I am in the beginning stages of a total build. I am wondering how many inches of sag will happen once I drop the body and engine onto the frame. I have a model A coupe and model A frame with model A suspension. The engine is a SBC with iron intake and heads and a manual 4+3 trans. I understand there are many other possible contributing variables but an approximation would be helpful. I figure someone should have some info/experience with this. Let me know if you need more info. Thanks in advance.
I can't believe no one has chimed in on your question yet. Maybe because it's the weekend? I did not allow for the proper weight of engine and body etc..... And my overall clearance may be an issue? I'm at 3.5 and would like 4.5". Not a huge problem as I may just go with a "regular eye" spring instead of the reverse and that should give me another inch I hope. I'm not the expert so I hope you get the right formula from one of the experts on here. Good luck.
Depends on leaf spring mat'l if the leafs were out of same pack ect.. Old ford or other ...No definitive answer and in all probability from the time the car first hits the ground 2-4 months later the springs will settle in that can mean 1/4" or as much as 1.5"
Body weight is a moot point- frame is designed for it. All gen.1 sbc motors weigh 575 lbs. with cast iron intake and heads. The stock A suspension is pretty stiff , and I've run small block Ford motors in Model A's with a stock front spring ( after adding shocks to the front suspension) without a problem. You will have to run a dampening member to stop lateral movement caused by the spring shackles. NAPA sells a kit for an F-100 that works great. The frame is a bigger consideration, being designed to twist (and put together with rivets). It should be boxed and have the crossmembers welded to stiffen it. Don't weld the center one till you figure out how you're going to hang the ******.--- You really didn't get into details like brakes , rearend ,etc. When you upgrade to juice brakes and a late model rear axle, everything is going to change anyway, and again the frame is your main concern. I'm sure others will chime in , but I hope this helps. Good luck with it.----extra tid-bit; when I set the front end up on this sedan, I didn't have the motor, so I put a piece of plywood across the frame rails and piled bags of Sakrete concrete mix on top of it. ---80 lbs. a bag- 7 bags = 560 lbs.(+/-) not high tech, but gives you something to work with!
Thanks for replies. Mike bowling, I have already swept the front and kicked up the back and just finished boxing the back. I could figure out the sag with roughly dropping it all on but I wanted to save the h***le if someone knew that it would sag like and inch or two inches. Makes a difference in stance, and we all know the importance of stance. Brakes and other stuff are unsprung weight so I'm not concerned with that regarding sag. Thanks
Some reason I didn't see your sand bag idea. Good idea, hopefully I won't have to do that but it might be an option.
I was more thinking about the rear end- if you're going to keep the stock spring in the back. And you and I both know the stance HAS to be killer! Good luck with it.Yeah- we're both on at the same time and info is getting crossed up.
Quain Stott once said something along the lines of building with only the main leafs - adding individual springs as you add weight.
Mine dropped about 2 inches when I dropped a abc in the frame but I haven't checked since I built the body.
what ever you think, you will have to "adjust" after the car is somewhat complete. but starting with about 2" is good. once the motor and all is in just add or remove leaves until it sits right. I just about wore out the bolt threads swappin in and out leaves to get what I wanted.....good luck!
I do it the hard way. I have a rig I mount springs in and then load them with a ram. I have a load cell so I know the loads applied. I can help my friends get the right spring rate and then tell them how much it will drop when installed. I get really close with this and the builder knows how to make the crossmember.
Neat. Have you done any springs that are going on a vehicle similar to mine that you may be able to enlighten me with the drop results?
The Posies I have tested ran about 250 lb/in per side. In other words, it takes 500 lbs to deflect the spring 1 in. You can multiply the rate by the sprung weight to find the drop. This is just ballpark. I feel different lengths would have different rates. All are stiff.
you would build your old school car the way the original old school guys did: by trial and error, you know "old school"!
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