Double Pulley on a 70GT?

[hrcollinsjr]

Originally Posted by David McCollam Depending on the year of manufacture, it could be for an A/C compressor or the Opel Emission Control System (OECS) air pump. That system was discontinued in 1970 I believe. Dave

I believe this is an air pump pulley since we're all in agreement about the A/C pulley.

Harold

[GTJIM]

Originally Posted by tekenaar Or to someone like me who wants to modify it for an entirely different function . . . convert it to a vacuum pump and use it for crankcase evacuation on my 2.2 SSD engine . . .

How about the alternator off a diesel motor - some of them have actual vacuum pumps tacked on to them for working the Vacuum brake booster - would not have to modify that as it is already a vacuum pump
Unless you want a "stealth" pump ...

[tekenaar]

Originally Posted by hrcollinsjr Why wouldn't you just do what drag racers do and use the exhaust to evacuate your crankcase? I suggested this to a friend running circle track and he swore it revved quicker. But then again everything he did made him go quicker. Harold

True, drag racer trick from the '70s and '80s, but recently, last five years, the trend has been to use vacuum pumps for crankcase evacuation. Anyway, been thinking along the pump lines for some time now . . . a little more effective and elegant solution in my opinion . . . even sticking with Opel parts, though modified.

[tekenaar]

Originally Posted by hrcollinsjr I believe this is an air pump pulley since we're all in agreement about the A/C pulley. Harold

Correct. If I recall correctly, WP and alternator pulleys are spaced forward ~1/4" to run off the larger front pulley. Airpump runs off the smaller rear pulley.

[ddoyle]

So a double pulley with a smaller rear is for an air pump, and a pulley with both grooves the same size is for A/C. On an A/C car the A/C pump was driven from the rear and alt and w/p off the front. How were the alt and w/p spaced foward? 1/4 spacers under the respsctive pulleys? Thanks

DAN

[tekenaar]

Originally Posted by ddoyle So a double pulley with a smaller rear is for an air pump, and a pulley with both grooves the same size is for A/C. On an A/C car the A/C pump was driven from the rear and alt and w/p off the front. How were the alt and w/p spaced foward? 1/4 spacers under the respsctive pulleys? Thanks DAN

They BOTH have larger front pulleys. Here's how to identify them:

A/C crank pulley: the smaller REAR pulley is the same diameter as a stock single crank pulley and the WP and alt are driven by that rear pulley. The larger front pulley ONLY drives the compressor, typically with an idler for belt adjustment. A 1/2" spacer is used on the WP between its pulley and the fan blade to space the fan forward for compressor clutch and crank pulley clearance. Crank/WP/alt belt path is UNCHANGED from stock non A/C!

Air pump crank pulley (only used on '68 engines): larger front pulley is the same size as stock single crank pulley and drives both WP and alt. Smaller than stock rear pulley drives air pump on passenger side. WP/alt belt path is moved forward by ~1/4" vs. single pulley belt path and spacers are used at the waterpump and alternator drive pulleys.

[David McCollam]

Otto,

I have both, or more correctly three different versions of the crank pulley. There is large front with small rear pulley. This appears to be made of stamped steel. The second version is a standard size rear pulley with a slightly larger front pulley. This unit appears to be machined from a casting. A third version that I have is a cast unit with a standard size front pulley and a slightly smaller rear. Is it possible I have the GM A/C pulley, an Opel OECS pulley and an ARA pulley?

I'll try to get them all out and arrayed for a photo.

Dave

P.S. Still got those oil filters for me?

[ddoyle]

That is just the info I needed, thanks OTTO.

Dan

[EJprovost]

Yes, thanks for the info! Just what I needed! I have carefully printed it out for my book of Opel knowledge.

[tekenaar]

Originally Posted by David McCollam Otto, I have both, or more correctly three different versions of the crank pulley. There is large front with small rear pulley. This appears to be made of stamped steel. The second version is a standard size rear pulley with a slightly larger front pulley. This unit appears to be machined from a casting. A third version that I have is a cast unit with a standard size front pulley and a slightly smaller rear. Is it possible I have the GM A/C pulley, an Opel OECS pulley and an ARA pulley? I'll try to get them all out and arrayed for a photo. Dave P.S. Still got those oil filters for me?

Yep, come by and get them any time, Dave.

[tekenaar]

Originally Posted by David McCollam Otto, I have both, or more correctly three different versions of the crank pulley. There is large front with small rear pulley. This appears to be made of stamped steel. The second version is a standard size rear pulley with a slightly larger front pulley. This unit appears to be machined from a casting. A third version that I have is a cast unit with a standard size front pulley and a slightly smaller rear. Is it possible I have the GM A/C pulley, an Opel OECS pulley and an ARA pulley? I'll try to get them all out and arrayed for a photo. Dave P.S. Still got those oil filters for me?

The ARA pulley on my first GT, a '73 bought in '76, was a cast piece with three spokes going to the crank mounting hub, if memory serves, not solid centers as the two cast dual crank pulleys I described in my post.

Haven't seen the stamped-steel dual pulley you described before. Maybe post-'75 Euro pulley? Got me curious now . . . definitely post pics!

[EJprovost]

Originally Posted by EJprovost Looks like Christmas vacation from College, the GT gets some help. Hmmm, wonder what this double pulley is for. Any advice is greatly appreciated.

Media Play got all the attention from Christmas vacation and the college students. (Seems they are going out of business and 12 hours a day took care of that) The good news is that all this great info has been printed out to help Kat when she finally gets to her GT project. The exciting thing was the Opel gifts under the tree for my two daughters! (Otto Starts, and rubber boots for the gear shifts).
An update on the progress of Kats 70GT: Originally we thought the engine was frozen, the good news is that we got it to turn several times by turning the ignition. The bad news is that the emergency blinkers won't turn off, and there is a lot of things to re-assemble, like the,radiator,water pump, weber, (Thanks Tim for the rebuild!), before we can actually feel good about putting the gas in the car to give it a good try. (Andrew got sucked into working at Media Play too) The good news is tho: All Recluse Spiders are dead now! That one thing sure makes it a lot easier to work on the GT! (Or want too)!

[kent]

do you still want that AIR pump ? I am just gettin ready to remove mine as I put in the sprint exaust ... if you want it let me know

[EJprovost]

Originally Posted by kent do you still want that AIR pump ? I am just gettin ready to remove mine as I put in the sprint exaust ... if you want it let me know

oh yes, I want it! Do you have the mounting brackets for it too?
Please leave me a PM, let me know how much you want for it OK.