1986 C10 Rear Suspension with some Power

[aotte1]

1986, C10 SB SS that will be street driven for fun, along with a few errands thrown in. Some 1/4 miles trips too. The truck will get a mild 350 C.I. 400 H.P. @5700 rpms /400 ft-lbs of torque, that is camed for a broad power curve. It is a MY6 4 speed that I will granny shift at the track, to give it a long life. Upgrading 10 bolt to 3.73 gears. The pretty much stock front suspension has been lowered about two inches by cutting one coil from stock spring.

Question: Getting close to a decision on rear suspension lowering to level it with front. From guidance provided here, planning to doing an axle flip, with new 51.5" springs that have more arch to bring the rear lowering to about 3" total. The flip is planned to be done by welding new perches vs kit such as "Western". Any suggestion. Also will be using cal-trac. KOOL-IT suggested I look here for assistance and knowledge.

A few picks of frame cleaned.

Les

[tinydb84]

Why not go with a shackle and hanger kit for that little drop?

[aotte1]

From responses in other treads here, they suggest that using the longer shackle/ hanger, introduces rear steer into truck handling. This is because of flex in the new part, not being fixed like factory set-up. The flex is the rear axle moving around under hard loading.

I plan to do some 1/4 mile drag racing, therefor, loading the rear hard and do not want axle rotating under high torque launch loads, and steering truck in a non straight direction. A well set-up 10 sec drag vehicle should be able to be driven down track with very little steering effort. Drag radial slicks at 25 or more psi ( which you can hook-up with properly set up 10 sec vehicle) make driving 1/4 mile trips capable with a lot less effort.

Les

[tinydb84]

If you are only making occasional trips to the track with 400 hp I wouldn't be that concerned (then again I don't drag race).

You could run the shorter hangers (2'') and modify the rear bracket that your shackles mount to in order to get that addition inch. Moving the front bracket up would also increase anti-squat from my understanding.

[aotte1]

David,

Good questions, on how best to lower rear body 3 inches. Hope we get a discussion going from others who drag race.

On your suggestions have you done them, and have you seen any rear steer, under heavy load conditions.

Les

[tinydb84]

I have only had flip kits and 4 links so I don't know if there would be any additional rear steer. When I did race (it was all street-I was young and dumb) I never got go enough traction for it to matter.

[Super73]

You are putting time money and energy in to the rear yet you have a stiif short front spring that is not going to transfer weight to the rear tires. Seems like a contradiction to your efforts.

[aotte1]

Super73,
I agree with you comment, this is more a street truck, with some fun trips to drag strip. Have lowered front, and want to lower rear to level truck out. If you have experience with the 1986 chassis, would appreciate your thoughts on how to do it. Definitely not a strip mainly truck; however, another chassis in garage will likely be one-another story- which will definitely have a very light front end.

Les

[Super73]

You don't need a light front end to get it to xfer weight to the rear tire.

I would personally find a long light spring rate spring for the front that gets you to your desired ride height in the front. This stores energy and makes it easier to transfer the weight. If you know what the front of your truck weighs, I could most likely give you some pointers on what length/rate ratio will be in the ball park.

Now as far as the rear leaf set up, lowering the front shackle will change instant center (reduce it). This will transfer some of the energy in to the chassis to reduce the hit to the rear tire (Squating the rear). This also aids in getting the front to rise. You could use a slide set up for the rear shackle. Caltracs are an added benifit!

Like the front, a softer rear spring will help absorb some energy and will most likely aid in your efforts to plant a radial tire with a stick shift.

You need to get the weight on the tire if you expect it to hook.

[aotte1]

Super73,

On the slider for the rear shackle, can you suggest a source, I saw AFCO sell them for cars.

Where do you think the IC should in relation to the CG center of gravity for this truck? In past for C/SA car had it just behind CG, at CG height in car. Tuned hit from their with AFCO shocks mostly, changed ride height a little to move IC only if traction was really bad. Dave Morgan was my teacher on this.

I will get the individual truck wheel weights, and provide info. It will take me a little time before truck is all back together.

Thanks for the help.
Les

[Super73]

Make sure to get the weight at the actual ride height desired and with you in the seat. If you have not sourced rest springs, try to make a solid mount in their spot.

As far as ic.. mine is set to 58" in front of the rear tire and 5" off the ground. It works no issues at my power level with a 315/60/15 drag radial out of the hole. I just need to tighten the front. If that doesn't fix it spinning 5-10 feet out, I will raise it some.

[aotte1]

Super73,
"Solid mount rear springs" means solid mount/ bushing in the eyes of the spring?

Thanks
Les

[Super73]

No, remove the spring and put something in its place to get the truck at desired ride height to pull it across the scales.

[aotte1]

Super73,

Got it now.

Sorry for your coolant leakage problem, hope you find solution soon!
Thanks,
Les