Quick question...does it matter where I connect the distributor vacuum advance hose, to the location marked in red or the one marked in yellow? Will there be a difference in performance or quality of function either way?

Red Yellow (Corrected as per @Captain Obvious )

Edited April 3Apr 3 by SteveJ

16 minutes ago, texasz said:

does it matter where I connect the distributor vacuum advance hose, to the location marked in red or the one marked in yellow? Will there be a difference in performance or quality of function either way?

Yes, it matters, and sorry to contradict @SteveJ , but the correct location would be the location you have circled in yellow.

The location circled in yellow is "ported vacuum" which is what the distributor wants. The other port (red) is direct manifold vacuum at all times, which is not what you want.

Just now, Captain Obvious said:

Yes, it matters, and sorry to contradict @SteveJ , but the correct location would be the location you have circled in yellow.

The location circled in yellow is "ported vacuum" which is what the distributor wants. The other port (red) is direct manifold vacuum at all times, which is not what you want.

That's okay. I just wanted to post the link. I was too lazy to go down to my cars to look.

12 minutes ago, SteveJ said:

That's okay. I just wanted to post the link. I was too lazy to go down to my cars to look.

Hahaha!! You just posted the wrong video!!

Thanks guys! Had to go check mine and it was reversed and the blance tube bolts were loose. All good now. Car is still waiting for spring, but when I get it out I will expecting 5 - 10 more HP 😃

I will disagree with CaptainO....sorry. Do some research into ported vacuum vs manifold vacuum for distributors. I totally understand that Datsun has really smart engineers building these cars and engines, but....I run both my 81 and 83 on manifold vacuum with slightly reduced static timing. Cars run fantastic.

I agree that the factory attachment was ported vacuum.

Try both ways and see how the engine performs. Adjust the engine idle to the proper spec when you switch.

Edited April 3Apr 3 by kickstand80

18 minutes ago, kickstand80 said:

manifold vacuum with slightly reduced static timing. Cars run fantastic.

Does it run better than with ported vacuum? You've described what you do but not why you do it.

Edit - there's a ton of discussion about it out there but most (all so far) of the reasons given by the various internet participants are opinion, many based on peronal theories about how engines work. Haven't found a solid explanation for why it was developed in the first place. I'll keep looking...

Edited April 3Apr 3 by Zed Head

Side note for discussion - once the throttle blades are cracked the engine is on manifold vacuum. Ported vacuum timing is an idle-only/throttle-closed condition. Any driving performance changes would result only from other timing changes.

Here's a good old paper. Unfortunately, the SAE controls many of the publications and they're behind a paywall. Interesting titles and abstracts, can't afford to read them.

Side note 2 - many states only check emissions at idle.

https://rosap.ntl.bts.gov/view/dot/8798

I run manifold as it makes my car run better. I have 3 Oxygen sensors on my 1983. One for the ECU (narrow band) and 2 wide band running 2 different AFR gauges. I wanted to compare the AEM to the Innovative meters. They were pretty close. The reason I did this was because the AEM sensor right out of the box was bad. I spent a week trying to figure out why a 1979 ZX ran really good but the AFR said it was way lean..........bad O2 sensor. My wife purchased the AEM for me for Christmas but I did not get around to installing it for a year......warranty ran out so I purchased the Innovative and purchased a new sensor for the AEM.

With both wide bands sensors installed I was showing the engine slightly rich, 14.0. Both showed this. When I crack the throttle, I would get a front fire (lean condition), some call it a backfire thru the AFM. I also have a 1981 that everything is new on that car. All original Nissan parts. I have always used manifold vacuum to the distributor on that car and it runs great. I switched the 83 to manifold vacuum, adjusted the static timing from 10° to 7°, reduced the idle speed and WHAM...no more front fire and the car runs strong.

Third car, a 1983 that I sold to someone in the Houston area (Greg). I recently drove back down to Houston to help him with some issues. (replace intake/exhaust gasket, fix some rust in the windshield channel, install a new AC compressor. When I reassembled the engine, I decided to switch the distributor over to manifold vacuum, reset the timing and idle. I talked to Greg about the difference and he was willing to see what it would do. The difference in the cars performance was really amazing. Greg had the car for 1 year so he was familiar with the original configuration performance and he was astonished on how much it changed how the car pulls.

Like I posted, swap between the two ports and drive your car to see how it affects YOUR car. Carb cars may react different than EFI cars. I dont have a carb car. Remember that your distributor has to be in good condition. The vacuum advance must work and the mechanical advance must work. It all works together.

Edited April 3Apr 3 by kickstand80