70 LT1 suspension resto dilemma

[Kim B.]

Re: 70 LT1 suspension resto dilemma

Kim----


There are a few other things I'd like for you to check for us on this car so that we might all learn some more about it:

1) What radiator is in the car? Is it the copper/brass with integral filler on the right side tank and using a plastic fan shroud? Or, does it have an aluminum radiator with external aluminum supply tank and a round metal or no fan shroud? If it's an aluminum radiator, what part number is stamped on top of the radiator?

2) What bellhousing is on the car? The part number will be embossed on the side of the bellhousing. It will be either 3899621 or 3858403;

3) This one will be tough to check but it will be VERY important. Check the forging numbers on the lower rear shock mount shafts. These are lightly embossed and may be difficult to discern. They will be on the unmachined portion of the shaft. A photo of a typical shaft with the APPROXIMATE location of the forging number is shown below;

4) Please check the casting numbers on each of the 2 inner front calipers as I have previously described. Pay particular attention to the last digit. Also, check to confirm that there is only one brake line fitting boss on the calipers as shown in the photos of the caliper half I have pictured above.

If you can get the above information, I think we'll know more about this car.

Joe: Here you go:
1. Car has a copper radiator with a plastic shroud # 3956109
2. Bellhousing is # 621
3. Shock mounts are: L - 3820929, R - 3820930
4. The inside castings have only one boss, the numbers are hard to read
but on Left - 5469588 and on right - 5469589 ( It is hard to tell 8 from
a 9 on these).
Hope this helps!!! Kim

[Richard K.]

Re: 70 LT1 suspension resto dilemma

Wayne B; I think you are on to something! Your discussion brings back a recovered memory of mine. In the spring of 1971, I was in college in New Jersey and was discussing a purchase of a new ZR-2, yes, no sh*t, a ZR-2! at Malcom Connor Corvettes. My salesman was a woman who when we discussed options and the fact that with the ZR-2, I could not have a radio or wheel covers (I thought ralley wheel covers), proceeded to laugh and tell me that if I wanted a factory style am/fm stereo plus the wheel covers, they would install them!-no problem-this was confirmed by her boss, the sales manager, who made it VERY plain to me that they wanted to sell that car to me!

[Kim B.]

Re: 70 LT1 suspension resto dilemma

I can see this scenario. When you consider that the ZR1 had nothing in the way of creature comfort but had a desirable power package I could see someone bugging a dealer to get the windows and radio added on. Those cars carried some nice profit margin and I seriously doubt Chevrolet would turn down an order over a radio and power windows. Think about it "we can leave off power steering, radio, air conditioning, etc and still charge the fools more!". Again, that gets into my distrust of GM record keeping. I could see someone in the office just fill the order as a special order car without bothering to check off that it was a ZR1. I don't think for one second that an office full of order clerks would care two cents about cross referencing what was on the car vs what was an "official" ZR1 to make sure the tally for ZR1's going out the door was correct...especially to accomodate a bunch of restorers forty years down the road. To them it was just another special order, another folder in their "in pile" to get moved across the desk to the "out pile" before five o'clock and happy hour. How hard could it be for a dealer? Start with an LT-1 order sheet and just check off the upgrades individually that make the ZR1 package adding ammenities like a radio and power windows. Presto! No ZR1 forms to get cleared by GM.

I'll bet dollars to donuts that wouldn't be the only time that happened either. Now I can see the argument that a ZR1 is defined by the exact package that it called for but I'll bet there are more out there that dealers skirted the "rules" on to make a sale. That's why I've always thought that the incredibly low number of ZR1's reported to have been produced might be "technically" correct but I wonder what affect dealer shenanigans would have to inadvertently make a whole different tier of cars. When I was in high school I had a friend whose father owned a large Pontiac dealership and I spent enough time there to know those guys are pushing tin (or in this case fiberglass) and not about to let anything get in the way of a sale...rules? what are rules? We're only interested in sales! And of course there is a very large manufacturer that is more than happy to take the extra cash.

Wayne:
You may be right because in this situation, according to the original owners letter, the dealer was a prime GM dealer with a great relationship with the GM west coast manager. The mgr ordered the car as his own so they could get the options the dealer's home town " Viet Nam boy" wanted. The special options he mentioned in the letter were Laguna Grey/ bright blue, heavy duty suspension, ZR1 package with special brakes, racing clutch, am/fm radio, PW, PB,PS,AC. GM said NO to PS and AC. The local dealer then sold the car to to his local boy. The mgr also said this was the first LT1 off assembly line after the showroom cars ( tag says B04). This kid was still in Viet Nam so I know price didn't matter so when he got out, he picked up his car. Crazy story, Huh! Kim

[Terry M.]

Re: 70 LT1 suspension resto dilemma

Well then my January car must be a "showroom car." It did spend a couple of weeks in the showroom because I didn't want to pick it up in the dead of winter.

I don't mean any offense, but I think that part of the story is salesman's hyperbole.

OH, and with a CTU code the original owner got cheated on the HD clutch unless the dealer did some work on it.

Edit add: This sounds like a real interesting car. It would be nice to see it as it is at a meet, especially one with a lift.

[Joe L.]

Re: 70 LT1 suspension resto dilemma

Joe: Here you go:
1. Car has a copper radiator with a plastic shroud # 3956109
2. Bellhousing is # 621
3. Shock mounts are: L - 3820929, R - 3820930
4. The inside castings have only one boss, the numbers are hard to read
but on Left - 5469588 and on right - 5469589 ( It is hard to tell 8 from
a 9 on these).
Hope this helps!!! Kim

Kim-----


Yes, this helps a lot.

First of all, the copper radiator with plastic fan shroud is the "standard" LT-1 configuration. ZR-1's had the 3007436 aluminum radiator with either no shroud or with a round steel shroud. If building a ZR-1 but using a "CTU" engine, the factory could still have installed the correct 3007436 radiator, but this was not done. So, that's a "strike" against it being an original ZR-1.

Second, the bellhousing is the one used on "standard" LT-1s. It works with the standard 14" flywheel and 11" clutch. However, it is also the one that would have been installed on an LT-1 engine with the "CTU" suffix code. THEORETICALLY, the factory could have converted a "CTU" engine code to a "CTV" CONFIGURATION by changing the clutch, flywheel, and bellhousing. In such a circumstance, the suffix code would have remained "CTU", but the engine would actually be a "CTV". That was not done here, of course, so the engine is exactly what the suffix code says it is----a "CTU" or standard LT-1.

Third, the transmission suffix code is "B". This denotes an M-21 transmission. If building a ZR-1 using a "CTU" engine, the factory could still have installed the M-22 transmission, but they didn't. So, that's another "strike" against it being an original ZR-1.

Fourth, the shock mount shafts on the car are the ones used with standard suspension. Cars with F-41 were supposed to have used different shafts and original F-41 cars I have looked at do have the F-41 shafts. So, this represents a "strike" against the car being a factory-installed F-41 car and, of course, that's also a "strike" against it being an original ZR-1. Most post-factory suspension "converters", either dealership or otherwise, would have been unlikely to realize that the shock mount shafts needed to be changed for F-41. The standard shafts would have fit and worked just fine with F-41, although if F-41 shocks were also installed it would have been a very tight fitment. Is it possible that the factory could have installed F-41 suspension and used the standard suspension shock mounts? Yes, I'd say it's possible, but quite unlikely.

I still have not figured this out about the inner, front caliper castings you have. However, I consider it very possible, even very likely, that they were originally used on some J-56 brake installations. I just don't know why.

So, what do we have here? I really don't know. However, I'm pretty confident that it's not an original ZR-1. However, it remains possible that it was a factory F-41 and J-56 installation. The only thing that bodes against that is the incorrect shock mount shafts. If it were a factory F-41 and/or J-56 installation, then I think it would have had to have been a COPO car. I don't think that J-56 and F-41 were even on the order form for 1970 Corvettes but I'd be interested in learning if anyone has any contrary information.

A few other questions I should have asked you previously, but didn't. Does the car have power steering and, if not, does it have the "6 quart" oil pan? Also, does it have a rear stabilizer bar and does it have F-41 shocks? Rear F-41 shocks are easily identified since there is no upper stone guard and the shaft is easily visible. I can post a photo of a typical F-41 shock if you need it.

[Wayne B.]

Re: 70 LT1 suspension resto dilemma

Kim,
I can see why GM would say no to AC, the high RPM of the LT-1/ZR1 would just throw the belts so it would be an instant service nightmare. This could be a very interesting car historically...how about please, please, pretty please dragging it on down to Kissimmee in January and letting everyone unravel this mystery? I'll bet everyone in the NCRS and most likely the Corvette Museum would love to find the "26th" ZR1

Terry - "hyperbole" from a salesman? You know there's some fluff from them, that's why I think there are plenty of treasures still to be dug up out there in each generation of Vette and still a lot of history to be discovered and written.

[Terry M.]

Re: 70 LT1 suspension resto dilemma

.... Also requiring change would have been the oil pan and oil pump.

A few other questions I should have asked you previously, but didn't. Does the car have power steering and, if not, does it have the "6 quart" oil pan? Also, does it have a rear stabilizer bar and does it have F-41 shocks? Rear F-41 shocks are easily identified since there is no upper stone guard and the shaft is easily visible. I can post a photo of a typical F-41 shock if you need it.

Joe,

How is the CTU six-quart oil pan and oil pump different than the CTV six-quart oil pan and oil pump?

[Tim G.]

Re: 70 LT1 suspension resto dilemma


Way back in 1977 I was in my hometown of Chicago while I was in college in Wisconsin. I saw an add in the paper for a 1971 ZR1 for sale at Mancuso Chevrolet in Skokie, Il.

[Joe L.]

Re: 70 LT1 suspension resto dilemma

Joe,

How is the CTU six-quart oil pan and oil pump different than the CTV six-quart oil pan and oil pump?

Terry----


I erred on this. I thought the "CTU" used the "5 quart" oil pan and "CTK" used the "6 quart". However, it is the the other way around. There is no difference between the oil pan and pump used for the "CTU" and "CTV" suffix-coded engines. So, the only difference between the "CTU" and "CTV" is the installed clutch, flywheel and bellhousing. Since the car involved here is a "CTU" code, I expect that also answers my question about power steering. It should not have it (unless the oil pan was changed and power steering added).

I've corrected the above post to delete the reference to the "CTU" having a different oil pan and pump than "CTV".

[Dan P.]

Re: 70 LT1 suspension resto dilemma

Terry----


I erred on this. I thought the "CTU" used the "5 quart" oil pan and "CTK" used the "6 quart". However, it is the the other way around. There is no difference between the oil pan and pump used for the "CTU" and "CTV" suffix-coded engines. So, the only difference between the "CTU" and "CTV" is the installed clutch, flywheel and bellhousing. Since the car involved here is a "CTU" code, I expect that also answers my question about power steering. It should not have it (unless the oil pan was changed and power steering added).

I've corrected the above post to delete the reference to the "CTU" having a different oil pan and pump than "CTV".

Joe- Don't forget that the ZR1 CTV coded engines also used a 1108351 L88-spec Hi-torque starter as well.


DSP

[Wayne B.]

Re: 70 LT1 suspension resto dilemma

Joe,

I think what makes the car most interesting isn't whether it fits the technical description of an "official" ZR-1 but more how dealers were able to create these variations. Zora's vision was a no frills race car and many liked it but "could you change this or add that" was sure to start as soon as it was released. So is it an LT-1? Noooo, too many ZR1 features. Is it a ZR-1? Nooo, not enough "official" features. It's a pretty short walk from the LT-1 to the ZR1 but sure enough you can count on the public and willing dealers to create a lot of stops along the way. That's what's fun about finding these cars, there's just a lot more history to these models than what Chevrolet officially wrote.

[Kim B.]

Re: 70 LT1 suspension resto dilemma

Kim-----


Yes, this helps a lot.

First of all, the copper radiator with plastic fan shroud is the "standard" LT-1 configuration. ZR-1's had the 3007436 aluminum radiator with either no shroud or with a round steel shroud. If building a ZR-1 but using a "CTU" engine, the factory could still have installed the correct 3007436 radiator, but this was not done. So, that's a "strike" against it being an original ZR-1.

Second, the bellhousing is the one used on "standard" LT-1s. It works with the standard 14" flywheel and 11" clutch. However, it is also the one that would have been installed on an LT-1 engine with the "CTU" suffix code. THEORETICALLY, the factory could have converted a "CTU" engine code to a "CTV" CONFIGURATION by changing the clutch, flywheel, and bellhousing. In such a circumstance, the suffix code would have remained "CTU", but the engine would actually be a "CTV". That was not done here, of course, so the engine is exactly what the suffix code says it is----a "CTU" or standard LT-1.

Third, the transmission suffix code is "B". This denotes an M-21 transmission. If building a ZR-1 using a "CTU" engine, the factory could still have installed the M-22 transmission, but they didn't. So, that's another "strike" against it being an original ZR-1.

Fourth, the shock mount shafts on the car are the ones used with standard suspension. Cars with F-41 were supposed to have used different shafts and original F-41 cars I have looked at do have the F-41 shafts. So, this represents a "strike" against the car being a factory-installed F-41 car and, of course, that's also a "strike" against it being an original ZR-1. Most post-factory suspension "converters", either dealership or otherwise, would have been unlikely to realize that the shock mount shafts needed to be changed for F-41. The standard shafts would have fit and worked just fine with F-41, although if F-41 shocks were also installed it would have been a very tight fitment. Is it possible that the factory could have installed F-41 suspension and used the standard suspension shock mounts? Yes, I'd say it's possible, but quite unlikely.

I still have not figured this out about the inner, front caliper castings you have. However, I consider it very possible, even very likely, that they were originally used on some J-56 brake installations. I just don't know why.

So, what do we have here? I really don't know. However, I'm pretty confident that it's not an original ZR-1. However, it remains possible that it was a factory F-41 and J-56 installation. The only thing that bodes against that is the incorrect shock mount shafts. If it were a factory F-41 and/or J-56 installation, then I think it would have had to have been a COPO car. I don't think that J-56 and F-41 were even on the order form for 1971 Corvettes but I'd be interested in learning if anyone has any contrary information.

A few other questions I should have asked you previously, but didn't. Does the car have power steering and, if not, does it have the "6 quart" oil pan? Also, does it have a rear stabilizer bar and does it have F-41 shocks? Rear F-41 shocks are easily identified since there is no upper stone guard and the shaft is easily visible. I can post a photo of a typical F-41 shock if you need it.

Joe: The car does not have power steering, looks like a 6 qt. (the sump area is 14" long) pan. No rear stabilizer bar and original shocks are long gone. The car does have HD front springs or they look like they are ( 7 coil, 11/16 thickness, 12" total spring length ). Again, I never thought it was a real ZR-1 but I did think I ought to check out all the suspension differences. Now after you know all this, would you still leave all this equipment on the car for judging? Thanks for your help!!! Kim

[Dan P.]

Re: 70 LT1 suspension resto dilemma

Kim -

I have another possible theory why your car could very well been delivered with the HD components; you 2744 VIN number indicates a VERY early car with an approximate build date of February 5, 1970.

The first day of the 70 production run was about 30 days before that, and some say the announcement of the ZR1 option wasn't made public until sometime in March/April.

What I'm driving at is that if a "ZR1-esque" car was ordered and all the specified parts weren't racked and ready on production line, they'd have to scrounge the HD bits to bolt the car together. Maybe that's the reason behind the odd calipers and non-typical configuration.

Can anyone share the (approximate) VIN of the earliest verified ZR1?

[Richard K.]

Re: 70 LT1 suspension resto dilemma

Hey gang; could this car be a prototype ZO-7?-remember, heavy duty brakes and suspension-on 73-75 cars as an option, made about 45-145 per year, $400 option-this car sounds like its got all the main pieces, the heavy duty brakes and the stiffer suspension, m-21 required on the Z0-7s,this car got that too, could order up to 4:11 s on the Z0-7s, whats the rear axle ratio on this 70 car?

[Joe L.]

Re: 70 LT1 suspension resto dilemma

Joe- Don't forget that the ZR1 CTV coded engines also used a 1108351 L88-spec Hi-torque starter as well.


DSP

Dan-----


Yes, they did, but that was a function of the different flywheel used. The "standard" LT-1 used the "high torque" starter for 14" flywheels. The ZR-1 used the "high torque" starter for 12-3/4" flywheels (the same reason the L-88 also used it).

St. Louis could only install the starter that was compatible with the bellhousing and flywheel installed on the engine. So, knowing that the car had the 3899621 bellhousing "automatically" lets us know what configuration starter was also installed.