C3 Rebuild

[Dominick M.]

I am in the process of getting my 69 Corvette back on the road.

Wondering about todays tire size vs F70-15 original tires. Most charts show 215/70R-15 as replacement, but that size is listed as for 7 1/2' wide rims max. vs the standard 69 8' wide rims. What size has anyone used? 225/70R-15 is listed for 8' wide rims, but is there a clearance problem on the front end?

Also, repair/replacement of A.I.R. pump and diverter valve. Have not been able to find anyplace that sells rebuilt units. Know of any shop or person that does? How rebuilding the units? Any reasonably priced shops that rebuild?

[Patrick B.]

Re: C3 Rebuild

I use 245R60-15 on my 70 without any issues, but if you care about A.I.R. pumps you may not like 60 aspect ratio tires.

[Ray K.]

[Duke W.]

Re: C3 Rebuild

Most manufacturer's specs recommend a 5.5 - 7.5" wide wheel for 215/70R-15 and 6 -8" for a 225/70, but the latter size is mostly van and trailer type tires, not sports car tires. Going a half inch over or under the recommended wheel width is not usually a problem.

If you like to drive in a sporting manner check out the Avon CR6ZZ and choose between the 225/65 and 245/60.

Duke

[Joe L.]

Re: C3 Rebuild

I am in the process of getting my 69 Corvette back on the road.

Wondering about todays tire size vs F70-15 original tires. Most charts show 215/70R-15 as replacement, but that size is listed as for 7 1/2' wide rims max. vs the standard 69 8' wide rims. What size has anyone used? 225/70R-15 is listed for 8' wide rims, but is there a clearance problem on the front end?

Also, repair/replacement of A.I.R. pump and diverter valve. Have not been able to find anyplace that sells rebuilt units. Know of any shop or person that does? How rebuilding the units? Any reasonably priced shops that rebuild?

Dominick------


As far as the tires go, I can tell you that I used size 245-60-15 on my original owner 1969 for many years with no problems, at all. However, that size will not fit well in the spare tire carrier unless one changes the lock bolt to a GM #345476 or GM #471903, both discontinued but available in reproduction.

As far as the AIR system parts go, that's another matter. The 1968-75 style pumps used to be fairly easy to obtain in remanufactured condition. A-1 Cardone was a major supplier. However, I think the core stock has "dried up" and Cardone rebuilds are pretty tough to find these days. I believe that Cardone and others will custom rebuild them if the customer supplies the core.

The diverter valve is a MUCH more difficult problem to obtain. The original style have been discontinued for many years and were never available in the aftermarket. GM did offer functional replacements after the originals were discontinued but these valves are constructed entirely of black plastic material. Even these have been discontinued for awhile.

The remainder of the AIR system components are not too difficult to obtain in used, rebuilt, aftermarket or reproduction. However, if you are able to obtain the critical components, I recommend that only NEW check valves be used, even if they do not exactly match original valves. A failed check valve will cause the destruction of a diverter valve.

There is a way to obtain the system you seek, though. Contact Bill Hodel who advertises in the Driveline. He's definitely the go-to guy for AIR system components, including diverter valves and pumps both of which he custom rebuilds and sells. Don't expect it to be inexpensive, though.

[Bill C.]

Re: C3 Rebuild

Hi Dominick - Please be aware if you decide to go with the 215/70R-15 tires, the installer may balk at installing them on 8" rims. I bought my BFG 215/70R-15 tires at a large national warehouse store and they absolutely refused to install them on 8" rally wheels. The problem was resolved by using 7" wide rally's instead.

[Steven B.]

Re: C3 Rebuild

Hi Dominick. I have run 255-60X15 and also 245-45X15 on 8" YJ-8's and 81/2 custom wheels on my '77 with Guldstarnd front and rear springs lowering the ride height. I had no problems on the street or autocrossing and trials at Mid Ohio or Indy Raceway Park road course. No rubbing or interference.

[Joe L.]

Re: C3 Rebuild

I use P255-R60s on my ‘71 &LT1 Coupe with no issues when driving, turning and/or going up driveways.
Ray K

Ray------


Keep in mind that the fender profile on 1968-69 Corvettes is not quite the same as 1970-82.

[Dan A.]

Re: C3 Rebuild

To add to Bill C’s comments above I recently bought a set of reproduction F70/15 Firestone Wide Oval radials for my 72. I took the wheels and tires to my independent tire shop that I have used for 45 years. They had an awful time mounting them on the 8” wheels but eventually got them mounted using a combination of spreader tools and shop heaters. They were glad to see them leave their shop.

[Jeffrey S.]

Re: C3 Rebuild

My first set of "smoothie" red line radials were 225-70's that fit very well with no issues. When it was time for a new set a couple of years ago, I decided to get the size closer to stock- 215's. I also had a discussion with the tire installer about the 215's being too small for the wheel but I insisted and they were installed. They look great and drive perfectly. From what I understand, the dimensions are very close to those of the F70's and if GM engineers felt that the 8" wheel and the F70's were a good match then that was good enough for me. I absolutely am happy with my decision to go with the 215's. I always thought that the 225's looked a little large for the opening but that is just my opinion.
Jeff

[Dominick M.]

Re: C3 Rebuild

Ok. Thanks.

[Dominick M.]

Re: C3 Rebuild

Thanks for the info. Did contact Bill and Paragon. Looks like the rebuild range is $900 - $1000 for pump and valve rebuild. Have to think about it.

[Joe L.]

Re: C3 Rebuild

Thanks for the info. Did contact Bill and Paragon. Looks like the rebuild range is $900 - $1000 for pump and valve rebuild. Have to think about it.

Dominick-------

Before you even consider having what you have rebuilt, you need to be sure that what you have is functionally correct and/or original. So, I'm going to do a little AIR system primer here for the possible edification of you and others. Since there are quite a few photos, I'm going to make this a "3 part" series:

The 1969 AIR pump:

The AIR pump used for most, if not all, of 1969 was GM #7803948. This same pump was used through 1974 for both small blocks and big blocks except L-88/ZL-1. It was available in SERVICE until January, 1976 when it was replaced by GM #7817809. Earlier examples of the 7803948 pump have a "white" centrifugal filter ("fan"); later have a black centrifugal filter. Otherwise, the pumps are identical. These pumps have no pressure relief valve as do all previous 1966-68 pumps. From 1969 onward the pressure relief valve was incorporated into the diverter valve assembly. The pump shown below, an NOS GM #7803948 [not for sale], is date coded 24132S. This decodes to the 241st day of 1973 (8/29/73), 2nd shift and pump model "S". Your pump, if original, should have a white centrifugal filter but be otherwise identical to this pump.

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[Joe L.]

Re: C3 Rebuild

1969 AIR System Part II


1969 Diverter Valve



Most, if not all, 1969 small blocks were equipped with diverter valve GM #7029199. This valve incorporates an integral pressure relief valve in addition to diverter valve functionality. It was used for all Corvette small blocks equipped with AIR through 1974. The last 5 digits of the valve part number are stamped on the valve body as shown. The valve shown is an NOS example [not for sale]:

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[Joe L.]

Re: C3 Rebuild

1968-69 AIR System--Part III


1968-early 1969 AIR Pump:


1968 and, possibly, very early 1969 Corvettes used AIR pump GM #7801512. In addition, I believe that 1969 L-88/ZL-1 did use this pump. This pump has an external and integral pressure relief valve but is otherwise identical to the 7803948. The 7801512 was never available in SERVICE, at least not under that part number. For SERVICE, from the very beginning of the 1968 model year, the pump was known as GM #7806686. So, what's the difference between the two? Well, they are identical except for one thing: the 7801512 had an installed pressure relief valve plug whereas the 7806686 had no installed pressure relief valve plug but was supplied with 5 valves with instructions to install the same valve as found on the replaced pump. You see, this same pump was used on a WIDE variety of GM cars of the period and, thus, GM did not want to inventory 5 different pumps which differed only by installed relief valve plug. The 1968 pump can also be used on any 1969-74 Corvette and, in the aftermarket rebuilt market, was often sold for all 1968-74 applications. However, the 1969-74 pump cannot be used for 1968 since it has no integral pressure relief valve. The NOS pump pictured [not for sale] has a date code of 25681Y which decodes to August 13, 1968, 1st shift, pump model Y. Also, the date code on the box is 9/21/68.


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