Front springs question

by 77mali Mon Dec 08, 2014 5:58 pm

I know there are different springs avail. for our cars depending on engine type/chassis/ac vs non ac, etc..

The question is this: Is there really that much difference if using front springs set up for a 305 w/ air on a 350 w/ air?

Can't imagine it would be a big difference on the stance- set me straight if you've had any experience with this scenario, please.

Yes, I'd like to reuse my 30+ yo springs, they're in great shape. No rot or dings or anything, just a little surface rust.

by chevellelaguna Mon Dec 08, 2014 6:55 pm

I'm sure that over the years your factory springs have sagged, and their originally designed spring rate has degraded over time. Does that mean they are junk, not necessarily. You said visually they look good. I'd be inclined to reuse them. However, you asked if there is a difference between the two options you're looking at, I'm sure they are made for different spring rates, because of the weight differences. Is it going to matter on a stock type application, probably nothing you will feel.

by Joe73 Mon Dec 08, 2014 7:16 pm

Paul, grab the part numbers off rockauto for the 305 vs. the 350 and match them up here. Should give you the info your looking for.

http://www.moog-suspension-parts.com/Universal_Coil_Springs.asp

by Roadcaptain S3 Mon Dec 08, 2014 7:21 pm

I wouldn't think there is any difference either. When I've looked in the past, the only difference is if you have a 454

by 77mali Mon Dec 08, 2014 7:25 pm

Thanks guys.

I am relying on the thread posted below by Bigredlaguna (who went to an enormous amount of effort with it!)
https://www.g3gm.com/t2376-front-spring-rates?highlight=spring

It says:
2771432 = SBC w/air, BBC w/o air
2771432 # Coil Spring Coils : 9.5 Coil Spring Free Height : 16.35"
Coil Spring I.D. : 4.08" Spring Rate : 400
Wire Diameter : .705"

Based on this info that part # does not classify 305 vs 350- just Small Block. I hear what you're saying though- I'm sure reusing my old springs is not "Ideal". I guess my big concern is ordering replacements & having them not sit like they're "supposed to". The steel made in those days was much better quality & made in the USA. I'm not confident in "made anywhere else" but here.

by chevellelaguna Mon Dec 08, 2014 8:20 pm

Yup stuff they make is junk, don't know what you're getting...still, companies like Moog have to conform to standards. I personally don't think those standards are as good as they once were.

by pila Mon Dec 08, 2014 8:44 pm

There were HD springs available on some A bodies, for HD suspension, like my '77 Elco had when it was new. I believe the accessories had something to do with front springs also, like AC, cruise heavy duty radiator, and even a HD battery,
In the NPD catalog for instance, there are accessories etc that added some weight to the front end. A 305 isn't gonna weigh any more or less than a 350 basically, since bore size is mostly the only difference.
Some catalogs show more than two springs for the same application, not including the big block type.

Kinda confusing I think....

In the NPD catalog for instance, there are 6 different springs for a '74 with a big block 454, and 5 different springs for a 350 small block

by 77mali Mon Dec 08, 2014 8:55 pm

Well...lol

I'm going to check the measurements referenced in what I posted from the thread. Then I'll compare to what MOOG/Rock Auto/Summit has to say. I went on the rock auto site so far but the spec's do not correspond to what we have here on the site.

And YES- VERY confusing! Very Happy

by jerry46765 Tue Dec 09, 2014 1:12 am

Paul -

Let's use common sense.
What weight have you added to the front of the car?

There is no discernible weight difference from a 305 to 350.
Did you add headers and an aluminum intake manifold?
Two to four barrel carb?
Add cooling capacity (bigger radiator)?
Remove (or add) air conditioning compressor?

Once you add up the plus and minus(es), how much weight are you talking about? Maybe 100 pounds?

Split that weight in half and you are talking about 50 pounds per wheel.
No big deal.

I would reinstall the production springs, because you aren't making a small block to big block weight change. Plus, I would bet you are changing the tire/wheel sizes which will affect ride heights.

You could play the part number game until you are blue in the face.
Make changes once you have more known quantities.

Thanks -

by bigredlaguna Tue Dec 09, 2014 2:14 am

Yeah, I burnt a few nights with that front spring post. I figured at the time that I better get that info before it got deleted because the NAPA site was the only one that had the specs.

At least if you have to get replacement springs, and you like the ride quality of the factory spring, you can get reasonably close with this info. You can also measure your old spring and use the formula to figure out what you have now.

by dynchel Tue Dec 09, 2014 7:54 am

Paul, if you like the way it sits reuse them. I've always ended up cutting (new) fronts due too high of a ride height.
I am very pickey, if it wasn't for exhaust clearance I'd lower mine more.

by 77mali Tue Dec 09, 2014 10:08 am

I too suffer sadly from "perfectionism". I'm still going to compare the springs to the posted measurements but will most likely end up restoring them if they are within tolerance of that 16.35" free height. Nothing significant has been added or removed to make that much of a difference anyway. The wheels will remain & if they change it'll still be the same diameter, tire height.

Thanks for all the replies. +1 for y'all. (those I missed will get +1 tomorrow) I think you can only give out so much per day it looks like!

by Wallyuph Tue Dec 09, 2014 10:46 am

dynchel wrote:Paul, if you like the way it sits reuse them. I've always ended up cutting (new) fronts due too high of a ride height.
I am very pickey, if it wasn't for exhaust clearance I'd lower mine more.

I would reuse what you have if you like the height also.

Mine is stock springs and after the LS3 swap and aluminum radiator and Light weight accessories its up over a inch and that's with original old springs. So that's my point if you replace parts down the line and go lighter you will be higher for ride height.

Just my 2 cents

by Dinomyte Tue Dec 09, 2014 6:33 pm

As a guy who's done this, the 350 doesn't weigh much more than the 305. You've really got to add up all the weight changes and see if it makes a difference.

If all you've done is replace a stock 305 with a stock 350 you might have gained 50lbs, if you replaced the stock cast iron intake with an aluminum one you've offset that by lots.

by pila Tue Dec 09, 2014 9:44 pm

On my '75 Elco project I just bought the Moog HD springs locally & bolted them in. Only reason for the HD type was the Caddy engine up front, which weighs 100 + lbs more than a SBC. Height seems OK to me.

by Joe73 Wed Dec 10, 2014 6:46 am

I just installed new Moog HD springs all around on my frame. I've run all the models of big/small block HD springs from moog over the years. They all increase ride height and harshness. Although the small block, w/a/c HD did settle out nicely over time.
I currently put in my correct springs which would be small block, HD, no a/c.

by dynchel Wed Dec 31, 2014 10:04 am

Here is a neat trick to remove rust (like front springs) from something you are not in a hurry for. Soak them in apple cider vinegar, it will take probably a month, but the end result will look sandblasted. I usually let soak a few days, hose off, and put back. Obviously the final time you would want to use acetone not water. Follow that with some rust converter & your golden.

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