Setting timing on my SBC

[MASTERBrian]

Correct me if I'm wrong, but is this somewhat a two part process?

I'm getting ready to do the break in on the engine. The Cam is advanced 4* at the chain, which I understand has nothing to do with total timing, so I'm guessing I just ignore that for now? The cam is an ISKY 270/280 Hydraulic Mega Cam

I could swear someone said to set the initial timing to 16* BTDC, to aid in starting the engine for break in. Is that correct? Right now, I've got the timing mark on 0 and the rotor pointing right at #1. I'm guessing I'll likely have to move the Distributor gear a notch over, but that's not an issue. Just need to know where to put timing mark for now.

While breaking her in, I can use timing light, or as someone suggested go by ear and just get her close for now. My main goal during break in I realize is running her 15-20 min and keeping RPM's in the correct range.

I've read and printed off a PDF or two talking about timing, etc and I see that most carb engines like 34-36 BTDC. I'm not really certain my timing mark goes that far, but I did read about how to find that. If I'm also not mistaken a dial type light I can set for that and it'll just put me at the 0* mark when on!

Am I correct, that I want to also plug the distributor timing port UNTIL after break in and until after I get the engine as close as I can without using that advance? If so I'll also need to plug the full vacuum port on carb, which I'm planning on using for distributor, unless it should come off the manifold directly....again, I think someone said carb is fine, just not to use the timed port. The carb is an Eddy 1405.

[GASoline71]

Once you get it started and you wind it out to 2,500 RPM's or so for the 20-30 minutes... don't adjust anything during that period. Just get the cam broke in first. Then you can set the timing and all that other malarky.

You just need it running and brought up to RPM immediately after initial light off. Setting the timing advanced a bit will aid in getting it started and running. You can set the timing mark on the balancer to around 10 or 12 degrees on the timing tab.

Also make sure there is fuel in the bowls of the carb so that way you don't have to wait for the fuel pump to prime the carb as the engine cranks...

Gary

[garyd1961]

Back you balancer timing mark back 12 degrees and then point your rotor button directly at the #1 terminal. This is how I do it and it works for me.
Sounds like you have your distributor in correctly.

[MASTERBrian]

Thanks! That's exactly what I wanted. My timing light also has a dial so when time comes to time it, I'll set to 32ish and start playing with it. At least I think that's where I think I read it should be. I'll also plug the other vacuum on carb and HEI until I get her broken in.

[cadillac_al]

I would plug the vacuum advance in and once it starts, turn the distributor until it is running smoothly and leave it alone until the cam is broken in. Timing doesn't have to be perfect at this time. Hopefully your carb is already set up. It is hard to break in an engine with a brand new carb that may need some adjusting. You want to start it and get it up to speed and running fairly smooth within 5 seconds. You'll be fine.

[MASTERBrian]

The carb was a previously running carb that I picked up and rebuilt, but I agree hopefully she's good to go.

[crazy longhorn]

If you roll#1 tdc, comp stroke, then advance 12-14 on the scale...drop the dizzy, & route your wires. On an HEI, turn the dist CC, untill the star lines up. it should lite right off.At this point, I would not worry about the vac advance, just get a little heat in to break the cam in(2200-2500 rpms), for 20-25 minutes. then, you might change the oil filter/add that 1 quart, that the filter takes....keep the revs down, not over 4000, in the first few miles (this will be a hard one)! There is no performance mill , that I ever assembled that did not see 5000-5500, around 200 miles...for a spurt Longhorn

[MASTERBrian]

Originally Posted by crazy longhorn

If you roll#1 tdc, comp stroke, then advance 12-14 on the scale...drop the dizzy, & route your wires. On an HEI, turn the dist CC, untill the star lines up. it should lite right off.At this point, I would not worry about the vac advance, just get a little heat in to break the cam in(2200-2500 rpms), for 20-25 minutes. then, you might change the oil filter/add that 1 quart, that the filter takes....keep the revs down, not over 4000, in the first few miles (this will be a hard one)! There is no performance mill , that I ever assembled that did not see 5000-5500, around 200 miles...for a spurt Longhorn

Dist, should be all set. I think timing at Mark is set to 12°, vac advance on dist is hooked to full vacuum on front of carb, should I leave that alone or unhook and plug the carb inlet?

You wouldn't drain all the oil, just the filter? It'll be a couple of weeks before she's road ready, still have suspension to iron out.

Tomorrow is planned go day. I still need to hook up aux fuel tank as mine is still removed to get rust out and seal. I'm using one of those old metal boat aux tanks. Any reason I can't prime system with the primer bulb and then run off that track with bulb attached?

[crazy longhorn]

Originally Posted by MASTERBrian

Dist, should be all set. I think timing at Mark is set to 12°, vac advance on dist is hooked to full vacuum on front of carb, should I leave that alone or unhook and plug the carb inlet?

You wouldn't drain all the oil, just the filter? It'll be a couple of weeks before she's road ready, still have suspension to iron out.

Tomorrow is planned go day. I still need to hook up aux fuel tank as mine is still removed to get rust out and seal. I'm using one of those old metal boat aux tanks. Any reason I can't prime system with the primer bulb and then run off that track with bulb attached?

You should be good to go, on the timing On the oil, the 1st 30-50 miles, I just do the filter & add to fill...(let the moly paste on the camshaft work). After a little break in time, I would change oil & filter (50 miles).....oil is cheap, compaired to what it cost you on that build longhorn

[MASTERBrian]

Ok, vacuum advance is currently hooked up. I had the engine set at 12°BTC. I got through the break in process, but she was a little out of time. I've now set the timing light to 32°BTC, and run the motor. I adjusted the distributor until the timing mark was at 0° and she seems to idle nicely around 1000, but starting and turning off are a little rough.

Any pointers here? I've read some things that seem to say leave vacuum advance unhooked, others seen to say hook it up.

I don't think it masters for this but cam is advanced 4° at the chain.

[donut]

Unhook and cap the vacuum while setting the timing, then re-connect. The idle may jump when the vacuum is re-connected, just drop the idle down.

[geezer#99]

Originally Posted by MASTERBrian

Ok, vacuum advance is currently hooked up. I had the engine set at 12°BTC. I got through the break in process, but she was a little out of time. I've now set the timing light to 32°BTC, and run the motor. I adjusted the distributor until the timing mark was at 0° and she seems to idle nicely around 1000, but starting and turning off are a little rough.

Any pointers here? I've read some things that seem to say leave vacuum advance unhooked, others seen to say hook it up.

I don't think it masters for this but cam is advanced 4° at the chain.

So now you're at 32 total, so that leaves you at maybe 8 initial if you have an unmodified distributor.
With your set up you need way more initial and adjust your mechanical.
Your 1000 rpm idle is too high. You're likely kicking well into the mechanical timing.
You need to get the idle down closer to 750 rpm.
Leave your vac pot unhooked until you get your initial timing, mechanical timing and total timing worked out.

[MASTERBrian]

Originally Posted by geezer#99

So now you're at 32 total, so that leaves you at maybe 8 initial if you have an unmodified distributor.
With your set up you need way more initial and adjust your mechanical.
Your 1000 rpm idle is too high. You're likely kicking well into the mechanical timing.
You need to get the idle down closer to 750 rpm.
Leave your vac pot unhooked until you get your initial timing, mechanical timing and total timing worked out.

Where should I get that initial with the advance unhooked? Then I guess I need th figure out how to mess with that.

[whytry85]

I usually shoot for somewhere around the 12* initial...

this is how I was taught to set timing on any sbc and make necessary tweaks from there to alleviate any spark knock or detonation you may experience.

https://www.google.com/url?sa=t&rct=...kBsd8jkVNFEUXg

[geezer#99]

A little reading for you.
http://www.badasscars.com/index.cfm/...d=76/prd76.htm

[whytry85]

Originally Posted by geezer#99

A little reading for you.
http://www.badasscars.com/index.cfm/...d=76/prd76.htm

Good info right there!!

[MASTERBrian]

I agree that's great info and I think she's more dialed in, just have to get idle down.

@ 3500rpm, I'm at 0° with light set to 36. Now, IF I hook up the advance, I have to figure out how to set that.

Thanks again

[geezer#99]

While 36 degrees all at 3500 rpm is great for a bone stock sbc it's not what you want for yours. Your heads, cam and compression dictate maximized initial with minimum mechanical and reduced added vac advance.
You can run it like you have it but you're only likely loosing 50 hp.

[MASTERBrian]

Originally Posted by geezer#99

While 36 degrees all at 3500 rpm is great for a bone stock sbc it's not what you want for yours. Your heads, cam and compression dictate maximized initial with minimum mechanical and reduced added vac advance.
You can run it like you have it but you're only likely loosing 50 hp.

I set it according to the link you attached, didn't I? Where would you put it?

[geezer#99]

No!!
Read the 6th paragraph.

[MASTERBrian]

Originally Posted by geezer#99

No!!
Read the 6th paragraph.

I've read that several times. I'm not sure if I'm missing something OR if I'm relaying it incorrectly.

He says in the 5th paragraph to ruin rpm at 3500 to get total timing. Then in 6th he says you only want about 10 from the distributor, I'm honestly not sure how much mine has, BUT I think I am gathering hours to figure that out. So if 10 is ideal from mechanical weighs in distributor, then at idle I should be around 26....correct? So if I set the dial to 26 @ idle and get 0° @ balancer, I should be golden....right?

I'll re-read again later, I've been out playing with the front suspension.

[geezer#99]

Originally Posted by MASTERBrian

I've read that several times. I'm not sure if I'm missing something OR if I'm relaying it incorrectly.

He says in the 5th paragraph to ruin rpm at 3500 to get total timing. Then in 6th he says you only want about 10 from the distributor, I'm honestly not sure how much mine has, BUT I think I am gathering hours to figure that out. So if 10 is ideal from mechanical weighs in distributor, then at idle I should be around 26....correct? So if I set the dial to 26 @ idle and get 0° @ balancer, I should be golden....right?

I'll re-read again later, I've been out playing with the front suspension.

Sure you might be golden, but does your motor like that.
Take those numbers as suggestions.
You need to find out what your combo likes. Advance the timing until it pings or is hard to crank when hot, record that number and then set your mechanical timing to add the needed amount to equal 36 degrees all in by 3200 rpm.
So if your motor likes 18 you need about 18 mechanical. If it likes 16 you need 20 mechanical.
Leave the vac advance plugged off until last.