I have a '71 SS, and I know everything on it is original, and that it has the F41 suspension that the SS had. However, my car is a small-block SS. I'm going to swap to a big block soon. Will the front coils hold a big block without sagging since it has the F41 suspension, or will I need different coils (maybe the coils aren't part of the F41 suspension?)? Thanks.

I think the F41 RPO only effected rear suspension components. Boxed lower arms, braces, and swaybar. I think that's it. Someone correct me because I'm not positive. I'm pretty sure it had nothing to do with the springs, though.

You will definitely want BB springs under a BB motor.

Tim.

You will need to change your springs. GM used different springs with different coil rates and weight rating & everything plays a factor including your engine and believe me speaking from experience that BBC weights alot more than a SBC and when i did my conversion over to big block it set down a couple of inches and espicially when i was driving and hit bump my fender well will scrub my front tires even in turning so change you springs.

only 150 lbs more than a smallblock, I left the smallblock springs in mine at first,only issue was the Hooker headers drug the ground,other than that I had no problems,switched to BB a/c springs and headers still hit the road occasionally,switched to 1.75 dynomax headers and problem gone.

I have a 70 malibu that I put a big block in and the front end dropped a lot. The cross memeber and the exhast pipes bottom out quiet a bit.
I'm looking for some big block springs now.