I am thinking of dropping in a chev 350, a 6000lb winch, and some tube work. I need to figure out how much suspension sag I should expect and how much additional lift I need to compensate. Was hoping to avoid the guess and test method. Anyone help me out w/ the formula I need assuming that I know the spring weight and such?

or is it just easier to assume 1"? 1,5? something like that for an additional ~300lbs on the front end.

All that on the front end is gonna make it very front heavy, you may need to go to stronger T-bars just to compensate. If it were me I would forget the v8 and see how it rides after the bumper, winch and sliders. Take a measurement from the rim to top of the wheel well before the armor adition and if you have a noticable drop then crank the t-bars.

Winch+Bumper+IFS+big v8 = a nose heavy little truck <img src="/forums/images/graemlins/smile.gif" alt="" />

Springs are rated in so many pounds to compress them an inch, at least on linear springs (like torsion bars are). For a quick estimate, measure the height in front, then slap on some weight (have someone get on the bumper for example) and measure the height again (to the same place). Find the height change (in inches) for a give weight (in pounds) and divide pounds by inches to get the spring rate of that end of the truck. Then use that to determine the sag for a given amount of weight added to the truck.

IIRC, a V-8 wont fit with it being IFS(assuming it is still IFS), you will need to do an SAS as well as a BL, you will also have to upgrade the drivetrain. A 4.3 Vortec will be cheaper/easier, and be much easier on the oem drivetrain than the V-8.

With just the winch and tube work, the stock torsion bars should work with a couple of additional turns, otherwise the 25mm bars from Sway-away would be the next best option.

Yeah it isn't going to stay IFS that is why I was asking about springs rather then torsion bars. I am only looking at the 350 because I can get a real good deal on one so it would be far cheaper then building a 4.3. Turns out it might end up a null issue. Found out that in BC any modification to the firewall will fail me for a VI. That includes wheel well tubing and even a little hammering to fit a V8. Bummer.

I have been looking into all the options for some time now so I know all the pros and cons. I am not overly sold on a V8 either, I am just finding it hard to justify the cost of a 3.4 or 4.3 swap for less then impressive improvements in power.

OK, so back to the question at hand. So for instance Trail-Gears springs have a 220lb/inch rate. What does that mean? Does 220lbs compress the pack 1" or each spring 1" so the pack would only settle part of that depending on the number of leaves? I have been searching online a bit but haven't found much that makes sense to the layman. I would just do it Rodgers simple way but since I haven't done the SAS yet I can't really do that. And I can't order springs for the SAS until I have a better idea of what my end weight and therefor ride height will be.

If the springs are sold as individuals and not in a pack,I am guessing the 220lbs/inch is for the individual spring, i.e., 220 lbs to compress the spring one inch.

I have been impressed with the performance of the 4.3 in Toy's. A buddy of mine runs one in his Toyota Trailblazer, and easily climbs the Sierra's to 7k loaded turning 39's with 5.29's. I think the 4.3 with some mods is a nice balance between performance and weight gain over the 22r. IMO you just don't need the power of a V-8 in the smaller trucks, especially out on the trail, all that extra power usually leads to breakage.

No, springs are sold as a pack of coarse. I am guessing that Marlins are the same rating since they are the same supplier. I was just trying to understand what 220lbs/inch spring rate means to a 4000lb truck.

I have a friend in my club w/ a built 4.3 and another w/ a 350. To build a 4.3 to much power seems to mean that you get abysmal fuel economy. I was also thinking about propane which means a sizable power hit w/ was why I was thinking that a 350 would be better. A 350 on gas is too much but one on propane is alright for power. There is not much for rocks up where I am. Gears don't solve everything. Dual cases are next to useless. Upgrading from a 22r/e, yes, ANYTHING is a sizable improvement in power. But from my 3.0 I would like to see at least 230hp/270lbs to justify the cost of an engine swap. Anyway, that is besides the point.

Post deleted by Poor A$$ Stock '93

Simple answer is 4 springs supporting 4000 pountds, or 1000#/spring. 1000/220 = 4.5" of compression of the spring from it's relaxed state.

Longer answer is that leaf springs are progressive, the spring rate increases as more and more of the leaves are brought into play. Also different weights on front and rear axles, etc.

I checked the spring rate of my rear Alcan/AOR springs and get about 180 lb/in., just measure the ride height before and after loading the back up with 600 lbs. of steel. I get abut 1.7" of sag with that weight.