I am seriously thinking about converting to Carb. And in this incident i will need to remove my computer controlled distributor, and replace it with a vac advance distributor.

however i do not have much to any experience working with these distributors.

I have found a vac advance distributor, its an HEI from an unknown vehicle. But it is a large cap distributor.

My question is, i am not the best with electronic ignition tuning. so how do i go about tuning a stock GM dizzy?

From my research there are springs holding a spinning piece together. Adn the fast it spins the more advance it adds. But then why have both vac advance and mechanical advance in one carb?

I'm trying todo my research before i get myself into a hole i dug too deep.

 

The mech advance is there for the actual advance on the car.. the vac advance is more there for fuel economy and such. at least that is my understanding.. One quesiton. why are you going from FI to Carb? I want to go the other way.

 

https://www.thirdgen.org/newdesign/tech/hei.shtml

 

Well that was a great article hey.. That may in facty help me out a ton lol... So just a quick question (because i have always wondered (even though i am pretty sure)) Does this mean ---->14 degrees initial advance + 20 degrees centrifugal + 16 degrees vacuum adv. = 50 degrees total

that you should have 14 degrees on the harmonic balancer at idle, than the centrifugal setup for 20 dergees and the vac advance set for 16 degrees?

(with the 14 degrees done by turning the disty?)

Also If it is not with the 45-55 area would that cuase the engine to knock a bit? If so then i think my centrifugal springs have given out taking away thier timing.....

 

45-50 degrees isn't excessive for an engine while cruising. As soon as you put your foot into it the vacuum advance goes away and you should have around 34 degrees of base + centrifugal advance.

 

Making the jump for ease of tuning. Dependable system, atleast for me, i hate all the sensors that love to go bad.

Plus right now the FI system is fugging up everything. Gonna go carb, and sell my entire TPI system soon after. It needs a good tune, and one is expensive, i did the 305-350 swap.

Care to make a bid on the TPI setup for when its done? Baseplate is highly ported. Few dents in the runners. Upper plenum is mostly stock. 24# LT1 injectors. Stock 305 Computer. Removed EGR. Throttle body is in Great Shape. Cant tell you which sensors are good. Becuase of all the problems i've been having. But ECM was working fine last i knew. Hopeing for atleast $300, but i realize the condition of all the sensors being unknown may not make that much from it.

 

Ok.. so basically the base timeing is what you get from moving the disty.... gotcha.. man no wonder the thing is all messed... I think my centerfugal advance it not working properly.. and the rest of it might be over timed... (i do not think the vac advance is letting out of it.... i do suppose that could cause some problems as well (like detonation..)

 

Never know it might be something that i have a buyer for... have been toying with the idea.. especially since i have all the software to get it done..

 

if you suppose the mechanical advance isn;t working properly, then just replace it.

They are like ~$9 at the local autoparts store near you. To completely retune your ignition.

When i take delivery of mine, i will be rebuilding the ignition advance system, the carb. And everything inbetween possible.

After looking around i have learned and after reading that great aritcle, adjusting ignition timing isn't hard with mechanical stuff.

 

yea that article helped a ton.. I figure i need to rebuild the thing. it is after all 25 years old... if nothing has been done to it before... I have replaced the cab and rotor, coil, ICM, the little canister in there.. lol. pretty much everything. As for the rest.. My carb is pretty much brand new now.. a nice holley 4160 600CFM Vac Sec carb, sitting on a decent edlebrock performer intake. Remember, if you have an auto for the TPI, you will need to get a new TV cable for you transmission (if it is a 700r4) because the cable for the carb application is actually shorter... Also, you will need to get all of the proper brackets for the TV cable and the throttle cable..

as for prices if you are thinking about 9$ then I am sure it will cost my around 15 to 18.. stupid parts stored out here take a pole to you ever time you go to one.. I have resorted to ordering most of my stuff from Summit, jegs, or one of the many Chevy parts places out there (and specialty camaro ones as well)

 

yes this is true.

i already know about TV and throttle cables, i actually already own them. I was at a junk yard like almost a year ago and told myself one day i might go carb might as well get these while they are here. Guy charged me $15. I was however stupid enough to forget the bracket, but since they cam with qjets i think it would not have worked.

 

Yep.. It will not work.. I had one for a little bit off an 80' qith a quad.. amazingly the thing actually worked well.. Just had to grind a little on it to clear a runner on the intake.. The thing with that though was it was huge... If you go with a holley carb they have brackets ranging from $15 to $80 for the throttle and then the TV cable braket atteches to it.. I have seriously thought of going with the expensive one, only because it looks nice, gives you a good place to hook the springs and all around works well and is sturdy.. (alot more so than the ones sold at automotive parts stores. I actually bent one in half.. POS.... ) I went and bought all the disty stuff and am rebuilding the thing as i type lol... all except for the adjustable vac can and the springs for the mech advance (no one had either) The thing you may find difficult perhaps is your Tranny.. it may not lock the converter, since I believe there is a Throttle sensor in the cc carb, or the in the FI systems... so You may need to get a switch.. I have this problem as well... drives me friggen crazy.. but the car does not go very far ever... and it has a tranny cooler in it... so I hoped that offest any heat buildupo because the converter does not lock.. for all of the 500 miles it has gone this summer.

 

i will wire up a switch. I'f i want to use lockup, i'll know it. I'll be on the highway cruising.

 

if you dont have the lock up hooked to a switch and your on the highway dont use overdrive. i burnt my 700r4 in my s10 blazer when i went to a carbed small block. so now i have a th350 4x4 in my s10 works great but i miss overdrive on long trips. i also miss first gear in the 700r4. if i look around i might have the tci lockup kit for a 700r4 around. ill look but i dont know if i kept it.

 

The car will shift into OD.. there is just a bit of heat buildup reguardless since the TC will lockup in 3rd gear as well at cruising speed (once it hits it's Lockup RPM) So haveing a cooler on it will help it last longer without the lockup.. but yea.. if you do not have a lockup it will not be very good for that tranny...

 

if you have that TCI kit that would be awesome.

All i would have todo however is rig up a sensor that detcts when 4th gear is applied, and when that happens, the TC will then lockup, once it shifts out, lockup is turned off.

I think there is one stock however.

 

Stock you have a switch in the transmission that tells you when you're not in fourth. You can easily replace it, or use a relay to figure out when you are in fourth though.

 

see, its an easy fix.

i dont see how the kits availible can charge $100.

All it is is a switch that is activated upon only certain surcumstances, and that being 4th gear driving.

I can make setup for like $25 nor that i think about it.

 

You do that and have it work let me know how you did that lol.. I need to do the same thing to mine.. and since it is in storage now.. I have time.. (also have to fix the trans x-member.. one of the bolts is completely stripped out where it bolts to the frame... dunno how it happened... wish it was an easy fix....

 

i will let ya know how to fix it. But ya know that 4 pin connector that plugs into a 700r4? I'm sure one of those goes to the switch. I just have to figure it out.

If it detects when i'm not in 4th gear, meaning it is activated while not in 4th gear, i can wire it up to turn the relay off when activated, and spring back to activate when it is not in 4th gear. Pretty easy. Just a little bit of wiring todo. Nothing a creative mind cant do.

but the crossmember bolts being spripped isn't that hard to fix either. just up the size of the bolt, and tap the already there hole to the next larger size thread, and use it. It that doesn't work. Drill the hole out with the bolt. and put a new bolt in position and weld it into place. The slots up forward of the frame are i'm guessing where they put them to begin with.

 

<img src="http://www3.telus.net/~crussel/tcc_wiring.gif">

 

wow its easier then i thought.


hehe, cool.

 

That may help a little. Ok.. Question does the 4-3 shift that is part of that plug work and function properly without that plug installed? Or will it work properly without a computer?

 

The computer has nothing at all to do with the actual shifting of the transmission.

 

ahh ok. so basically ya hook up a relay switch to the proper wire... and unplug that 4 prong thing... and then everything would still be fine.... That is great.

 

Well no, you want to leave it plugged in. Connect the relay coil between pins A and B, and the N.C. contacts on the relay between pin D and ground.

 

each of those connectios does one thing.

terminal A tells the ecm that 4-3 downshift occured.

Terminal B tells the ecm if 4th gear clutch is applied.

Terminal D is the TCC solenoid Ground.

Terminal C will most liekly be positive for Solenoid.



So in perspective, i make a circuit that senses when the 4th gear clutch is applied, and make it ground the TCC lockup solenoid, and that all i need todo.





its funny, people always come up with the world changing ideas, in the wrong conversation. Not complaining here. you always think up things during a conversation but forget later. And here we are tlaking about Vacuum advance, and are developing a TCC lockup system. Hehe, its cool... Its cool tho, if i do this successfully, parts cost about $20, and that would save so many people so much money.

 

You could always put a switch on the shifter braket that when you put the shifter into 4th gear is completes the circuit and grounds the pin, there for locking it up only in 4th gear.

And yes.. It is cool how one thing can turn into another thing lol.. As for leaving it pluged in.. uh.. I do not even have a computer in my car now lol... It uh.. became water logged... sorta fried...pretty much why i went non CC on the engine.. and was trying to get the trans to be completely non cc... thanks for the help Apieron...

 

well, sorta, on an auto there is no 4th gear position on gear shift. Thje only way we can tell is through that 4 pin connector.

If you remember correctly an auto, all you do is put it in Drive(or overdrive in this occasion) and it shifts for you.

But you can hok the 4th gear band sensor up to a reverse relay. that stops the circuit from being completed, until the sensor detects nothing. then the TCC will lockup, when 4th gear is applied.

Relays are cool, if you have ever taken one apart, all they do is automate a high amp switch, by having a low current electromagnet to pull an arm down to connect the circuit.

if you learn how they work, you can even repair them. 12volts isn't enough voltage to electronically fry a relay. ITs old age and oxidation that hurt them.

 

Pin A is +12v power for the solenoid, which is interrupted by the switch on the brake pedal.

Pin B is is grounded in all gears except 4th.

Pin C has no connection.

Pin D is grounded by the ECM to lock the TCC.

This same topic has been discussed several times at length on the transmission board.

 

So then why have i not heard of people making these before?


Has anyone on the board actually made one yet?

 

Yep I knew i seen it there... But it would be easier if someone made a tech article that was in depth so we would not have to trudge through several hundred posts to find the info we are looking for.

 

i dont have it anymore. but i will work on figuring out a way to do it right cheaply. from the top of my head
a vacuum switch - to disengauge clutch under heavy acceleration
presure switch (tranny 4th gear) - to tell it to lock up in 4th only
brake switch - to disengauge lock up when brakes applied
rocker switch - for you to control lock up
that pretty much it. ill draw a diagram for wiring
hope this helps and yes they charge way to much for these kits.