FB II

be it you use holley, weber, etc.. what did you do about your vaccum advance? i have a racing beat manifold with a holley and i dont see anywhere to hook up the vaccum advance hose. hmmm....

vipernicus42

iTrader: (4)

Zac you little bugger... Take it easy on the trigger finger And hook yourself up some h1gh 5p33d.

Jon

edit: and as I say it, the doubleposts dissapear...

FB II

lol, yea i didnt see anything. but it was taking a while so i could have double posted. sorry bout that guys! WOOOOOOOOO! just a little anxious.

Rx7carl

Tee it into the brake booster fitting?

FB II

would that actually work? lol i thought it needed manifold vaccum.

rx-7ames

iTrader: (1)

maybe this is a good time to ask stupid questions. please don't get mad or think i'm too stupid. on "normal" distributors, there is only one vacuum hose for the vacuum advance. i know there is two on the rotory's distributor. one for each coil right? can someone just explain this to me? which would you tee into the brake booster fitting?

Rx7carl

Nevermind, brain fart. Dont do that. Just leave the vac advance uncapped at the dizzy. Carry on.

FB II

they run in conjunction to a vaccum source. the distributor itself needs to see vaccum to know when to advance with the rpm's. if not your car wouldnt be that streetable. well, i dunno how bad it gets on an rx7 without advance. haha, i hope i dont have to find out.

FB II

carl, really? i can just leave the vac advance left open? what should i do about my timing then? fully advance it?

Rx7carl

Nah, your gas milage will drop slightly, but then with the Holley you wouldnt notice anyway. Leave the timing as stock. You will still have centrifugal advance my man.

mwatson184

Drill and tap the manifold for a vac fitting.

FB II

bah carl! this holley was tuned specifically for the 12a woooo! we'll see though. i'm just trying things. but anywho, if i leave it without the vac advance, it wont stumble or anything right? eventually when i get the chance i will tap the mani most likely. oh and i thought centrifugal advance only came up way high in the rpms just to slightly turn the rotor button. i are lost.

kettlman

iTrader: (2)

i have the holley hook up and left my advance undone. no problem here at all. works fine.

Tiers

the vaccum advance needs a part throttle vaccum. deffinatley not the manifold, lol, i think you would pop your motor if you let off at 8000 rpms, pulling 20 in of vac. but i dunno. on my mikuni, the vac advance port is right infront of the throttle plates as to pick up vaccum only when the car is cruising,

Carl.

mwatson184

^hmm interesting point, i haven't had a problem with the mani source, maybe i'm lucky

FBII, the centrifugal advance actually maxes out around 4000 - 4500 rpm

hornbm

I dont have my vacuum advance and my car runs fine with my weber. However my buddy has a FC with an edelbrock carb, and he recently decided to hook up his vacuum advance and he said it made one hell of a difference in the low end.

Sanspistons

Wow! -and to think I was about to post on this very subject...

I've run ported (part time) vacuum advance on my Edelbrock SP for over a year now with excellent results (21mpg city) and just recently switched to "straight" vacuum as an experiment. As hornbm says BIG difference on the low end; feels like it's a 13B now. First tank so not sure of mileage gains (if any). A strange problem has cropped up, however. When I switched to the spring loaded "off-road" inlet needles it cured a low speed corner-light throttle bog I've also had. Then when I switched to straight vacuum it came back!! I think that turning the idle speed down with the straight setup made the transition slot of the carb a little sensitive. I'll switch back to ported for autocrossing.

I have the same concerns as Tiers running straight vacuum but have had no signs of high rpm drop throttle detonation yet. This is a real problem on high compression racing piston engines but I can't see a problem on the (relatively) low compression rotary. After all, many stock piston engines have used this setup for a very long time.

How about a compromise? Run the leading on straight vacuum and the trailing on ported?! That way the sensitive trailing (according to what I read) timing will retard at hi-rpm drop throttle and this might kill possible detonation. Of course at low loads the leading will be highly advanced and the trailing only a little. Have ABSOLUTELY no idea what effect this timing split will have on the engine and kind of reluctant to find out!!!!! Might try it anyway; no pain, no gain....

BTW; vacuum advance is almost completely a fuel mileage concern; with either setup any throttle opening above about 1/2 vacuum advance is effectively zero.

Sanspistons for more wobbling

FB II

mwatson184; so where did you put your vac source? what manifold do you have?

red13brx7

All I know is in the Racing beat kit is says to leave the vacumm advance un hooked. So thats just what I did. I think the thing runs real storng. I love the holley on the 6-port rotary, it really screams

FB II

well, sounds good to me then for now. haha, all the guys at work (i work at a dealership as a service technician in training) think i should hook it up somehow. when i get it running, they want to take a good look at it and see what could be done. they say the vaccum advance is there for a reason. i've just never come accross this situation before. lol

mwatson184

The reason for vac advance is to optimize the spark timing under light load. It will increase your gas mileage and maybe make a power difference down low. I just tapped the manifold (racing beat) for my vac source on my 80 and its been running fine for a couple months now. I am waiting on another carb to modify and then I am pieceing together a nice turbo setup. The vac advance will be gone anyway when i lock the distributer, so i guess it is the way it is temporarily.

-Marques

heb09

I dont run the vacum advance on my holley, but aparantly it used to be hooked up.

FB II

i'll probably end up tapping the mani then. when i go turbo, i want to use the msd with a btm to control retarding.

mwatson184

^that is what i did with my t2. You need 2 btms though, one for leading one for trailing, stuff gets expensive pretty quick. Locking the dizzy works if you are on a budget, then after you get the btms on you can get put some advance back in. Sounds like you are going to have a near identical setup to my TII.

Here is a link for some pics if you are interested:
http://www.teamfc3s.org/forum/member...otos&car_id=55

rxtasy3

iTrader: (2)

i don't have vac to my dist. my carb is the rb streetport holley setup.