale)
    UMI Performance weld-in lower control arm relocation brackets #4010 (have)
    UMI Performance double adjustable upper & lower control arms #402717 (have)
    Bmr Fabrication Control Arm Mount Reinforcement Braces RB002 (have)
    Bmr Fabrication drive shaft safety loop DSL007 (have)
    Tru-Coil® Rear Racing Springs 5" x 10-1/2" 150# (have)
    Coil Spring Spacer (need) {do I need these?}
    Adjustable Hidden Spring Shim:
    TD 0" - 2-1/2" rear (have)
    1" Hotchkis rear sway bar (have)
    Rear upper coil spring isolators (have)



    Am I missing anything?
    The car has factory power steering according to PHS what needs to done to swap out to a Lee 670 steering box? <nothing, this is a bolt in deal>
    What is the ratio of the Lee 670 steering box? 12.7:1
    Do I need to do more than drill new holes in the chassis to bolt/weld the ATS LSX engine plates in the correct location for the new engine? <not exactly>
    If I want to get the frame powder coated is the best way of getting it setup correctly is to mount everything with the engine and transmission then pull everything off it?
    I assume that I would order the driveshaft last after I confirm that the engine and transmission are sitting right and everything is bolted back in? <yes>
    I have a 1" Hotchkis rear sway bar, should I even bother installing it? <It needs to have a front sway bar to go along with it>
    For the rear springs should I with Tru-Coil™ Rear Racing Springs 5" x 13" 150# instead? NO
    Should I consider 750# springs for the front instead of the 925# ones ? 575# or 650#
    Which shocks should I get for the front and rear? Alston Varishocks 16 adjustable settings
    I have the complete rubber bushing body kit from OPGI will this be stiff enough? <should be>

    thanks
    Josh
    1968 GTO http://www.pro-touring.com/showthrea...ject-Grey-Goat
    Trying to accomplish the impossible, with no resources in the minimal amount of time possible.


  2. #2
    Join Date
    Feb 2007
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    East Freetown, MA
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    516

    Default

    Don't see a front sway bar on the list....


    Factory auto crossmember should bolt right up...



    Make sure the engine is square and the angle should be about 3 degrees with the trans mounted.

    You will have to mock everything up to make sure it fits, then pull it all apart again. Make sure you know where your firewall is before you set up the engine, if the body is already off... If you're running A/C, you'll probably have to notch the front of the crossmember to get clearance for the lines.

    Correct on the driveshaft assumption. Even if someone has done the same swap, measure your setup and use those numbers. You're placing the motor mounts where you want them, not where the SB chevy holes are drilled (or not drilled on a Pontiac frame).

    I have the same dilemma for front and rear springs. The LS-x motors are pretty light compared to what else is out there. I would assume the front springs need to reflect that.

  3. #3
    Join Date
    Mar 2006
    Location
    Fort Campbell, KY
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    Default Any more comments?

    Any recommendations on shock selection?
    Should I use the hotchkis/blisten ones? or would the Koni units be better for spirited driving/auto X? Where I live there are planty of twisties to drive on.
    Should I install just a front sway bar or both, the car originally came with a rear one.
    no recommendations on the weight for the coil springs or how to set them up?
    are the body mounts from OPGI stiff enoughf?

    thanks
    Josh
    1968 GTO http://www.pro-touring.com/showthrea...ject-Grey-Goat
    Trying to accomplish the impossible, with no resources in the minimal amount of time possible.

  4. #4
    Join Date
    Sep 2006
    Location
    Southern Indiana
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    Default

    Hey Josh if I had my druthers, look at a set of ShockWaves from Air ride Technologies and CoolRide in back. I had the rear CoolRide on back of my 71 Monte and it rode AWESOME and it hooked like a well tune 4 link drag car and it handled through the hills to Morresville North Carolina for the 98 East Coast Power tour .
    You wont believe how good it will handle and ride and you can carry a heavy load and still run the chassis hard.
    ART also has the StrongArms and and rear controlarms too so you can step up to some super tought stuff.
    The setup doesnt NEED the electric/electronic controlss but it does make a sweet way to lock your car, simply drop it down on to special wheels chocks(seen this done, the car had ahole with a coresponding pin for the wheel chock that locked his wheels when dropped, it couldnt even be towed with a flat bed.) and the car stays put.
    Anyway something to look at.
    Lee

  5. #5
    Join Date
    Sep 2004
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    PA.
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    Default

    Overall it looks like you`re doing pretty good. Only a few exceptions. 925# front spring are rediculously stiff for your application. 725# is also. All you`re going to do is add understeer whith you should be trying to get rid of because these cars have way too much in the first place. Try 600#,a much better match to the 150# rears. The improved geometry,raised roll center and much shorter than stock front moment arm make this even more so. Folks usually use the tall Speedway adj. in the front. You can use short ones in the rear.
    With your revised geometry and front spring you can run a very small front bar. I`d go for a factory 7/8" and go from there. The 1" rear will be fine and will help turn in.
    The Lee 670 box is a direct bolt on. All you need is their hybrid rag joint to bolt it in. Ratio is 12.7:1. You`ll be really happy with it we`ve had nothing but great feedback on them.
    Bolt everything in place on the frame,do any and all mods to it then when everything`s done pull it all apart again for powder coat and paint. It`s a pain but it`s the only way to be sure you don`t have to modify parst that have already been coated.
    Hotchkis Bilsteins would be okay for a street driven car. Bilstein makes really high quality shocks. But they`ll be under dampened for track or auto cross use. Adj. shocks would give you the best of both worlds. I`d suggest Alston Varishocks as the best bang for the buck. 16 setting knob adj.,machined aluminum,really high quality,well thought out pieces. We have them on sale right now too.
    OPGI body bushings should be fine. You might consider boxing the frame though (at least the center span),if you haven`t already. Mark SC&C
    ----Savitske Classic & Custom----
    -------Suspension Solutions!---------
    SPC,Varishock,ATS,Baer,Currie,Chassisworks,
    Hydratech,SpeedTech,Lee,Hellwig,Total Control
    Author of "How to Make Your Muscle Car Handle"
    www.SCandC.com sales@scandc.com
    (610) 381-6100

  6. #6
    Join Date
    Dec 2006
    Location
    Los Angeles
    Posts
    322

    Default

    Quote Originally Posted by Marcus SC&C
    Hotchkis Bilsteins would be okay for a street driven car. Bilstein makes really high quality shocks. But they`ll be under dampened for track or auto cross use. Adj. shocks would give you the best of both worlds. I`d suggest Alston Varishocks as the best bang for the buck. 16 setting knob adj.,machined aluminum,really high quality,well thought out pieces. We have them on sale right now too.
    OPGI body bushings should be fine. You might consider boxing the frame though (at least the center span),if you haven`t already. Mark SC&C
    OK, I'll bite...how much for the shocks? I currently have Bilsteins, but they are not too helpful with my 60' times at the strip.

    Can the frame center span be boxed with the body on the car, or am I asking for problems and a fire?

    Thanks.

  7. #7
    Join Date
    Dec 2003
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    Default

    Quote Originally Posted by Marcus SC&C
    Overall it looks like you`re doing pretty good. Only a few exceptions. 925# front spring are rediculously stiff for your application. 725# is also. All you`re going to do is add understeer whith you should be trying to get rid of because these cars have way too much in the first place. Try 600#,a much better match to the 150# rears.
    You think so Mark? I know I was very happy with the 950#. The 1100# were a bit overkill but the 750# were too light IMO. Troy also runs the 750# plus in his driver and loves the ride. I have yet to see a decent handling "A" body running anything less than ~700#.

    150# in the back is going to need a whole bunch more than 600# to balance it. With 600# I would be looking at ~125# in the back.

  8. #8
    Join Date
    Feb 2007
    Location
    East Freetown, MA
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    Default

    Sinned, he's got a LS-x motor going in the car. Not a Pontiac motor. Much lighter!

  9. #9
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    Default

    I was running a 350, Troy runs a 350, Dave runs a 350. Engine weight never even entered my mind, most guys who worry about BB vs. SB are running stockish rates and need that information to maintain ride height.

    With so many variables the only way to know for sure is testing and corner weights. My opinion is to start at something of at least 750is and go up from there.

  10. #10
    Join Date
    Mar 2006
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    Fort Campbell, KY
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    Default consensous on springs

    I took the weight recommendations from Dennis web site.

    What should I do about the rear lenght, the Tru-Coil® Rear Racing Springs come in 5" x 10-1/2" or 5" x 13". Should I change to 575# or 750# front with 125# rear? I will be using 18" rims and 255/40/R18 tires, at least I plan on that combo. What about ride height? I am guessing that the car will be sitting at least 1" lower.

    I am using adjustable hidden spring shims:
    TD 0" - 2-1/2" front (need) & TD 3-1/8" - 5-1/4" rear (need)

    should I go with a Hotchkis front sway bar, it is a 1 1/8" hollow bar.

    Where would I get a "stock" 7/8" front sway bar for a 1968 GTO?

    OPGI has 7/8" for the rear, listed as a factory original rear sway bar and nothing for the front listed.

    do I need the rear upper coil spring isolators with my setup?
    Josh
    1968 GTO http://www.pro-touring.com/showthrea...ject-Grey-Goat
    Trying to accomplish the impossible, with no resources in the minimal amount of time possible.

  11. #11
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    Sep 2004
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    PA.
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    Yep,the all aluminum LSX motor makes a big difference. We`ve run an LSX with 700lb/in front springs and the car had way too much front roll couple. It cornered super flat and had great mechanical grip but the turn in and responsiveness weren`t what we wanted. We went to stiffer (166lb/in) rear springs and changed the shock settings to balance it out but that still didn`t go it. A larger rear swaybar balanced the car out pretty well and got the turn in nice and crisp with just a hint of understeer at the limit. Then we changed the rear suspension around and had to start all over.

    We recomend Eibach Pro springs (550#/135#prog.) to many of our clients. We`ve found them to work very well for most of them provided they follow our advice for the overall set up of the car. Some are even racing and winning with them. Ex. 2 clients with a G body that run Big Bend,Silver State,Sand Hills open course road races every year with those springs,Varishock QS1s,SC&C Stg.2 etc. and regularly place top 5 (usually top 3) in their class (GrandSport) against Vipers,Porsches,C5s etc. For anyone that doesn`t think an A or G body can handle without super stiff front springs BigBend is coming up later this month and registration`s still open...

    Josh, 125# is roughly stock. That`s not going to do much (anything) for performance. Adding stiffness to the front without increasing it in the rear will make a car understeer more and these cars already understeer way more than their fair share.
    Use whatever front swaybar you have now,then *drive the car* and get the feel of it. Then determine if YOU feel it understeers or oversteers more than you`d like,if it turn in nice and crisp or not then make changes based on that. Everyone`s driving style is different and swaybars are a tuning aid. They`re cheap and easy to change so don`t be affraid to play with them to get the car the way you want it. Mark SC&C
    Last edited by Marcus SC&C; 04-12-2007 at 06:12 AM.
    ----Savitske Classic & Custom----
    -------Suspension Solutions!---------
    SPC,Varishock,ATS,Baer,Currie,Chassisworks,
    Hydratech,SpeedTech,Lee,Hellwig,Total Control
    Author of "How to Make Your Muscle Car Handle"
    www.SCandC.com sales@scandc.com
    (610) 381-6100

  12. #12
    Join Date
    Mar 2006
    Location
    Fort Campbell, KY
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    Default Motor Choice..........

    Well I may have to change my mind on the engine selection now that I have started reading up on the LSX iron block.

    I was originally going with a LS2 but then the L92/L76 came out.

    The LSX is overkill but I could get it set up as a 455ci and get the 600rwhp I want. Too many options, thankfully I don't have to make a decision right away as I still am collecting suspension parts before the body comes off the frame.

    I don't know how much weight difference between a LS2 and a L92/L76 combo, the LSX weight a great deal more.......

    So I may be needing the heavier springs up front....
    Josh
    1968 GTO http://www.pro-touring.com/showthrea...ject-Grey-Goat
    Trying to accomplish the impossible, with no resources in the minimal amount of time possible.

  13. #13
    Join Date
    Feb 2007
    Location
    East Freetown, MA
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    Default

    You'll be making a big mistake going with a iron block. The LS2 will get you where you want to go (you can use the L92 heads and intake on it) and the blocks are almost as durable as the iron ones.


    BTW, I understand the weight difference is around 70lbs........

  14. #14
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    Default

    Unless your trying to get mega cubes or going to make 1000+ HP the LSx block is overkill. I would go with an LS2 based 402. Call it a 400 if you want it to sound like a Pontiac engine...LOL

    I would also go with a spring between 500-600lb/inch

    Andrew
    1970 GTO Version 2.0
    V8TV feature vide0
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    "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her


  15. #15
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    Nov 2004
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    http://www.sdparts.com/product/SDLS9...CIFlatTop.aspx

    aluminum block 416 cubes assembled $4500. If I did not already have a brand new 540, I'd be installing this with l92 heads.

  16. #16
    Join Date
    Mar 2006
    Location
    Fort Campbell, KY
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    Default Two unanswered questions on my suspension configuration

    Ok

    I still don't know if the "factory" rear upper coil spring isolators are these needed with my spring and adjuster setup?

    Tyler @ ATS said to use the LSX engine mount plates with the rubber/polyurethane engine mounts I need to switch over to SBC frame stands from Year One or Classic Industries.

    Maybe I am not looking in the right place on their web sites?

    I found engine frame brackets and front frame mount brackets. The closest item(s) were front frame mount brackets from year one.

    can any one give a specific part number or link or page in their catalog or website?

    thanks
    Josh
    1968 GTO http://www.pro-touring.com/showthrea...ject-Grey-Goat
    Trying to accomplish the impossible, with no resources in the minimal amount of time possible.

  17. #17
    Join Date
    Feb 2007
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    East Freetown, MA
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    Default

    I ended up just e-mailing all the guys on Craig's List that had Chevelle parts for sale and I got a set that was already sandbalsted and painted gloss black for $15....

  18. #18
    Join Date
    Mar 2006
    Location
    Fort Campbell, KY
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    Default Update on the body bushings

    I have ordered the: 68-72 Chevelle body mounts, part number 3.4115 from Performance Suspension Components.

    I plan on getting most of the suspension components installed.
    I ended up ordering more UMI parts because of a good sale:
    UMI Tie Rod Adjusting Sleeves
    UMI 1968-1972 GM A-Body Double Adjustable Upper & Lower Rear Control Arms - Color: Black
    UMI 1964-1972 GM A-Body Rear Lower Control Arm Relocation Brackets weld-in

    The old UMI stuff is up for sale....

    The shiping time is 6-8 weeks, I doubt that any of these items will show up while I am on leave, so another couple of weeks before the frame is powder coated.
    Josh
    1968 GTO http://www.pro-touring.com/showthrea...ject-Grey-Goat
    Trying to accomplish the impossible, with no resources in the minimal amount of time possible.



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