rear spring 66

[bbp]

can any one tell me,whats the difference in ride between a 7 and 9 leaf spring?

 

[WayneC]

The 7-leaf is the heavy duty F40 spring, so it's ride will be quite a bit stiffer.

 

[magicv8]

Normally the 7 leaf is in all BB cars or SB with f40, but when GM discontinued 9 leaf springs (as replacement parts) they recommended 7 leaf as replacement parts for 9 leaf cars.

Normally a car with 7 leaf sits 1/4 inch higher in the rear than with a 9 leaf.

 

[66427-450]

9 leafs were std (SB & BB), 7 leaf is significantly stiffer, used in F-40 and F-41. For street sport driving stick with the 9, if you do go with the 7, you also need to change the front springs and sway bar to retain balance. All BB's had rear sway bars (no SB did).

 

[magicv8]

I have heard experts say BB cars came standard with 9 leaf springs, but neither the old Chevrolet Parts manuals nor the assembly manual nor personal observation nor any BB owner I have ever talked to has shown me an original 9 leaf BB spring. IMO 9 leaf BB cars are/were created by owners who want soft rides - the same way they use the plastic springs.

In the Assembly manual l72 standard 427 suspension front and rear is listed Same as RPO F-40 - my guess is that due to the 120 pound extra load of BB cars - they all came that way.

In the 73 parts manual there are only 3 kinds of C2 suspensions.

IMO the BB cars were all (as the parts manual reads) HD Susp., while the designation you refer to is Spec.Perf.Sus. - both of which got 7 leaf springs.

If you know of another suspension besides F40 that got the Spec.Perf.Susp. designation, tell me about it - please.

 

[66427-450]

In 66, BB's had either:
-- "std" front springs
-- With "AC" front springs, or
-- "F-41" springs (same spring, BB or SB)

That's what's in my notes.

and I believe my above post on rear springs is correct (no offense

 

[magicv8]

That's what's on my BB with A-C, the stiffest springs going and all original front and rear.

By your definition my car's suspension is f-40. By my definition it's BB with A-C.

The coil spring tags match f-40, but I find it hard to believe a 66 roadster with 2 tops, A-C, PS, PB, radio and 4 speed was ordered with f-40. I believe - as do my fello BB owners that all 427 cars got the 7 leaf springs.

Have you ever seen a factory BB with a 9 leaf spring?

If your notes are NCRS judging notes, I don't have more faith in their accuracy than the Chevy parts book - no offense - but my late (#25998) car has a lot of conflicts with the JG - which was written for early cars.

 

[66427-450]

I believe the designation was F40 for 64 & 65....and then changed to F-41 before 66 production began

Another thing to check is the front bar, 7/8" on std susp BB cars, 15/16" in F41 cars.

My F-41 notes came from GM parts manuals (early 70's vintage), and have been confirmed by the Noland Adam's book and several other sources.

- BB base front spring was GM # 3888250 "EB" on the tag
- Air BB spring was # 3888251 "EF" on tag
- F-41 was # 3832518 "EA" on tag, and there was a dark green paint dab on the spring (same spring as F40, and 63 Z06)

F-41 rear spring was 3828811 (later listed as 3877578 in the GM parts books)

Have I seen 9 leaf BB cars? yes, with EB front springs, and 7/8" bar...... but who knows if they were altered.


I know we're not trying to argue, we just have different "beliefs"

BTW: my 66 is a very early car (first 2 weeks of production) and differs slightly from the NCRS IM/JG as well

 

[IH2LOSE]

This is NOT an argument ,This is important information here and I for one am very interested in what is actually factual.

Mike as you remember we had a phone confersation on this in the spring of this year and as magic say's I also thought that to be true.The information you had shared with me sent me back the other way.I have spent hour's going thru the archives of the NCRS board and found what mike says to be substantuated in there archives.

This is a freindly board here and for sure a debate over this will not turn into a argument,All Great folks here

 

[magicv8]

That's fine - I can take your word for F-41 - but the AIM says L79 427 suspension is the same as F-40, not F-41.

I love trying to figure out exactly what the assembly line people did and didn't do - 35 or 40 years later, but I see the original suspension in my car (and I have talked to all but the original purchaser, who owned the car for a year and traded it in for a new one - according to the second owner).

 

[JohnZ]

The year-ending ECL (Exception Control Letter) production records for both '66 and '67 show clearly that F-41 (7-leaf spring)was released by Engineering (and produced) only for usage with L-72 (1966) and with L-71 (1967), and couldn't be ordered with any other engine (except with L-88 in 1967). The notations in the Assembly Manual indicate that F-41 parts "assemble same as production", not that they are the same parts as production - this notation is used all through the A.I.M. where option parts use the same attaching parts, but the part numbers aren't called out on the sheets - the notation also indicates to refer to the Engineering Bill Of Material for those particular option part numbers. The only option-related parts and part numbers shown in the A.I.M. are those which actually assemble differently and use different attaching parts than the base production part they replace.

The ECL codes tell the story, as they were assigned with the original Engineering releases as Bill Of Material coding which drove generation of parts lists, assembly plant Broadcast Sheet codes, pricing, and ordering information; if a dealer order was submitted for any option combination not released by Engineering (didn't have an assigned ECL code), the order was automatically rejected and returned to the dealer for correction.

 

[IH2LOSE]

John I am sorry but I am still not clear on the rear spring with your explanation. 7 or 9 with a big block And is it defenate on weather you could get a standard suspention? with the 425?

 

[Tom Bryant]

This isn't going to help much but my '67 L36 coupe had a 9 leaf. Was it a replacement? Who knows. The tank sticker listed only 427/390, 4 speed 3.36 posi, headrest seats in black vinyl and AM/FM radio as options.

I assumed it was wrong and all BB cars had 7 leaf springs. Wish I would have taken better notes on that car while I had it.

Tom

 

[396 RAT]

FWIW, my 65 BB has a 7 leaf with the ends turned up a bit.
I understand that was the stiffer spring F40? STD 65 BB?
Front coils were swapped out long ago, but the orig coils
have a green sticker on them as I recall. There on a shelf
in the garage. I can double check if it matters?
BTW the 7 leaf does not feel harsh to me.
But my susp is far from stock. My homepage below
details the changes that were made.

 

[Tom Bryant]

BTW the 7 leaf does not feel harsh to me.
But my susp is far from stock. My homepage below
details the changes that were made.

I never thought it was too harsh either. I had a nut break or fall off the end bolt on my '65 327/300 in '71 and the main leaf hit the ground and rolled under. I replace that stock 9 leaf with a 7 from a '66 427/425 parts car a friend had. It was noticably stiffer but then I went from the 9 to the 7 on the same day with no other changes. It also flattened up the cars cornering without causing any push or understeer. I liked it actually.

Tom

 

[JohnZ]

F-40 didn't exist for 1966 production - it was to be released as available for use with all engines, but was cancelled just prior to start of production (after the parts book and the Assembly Manual were released) and replaced by F-41, which was released as only available with the L-72 BB.

 

[66427-450]

John I am sorry but I am still not clear on the rear spring with your explanation. 7 or 9 with a big block And is it defenate on weather you could get a standard suspention? with the 425?

Larry -

I think what John is saying is that in '66 you could only order F-41 with L-72. (I read he agrees that 9 leaf was std, with L-72)

 

[JohnZ]

Yup, I agree; 9-leaf on everything unless it was an L-72 ordered with F-41, in which case it got a 7-leaf.

 

[bbp]

Thanks for all the posts. Now im really confused. You say no small blocks had rear sway bars. I just bought 66 small block. I't has sway bar and 9 leaf spring. The spring need to be replaced, just wonder witch one to go with.I Don't want a real stiff ride, but don't want a soft mess. Will it make a big diffrence if a put in a big block for my spring selection?

 

[396 RAT]

"F-40 didn't exist for 1966 production - it was to be released as available for use with all engines, but was cancelled just prior to start of production (after the parts book and the Assembly Manual were released) and replaced by F-41, which was released as only available with the L-72 BB."

So John, whats on my car? Its a 7 leaf with the ends each leaf
slightly turned up. F40?
Thanks!