1965 rear leaf spring

[38243]

What was the standard spring used on a fuel injected car, 7 or 9 leaf? Were they gray?

[Gary B.]

1965 rear leaf spring

For 1965, the standard suspension included a 9-leaf rear spring, while the F40 (heavy duty) suspension included a 7-leaf rear spring. In both cases, the spring leaves were painted gray. I don't think knowing that it was a FI car is enough to determine if it had the standard or HD rear spring.

Gary

[Roberto L.]

Re: 1965 rear leaf spring

Checking the leaf spring in my 70, which are at present out of the car, they seem to have been painted in the lower side only (in upside down position). I found only original paint in that side, mainly in the central section.

Thats confirms some recent post about a Bloomington workshop or something like that. The main, longer leaf shows an emboss in the central border which reads something like GMU or GMO, not an stamp (?). This is a 70, not a 65, but suspect the springs are similar.

Roberto, NCRS #30019, RMC

[Joe L.]

Re: 1965 rear leaf spring

Roberto-----

The 1965 and 1970 springs (both 7 and 9 leaf) were of the same part numbers, although manufacturing nuances may have varied a little bit.

[Joe L.]

Re: 1965 rear leaf spring

Gary-----

Yes, I don't think that F-41 was a requirement with the L-84 engine for 1965. While many L-84s likely were also ordered with F-41, they didn't have to be.

[Roberto L.]

Thanks *NM*

[Duke W.]

Re: 1965 rear leaf spring

Joe - The only available HD suspension in '65 was F-40 and it was only available on SBs - without restriction as far as I know, so you could order it with any SB all the way down to the base 250 HP engine.

F-41 was first available in '66 and only on big blocks. F-40 was not available for SBs after '65. The '65 L-78 had a unique suspension tune that was part of the engine package. It included front and rear anti-roll bars, and there was no optional suspension for L-78.

As far as I know the springs for F-40 and F-41 were the same - 550 pounds/inch front and 305 pounds/inch rear, which were about double the base '63 linear rate springs, but F-41 for the BB had a different anti-roll bar setup including a rear bar. F-40 only had a front anti-roll bar.

Duke

[Joe L.]

Re: 1965 rear leaf spring

Duke-----

Yes, I erred on the 1965 F-41 nomenclature; 1965 was the last year for F-40. However, F-40 and F-41 are, essentially, the same; I don't know why GM changed the nomenclature for the option beginning in 1966.

Also, as far as I know, F-40 was available with the L-78 for 1965 and there was no unique suspension system for L-78-equipped Corvettes. F-40 may have been a mandatory option with L-78, though; I just don't remember at the moment. If it wasn't mandatory, then non-F-40 L-78 Corvettes received the same suspension as small block Corvettes.

The rear sway bar was never part of any suspension option during the 65-74 period. During those years it was supplied as part of the big block engine options only. All 1965-74 Corvettes with big blocks were supplied with 9/16" rear sway bars (with the POSSIBLE exception of 1968 which MAY have used a 7/16" rear sway bar). NO 1963-74 Corvettes with small blocks were supplied with rear sway bars, regardless of standard or F-40/41 suspension.

1963-74 Corvettes with small block and standard suspension utilized a 3/4" diameter front sway bar;

1963-74 Corvettes with small block or big block and F-40/41 suspension utilized a 1" front sway bar;

1965-74 Corvettes with big block and standard suspension used a 7/8" front sway bar;

For 1975+ Corvettes equipped with FE-7 HD suspension, a 1-1/8" front sway bar and a 7/16" rear sway bar were used. This was the only use of a rear sway bar for smallblock Corvettes.

For the 63-65 and 66-74 periods, the F-40 and F-41 front springs were identical (GM #3832518) and the F-40 and F-41 rear springs (GM #3828811) were identical. The 1" front stabilizer bar used with F-40 and F-41 was also the same (GM #3831972)

[Duke W.]

Re: 1965 rear leaf spring

I think we've got some differences in the semantics and the details. F-40 and F-41 substituted the same springs and front anti-roll bar for base suspension components on small blocks and big blocks respectively, and in either base suspension or F-41 trim, big blocks received a 9/16" rear bar. I suspect GM changed the option number to highlight the fact that from '63 to '65 a HD suspension (F-40) was only offered for small blocks, but beginning in '66 a HD suspension (F-41) was only offered for big blocks. You are correct in saying that they are the same in the sense that they both substitued the same springs and front anti-roll bar in place of the base components. The subtlety is that the base big block suspension included a 9/16" rear anti-roll bar and this remained unchanged with F-41, whereas base small blocks had no rear bar and a rear bar was not included with F-40.

The L-78 suspension was unique in that it included a different anti-roll bar setup than either the small block base or small block F-40 HD suspension. L-78 had a 7/8" front bar and 9/16" rear bar bundled with the engine option. Off the top of my head I believe the spring rates are the same as the small block's base suspension progressive rates, but the fronts might have been slightly longer to keep the ride height at the proper level with the heavier big block engine. To the best of my knowledge F-40 was not available with L-78, but installing the F-40 components on a '65 L-78 would have yielded the '66 F-41 setup. Maybe I'm wrong on the availability of F-40 with L-78, so I'd like to get confirmation one way or the other with a reliable reference.

Beginning in '66 the HD suspension was only available on big blocks and was identified as F-41 to distinguish it from the '65 SB only HD suspension. F-41 included the 550/305 lb/in springs from F-40, a 15/16" front bar - same as F-40 and F-41 retained the 9/16" rear bar that was part of the BB base suspension. The big block base suspension bars remained as with the '65 L-78. The above info summarized from Corvette News Vol. 9 No. 4. The same Corvette News article about all the '66 HD options quotes the base suspension rates at 207-380 lb/in front and 140-168 lbs/in rear and implies that these rates are the same for both SB and BB base supensions. The constant rate base '63 springs are 280/160 lb/in, front/rear.

What falls out of this is that checking any big block engine option generated production codes to install the big block specific base suspension components, which included the specific front and rear anti-roll bars required to rebalance the chassis due to the big blocks higher weight - all of which was essentially on the front end.

It could be argued that F-41 is the same as F-40 in that the changes to the suspension components only affected the springs, front bar, and shocks, because either the big block base or F-41 supension included the 9/16" rear bar, but I like to distinguish between them.

Both F-40 and F-41 included specific shocks, but I've never tried to keep track of them because shock calibration is something that was frequently changed.

Anybody else want to through in their two cents?

Duke

[Joe L.]

Re: 1965 rear leaf spring

Duke------

1) F-40 was available with L-78 for 1965. Among other references, that information is contained on page 271 of Noland Adams' "Volume 2". It seems that 326 L-84s were equipped with F-40 and 649 L-78s were equipped with F-40. Considering that 2,157 1965 L-78s were built, this would mean that 1,508 were manufactured with standard suspension. Presumably, Noland could be considered a "reliable reference" in contrast to the information which I provide;

2) Considering the above, if the fact that the rear bar coming into play for big blocks was the reason for the change from F-40 to F-41, then it would seem that the change should have occurred for 1965 and not 1966;

3) For 1966-69, the F-41 suspension was limited to big block applications. However, F-41 was NOT always limited to big blocks. F-41 was part of the package of options that were supplied as part of the 70-72 ZR-1 package which, of course, otherwise included the LT-1 small block engine;

4) The 7/8" front bar/9/16" rear bar was not unique to 1965 L-78s with standard suspension; all big block Corvettes from 1965 to 1974 with standard suspension used the same combination;

5) 1965 Corvettes with L-78 and standard suspension used the same front and rear springs as standard suspension small blocks. These were GM #3851100, front, and GM #3850839, rear. Front end "sag" when these springs were used with the L-78 led to different springs being used for 66-74 big blocks with standard suspension. However, for F-40/41, the exact same front springs and rear springs were used throughout the 63-72 period, big block, small block (or, even, medium block, if they had made any). These were GM #3832518, front, and GM #3828811, rear. [note: it is POSSIBLE that some 1965 Corvettes with L-78 and standard suspension MAY have received the 1966 standard suspension 427 spring, GM #3888250. I doubt it, though. I don't think that this spring was even released in time for original installation on any 65 models. It may have been installed in later warranty SERVICE to correct owner complaints, though];

6) The shocks used for all 1963 through 1972 Corvettes with either F-40 or F-41 suspension were the same. In PRODUCTION, these were GM #3171488, front, and GM #3171489, rear.

7) The front stabilizer bar that I refer to as "1 inch" might be more appropriately described as 15/16". I have measured these bars and, depending upon where you measure them, the thickness dimension varies from 15/16" to 1". So, I often refer to them as 1" bars, but I am referring to the NOMINAL thickness. In any event, this bar, GM #3831972, was used on all 63-72 Corvettes with F-40 or F-41, regardless of whether they were small blocks, big blocks (or, medium blocks).