84 Monticarlo Suspension Limits for 550 Horsepower

[user-612937456]

I have a customer that wants me to build a 550 HP 383 and install it in his 84 Monticarlo Saturday night cruiser and a 9" rear diff. After thinking on it over the weekend I am concerned about what it will take to get the power to the ground and if I get it to hook will the car twist so much that it really needs a roll cage. First I am sure that the upper control arm cross-member will need to be reinforces as well as the frame to be boxed in. If he doesn't want to do a roll cage how much H.P. do I need to recommend him to put in his chassis? If he is OK with a cage will an 8 point be sufficient? Any other suggestions or discussions welcome.

[lefty o]

an 8ptcage will stiffen it up nicely. the hard top cars flex alot less than the t-top ones. with the cage, i personally wouldnt worry about boxing the frame, without it, it is needed, as the frame is fairly flimsy. strengthening the rear crossmember in the car is a good idea. ive got an 87 w/t-tops and i twisted the body up pretty good with a 474hp 355 lol.

[Krooser]

Keep the tire size down and you shouldn't have any problems… big tires change all that.

[user-612937456]

by tire size do you mean 12X29's or smaller

[lefty o]

even with a small tire, they can be made to hook hard today.

[CanadianC10]

depends what kind of converter? trans brake?

if hes running a 4000+ stall converter and a trans brake, hes gonna need a sway bar in the rear. Box in the 4 link members and call it done.

Even the converter alone will pull up the front right wheel. What gears? If he does not want a cage put a sway bar in the rear and that should keep it from twisting.

my 2 cents

[user-612937456]

leaning toward a 4.10 gear and a 3500 stall nothing set in stone yet that is why I am here researching first all I have is a platform of the 84 monticarlo and 383 forged short-block so far this is a rod run/Saturday nite beast. The goal is a 7-7.5 second 1/8th mile car

[CanadianC10]

example - 550 Flywheel Hp 383 G body regal - 9" 4.10 spooled Coil over stock triangulated 4 link - th350 5500 stall trans brake - 90-10 race shocks - with a cage - no backseat - fuel cell and battery in the trunk - best of 11.31 1/4 mile - With a cage it still trys to twist the body in on itself.

[bigfoot584]

79Malibu.jpeg

I'm not sure what the other guys are doing but I'd no problem hooking my 79 G body as you'll
see in pic. The cure was I raised the upper control arm mounts on the 9" ford approx. 2 1/2"
from stock then made boxed control arms with poly bushing and bolted 1 3/8" sway bar
(you'll see that in the pic.) between the lower arms. I used stock shocks front and 3
ways in the rear it shocked the rear tires so hard I had to run the firm setting on
shocks in rear or it would slow the 6o" times.
When I owned it it run 7.30's or 6.90's w/NOS all day with 425 HP 355 in the 1/8 mile.
New owner is running 11.00's in the 1/4 mile with 383 in it.
Rollbar (no cage)
9" slick
4400 converter
3.70 rear gear
350 TH w/brake ( new owner PG w/brake)

[F-BIRD'88]

On these cars its all about the geometry of the LOWER rear control arms.

(althou correcting the Upper control arm geometry helps too) Your biggest concern on this car is the lower control arm geometry and action.
Adding AIR LIFT air bags to the rear springs really really helps these cars hook up. They are simple bolt on and they WORK.
Allows preload of the right rear spring. Increases spring rate and corrects the lower control arm geometry, stops rear body squat on launch. You can replace upgrade the stock OEM control arm bushings if sloppy.
The replacement Lower control arm re-location brackets help a lot too.
Replace the OEM lower control arms or box them in and add urethane bushings.

IF the upper rear control arms mounting point and top shock absorber body mount point
is rusted repair and reinforce.

A six point or 8 point roll bar is not nessessary for most track up to 11.50 ET. (1/4 mile)
But not a bad idea if it gets that fast.

Body--- chassis twist:
The OEM rubber body mounts are usually degraded and or loose. Thus the body is not "coupled" to the car frame.
The frame-body mounts can be replaced with urethane or steel body mounts to great effect
on these cars. That will stiffen up the whole chassis-body a LOT.

Check the NHRA-IHRA rule book for roll bar construction spec details.

Again, for a simple 11 second street- strip car the AIR LIFT air bags work wonders on these
cars. GET SOME. http://www.airliftcompany.com
control arms, bushings and relocation brackets:
http://www.spohn.net
http://www.umiperformance.com

With these simple mods the car will not squat and twist on launch and will
hook up.

[lefty o]

just curious, how does an air bag correct lower control arm geometry?

[F-BIRD'88]

just curious, how does an air bag correct lower control arm geometry?

When you add air to the air bag the ride height increases and the angle of the lower control arms changes.
Goes from negative to positive angle. Makes the car's rear lift on launch (when engine torque is applied) instead of squatting on launch caused by the neg lower control arm angle when sitting at the stock ride height.

Further, once weight transfer is established at launch, the lower control arm cannot return to a neg angle by the added car weight
on the rear, cause the air in the bag adds to the rear spring rate, supporting the now increased weight on the rear spring.

(The rear does not squat down from the added weight at launch)

The rear of the car does not squat on launch. You can also adjust the right left rear tire traction bias by biasing the air bag pressure
on the right rear air bag. This makes a limited slip posi work a lot better.
Eliminates rear wheel hop which is what kills rear axles, differentails, drive shafts, and torque converters.

You can see the effect for yourself just by simply jacking your G body car at the rear frame, a bit while watching the rear lower control arm angle change as you jack it up. The air bag does the same when you add air.
They work great on all cars with rear coil springs and conrtol arms. Like the G body and the old Chevelles and 3-4 gen F body cars.

Its adjustable. Usually you run a bit more air in the right rear air bag. You can let the air out for normal street driving, if you like. Or leave it in....or... You will find the happy spot. They work great.

[pdq67]

May I suggest this and please bear with me because I don't know if it is of use for a full framed car?

1st Gen guy's can buy bolt-on open square cages that fit from the sub frame connectors on each side of our cars. This tie's the front of the rear leaf spring perches to the front sub frame ends cross-ways. This effectively open "boxes" the underside of our cars and allows the driveshaft to fit.

Just an off the wall idea to try to stiffen our cars frames, etc.....

pdq67

[Geezer]

An old post, I know. Just my $.02 A good quality arb does away w/ the air bag crutch...

[peejay]

550hp is a "mild" Grand National and they don't twist the chassis like pretzels. Some beefening needs to be done in the rearend but you only need a rollcage after you drop below 10 seconds...