SBC Timing/total timing NEED HELP

7* initial all in at 36* 18* total timing with vac can dissconnected.

Is this correct, it seems to start good etc but is there more power to be had with changing it? I have a curve kit.

Im not sure the rpm the total timing is in by didnt have someone watching the tach.

What next? thanks guys

 

you want around 34 total with the vacuum disconnected, and it'll go way up when you apply vacuum (50+ is common)

 

So many things to consider, fuel ,carb settings ,exhaust backpressure. Just experiment and have fun!!

 

Chevrolet take on timing for a racecar.
For the street you might want to drop the initial to between 10-15 to make sure the starter will turn the engine over hot.
Otherwise it's probably about right, even though you might have to do some tinkering and adjusting to get everything working with a vacuum advance.
Larry T

 

I just got my fuel pressure set @ 5.5 (edelbrock) starts better. I needed to adv timing a hair. So i just got the gun out.

Larry T-if i drop the initial the total will drop as well right (or it will change)

Thanks

 

Vac can hooked up to full vacum

 

Ps can I hook my vac can up to the port behind the carb on the intake manifold im running full manifold vacumn, id like to make the bay cleaner and run my hose there instead?...

 

you want about 34 degrees total all in at around 2500 rpms any sooner she will ping.but you have to make sure your initial is not too high.if so youll have to reduce the mechanical advance by welding the slot up(on a factory dist) or using bushings (msd).the initial shouldnt be more than 10-12 degrees.when recurving sbc i never use the vacuum advance.that changess the whole game

 

You want the total to be around 34, so if you need to drop the initial, you'll need to modify the distributor to have more mechanical advance, and then when you drop the initial timing, the total will be the same. I'm pretty sure that's what he meant.

 

So in order to get my initial mech adv higher I need to get a bushing (dont like the idea of welding my distributor because im not exactly sure what im supposed to be welding)

Can I buy JUST the limit bushing (i ordered a summit kit but no limit bushing)

Where is the best place to buy adj vac adv?

 

Im not sure what my 'all in' is yet either will know asap though


Is it OK to drive it like it is 'for now' until I get my needed parts to finish?

 

Someone said they used a zip tie? That'd be more up my alley but where do I put it?? lol

 

Bump for more imput lol

 

Need to know some info on the engine? Is this a bone stock 8 to 1 sbc?

 

Sorry

355 4 bolt main .30 over flat tappet 279 comp cam thump 9.5-1 compression (gotta run 93 octane) summit 'vortec' heads 67cc chambers ram horns edelbrock 600cfm regulated to 5.5psi stock hei 373:1 rear gear ratio 3spd manual transmission

 

I'm not understanding your initial post. Can you clarify how much total advance you have without the vacuum advance hooked up? Also, how far up is it going after you plug in it in?

 

Sounds like you have a nice street set up. I would disconnect the vacum advance all together. Set your total mechanical advance timing to 36-38 degrees. Tell me what your timing is at idle.

 

7* @ idle with vac adv plugged

36* WOT (kept reading this is what you want for total timing?)

Not sure of the RPM its 'ALL IN' by because I cant hold timing gun and look at tach on column at the same time.

WOT 18* with vac. adv plugged

NOTE: Degrees may be off a degree or 2 at the most but they are very close

 

Cold it starts up great etc. Not sure about hot/or how it performs...

 

I'm having a hard time following your info:

7* @ idle with vac adv plugged - OK, good.

36* WOT (kept reading this is what you want for total timing?) - Is the vac adv still plugged? If so, good. This should be just your mechanical advance plus initial. So you've got 28 or 29 drgrees of mechanical advance.

Not sure of the RPM its 'ALL IN' by because I cant hold timing gun and look at tach on column at the same time.

WOT 18* with vac. adv plugged - This is where you loose me. Unless you mean the 36* WOT above was with vac adv hooked up - which is not good.

 

7 degrees @ idle with no vacumn advance line plugged

36 degrees with vacumn advance hooked up to carb WOT

18* WOT with no vacumn advance and line plugged

Sorry im learning and not sure the info I need to give you guys

 

Yup, I am wondering on that one too. I think he is saying there is 18 degrees advance added with the vac adv. If so that is about right for the best fuel economy.

No vac. advance equals poor economy....

 

Whoops, just saw your reply.

You are only getting 11 degrees advance which is actually not a bad thing because you can run up the initial. On a setup like yours I would run 20-22 initial advance if you can still start it okay, which with a good starter should not be a problem. It will make the engine much more responsive.

That said, I think your distributor has something limiting advance already. You should be seeing 20 plus degrees mechanical advance.

On the vac. advance you will not have any vac. advance at WOT because there is not vaccum....but, at high idle you will have high vaccum and will see the advance.

Is it high idle or true wide open throttle?

Basically, you have high advance at idle and cruise speeds and as the throttle opens, the advance drops.

 

Check this out, it's at the end. 1st part is carb setting, last is timing.

http://www.youtube.com/watch?v=EEeKYZS-Stg

 

Hate to be a pain but can someone give me a definition for dummies for all the terms i want to be make sure im using them correctly and know what they mean

thanks guys

 

Initial advance is the timing at idle with the vac. advance unhooked. Total advance is the timing at 3000 or more with the vac advance unhooked. Those are the two you really need to know. Most stock harmonic dampers aren't marked for checking total advance. You with need to get some timing tape for the damper or use a dial type timing light so you can dial in the timing you are looking for and set the mark on 0. As a side note, I've checked the dial type timing lights against a fully degreed damper and the light wasn't perfectly accurate.
Or you can mark the damper at 36 (or 34 or 38) and check it against the TDC mark for total advance.
Larry T

 

I just bought a dial back light. Hopefully its good nuff for now and i'll mark the balancer in the future to check everything.

Ive already checked TDC mark is accurate on balancer it is right.

I thought total adv was with vac adv hooked to carb..? thanks

 

It get you in the ballpark for sure.
Total is the initial advance + the centrifigal (sp??) advance in the distributor. The vac. advance is a whole different deal.
Larry T

 

Ah im lost I thought my goal WAS 36 degrees total advance, well then whatta bout the distributor

I wanna run vac adv

anyway thanks yall

 

This thread is getting tedious.
Take the distributer out.
Take it to a professional repair person who has a distributer machine.
Tell him everything there is to know about the car, engine, transmission and how it will be used.
DO NOT LIE TO HIM IN ANY WAY, SHAPE OR FORM.
DO NOT EXAGGERATE, OVER STATE OR EMBELLISH WHAT THE PURPOSE OF THE CAR WILL BE.
Pay the man what he wants to perform these services.
Take the distributer home and install.
Please do not install distributer 180* off and wonder why the engine back fires and pops when attempting starting.
16* initial, (hopefully) 36* total by 3000 rpms, all timing done with vacuum advance disconnected.
Connect vacuum advance.
Readjust idle.

That's it.

On to the next challenge.