Classic & Vintage - Old Shimano 600/Dura Ace Brake Info?

I just got a 1986 Centurion Iron Man that came with full Shimano 600 6 Speed SIS and Dia-Compe Gran Compe aero brake levers. While working on the bike I noticed that the brake levers do not have return springs and the brake calipers have super strong return springs (as compared to my 1989 Shimano 600 single pivot brake calipers). I gues this makes sense so that combo would work well together. But because the Shimano levers are more comfortable to me, I put on older Shimano brake levers to see how I would like them as compared to the Dia-Compes. Unfortunately I found it took a lot of sqeezing force to stop the bike, so I switched back. Then I saw a photo of Raul Alcala on the 7-11 team from 1986. I could see from the photo that he used what looked like the same generation brake calipers as mine but he was using Shimano levers. My question is this: Did Shimano make brake levers in the mid '80s without the return assist spring or is Alcala just using the combination of caliper/lever that takes a lot of strenth to pull?

The Shimano 600 (BL-6207) non-aero levers that belong to the 1984 Shogun 1000 I just rebuilt didn't have any return springs.

Shimano 600 levers up through BL-6208 have no return springs; the first ones were the 6209 (without oval holes in levers).

My 7400 Dura Ace levers had no return spring.

Thanks for the info!

My 600 arabesque era calipers have strong return springs.

Shimano's brakes with the return springs in the levers were called "SLR" ("Shimano Linear Response") and were introduced sometime around 1986 or '87 on their 105 brakes and then "trickled up" to 600, Sante, and Dura Ace. When they went to dual pivot, they were called "Super SLR".

Anyway, I think DiaCompe did it first by a couple of years with their "BRS" ("Balance Response System") brakes + levers.

The 1986 Ironman was OEM with the DC levers and the 600 calipers. I believe the DC levers also had a "leader" cable housing that went under the bar wrap? They are fine levers and did not have a return spring. I found them better than the 600EX levers on my Comp TA. The bike also had very nice coppery Araya rims, which I've not seen elsewhere.

Some of those DC levers had colored hoods, too, which made styling more interesting on some of those bikes.

We will need pictures of that Ironman posted on the Centurion Serial No. database thread, which will allow us to send you the cult kit.