Ok, just wondering if running the vac advance is all what it is cracked up to be?
I have noticed several rotaries with the vac advance on the dist. wide open.

So I am trying to figure out why and why not to run it? When I set my timing with the advance off, I set it dead on the mark. Then when the advance is hooked up it goes about 15 degrees advanced.

On the repu truck it is not hooked up, on several other 7's I have seen it not hooked up so what is the benifit to leaving it off or hooking it up?

 

The benefit of leaving it disconnected is mainly for people who are afraid of vacuum hoses. Which is most of them given the number of "gonna rip out my rats nest !!! ahyuck ahyuck" posts.

If you like good fuel economy, good part-throttle power, cleaner spark plugs, and a marginally quieter exhaust, then you'll leave the vacuum advance functional.

 

I agree with PJ whole-heartedly.

The vacuum advance helps with throttle response to get the force of the rotors working to increase the rotational speed of the rotors - this is only a good thing in a car that has a lightweight rotating mass and not much torque at low rpm's.

Unless you feel that driving need to rip out your Rat's Nest and then put it back in, ahyuck.

 

Hmm my vac advance is kinda disconnected. The two pots are connected to each other with a vac lead... but they connect to nothing else...

I'm wondering is there any advantage from this ? Will I get better performance with the vac advance?

Can I hook both of these to a T join and into one of my other vac lines then ?

Cheers!!

Paul.

 

I would say so, but that is the main reason I started this thread.

Hook them into a T and run them off a spare vac nipple (if you have one) on the Upper Intake Manifold. Well, that is how mine are setup.

 

I think all my nipples were welded up lol.. so would it make a different if I ran it off a T ?

Also would I need to reset timing after reconnecting the vac lines to the dizzy pots?

Cheers

 

peejay, if you were thinking about hooking up vacuum advance on an engine that never had it as long as you've been its caretaker, would you connect a vacuum line to a manifold source for constant vacuum? Or to the carb for a periodic/staged/semi-omnipresent source? Heh. I've always treated mine like 7-Up (never had it, never will) but I'm just curious enough to want to try it and need a little more info. Thank you.

 

[QUOTE=H4Inf]I think all my nipples were welded up lol.. so would it make a different if I ran it off a T ?[QUOTE]

That should work then.

yes, reset it or atleast check it.

 

Depends on what mods you've done to the motor. Are you running a stock carb? I have mine locked out, for reliability and performance; per RB specs. No noticable low end performance loss. The engine timing is dependent on porting and intake/exhaust mods. Stock engines should have the vac adv. in place and hooked up. Locking it out to a specific setting is user dependent.

Keith

 

Well the 7 is a gslse with s4 rotors and housings. It is FI not carb'ed and has a mild streetport.

 

It depends on the engine! Usedtabe it was done with manifold vacuum. Ported vacuum (vacuum source is just above the throttle blades - no vacuum at idle basically) works somewhat better, but some engines do like vacuum advance at idle. Other times manifold vacuum at idle causes weird hangup thingies, like you rev the engine and snap-off the throttle, manifold vacuum goes way high so the vacuum can maxes out, and with that much advance it never settles down to "idle". Or vice-versa, from a start it idles too low.

 

Since my engine currently has no advance at idle and run fine, a ported carb source is what I'll start with. Thanks.

 

That's where I'll be taking mine on the P-port.

Which, by the way, is in the car as of today!

Sitting on the passenger floor.

It gets thrown into the engine bay tomorrow.

 

That's pretty cool. I get to remove an RX-4 engine tomorrow to freshen up the seals and maybe give it a modest port job or perhaps just clean up the casting flash and the sharp milled edges. You know what that means, don't you? It means I have yet another ribcase tranny around here. I think I'm up to seven of those things now.

 

Damn you. DAMN YOOOUUUUUUUUU......(echo echo)

We work closely with a trans shop. They can locate odd stuff. (The owner is the only guy who knows how to rebuild certain trannies from back from the 20's...) They can't find me a ribcase anywhere. And all I want is the bellhousing!

Oh well, I'll just keep breaking smoothcases...

 

My REPU vac adv was disconnected when I got it. All the vac lines are removed and plugged. Does anyone have a stock REPU-74 that can tell me which port on the carb or intake to hook the vac to the adv up to. Pics would be great.

 

On a '74 carb, it's one of the nipples on the carb but I'm not sure which. I'd have to look at the guy's truck again. From memory, it's closer to the front rotor near the oil injection nipple.

peejay, there is an extremely slight possibility that I may have a ribcase bellhousing for you some day. It depends on a number of factors such as maybe putting a 12A back into my MG and stuff like that. I will keep you in mind and see if I can come up with a plan that will result in one leftover bellhousing. I was most likely going to use it on an engine test stand, but a smoothcase bellhousing works just as good, although a little longer.