Zerocyde

So, got the new carbbed 350 and I'm having fun, but got a few things to get down pat. One of which being the timing.

So, I bought the timing gun with the dial on it, everyone said I would need it, but how they tell me to use it makes no sense. They say, set the dial to like, 35ish, have someone hold the rpms at 3500ish, and adjust so the mark shows zero. Then, they say, with the engine at idle, set the dial to zero and the timing should show between 8 and 12 advanced (depending on who I talk to). My question is, why the hell not just set it to 8 or 12 or whatever at idle with the dial at zero to begin with?? Does it have anything to do with the fact that my cam is a thumper?

Why not just set the engine to TDC, mark the pully at zero with some chalk or something, then at idle, turn the dizzy till you get the timing you want?

camaronewbie

I've never used a fancy dial timing gun, so I have no idea. I just set my timing to a number, then check motor at WOT - if I get spark knock at WOT, then I set it down a tad and try again until I get it down where there is no spark knock at WOT.

In theory, you'd like to get 34 - 36* BTDC at 3000 rpms, and you set your initial to obtain that. But it won't happen without different springs & weights in the distributor - they just don't package the right ones already in the distributor. Without the springs/weights, you get spark knock because the timing has to be set too far advanced to reach those 34-36 numbers. With lighter springs and heavier weights, you get more centrifugal advance and get it earlier, so that you can reach that 34-36 number without having to have an initial setting of 16+ degrees.

So, you just have to set it as high as you can without getting spark knock, and live with it until you get a dist spring/weight kit. Right now, mines set at about 14* BTDC - I get up to about 28* total at 3000 rpms there with no pinging. I cannot 'hear' any pinging at 16, but at 17 I do - so I went down to 14 to be safe, as there is always knocking that can happen well below a level that the human ear can hear.

That make any sense? Don't know how it all applies to any fancy dial back light - but I assume you can dial it to zero and it acts as any old timing light.

I think what happens with a dial back light, is that you can set at what timing you want to see the mark flash at zero on the tab. So say for instance you want to see 20 *BTDC - you can't normally see that because the tiing tab only goes to like 8*BTDC. So, you set 20* on the dial, and the gun will change when the light flashes - so that when the car is at 20* BTDC, the light flashes when the balancer mark is equal with the ZERO on the tab - that way you can see 20* BTDC. And when you rotate distributor clockwise so that the balancer line is at 4*BTDC on the timing tab, that is actually 24* BTDC, since the light is flashing ZERO when it's actually at 20.

Make sense?

Irockz

iTrader: (1)

First,camaronewbie,I REALLY wish you would aquire some usable knowledge.I have watched you give so much BAD advice,that it is sickening.You are a rookie,at best,giving out inaccurate information all over this site.

To the original poster,36* is usually the magic # for a SBC,not always,but usually.Only a dyno or a timeslip can give you exact info,but it is a darn good starting point.Weights and springs,and an EGT can be wonderful tuning tools.

In short,the weight/spring package for whatever distributor you have is money well spent,you can't get a proper tune without it.Your initial should end up 6-8* BTDC,at idle.

Zerocyde

Before I made this post I had no idea that adjusting idle timing and mechanical timing where two different processes. I was turning the dizzy with the rpms at 3500 with the light dial set to 35 until it read zero on the balancer.

So I take it, from your post, that I should set the dial to zero, adjust the dizzy to 6-8 advanced at idle, then mess with the weights and springs until it will read zero at 3500 rpms with the dial set to 36 or whatever is best for my application.

Is that correct?

camaronewbie

You, my friend, need to take a huge chill pill!

I don't comment here, or anywhere else, on any subject that I don't have at least some usable knowledge on.

I try my best at all times, to make everyone aware when I'm theorizing on something. And I try my best to make sure it's understood when I'm not 100% confident on my replies. I think I pretty well made that apparent above - specifying that I never used a dial light before. There may well be times when I didn't imply or state strongly enough that I was guessing in a post - but I am in fact human, and I do make mistakes and don't always choose my words as best as they could have been chosen.

It may well be the case with some cars - EVERY motor is different ... but I've rarely ever seen anyone get a successful carbed tune with as little as 6-8* BTDC. Just about everyone advances timing well above that, much closer to 10 or higher.

I've been here at TGO for many years, reading, learning, and helping others. I've had my share of wrong answers both given and received, as has everyone else. And I've never once, in any post I've ever made, claimed to be an expert at anything .... If I were some great car guru I'd probably be out making money at it, rather than wasting time here. But, I enjoy being here, learning and helping where I can. It's MY choice, MY hobby - and until TGO removes me as a member, I guess you'll have to either live with me, or stop reading my posts.

Exactly what have I stated above that is so incorrect as to justify your remark? I have stated same as you -

1) 34 - 36* is usually the magic number.

2) to get that magic number, you either need to advance your initial high enough without detonation, or else you a) live with a smaller number, or b) change weights/springs in dist in order to obtain that 'magic' number.

3) I stated that there is spark knock that the human ear cannot hear, and so it's wise to retard timing a few degrees lower than the point where you can't hear the pinging

4) I stated that usually distributors do not have the right weights/springs already installed to get the total timing most desire, and that an additional kit would be required to get those weights/springs

5) the ONLY other thing I stated was admitting MY OWN IGNORANCE when it comes to using a dial back light, and I guessed at how it works ... but I implied as plain as the nose on your face that I didn't know and was guessing about how a dial back light works - I assumed that if I was wrong with my theory, that it would at least spark enough interest for the OP to read the book that came with his light and figure it out (I also kinda hoped I was wrong, so that someone with REAL KNOWLEDGE rather than USELESS CRITICISM would post how a dial back light works so I could learn myself)

So, since I basically stated the same as you oh mighty one ... what is so innacurate in my post?

ZEROCYDE - I hope you get it figured out bud. And I would be greatly interested in learning what you learn about using that dial back light. Good Luck!

Apeiron

Mess with the weights and springs so that it's fully advanced between 2500 and 3000 RPM. Then set it so that the balancer mark lines up with the zero mark on the comb with the dial set to 34. Try some WOT acceleration runs with the engine fully warmed up. If you get pinging, retard the timing by 2 degrees at a time until you don't. If you don't get pinging, advance the timing by 2 degrees at a time until you do, then back it off by 2 degrees.

If you care after that point, use your timing light to see what your initial timing is.

Zerocyde

1. By "set it" do you mean turn the dizzy?
2. Do this with the rpms at 3000 or at idle?

camaronewbie

After some further internet reading, I have also confirmed that my explaination of how a dial timing light works is also correct - although it could have been worded differently/better I'll agree.

ZEROCYDE - look through these simple directions for a timing light with advance dial, and you should better understand: http://manuals.harborfreight.com/man...0999/40963.pdf

Basically, you hold the rpms at 3000, flash the timing light, and change the dial on the back until your balancer line is at the ZERO mark on your tab - then you can see what your total timing is at 3000 by reading the dial on the timing light - if it says 30, then at 3000 rpms your total advanced timing is 30*BTDC. From that point, you adjust your initial timing as high as you can WITHOUT detonation to make it so that, when you are holding the rpms at 3000, you get to the 34-36 number on the dial.

Of course you will (probably) not see 34-36 total with stock distributor springs/weights with getting detonation, so you have to drop the timing back down some.

All your doing is setting the position of the distributor so that the spark plugs fire at the best time. Its all just a reference point of numbers - so don't get wrapped up in the numbers themselves, just the fact that they are getting bigger or smaller (advanced or retarded) as you twist the distributor one direction or the other.

So, with your light dial set at ZERO, and with the car running at operating temp ...

1) at idle, set the initial timing at about 10*BTDC.
2) hold rpms at 3000, and turn the dial on your timing light until the balancer mark comes back to ZERO - then read the dial on the light - I'll take a total stab in the dark here and guess it'll read something like 26
3) whatever the difference is between say 35 (the 34-36 'magic number'), that's how far you'll have to advance your initial timing to get the 'magic number ... so in my example you'd have to go another 10 degrees advance for an initial timing of 20 degrees BTDC.
4) BUT - you really can't set your inital to 20*BTDC because you'll have detonation long before that - so that's why you can't reach the 34-36 numbers - the springs and weights need to be changed in order for the centrifugal forces of the mechanical advance to get the timing advanced that far and get it done faster - before the pinging starts.
5) So - we are at 10*BTDC - you then take the car for a drive, and punch it! If you don't get any pinging, then you can advance it more - say to 14*BTDC (this is at idle, with light dial set to ZERO). Take the light with you and do it on the side of the road.
6) Now - drive again, and WOT again. No pinging, then try 16* BTDC, if you hear any pinging, then come back down to 12, and try again.

You want to find the spot where, at WOT, you just do hear pinging - then you want to come 2 degrees below that to CYA.

Now - when you get new springs/weights for the dist, you just install them then you run your engine at 3000 rpms, and turn the timing light dial until the balancer mark reads ZERO on the tab. Read the dial - if it states higher than 34-36 (which I'd hope it would with lighter springs and heavier weights), then you turn dist to lower your timing so that at 3000 rpms, when you put the light on it, and turn the dial to get to ZERO, your dial reads in that 34-36 range. Then, you can set your dial to ZERO, and at an idle, put the light at the tab to see what the final initial timing setting is with thsoe springs/weights - so you know for future where it should be.

Basically, the only thing the dial on your gun is doing is retarding the light (not the actual timing) when you turn it, so that you can see what total timing is at a certain rpm (since the timing tab only goes to like 8 or 10).

I hope that makes sense! Good Luck!

Apeiron

Yes, turn the distributor

At 3000, or wherever the timing is fully advanced.