Help�65 396 Front Springs part numbers?

[Rick B.]

small block-----GM #3851100----15-13/32" O.L., 11 coils, 0.600" wire diameter and that in 1965 Corvettes with L-78 and standard suspension used the same front springs as 1965 Corvettes with small block, GM #3851100. GM replaced some of the springs with higher rate springs first used in PRODUCTION for 1966. However, there was no recall; if you complained about it you might have gotten a replacement (after the replacements became available in SERVICE)."BUT it goes on to say.." big block w/0 C-60-----GM #3888250----17.35" O.L., 10 coils, 0.600" wire......"
So the questions:
What was original coil spring for L78 396 for standard suspensions? I am confused i.e. AIM L78 page :Same as UPC F40" which would lead to #3832518 not #3888250.
Was there a third spring for standard big blocks in 1965 as the JM states. #3888250?
When Did part number #3888250 get introduced?
Or Was this coil spring part number specific to 66 and 67 big blocks?
and last, What would of been available in Service for 396 L78s?

Again any help so very much appreciated and hope everyone is well!

[Joe L.]

Recently have been trying do some research on 65 396 Front coil springs and have had difficulty in determining what version/part number was used in production for standard suspension L78 396s and then what was available in service.

That said here is what Im seeing and just NOT sure how to interpret. Any help very much appreciated.

For context.

JM For what its worth.
Pg210
Front spring part numbers:
SB #3851100 Green tag ED
BB #3888250 Green tag EB
F40 #3832518 Green tag EA


AIM. The aim non illustrated UPC L78 A2 states sect. 3 front suspension — "Same as UPC F-40".
UPC 3 shows the two part numbers in a chart #3851100 Std. and #3832518 F40 with NO third part number for standard big block suspensions.



In PARTS accessories Catalog effective Oct 65.. Gr. 7.412. This catalog only incorporates 1965 In the following;
63-66 2nd design (exc. HD sp. perf. susp.) #3851100
63-66 w/ sp. per. susp., HD susp. #3832518
(NO mention specifically of 396 special high performance)
(No mention of spring #3888250)

as a another point, while an Archived post Confirms that "small block-----GM #3851100----15-13/32" O.L., 11 coils, 0.600" wire diameter and that in 1965 Corvettes with L-78 and standard suspension used the same front springs as 1965 Corvettes with small block, GM #3851100. GM replaced some of the springs with higher rate springs first used in PRODUCTION for 1966. However, there was no recall; if you complained about it you might have gotten a replacement (after the replacements became available in SERVICE)."BUT it goes on to say.." big block w/0 C-60-----GM #3888250----17.35" O.L., 10 coils, 0.600" wire......"
So the questions:
What was original coil spring for L78 396 for standard suspensions? I am confused i.e. AIM L78 page :Same as UPC F40" which would lead to #3832518 not #3888250.
Was there a third spring for standard big blocks in 1965 as the JM states. #3888250?
When Did part number #3888250 get introduced?
Or Was this coil spring part number specific to 66 and 67 big blocks?
and last, What would of been available in Service for 396 L78s?

Again any help so very much appreciated and hope everyone is well!

Rick------


All 1965 Corvettes except those with F-40 suspension were originally equipped with spring GM #3851100. This includes both small blocks and big blocks. Those with F-40 suspension used spring GM #3832518. There were no other springs originally used for 1965.

The GM #3888250 spring was not released and used in PRODUCTION until the 1966 model year for big blocks. It did not even exist during the 1965 model year. It was also RETROFIITED to some 1965 Corvette with L-78 due to owner complaints of front spring "sag" (i.e. low front ride height)

[Rick B.]

[Gary B.]

[Rick B.]

[Gary B.]

[Bill M.]

Joe as always much appreciated!!!

Since writing this post, Been reviewing many of the archived posts around 3851100 and it seems to be some specification discrepancies. i.e AMA CE AIM Nolan etc. If possible would love to get some clarity. An exchange in 2016 between yourself and Bill Mashinter and even earlier with John Hinkley identifies Free length at 15 7/16 15 13/32 15.40 16.82 16.88. Possible to get clarify on the Free length, Coil dimension? Seems to be consistency on the .600 Wire diameter. And last, is it Safe to assume the production 3851100 specifications are the same as the GM service pieces with the yellow stickers?

Boy its been a job consolidating, correlating C2 springs to specs based on past posts. Any help would be fantastic. Maybe someone has put this in a spreadsheet? IF not be happy to start.

I know from outside OE world all this data is confusing. The part drawing is the definitive authority. The 3851100 drawing has a free length at 16.88.

By the way, the 3888250 free length is 17.35 on the drawing. I measure my NOS 3888250 at 17-1/4. (I don't have NOS 3851100.)

[Rick B.]

[Bill M.]

Bill, thanks for weighing in!! Yes saw that you had stated the length from CE, very very helpful. Curious the Diameter of the Spring (Width)? Previous posts I have seen state 5 3/16 or 5 7/16 and there may be others. Any detail here?

I did not get that data from the drawing. But I measure my 3888250 pitch diameter at 4.5. That is the dimension used for spring calculations. That makes the OD at 4.5 + 0.6 = 5.1. The 3851100 will be the same. The springs are the same except the 3888250 is wound longer.

[Stewart L.]

[Joe L.]

I know from outside OE world all this data is confusing. The part drawing is the definitive authority. The 3851100 drawing has a free length at 16.88.

By the way, the 3888250 free length is 17.35 on the drawing. I measure my NOS 3888250 at 17-1/4. (I don't have NOS 3851100.)

Bill------

I do. I measure the 3851100 at 16.56" end-to-end, 12 coils. Wire diameter is 0.60".

I also measured an NOS GM #3832518. It measures 12.0" end-to-end, 7 coils. Wire diameter is 0.693".


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[Rick B.]

[Joe L.]

Gentlemen, thank you for your inputs and interest in this thread. I really do appreciate!

Joe, again should we assume the production springs (3851100) would be the same specs as the yellow tagged NOS pieces from 65-67?

I do wonder what kind of tolerances from CE would be acceptable. Bill's i.e 16.88 (16 7/8) to Joe your 16.56 (16 1/2)?

Rick------


I would assume they would be the same and, certainly, if the PRODUCTION and SERVICE springs were manufactured at about the same time. However, the ones that I have were almost certainly manufactured later. In any event, there must be some sort of tolerance range on the original drawings/specifications.

[Rick B.]

[Bill M.]

[QUOTE=Joe Lucia (12484);881621]Bill------

I do. I measure the 3851100 at 16.56" end-to-end, 12 coils. Wire diameter is 0.60".

I also measured an NOS GM #3832518. It measures 12.0" end-to-end, 7 coils. Wire diameter is 0.693".

Thanks Joe