Another LS3, T-56 swap into 1981 C3

[zimmej51]

Originally Posted by C4forlife

That is a ton of work to get things squared away. For my 77 thinking start with the bare A.C./heat unit and build from there using factory duct work as much as possible. Anyone have a solid shot of how far the unit sits below the dash with a focus on the foot well?

C4forlife while I was in the shop today I got some shots of the passenger side with the Gen IV VA evap box installed. From the lowest point of the box to the bottom of the floor pan is slightly over 10 inches. You'd probably want to subtract 1/2" or so for carpet/padding. Like I said, it does hang down but it cannot be mounted any higher without serious mods to cowl and firewall. For comparison, I measured my wife's Cadillac ATS, it has almost 12" in the same area. The photo doesn't show it but there is actually a pretty good space between the box and firewall. I had a couple of friends "test sit" it and they didn't feel like it would be a problem. C3's are not known for roomy foot space even when stock! Here's a pic.

[zimmej51]

Originally Posted by C4forlife

That is a ton of work to get things squared away. For my 77 thinking start with the bare A.C./heat unit and build from there using factory duct work as much as possible. Anyone have a solid shot of how far the unit sits below the dash with a focus on the foot well?

C4forlife - Don't know if this will help any but not sure I've ever seen all the ducts put together outside of the car. In any case if nothing else it provides a perspective you don't see very often!



































I have a couple of comments for what it's worth. I seriously thought about retaining the stock HVAC because I could see a LOT of work ahead of me otherwise. Here is why I decided to ditch it and go with a Vintage Air system even though they don't make a kit for the 77-82.


1. I had the car completely disassembled for a resto mod. I had the opportunity to replace all the components and no desire to tear it all apart after it's finished because of some failed part.



2. The cost of replacing all the potential failure points significantly exceeded the cost of an all new VA sytem.


3. I've had several people that I trust describe one of the most common failure points of the stock system. The fresh air/recirculate "flapper" and the vacuum motor that moves it are highly failure prone. If you've ever seen the flapper you know what I mean. It is such a goofy shape that it often gets stuck in the fresh air position meaning that you can't recirculate the air for max cooling. In addition, the vacuum motor is known to fail. On top of all that, it is incredibly difficult to access these components for repair. When I took mine apart, sure enough the flapper was stuck tight and the vacuum motor was inoperative due to a major leak.


4. The clincher was that back in 1982 I bought a brand new 82 Corvette. The AC was marginal at best. If I drove it during one of our Oklahoma 104° summer days under cloudless skies it was close to unacceptable, especially with the glass t-tops. Had it back to the dealer several times and listened to them tell me it was normal. I don't want to try to resuscitate a 38 year old system that has a questionable track record.


Anyway, I hope these pictures might be of use to someone!

[69MyWay]

Really looks great - you do very nice clean and well thought out work. And sometimes it takes a few bites at the apple to get it perfect no matter how right it looked the first time. I've installed many Vintage Airs over the years - mostly in custom applications where you have to go off the beaten path. I actually prefer to do custom applications as I hate following directions.

No matter what you do, the center vent stack area is a problem. On a Sure Fit system (as I'm wrapping one up in a 74 right now) - the tubes all have to be kind of squashed in place as you set the center gauge panel in place. Makes me cringe every time - but it works. What I'm saying, is even if you had a direct fit kit you'd find yourself wanting to re-work that center area and vent tubes.

I wish they could make a once piece manifold to better route them so they don't get crammed back there as they do now.

The LS part looks awesome. I know some like to switch to a remote power steering reservoir and hang it off a bracket between the master cylinder and fender (where it bolts to the booster). Otherwise, you have a hard time with clearance around the control arm upper mount bolt area.

I'm very impressed - keep up the good work.

[zimmej51]

Originally Posted by 69MyWay

Really looks great - you do very nice clean and well thought out work. And sometimes it takes a few bites at the apple to get it perfect no matter how right it looked the first time. I've installed many Vintage Airs over the years - mostly in custom applications where you have to go off the beaten path. I actually prefer to do custom applications as I hate following directions.

No matter what you do, the center vent stack area is a problem. On a Sure Fit system (as I'm wrapping one up in a 74 right now) - the tubes all have to be kind of squashed in place as you set the center gauge panel in place. Makes me cringe every time - but it works. What I'm saying, is even if you had a direct fit kit you'd find yourself wanting to re-work that center area and vent tubes.

I wish they could make a once piece manifold to better route them so they don't get crammed back there as they do now.

The LS part looks awesome. I know some like to switch to a remote power steering reservoir and hang it off a bracket between the master cylinder and fender (where it bolts to the booster). Otherwise, you have a hard time with clearance around the control arm upper mount bolt area.

I'm very impressed - keep up the good work.

69MyWay - Thanks for the kind words and the info about the center vent and power steering pump. It's always encouraging when someone else with a lot more experience makes positive comments.


Wadding up all those flexible tubes has always left me a little cold, that's the main reason I decided to try the "low" road, with the crossover duct mounted low on the evap box. Helps a lot with the congested area just behind the center gauges.


I considered trying to fabricate a rigid duct from the center vents down to the evap box. For simplicity I decided to just try the custom duct with hoses down to the evap box. But I haven't given up the idea, although I have put it on the back burner for now.


Prior to this, I had zero experience with vacuum forming ABS, but with some help from YouTube and a lot of experimentation I think I'm getting a handle on it. Not as easy as it looks!

[zimmej51]

I finally got past the air conditioner duct-making phase, so now I am moving on. Glad to be back on the main project!


Earlier in this thread I described the problems I would encounter when routing the exhaust system due to the drivers side floor pan. To accommodate the power seat, the floor pan was about 4" lower than the passenger side. I could not see any way around having to route the drivers side exhaust over to the passenger side, then back around to the drivers side. That was not acceptable to me.


So I decided to hack out the drivers side floor pan and replace it with one made for a non power seat. Got the pan in and was all set to install it when I discovered how easy it was to stand up under the car and reach up under the dashboard! So I waited until I got all the pedal cage and hydraulic clutch mods done to re-install the pan.



Got the majority of the fitting done and held in place with Clecos, plan to weld er up tomorrow.

[77blue]

zimmej51 - best accessory I ever bought for my Vettes was my 4 post lift. I really justified it to myself as an additional winter storage spot but it has been invaluable (especially as I get older and less nimble).

[zimmej51]

Originally Posted by 77blue

zimmej51 - best accessory I ever bought for my Vettes was my 4 post lift. I really justified it to myself as an additional winter storage spot but it has been invaluable (especially as I get older and less nimble).

You got that right! I have a 2 post, like you said it's the best tool I've ever bought. I spent a LOT of years laying on my back!

[zimmej51]

Ok, I sure could use a hand here. I intend to put C6 seats into my C3. Did some research on the subject and I pretty much concur that you have to remove the power track assemblies from the C6 and mount the C6 onto the C3 manual adjuster tracks. Otherwise they are too tall.


The catch is that I don't have the C3 tracks! And they seem to be difficult to find, especially the driver side manual track since most 81-82's came with a power seat and the lowered seat pan.


Here's the question: Does any one know of some other seat track from a different car that will fit the C3? Or one that is at least close enough to modify to fit?


(I should probably post the below in the classifieds, but I have some new never used C3 front end parts and a bunch of other stuff I'd be willing to swap for a pair of C3 manual seat tracks)



Thanks in advance....

[7TRoadster]

Have you tried looking for the early C3 seat tracks? I believe they were mostly all manual. Mine are only about an inch high.

[zimmej51]

Originally Posted by 7TRoadster

Have you tried looking for the early C3 seat tracks? I believe they were mostly all manual. Mine are only about an inch high.

No, I haven't. Someone told me that the 77 up C3 tracks were different from the earlier C3's, but I have not confirmed that. Since yesterday I have found a few on line but they are pretty pricey. Do yours look anything like this? These are from an 81. The fore/aft distance between the mounting holes is 19-3/16" and the height is just a little over 3/4".

[7TRoadster]

Well they certainly are similar, the knob is in the same place. My seats have been in the car for a while and can't remember exactly. I looked through my photos and I didn't grab a picture of them.

My guess is that you might have to adapt them to your seat. I can try to measure length tomorrow. Don't know how much luck I'm gonna have but will try.

[zimmej51]

Originally Posted by 7TRoadster

Well they certainly are similar, the knob is in the same place. My seats have been in the car for a while and can't remember exactly. I looked through my photos and I didn't grab a picture of them.

My guess is that you might have to adapt them to your seat. I can try to measure length tomorrow. Don't know how much luck I'm gonna have but will try.

Well, I believe I have uncovered a few things about the seat tracks. I have been unable to positively confirm the info below, I have assembly manuals from 78-82 but they do not show anything related to the seats or seat pan. Nor does the service manual.



C3's that were built without the T/T steering wheel had a shallow drivers seat pan like the passenger side. So when I installed the shallow seat pan on the drivers side I essentially converted it to the non-T/T configuration. I am fairly certain the seat track part numbers are as shown:


470645 is the left outer and right inner adjuster
470646 is the left inner and right outer adjuster.


Then it gets a little crazy if the car does have the T/T steering wheel and does NOT have the power driver seat. In that case, the drivers floor pan is significantly deeper. Again, I have been unable to confirm these numbers.


471999 is the left outer adjuster
472000 is the left inner adjuster
470045 is the right inner adjuster
470046 is the right outer adjuster


So I think what I will be looking for is the 470645 and 470646 (2 each). There are some out there, but they are definitely on the pricey side. More to come on this.

[zimmej51]

Originally Posted by zimmej51

Well, I believe I have uncovered a few things about the seat tracks. I have been unable to positively confirm the info below, I have assembly manuals from 78-82 but they do not show anything related to the seats or seat pan. Nor does the service manual.



C3's that were built without the T/T steering wheel had a shallow drivers seat pan like the passenger side. So when I installed the shallow seat pan on the drivers side I essentially converted it to the non-T/T configuration. I am fairly certain the seat track part numbers are as shown:


470645 is the left outer and right inner adjuster
470646 is the left inner and right outer adjuster.


Then it gets a little crazy if the car does have the T/T steering wheel and does NOT have the power driver seat. In that case, the drivers floor pan is significantly deeper. Again, I have been unable to confirm these numbers.


471999 is the left outer adjuster
472000 is the left inner adjuster
470045 is the right inner adjuster
470046 is the right outer adjuster


So I think what I will be looking for is the 470645 and 470646 (2 each). There are some out there, but they are definitely on the pricey side. More to come on this.

Ok, so here's where I am today. I haven't completely cracked the code on this seat track issue but I have learned enough to proceed with my installation.


I haven't been able to positively confirm any of the information below (or above) but I think it's close.


I think that for years 77-80 if you ordered a C3 without T/T steering wheel then you got a shallow drivers floor pan. The seat tracks were identical on both sides.



I think that for years 81-82 you got the deep drivers floor pan no matter what. The power seat fit down in the deep pan and the manual seat had tracks that had "legs" on them to get the seat at the right height.


So when I replaced the deep drivers floor pan with the shallow floor pan, I essentially converted it into a 77-80 configuration. Therefore I need 2 sets of the manual seat adjusters, preferably 81-82, since those will fit the passenger side pan with no mods. The new drivers shallow floor pan is only drilled for the front mounts so I can position the rear mounts to match the tracks.


This seat track thing turned out to be a lot more confusing than I would have ever guessed, but I have a way forward now so I'm going to move on. I welcome any additional ACCURATE information and hopefully this will help someone going down the same road. Cheers!

[zimmej51]

Made it to the body prep stage, finally! The only major flaw anywhere on the body is this crack, about 3" long, on the rear wheel arch just behind the passenger door. I carefully and slowly sanded the area with 320 grit to see what was going on under there.


Is the pinkish area in the photo the bonding strip? The crack is on the upper edge of the pink stripe. You can hang a fingernail on it so it has probably de-bonded.



I've done quite a bit of metal body work, but this is my first adventure into Corvette SMC, so I would appreciate anyone that can tell me what I'm seeing here.

[zimmej51]

I hate to return to the seat track fiasco that I posted about earlier, but something else has come up once again. I thought I had this put to bed.



Does anyone out there have a genuine GM parts catalog for the 1981 C3?



What I need are the part number(s) for the PASSENGER side manually adjusted seat tracks for the 1981 C3. On the passenger seat tracks, one has the latch mechanism and the other one just slides, so there should be 2 part numbers, or they may be listed as a set with a single part number.



I would be most grateful to get these part numbers. If no one can help then I guess I'll try to find a parts catalog for sale and go from there, but I'd rather be spending $$$ on parts if I can!


Here's a pic of what they look like.