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Studebakerboy
03-21-2007, 10:18 AM
Hello Guys:

My son and I are just about to finish up his Avanti. All that's left is to hook up the hoses and get it started.

I found a small canister with a bracket. It's about 2.5 inches in diameter, 2.5 inches tall, two blade connector and one small nipple at one end, and two nipples in an L at the other. I found a connector by the no 8 cylinder witch seams to fit it, I need help with how this is routed into the vac system. Also:

Not sure which tap was used for the vac advance and how the fuel vapor canister is hooked up.

It was looked at by a potential buyer and left for dead years ago. Some of this stuff was disconnected then.

I'm going to try to find some pictures or a vac diagrahm.

Thanks for all your help.

Kevin Edwards

http://airlandandseaparts.com

Skip Lackie
03-22-2007, 03:41 PM
Don't take this as a certainty, but I think what you're talking about is a vacuum-controlled spark solenoid. It's an early emissions-control device that probably could just be disconnected (except that if you take it out of the system, then you may get too much advance under some conditions). Basically, it prevents vacuum from getting to the vacuum advance under some conditions in order to retard the spark and reduce emissions. The single nipple gets connected to a port on the lower right (pass side) front of the carb. This is the source of vacuum that holds the internal diaphragm open (or closed, I can't remember). One nipple on the back goes to the vacuum advance, and the other goes to a port on the top back of the carb. I believe the wires go to a switch on the transmission. In high gear, the vacuum advance is always connected to the vacuum source. If I'm wrong, I hope someone who is familiar with early 70s Chevy engines will jump in and correct the above.

BTW, I wouldn't be surprised if the d--- thing didn't work anyway. I tried to find one a few years ago for a 70 Camaro, and found that they were NLA from Delco and had not been reproduced. One vendor had some NOS ones for $150 apiece. I'm still waiting for someone to reproduce them and bring the price down.

You might want to buy a 72 Chevy chassis shop manual. As far as I know, the Chevy engines were dropped more or less intact into the Avanti IIs, as Avanti Motors was piggy-backing on GM's emissions compliance certifications. If you send me your engine number, I might be able to tell you what shop manual to buy. Although the engines were all fundamentally the same, things like vacuum hose routing depended on the horsepower and what model Chevy the engine was intended to be installed in.

Skip Lackie
Washington DC

bige
03-22-2007, 04:15 PM
The mystery canister may be a disconnect for the A/c. Some vehicles would turn the compressor off at full throttle.

The vacuum advance was probably routed through a ported temperature activated vacuum switch on the thermostat housing, but a lot of people bypassed that stuff long ago. Use ported vacuum on the carb if yours is gone or you wsh to bypass. Ported vacuum has a signal only when the carb plates are opened past idle as opposed to a vaccuum signal at idle.

As for the vapor canister, one hose would go to the carb or air filter housing, one from the tank. I don't think they had a vacuum signal to them but I may be able to reference an old Chevy shop manual for you. If I remember correctly, the canisters themselves ahd markings at the nipples for hose routing.

ErnieR

http://i146.photobucket.com/albums/r241/AvantiR2/avnatiglamour007.jpg

bige
03-22-2007, 05:27 PM
I think Skip may have the answer on the mystery canister.

ErnieR

http://i146.photobucket.com/albums/r241/AvantiR2/avnatiglamour007.jpg

Studebakerboy
03-22-2007, 10:31 PM
I should have mentioned that the car is a 4 speed, with crusie control, and uses and E-brock with a Holley. I rebuilt the carb in Oct and can't remember the model, but I'm sure it was 600cfm.

Looking at that device I thought it could be for retarding the spark for cleaner air. I'm guessing it was just disconnected and as only one hose was attached.

As for the vapor canister, I put my glasses on and could clearly read: PVC, Carb, Tank. Only problem is that the hoses were not all connected as they should.

I'll have to do some more research and see what I can turn up.

Thanks again!

Kevin Edwards

http://airlandandseaparts.com

Skip Lackie
03-23-2007, 07:58 AM
Since these threads are archived indefinitely, let me correct my earlier post: I believe it's called a TRANSMISSION-controlled spark solenoid, not a vacuum-controlled . . . . I have two vehicles with them: a 70 Camaro 350 and a 74 Avanti 400, both with 4-speeds (so it's possible these things were only used with standard transmissions). Both of my cars have a TCS connected to the vacuum advance, though the 74 only has two hoses attached to it. The switch on the transmission allows full advance in high gear. You can test if it's working (and whether I'm right or not) by shifting through the gears with the engine at idle (and the car not moving). The RPMs ought to increase when you shift into high gear. I hope that makes sense.

Since you have a Holley, you should disregard my comments about where to connect the hoses, which only make sense with the original Quadrajet.

WRT buying the appropriate Chevy shop manual: Chevy often published a different shop manual for different product lines; i.e., Camaro, Corvette, etc. Although 90% of the contents are the same, there are enough differences in external engine plumbing and accessories to justify buying a book that matches the engine in your car. The engine in my 74 Avanti was originally intended by GM to be installed in a Chevelle Malibu, so that's the book I bought.

Skip Lackie
Washington DC

Studebakerboy
03-27-2007, 03:19 PM
Skip:

Thanks for the great info. I had to leave the car behind at my mothers in order to get my son back home to school. I'm flying back tomorrow and bringing it home over the weekend. I bought an aluminum trailer off Craigs list to pull it behind the RV.

I'll give the test a try and see if I get an increase in RPM. My dad's 73 Avanti with auto does not have this device.

How did you determine which car your engine was supposed to go in? I went through the list at Carparts.com for 400 equipped cars, trucks and vans for 72, but did not come up with anything to narrow it down further.

Kevin Edwards

http://airlandandseaparts.com

Skip Lackie
03-27-2007, 04:58 PM
Chevy engines of that vintage are stamped with a series and date code serial number, just like Stude engines did in 64. I don't have access to my Avanti II at the moment, but my recollection is that the serial pad is on the right front of the block, just behind the water pump and below the right-hand head. (Owners of 65 and 66 Studes equipped with a 283 can confirm whether my recollection is correct.) It'll include a three-letter code like CKW, which indicates car line, horsepower, and what trans it was intended to be mated to. Chevy parts books included tables that allowed dealers to identify engines from these serial numbers. I have some Chevy parts books from that era, and might be able to identify the engine if you let me know the engine serial. And some of the Chevelle, Camaro, etc Web sites include links to this same info, and similar ID info for transmissions, rear ends, and other major components.

All that having been said, probably any 72 Chevy chassis book will provide the necessary info on the vacuum system. Those books are cheap and readily available.

Skip Lackie
Washington DC