1963 J-65 & 7 Leaf Spring??????????

[Franz E.]

Recently I spoke with a 63 J-65 brake owner with a seven leaf spring. There appears to be a correlation between metallic brakes and the Z06 heavy duty rear spring. For the 63 model year the hobby has documented heavy duty suspensions were only available with the Z06 option. However, there are a number of "original" 63 J-65 cars which also have the same Z06 spring. Possible answers:
1. Chevrolet assembly was experiencing supply problems and released the seven leaf spring as an acceptable substitute for a number of vehicles? St. Louis resident engineering, in conjunction with central engineering would have issued a "Deviation Request" substituting the seven leaf spring for a "number" of vehicles.
2. Due to the appearance similarities between metallic brakes and Z06's the operator installed the seven leaf spring in error?
3. Early in the vehicles life it was returned to the dealership with a "sagging" spring and the performance minded owner had it replaced with a "heavy duty spring"? Remember heavier is better mentality!!!!!!
I'm conducting an informal survey to determine how many 63 J-65 cars were assembled with seven leaf springs. In addition, determine if these cars were assembled during a particular time period or vin# range. Any information would greatly be appreciated. Thank You

[Wayne M.]

'63 # 7055 had J65 w/9-leaf

black/black FI convertible, 2-tops and PW. This was back in 1976.

[Michael H.]

Re: 1963 J-65 & 7 Leaf Spring??????????

Franz,

I've owned too many original unrestored 63's with met brakes and an original nine leaf rear spring to agree with that paperwork. I currently own two such cars and I know of a few original owner cars that were equipped the same way. (one in particular is Dukes, if I remember correctly)

Also, there are several 63's that have been documented with HD suspension but are not Z06 cars. I have (somewhere) several good 1963 assy line shots that show the fat shock absorber but without finned drums. I also have a pic of a new 63 that shows the large shock upper washer but also shows standard non Z06 drums.

I doubt engineering would have recommended replacing the 9 leaf spring with a 7 leaf as the handling of a C2 Corvette become absolutely scary dangerous with that mix of soft front/heavy rear springs.

It's not likely that the diff assy was sent to the line with a 7 leaf spring because the worker saw the code for met brakes. The complete rear drive, including differential, crossmember, trailing arms and drive shafts was built in the basement and elevated to the main floor of the assy plant without a spring attached. The spring was attached after the complete rear drive unit was installed so the worker didn't even know the unit had met brakes as the drums would have been installed in the basement.

I have a huge stack of "deviation requests" for 63 suspension but I've never seen one that mentions the substitution of the 7 leaf spring for the 9 leaf.

[Duke W.]

Re: 1963 J-65 & 7 Leaf Spring??????????

I think any J-65 cars with a seven leaf spring are strictly "owner inspired".
I certainly don't think Chevrolet Engineering would approve such a substitution.

Doubling the rear spring rate with the seven leaf spring without a similar increase in front roll stiffness via increased spring rate or a bigger anti-roll bar would bias the chassis toward oversteer, and they are alreade "scary neutral" at the limit with the base spring and bar setup, but I have no doubt that typical owners who have absolutely zero vehicle dynamics knowledge would do such a bone-headed modification. Same applies to dealer service personnel. If an owner requested installation of a HD rear spring on a base suspension car, they would probably comply as they don't know any better.

Like Franz said, to most a "heavy duty" part must be better!

My SWC is original J-65 and has the base springs.

Duke

[Alan Drake]

Re: 63 Brake vs Spring, no correlation

Check out Corvette Restorer, Spring 2004 (V30 #4). Was under same impression that if I had J65 the HD suspension came with it. Said article made it clear that the two options are independent.

[Duke W.]

Re: 63 Brake vs Spring, no correlation

For '63 the only way to get the HD suspension was to order Z-06, which also included HD brakes. For '64 all the Z-06 equipment was unbundled to separate options, so you could order the HD suspension (F-40) independently.

For '64 both F-40 and J-65 could be ordered independently, and I don't think there were any restictions except you could not order both J-56 HD brakes AND J-65 metallic brakes.

Duke

[Michael H.]

Re: 63 Brake vs Spring, no correlation

Duke,

There seems to be some info that shows there actually were some F40 optioned 63's without the Z06 package. I know it wasn't listed as an available separate option, at least initially, but I believe it did surface at some point in production. I'll try to dig out some info on this later.

[Alan Drake]

Re: 63 Brake vs Spring, no correlation

Check out Adams page 125 for J65 brake comment and
page 176 for Z06 comment (various suspensiton upgrages)
Seems that the J65 brakes could exist with out any suspension upgrade (63/64 Tech & Judge Manual does not list a F40 for 63).
FYI - I'll listen for true results since it's over my head now.

[Mike L.]

Re: '63 # 7055 had J65 w/9-leaf

I own a 64 FI car that has J65 brakes, F40 suspension, seven leaf rear spring, and 15/16 front sway bar. My car was orignal three owner car, never taken apart.

[Duke W.]

Re: '63 # 7055 had J65 w/9-leaf

No question that J-65 and F-40 were an available combination in 1964, but not in '63 because the HD suspension components were only available as part of Z-06, which included the HD brakes that were not available separately. The individual group components like HD suspension and HD brakes were not unbundled and available separately until the 1964 model year as F-40 and J-56, respectively.

For this reason the Z-06 option was discontinued for '64 because all the components that made up either the first or second '63 Z-06 interations were available separately.

If you wanted a '64 "Z-06 equivalent" you just checked off the proper individual options beginning with L-84, M-20, G-81, F-40, and J-56 for the second iteration "equivalent". If you wanted to duplicate the first interation you added N-03 and P-48 nothwithstanding the fact that no '63 models (other than a few pilot line cars with the "gear drive" two-bar design) including Z-06 were ever delivered from the plant with KO wheels.

Duke

[Duke W.]

Re: 63 Brake vs Spring, no correlation

The only exclusion to J-65 was Z-06 because Z-06 included a different brake system. You could even order J-65 with J-50 power brakes, but I don't think it was a very good idea being as how when very hot, J-65s became extremely sensitive to pedal effort and were tricky enough to modulate without a power booster. When very hot they ACTED like power brakes even without a booster, and with a booster would be SUPER senstive.

Duke

[Franz E.]

Re: 1963 J-65 & 7 Leaf Spring??????????

Hi Michael: I certainly agree that suspension design is a complex combination of variables. Spring rates, shocks, tires and in extreme applications frame beaming. I find it very difficult to accept that engineering would permit substituting the spring without addressing the remaining suspension; front springs rates, stabilizer bar and shocks. My friends car, who wishes to remain anonymous, exhibits the features of being original and his restorer concurs. The rear suspension was assembled off line in the lower level (Basement as you've pointed out) and mated with the chassis prior to the chassis "rollover" operation. However, the spring was assembled to the module prior to being sent to the main chassis assembly line. It appears the discussion board's consensus is option #1 is least plausible. Option #2 is probable, however highly unlikely. Option #3 certainly has the majority of support as being the most acceptable explanation. As an old suspension designer, assigned to the "Y" car, I concur.

[Michael H.]

Re: 1963 J-65 & 7 Leaf Spring??????????

Franz,

I agree, #1 can be eliminated completely. #2 and #3 are definitely possible. Unfortunately, we'll probably never know the whole story.

I'm not 100% sure when/where the rear spring was attached to the rear susp/drive for the 1963 run but it was definitely not in the basement in the 70's. The entire rear unit came up from the lower level through the opening in the floor minus the rear spring. Once the unit was mounted to the frame, the rear spring was attached but before the four mounting bolts were torqued, the spring ends were compressed to design height to simulate a loaded condition. I'll post a pic of this operation.

I also have a few interesting pic's of a nearly brand new 63 that has standard brake drums, yet has the F40 shocks and also the appears to have the correct F40 lower shock pin.

Certainly is difficult trying to figure out what occured 40+ years ago but definitely interesting. I enjoy the research.

[Michael H.]

Diff & Rear Drive On The Hook

This is the entire diff and rear drive coming up from the basement to join the chassis line. The rear spring is not in place at this time. It was added once the entire unit was assembled to the frame.

[mike cobine]

Re: Diff & Rear Drive On The Hook

That's one of them funny metal ones that the magnets don't stick to. Maybe it gets a plastic spring and so they were worried about breaking it on the way up, or being wider, they couldn't get the hooks on.