Timing Engine - To What Degree

[camaro1969]

I am timing my SBC, since it has a lot of aftermarket parts, i cant really go to a spec book and see what i should time it to. I was hoping to get you thoughts. :cheers:

Engine specs below

SBC 350, Th350 Auto, 12 bolt rear 3.07 gears, 15 inch bfgoodrich t/a radials...

Cam:
Comp Cams #249-CL12-242-2
Xtreme Energy XE268H Hydraulic Flat Tappet Camshaft
Lift: .477''/.480''
Duration: 268°/280°
RPM Range: 1600-5800

Other:
1479H keith black pistons .30
139 piston rings
CLE-CB663P rod bearings
CLE-MS909P main bearings
CCA-817-16 compcam lifters
SLP-260-1000 gasket kit
CCA-981-16 compcam valve springs
CCA-1412-16 compcam roller rocker
ARP-134-6003 arp connecting rod bolt
Non electronic distributor or electronic ignition

[ProdigyCustoms]

We got everything but cylinder head info which is probably the most important info of all.

If it has factory heads, I would time it at 3000 RPM at 38 and then blip the throttle up from these and make sure it is all in at 3000RPM. And then I would see where it is at ldle (14-16 or so it should be)

If it has killer aftermarket heads it may like less timing, mabe in the low 30s.

[ccracin]

I think Franks got it for you. If it's not all in by 3500 for sure work on it. I like 3000 with good gas, but will take 3500 with crappy gas. My .02. Good Luck.

[Vegas69]

My new engine made the best power at 34. I'd error on the side of caution until you chassis dyno. 34-36 total and you won't burn it up.

[camaro1969]

factory steel heads..

since i have a rowdy cam, should i be idling aroud 18-19 btdc?

When i have it too far advanced, my flexplate kicks back, and has already ruined one starter!

My vacuum advance on my distri is plugged for now, until timed

so at 3000 RPM around 38, i should have an idel around 15?

[Vegas69]

Total timing is your main concern. If it has a vaccum advance, you need to detach it from the distributor and plug in off. You need to rev it until it quits gaining advance. Changes can be made to initial timing if you can't achieve a clean idle or have a stumble. I'd go 34-36. More is not always better.

[ccracin]

Total timing is your main concern. If it has a vaccum advance, you need to detach it from the distributor and plug in off. You need to rev it until it quits gaining advance. Changes can be made to initial timing if you can't achieve a clean idle or have a stumble. I'd go 34-36. More is not always better.

Amen!:thumbsup:

[GregWeld]

Vic ---

They've got it right in the above posts -- except I would ADD some info...

A distributor has "X" amount of advance built into it. Since we don't know what you're using and or whether or not it's been modified etc.... "WE" don't know how much advance your distributor has... or doesn't have.

So setting it at 34* or 36* revving the motor up -- to 2500 or 3000 rpm -- will (should) max out your TOTAL advance (minus the vacuum advance since that is not being used at this point).

Okay -- when you drop her back to idle -- you'll note with your timing light - what that is at.

Lets say your distributor is bone stock - and you set it at 36* per the above instructions.... and at IDLE you're at 10* (so your distributor would have 26* of advance built in)..... well.... that might not be enough advance at idle given your "roudy" cam. I'm going to ASSume that your idle is around 800 rpms... This is just INFO that we need to diagnose and to help you figure out what's going to work for you.

An MSD distributor (I'm using this because I'm familiar with them) has advance "stop bushings" that come with them. I personally use the 18* stop bushing in mine... because that gives me 18* of total advance -- so if I set the engine at 3000 RPMs -- at 36* -- then my IDLE is going to be 18* less than that - or idle timing of 18* and that works well with a roudy cam.

NOW ---- there is also the RATE of advance.... and you can build yourself a little chart using a piece of paper showing you the RATE of advance that your distributor has:

Starting at idle - write down the advance
Bump the motor up 500 RPM - check the timing and write that down
Ditto - another 500 RPM - make note of the timing
Go 500 RPMs at a time -- until you've reached the MAXIMUM timing

This is all easiest using a DIAL BACK timing light....

Now with your "chart" you just built - you can see the rate of advance.... This is important because it has a lot to do with how the motor will perform... not fast enough rate and the motor is a dog -- too fast and she'll ping...

MSD's come with different springs -- and they have various charts showing different rates of advance -- you choose a "rate" based on your info of the car - and use the combo of springs in the chart that matches your application. It ain't rocket science and you can get 'er pretty close using some common sense and "our" help.... there's lots of guys on here with the experience to get you going right.

If you have a stock distributor -- posting up your "RATE" of advance -- Your total timing - and your idle timing ---- "we" can look at those results and help to guide you how to best proceed.

But for right now - the total timing has to be set -- because you can damage an engine with too much timing (or too little but too much is worse)... So go do your work and post up the results.... and we'll all be able to see what's going on. :cheers:

[Vegas69]

I wouldn't be in a hurry to get rid of a vaccum advance. They work great for extra timing and efficiency at cruise. Greg is right, more initial is normally a good thing to increase carb signal. I have a custom bushing in my MSD that nets me 23 degrees initial. That cam doesn't look roudy enough to be a concern. I'd say you have really good engine vaccum and most of this talk should go in one ear and out the other.

[GregWeld]

Todd --

You're right on the cam. I used his description on the "roudy" part... 'cause a XE268 ain't roudy...

But Vic has had "issues" with this motor all the way thru -- or I should say - starter issues and getting this thing running...

Half the time I've helped someone - they've gotten a motor from somewhere - and they really don't know where the balancer came from (what it's off of) - or the timing cover... whether it's been checked against TDC... and they've no idea what the distributor is out of. Could be out of a truck for all they know... so this is the routine I go thru when things are "unknown".

Just had this with a buddy here - couple drunks put a "motor" in - he had more issues than you could write about. Bet he spent 1500 bucks on "tune ups" - and it just was a dog. I finally asked him if ANYONE had actually checked to see if the timing marks everyone was using were indeed what they said they were. They were off about 8*.

I had to do the old --- pull all the plugs -- put in a piston stop. Roll her forward make a mark - roll her back - make a mark - in the middle is 0*...
WAY OFF... Woke the old pig right up getting the timing where it was supposed to be.

[ProdigyCustoms]

A piston stop to find true tdc is you best friend right now. Like Greg mentioned, if the balancer has spun and the TDC mark is off, everything your seeing could be a lie!

As for too much initial and starter kick back? My street racer is locked out at 39 and starts effortlessly hot, cold, whatever. And I run a little bitty [email protected] / [email protected], .686 / .686 on a 106LC! Now thats a hell raiser!

[Pantera EFI]

True, when I "tune" the Spark Instant, I first REMOVE (lower) spark advance, watch for a major power reduction and STOP the retarding, then I add back 1 or 2 degrees.

Now, a "tip" for understanding the Spark Instant difference in an engine with "crank-fire" DIS vs "cam-fired" Distributed Ignition.

Lets state a know good value of 36 degrees Advance with the Distributor. (Distributor Triggered)
The same Spark Instant event would take place with a 32 degree Advance amount WHEN a Crankshaft Ignition is fitted. (Crankshaft Triggered)

This result is from Timing Chain/Timing Belt stretch.

Lance

[GregWeld]

True, when I "tune" the Spark Instant, I first REMOVE (lower) spark advance, watch for a major power reduction and STOP the retarding, then I add back 1 or 2 degrees.

Now, a "tip" for understanding the Spark Instant difference in an engine with "crank-fire" DIS vs "cam-fired" Distributed Ignition.

Lets state a know good value of 36 degrees Advance with the Distributor. (Distributor Triggered)
The same Spark Instant event would take place with a 32 degree Advance amount WHEN a Crankshaft Ignition is fitted. (Crankshaft Triggered)

This result is from Timing Chain/Timing Belt stretch.

Lance


Lance ---

Are you sure you're answering the right thread? This guy doesn't have EFI - doesn't even have an electronic distributor... so not sure what you're responding to here.

[camaro1969]

Todd --

You're right on the cam. I used his description on the "roudy" part... 'cause a XE268 ain't roudy...

But Vic has had "issues" with this motor all the way thru -- or I should say - starter issues and getting this thing running...

Half the time I've helped someone - they've gotten a motor from somewhere - and they really don't know where the balancer came from (what it's off of) - or the timing cover... whether it's been checked against TDC... and they've no idea what the distributor is out of. Could be out of a truck for all they know... so this is the routine I go thru when things are "unknown".

Just had this with a buddy here - couple drunks put a "motor" in - he had more issues than you could write about. Bet he spent 1500 bucks on "tune ups" - and it just was a dog. I finally asked him if ANYONE had actually checked to see if the timing marks everyone was using were indeed what they said they were. They were off about 8*.

I had to do the old --- pull all the plugs -- put in a piston stop. Roll her forward make a mark - roll her back - make a mark - in the middle is 0*...
WAY OFF... Woke the old pig right up getting the timing where it was supposed to be.


LOL.. quite the story, ill be timing tomorrow morning, ill post up results after i do my work.. thanks for the support

[GregWeld]

Vic -- Pick up the pace DB! We're waiting! :rofl: :rofl:

[camaro1969]

awful awful weather, NW hit us hard with winds and constant rain! i have no exhaust, so i cant pull the car out to time! dont expect a peek of sun til THURSDAY!.. ill keep my fingers crossed for some early nice weather.. :willy:

[GregWeld]

Weenie!





It's blowing hard here now and blew all night - and poured rain... :cheers:

[ProdigyCustoms]

Open headers will change everything also. Not so much timing, but carb tuning. Open exhaust will cause a lean condition in a otherwise tuned car, which can cause back fires through the carb that will blow your eyebrows off. Make you think you have a timing issue.

I would not spend too much time tuning without exhaust.

[GregWeld]

Good point Frank....

The ol' back pressure issue. Gee - maybe that's why headers add a good percentage of HP... ya think? :yes:

[Pantera EFI]

Yes, I am correct with my report.

I state that "safety" is BEST.

There are some users that state "add timing to find best torque", this is WRONG !

Now for the "tip", all tuners should have a "starting point" in their mind.
That is the reason I make the CAS/CS report.

Another method to find the correct "Spark Instant" is to record torque over a period of time.
When the torque value drops as time increases, the ignition timing may be too great.

Lance

[GregWeld]

In other words -- VIC -- Set the timing at 36* at 3000 rpm and you'll be fine...

:rofl:

[ProdigyCustoms]

In other words -- VIC -- Set the timing at 36* at 3000 rpm and you'll be fine...

:rofl:

ROFLMAO!

[camaro1969]

I came late from work, and had decent weather, but took Franks advice to not time until after exhaust..

i thought I would do some work, and put my timing tape on, and read the instructions.. i installed tape so that it faces clockwise, so when the tape is on TDC, the numbers to the right are 10,20,30 degrees etc. BUT on my timing tab, the numbers to the LEFT say BEFORE and say 2,3,4,6..

pictures if you have NO clue what i am talking about.... basically what i am saying is, my timing tab has "before" written on it, on the LEFT side of the 0*. Does this mean my timing tab is incorrect? or did i put my timing tape wrong?

http://i361.photobucket.com/albums/oo52/camaro_1969/6DSC01137.jpg

[ccracin]

I came late from work, and had decent weather, but took Franks advice to not time until after exhaust..

i thought I would do some work, and put my timing tape on, and read the instructions.. i installed tape so that it faces clockwise, so when the tape is on TDC, the numbers to the right are 10,20,30 degrees etc. BUT on my timing tab, the numbers to the LEFT say BEFORE and say 2,3,4,6..

pictures if you have NO clue what i am talking about.... basically what i am saying is, my timing tab has "before" written on it, on the LEFT side of the 0*. Does this mean my timing tab is incorrect? or did i put my timing tape wrong?

http://i361.photobucket.com/albums/oo52/camaro_1969/6DSC01137.jpg

I'll take a stab here, but I hope someone jumps on and confirms or says I'm an idiot. I have not used timing tape in the past. My timing light has a knob on it to set the advance and I just use the TDC timing marks. It looks to me like you did it correctly. First, did you confirm you were at TDC with a piston? If so, look at your picture. When you time the engine and advance the timing before TDC the timing mark on the balancer would move to the left. This puts you in the area labeled "before" on your tab. This will in turn bring the numbers on the tape to the left under the tab. You will read the tape comparing the 0 or TDC mark on the tab to the numbers on the tape. For example, if you were to set the timing to 12deg BTDC the 12 on the tape would be lined up with the 0 on the tab and the TDC on the tape would be lined up with the 12 on the tab. So, I think you have it. This is just me reasoning through it. Does anyone second my motion? I hope you get her sorted out soon, time to enjoy. Good luck.:cheers:

By the way, I would really recommend purchasing a timing light with an advance dial. They are so worth the 100 or so bucks.

[Vegas69]

Yep, use the timing tab and your 0 mark on the balancer or your timing tape and your 0 mark on you timing tab. For total timing you will have no choice but to use the timing tape and the 0 mark on the timing tab. Timing is not affected by open headers. Timing is timing. Frank was talking about carb adjustments.

[GregWeld]

Exactly.

[GregWeld]

You are both correct with your report.

[camaro1969]

thank you, thank you, and thank you, lol..

good weather today, i will do what i can tonight, be back with teh results.

[camaro1969]

alright fellas, this is what i got..

at 3000 rpm, i have it at 36* btdc, pushing it down to idle, i am on 18*, with an idle of around 800-900 rpm, this is without advance..

with advance, i idle around 19-20*...

i put it in drive, and dont get a jerk, and runs and starts perfectly now, starts right up without a struggling cranking or bad turn over..

but again, with my car, it isnt right until i get a problem once again! my trans pressure pipe is now leaking. the pipe that leads to my radiator for a cooling..

now question is.. can i block these tubes for the time being, until i get new pipes ordered? I will not be doing an drag or strip racing, just casual driving to and from work during the summer times...

[GregWeld]

Good to hear Vic....

Now --- Make certain your VACUUM ADVANCE is plug into the port with no vacuum at idle... you should have TWO ports (small tube - say 3/16) - one is PORTED (vacuum at idle) and one is UNPORTED (NO vacuum at idle) ----- You want the UNPORTED for your advance. This gives you vacuum only when the throttle blades are "being used" or in other words - you're doing something more than idling. That will / should lower your idle timing back to the 18* - which with your motor - and a street motor - is all you need.

NOW --- Leaking tranny lines -- NO you can't plug them and drive around... you'll burn up your tranny. Just fix it.

[ccracin]

Good to hear Vic....

Now --- Make certain your VACUUM ADVANCE is plug into the port with no vacuum at idle... you should have TWO ports (small tube - say 3/16) - one is PORTED (vacuum at idle) and one is UNPORTED (NO vacuum at idle) ----- You want the UNPORTED for your advance. This gives you vacuum only when the throttle blades are "being used" or in other words - you're doing something more than idling. That will / should lower your idle timing back to the 18* - which with your motor - and a street motor - is all you need.

NOW --- Leaking tranny lines -- NO you can't plug them and drive around... you'll burn up your tranny. Just fix it.


:yes: :thumbsup: Good job!

[camaro1969]

I dont understand the leak, it isnt even leaking from the thread, its leaking from the behind the thread..

the nut is free to moving on the steel pipe, but when mounted to the trans, and threaded to the outflow, it seems as if the leak is coming from the being the threaded nut, and not the thread itself..

i dont think i made sense, i will take pictures and post

[ccracin]

I dont understand the leak, it isnt even leaking from the thread, its leaking from the behind the thread..

the nut is free to moving on the steel pipe, but when mounted to the trans, and threaded to the outflow, it seems as if the leak is coming from the being the threaded nut, and not the thread itself..

i dont think i made sense, i will take pictures and post

Sounds like you might have a bad or cracked flare. Get some photos.

[camaro1969]

got the leak fixed, i dont know how, but i loosened it, and retightened it, seems like it got a better thread lock then before. I didnt put teflon tape on it, should i?

I filled up my trans with atf, and go enough for the convertor to get the trans into gear, and move the car back and forth,... so that was yesterday.. i was going to take teh car around the block just to see how it runs, but when i start it, i hear a LOUD popping, scares the crap outta me.. could this be a misfire? or just gas vapor popping in my headers? It is open exhaust right now, mufflers are not on yet...

suggestions? I heard 3 pops before i turned her off...ran it for like about 20 seconds, and reved it to about 2..

[Vegas69]

It's not uncommon to need to loosen a flare fitting and re seat it.

I am assuming your popping is out the exhaust? That would be caused by excess fuel in the exhaust. Did you foul a plug playing around with timing and starting it so many times cold?

[camaro1969]

It's not uncommon to need to loosen a flare fitting and re seat it.

I am assuming your popping is out the exhaust? That would be caused by excess fuel in the exhaust. Did you foul a plug playing around with timing and starting it so many times cold?

wow, i must admit you know your stuff!

I went and check with the wiring, and i noticed the problem YOU suggested right away, number 8 cylinder plug was off the spark plug! I had a few guys helping me while i was fixing my leak with the trans (had to remove the header), so we removed the number 8 plug... that doesnt damage the piston or the cylinder does it?

Assuming it was squirting gas into that cylinder and not firing, and therefore when the exhaust stroke occurred, sucked it up and popped in the header...

Thats Todd, smart ass!

[GregWeld]

If he hadn't told you that -- I would have.... :rofl: :woot:

Glad you found it.

[Vegas69]

Hey man, I've been around the block. Luckily not as many times as that old man Weld. :D The cylinder will be fine. Just screw in a new plug and take her for a ride. You can pull your dipstick and see if the oil has a gas smell. If you ran it an extended period of time, an oil change isn't a bad idea. Doesn't sound like you did.

[camaro1969]

video coming soon of its first take off!:D