Motor back together, first start, goofy idle timing advance

[Lee_in_KC]

This is an update to my earlier saga here... Sudden Increase in Blow-by

Finally got the motor fully back together and back in the car. Had to get a new seasoned block as the old one had two cracks in the water jacket inside the lifter valley. Upgraded to forged pistons and better rods, otherwise the motor is exactly the same as before I pulled it out.

So, I started it up for the first time today. I put in about 10 degrees of advance when I stabbed the distributor (MSD Pro-billet with a 6AL ignition box). Cranked the motor with a remote button while tending the carbs and the distro. No fire. Added a little advance and it started hitting a little. Added a little more advance and it started. With the blower, this motor runs very rough on a cold start until some heat is built up. I used the idle screw to hold the throttle open at about 1200 rpm and adjusted the distributor to get it as smooth as I could and let it warm up. I checked the timing and it was at 30 degrees!! I backed it down a little and it started running rough again. So I put it back to where it was smooth again and let it run for about 15 minutes to break in the new ring job. After it was showing about 150 water temp I tried backing down the advance again and it went rough within about 5 degrees of retard.

When I built the motor, I spent a lot of time degreeing the cam and making sure I had TDC set dead nuts when I set the timing indicator. I have BDS's shpanky degree indicator set...

Using a yellow paint pen I marked TDC and the 10, 20, 30 and 35 degree ticks.and the tip of the pointer on the indicator. I have MSD's timing light which accommodates the "multi-spark" feature of the ignition box. I am highly confident that what the timing indicator is telling me is accurate +/- a degree or two. I would bet a paycheck on it!

So why is this thing wanting to "idle" at 30 degrees advance?!?! 1200 rpm is 200-300 higher than normal idle (because of the lumpy cam), but the mechanical advance shouldn't be kicking in that low (no vacuum advance installed).

 

[railroad]

I had something similar once, due to my own tinkering. I was trying to increase the mech adv rate in the dist and got too soft spring rates. The mech adv would not pull down to zero mechanical with the engine stopped, but would come up to total advance about 2600 rpm. Long story short, twist the rotor button and see what kind of resistance you feel. If you have dealt with this before you should be able to tell if it is too loose. I know you have confidence in the timing tab being correct, but stranger things have happened. Any chance your timing light has the adj advance dial on it. Mine works on MSD and has the dial. Just went through a new crate engine timing tab being off. We did not have a confirmed TDC. Used the thumb on the #1 plug hole and turned the engine with a pull handle, stabbed the dist and the thing fired up in less than half a turn. Strange, I had to turn the timing light dial 30 degrees to get the timing marks near the pointer/tab. Also a vacuum leak can do similar things. Glad to see you get it back together.

 

[one finger john]

Quick verification - you do not have an electronically controlled distributer, correct? Manual advance & vacuum advance ?
Put the heaviest advance springs in and see what it does. If that doesn't work, reinstall the distributer advanced a tooth and see.
Spark plug wires in the correct order?
Was it blowing black smoke at idle? What do the plugs look like? Nice and clean? Hollys or Edelbrocks ?
Are you running an advance retard box and did you wire it correctly ? Did I mention distributer rotor phasing, was it checked ?
Bring it up to tdc firing with the rotor pointing directly at the no. 1 electrode (just to verify).
Pictures would be nice.

Let us know what is happening - we care about your horse power.

John

If all else fails, blame any problems on the guy that helped you.

 

[PotvinGuy]

I'm confused. My SBC loves to idle at 35 degrees (20 initial + 15 vacuum). Does that seem somehow wrong? If I turn it down, the idle gets rougher.

Or are you saying that you appear to set it lower, and it reads higher?

 

[fletcherson]

Did you run a vacuum advance before? I would time it to where it is happy and let it run, check the plugs and exhaust temps and not worry about the light. They need more initial timing if you aren't using a vacuum or electronic advance. Smokey used to advocate locking out the distributor,,advancing the timing, and installing a toggle switch seperate to power the coil so the engine would turn over before firing to start, otherwise the initial timing was too advanced to allow it to turn over.

 

[PotvinGuy]

When I had BDS freshen my 6-71 and told them it was on a SBC crate motor, they snorted and said to just lock the advance at 35 and forget about it. But kinda hard on the starter, and I wanted to be a bit more refined re timing. I use a Mallory MaxFire dist which is all electronic, no springs, bushings, etc. You can pick from 6 speed and 2 vacuum curves, or connect a laptop and design your own curves. Also has boost retard.

 

[fletcherson]

When I had BDS freshen my 6-71 and told them it was on a SBC crate motor, they snorted and said to just lock the advance at 35 and forget about it. But kinda hard on the starter, and I wanted to be a bit more refined re timing. I use a Mallory MaxFire dist which is all electronic, no springs, bushings, etc. You can pick from 6 speed and 2 vacuum curves, or connect a laptop and design your own curves. Also has boost retard.

The hard start thing was what I was referring to with the Smoky story. He advocated the same thing with the locked timing, and used a seperate coil switch. The motor was already spinning before it fired. you should be able to imitate the vacuum advance electronically. The initial advertised timing is intended to be set with no vacuum advance, and at a low enough RPM that the centrifugal advance isn't activated. The vacuum advance is intended to be full advance on most engines under hi vacuum, idle, then drops off at low vacuum under acceleration to control preignition, then the centrifugal advance comes in at the predetermined RPM, the vacuum also comes back some after RPM stabilizes. You likey know this, but that's why it wants the timing at low RPM. Now, I don't know what all mods you have, or what the cam and blower requires for timing, but if it were me, I would look for or create a timing program that imitates that model and fine tune from there, if the locked timing wasn't acceptable. This is where the guys with access to dyno's have the big edge. What's with the blow by? Are you seeing excessive crank case pressure? Is the PCV or whatever evacuation process you have functioning?Are you running moly or cast rings? I've heard of moly rings not sealing if the cylinders were not honed for them. ??? You likely need Screaming Metal to chime in on the blower tune, he knows them well.

 

[fletcherson]

The hard start thing was what I was referring to with the Smoky story. He advocated the same thing with the locked timing, and used a seperate coil switch. The motor was already spinning before it fired. you should be able to imitate the vacuum advance electronically. The initial advertised timing is intended to be set with no vacuum advance, and at a low enough RPM that the centrifugal advance isn't activated. The vacuum advance is intended to be full advance on most engines under hi vacuum, idle, then drops off at low vacuum under acceleration to control preignition, then the centrifugal advance comes in at the predetermined RPM, the vacuum also comes back some after RPM stabilizes. You likey know this, but that's why it wants the timing at low RPM. Now, I don't know what all mods you have, or what the cam and blower requires for timing, but if it were me, I would look for or create a timing program that imitates that model and fine tune from there, if the locked timing wasn't acceptable. This is where the guys with access to dyno's have the big edge. What's with the blow by? Are you seeing excessive crank case pressure? Is the PCV or whatever evacuation process you have functioning?Are you running moly or cast rings? I've heard of moly rings not sealing if the cylinders were not honed for them. ??? You likely need Screaming Metal to chime in on the blower tune, he knows them well.

Ignor my comment about blow by, I just realized that was a different discussion. Sorry.

 

[Lee_in_KC]

Thanks for the replies, guys. Just now able to respond. Before blowing the motor apart as described in the other thread, it idled at 800-900 rpm with 18 degrees initial timing. No vacuum advance installed, purely mechanical. The MSD 6AL iginition box does not modify timing, only creates the multi-spark and has a rev limiter. Mechanical advance was set to start coming in at 1800 and be all-in at 36 degrees by 3200. It ran this way for almost ten years and made a good, strong motor.

When re-assembling the motor, I put it back exactly as it was before except for the new forged pistons and stronger rods. The carbs were not touched, other than draining out the fuel when I took them off. The distributor was not touched, other than to take the cap off to stab it on re-assembly. This is why I expected it to idle at 18 degrees as before. Everything I have ever read says SBCs idle in the mid- to high teens!

So check my logic here. The timing light (it is the simple version, no dial-back or readouts) does only one thing... it senses current in the plug wire and fires a strobe to "freeze" the timing indicators, right? So if I'm right about my degree wheel and pointer being dead nuts, what I am seeing is in fact the number one plug firing at 30 degrees at idle. I set the idle timing at the distributor by ear, not by the timing light. So when I have the distributor adjusted to get the smoothest idle, it ends up being at 30 degrees. That is where the motor now wants to be. The timing light doesn't care what's going on with mechanical or electronic advance... it's just telling me when it senses the number one plug firing.

So I have been thinking, why would the motor now want more timing than before? How about a change in air/fuel mixture? Maybe I have a clogged jet or a stuck needle or something? I checked the exhaust temps and they were are in the 400-500 range. Is that where they should be at idle?

One more bit of news. I pulled the rotor off the distributor to check the mechanical advance set-up. The springs are GONE!! No sign of them. I know they were there when I first set the motor up, because I personally set up the mechanical advance curve, which was working as intended last time I checked it, which was probably several years ago. There is a lot of rust on the metal parts of the magnetic trigger mechanism. I knew about this problem with the early Pro-Billet distributors... MSD has since gone to a vented cap and better sealing of the internal parts. I'm wondering if the advance springs corroded or rusted, fell off, and then fell out when I popped the cap off.

Now some of you are going to jump to the same conclusion I initially jumped to... the missing springs explain the excessive advance! The distributor is going to full or almost full advance on start-up. Yeah, but since I am setting the idle timing by ear I am theoretically backing some or most of that advance out, aren't I?

Well, bottom line is, I'm going to order a new distributor. I think mine is marginal at best. That may or may not resolve the idle timing issue. I probably also need to freshen up the carbs to make sure I don't have a mixture problem. Any other ideas?

Hot-rodding is fun!

 

[one finger john]

See, I told you to blame the guy that helped you reassemble the engine.
Did you pull the plugs to see if it idling too rich (if it is too rich) ?
Is it running with old gas ?
Old gas filter ?
Distributer advance springs were GONE. Vanished, Disappeared. ??? They were there a few years ago ??? Better to blame your helper.
Oh please !!! Somebody (probably a well meaning "mechanic" friend) suggested to remove the springs so it would start easily then go to full advance when it started, therefore bypassing the need to properly wire in a retard switch and do the job properly. "Old speed secret" Jheeze !!! 36* locked out ? I don't know 'bout that either.
Order a computer controlled distributer from MSD, along with a boost retard,(spark box probably already has a plug in receptacle), a couple of AFR wide band set ups (one for each bank, oh boy, two more gauges) and join the 21st century. Maybe a detonation sensor (hydraulic rollers, right?). Oh and get a couple of rev limiter chips while you are at it.

You have a street driven blown sbc. Not a full race engine for 1/4 mile only. Treat it like the street driven, semi-sophisticated engine it is (to be truly sophisticated it would need to be fuel injected).
The fact that you have a light weight, 3000 stall ride covers up a lot of sins. If you haven't washed the cylinders down, you can start to tune this pup and get it to run right.

John

 

[fletcherson]

Thanks for the replies, guys. Just now able to respond. Before blowing the motor apart as described in the other thread, it idled at 800-900 rpm with 18 degrees initial timing. No vacuum advance installed, purely mechanical. The MSD 6AL iginition box does not modify timing, only creates the multi-spark and has a rev limiter. Mechanical advance was set to start coming in at 1800 and be all-in at 36 degrees by 3200. It ran this way for almost ten years and made a good, strong motor.

When re-assembling the motor, I put it back exactly as it was before except for the new forged pistons and stronger rods. The carbs were not touched, other than draining out the fuel when I took them off. The distributor was not touched, other than to take the cap off to stab it on re-assembly. This is why I expected it to idle at 18 degrees as before. Everything I have ever read says SBCs idle in the mid- to high teens!

So check my logic here. The timing light (it is the simple version, no dial-back or readouts) does only one thing... it senses current in the plug wire and fires a strobe to "freeze" the timing indicators, right? So if I'm right about my degree wheel and pointer being dead nuts, what I am seeing is in fact the number one plug firing at 30 degrees at idle. I set the idle timing at the distributor by ear, not by the timing light. So when I have the distributor adjusted to get the smoothest idle, it ends up being at 30 degrees. That is where the motor now wants to be. The timing light doesn't care what's going on with mechanical or electronic advance... it's just telling me when it senses the number one plug firing.

So I have been thinking, why would the motor now want more timing than before? How about a change in air/fuel mixture? Maybe I have a clogged jet or a stuck needle or something? I checked the exhaust temps and they were are in the 400-500 range. Is that where they should be at idle?

One more bit of news. I pulled the rotor off the distributor to check the mechanical advance set-up. The springs are GONE!! No sign of them. I know they were there when I first set the motor up, because I personally set up the mechanical advance curve, which was working as intended last time I checked it, which was probably several years ago. There is a lot of rust on the metal parts of the magnetic trigger mechanism. I knew about this problem with the early Pro-Billet distributors... MSD has since gone to a vented cap and better sealing of the internal parts. I'm wondering if the advance springs corroded or rusted, fell off, and then fell out when I popped the cap off.

Now some of you are going to jump to the same conclusion I initially jumped to... the missing springs explain the excessive advance! The distributor is going to full or almost full advance on start-up. Yeah, but since I am setting the idle timing by ear I am theoretically backing some or most of that advance out, aren't I?

Well, bottom line is, I'm going to order a new distributor. I think mine is marginal at best. That may or may not resolve the idle timing issue. I probably also need to freshen up the carbs to make sure I don't have a mixture problem. Any other ideas?

Hot-rodding is fun!

The thing with the springs being gone is you don't know for sure if or when it's advancing, or if it's consistent. That is the first issue to resolve. Like John said, now is the time to upgrade your ignition. I had a motor give me fits several years ago, I ended up with a MSD timing computer to get it worked out. I went through various springs,,weights, vacuum curves, etc... I could get it to run good, but the preignition... The computer cured it. Do your homework before ordering to make sure everything is comparible, that would be my advice. Also, I try to only change one thing at a time, then see if it changed and how much. I have found changing more, just adds the possibility of more confusion, more variables...

 

[Lee_in_KC]

OFJ, yes old gas and filter. No black smoke. Plugs look great... nice and tan.

When you guys say computer distributor or ignition, which product do you have in mind? I see MSD has an "E-Curve" distributor, and of course they have several programmable ignition boxes. I don't want to get too fancy or expensive. My T ran great for almost 10 years on just the Pro-Billet distro and the 6AL box. Even with the advance (actually retard) springs missing!! Here's a coupla pix of the distributor...

 

[one finger john]

Just had a Snickers and I feel much better.

Just what is your budget? I would call MSD and explain the situation and see what they say. Surprised you didn't catch the distributer before start up. Surprised it ran at all. As a matter of fact, I would change all fluids (engine, trans, and rear diff) and check u joints for wear & play. Also ck. steering box and front end. Make it a Spring tune up. Hmmmm ..... check battery. Ck tires for nails & tread bulges or separations. Are the inner tubes ten years old too ?
Take the car for a hundred mile cruise. Vary speed & load. Take your cell phone & AAA card. That'll shake the bugs out and let you know what's happening.
Ck. axle bearings front & rear.
Ck. and tighten every nut and bolt. Not every nut and bolt you can get to but EVERY NUT AND BOLT ON THE CAR.

I'll think of more.

John

Fresh gas & filter.

 

[Lee_in_KC]

Actually, I've known about the corrosion in the distributor for several years. It was running fine, so I just decided to run it 'til it died. The time has come, apparently.

 

[RPM]

Actually, I've known about the corrosion in the distributor for several years. It was running fine, so I just decided to run it 'til it died. The time has come, apparently.

I'd contact MSD and see if they offer an easy inexpensive fix.

 

[fletcherson]

If it ran good and you liked it, the easiest and cheapest fix would be to repair the distributor. The parts are likely available, if not get the upgrade, whatever it is. I don't want to suggest something new to you, I don't have enough details about your components, or even what the current systems are that are available. Most of the well known companies have tech support staff who will be more suited to match their product to your application. You may be well served to spend some time speaking with a couple of them and compare what they say to your situation.

 

[Lee_in_KC]

I contacted MSD when I first noticed the corrosion. They were aware of the problem and were replacing units under warrantee. Mine was five years out of warrantee. They said they would rebuild it for the price of the parts... $200. I decided to wait it out and go for state of the art when it died.

 

[one finger john]

Ahhhhhh, the plot thickens. Has the car spent most of its time in Florida or Kansas ?

Corrosion that bad usually comes from spending a lot of time under a blue plastic tarp in wet weather.

 

[Lee_in_KC]

You have quite the imagination, OFJ! I built my T in a hangar in Gardner, Kansas in 2006. It has since been to Arkansas, Illinois, Colorado, Ohio, Tennessee, Indiana and Wisconsin. It has never been under a tarp, but rather in my garage next to my daily driver. The corrosion in the distributor was a known problem with the MSDs made in the mid 2000s.

 

[one finger john]

Must be the Snickers.