Motor back together, first start, goofy idle timing advance

[Screaming Metal]

Hahaha...nice pic of distributor innards...sweet. Missing springs...thats kinda scary. Anyway, go fancy if you want, but remember the KISS theory, usually the best option is often the simplest....Just sitting here, drinking a cup of coffee, eating a piece of pizza and checking in...
Its your car, you gotta be happy with it, but a MSD w/6al is a great street system. Hard to beat

 

[Lee_in_KC]

OK, I am totally baffled, now! Just stabbed the new distributor... new version of the same one I had before. Pre-set what looked like 10* to me. Turned on the fuel pump to fill the newly overhauled carbs. Checked the pump squirters for flow. Checked for stuck needle valves. All good. Cranked it and it fired within one revolution. Idled a little ragged. Opened up the idle air screw to get the idle up into smooth territory... about 1200. Let it warm up, then checked the timing... 35 frickin degrees!!! Backed down the timing to where it got ragged again, still 25 degrees!! Ran it back to 30 degrees, then backed off the idle air screw completely so it was idling only on the idle mixture screws... about 800 and pretty ragged. Richened up the mixture about half a turn on all four mixture screws and it smoothed out to it's usual rumpity cam idle... advance still at 30 degrees. I just don't understand what is going on.

 

[2old2fast]

Same damper as before ? Same timing pointer ?
dave

 

[Lee_in_KC]

Yes, same everything. I'm going to break out my my CarTech book on performance ignitions and re-educate myself!!

 

[Indycars]

Looks like 2o2f is trying to get you to confirm TDC. The outer ring on the balancer may have shifted.

You won't know for sure about your timing until you confirm TDC on the balancer.

 

[Lee_in_KC]

The outer ring on the balancer may have shifted.

Indy, check the first page of this thread to see a picture of my timing indicator set-up.

 

[Indycars]

OK, I see it, what point are you trying to make?

 

[Lee_in_KC]

My point is, I don't understand why a motor that idled fine at 18* advance before rebuild now wants to idle at 30*+ after rebuild with all the same parts and set-up except for a newer version of the same block I had before?!?!?

 

[2old2fast]

I'll go out on a limb here [probably shouldn't] the old block had an internal water leak & there was evidence of an oil leak in the plenum area , is it possible that you had a vacuum leak before that was affecting the idle/mixture & now with things sealed up you're seeing different results ??
dave

 

[old round fart]

My thoughts exactly.

 

[fletcherson]

Bottom line, you are talking about two different engines. You need to forget about trying to match or run like the other one and figure out what's going on with this one. No offense, I have worked on cars since the late 70's and still run across one that fools me once in a while. I would start from the beginning and recheck everything from tdc, distributor installation, compression, firing order, balancer, be sure that the tdc on the pointer is actually tdc, valve adjustment, vacuum, etc. a vacuum leak can drive you crazy and cause weird timing issues. I think I remember you saying that you degreed the cam, so the timing set timing marks shouldn't be an issue, but it would t be bad to at least verify the valves are closing when they should via removing a valve cover. That's my best advice. Something that stood out to me was that you said it idled differently with the same cam, you didn't get the expected lopy idle... That infers cam timing issues, but could be a vacuum leak. After you degreed the cam, did you look to see how close it was to the actual timing marks on the timing chain? I remember on the old dual point distributors, they instructed to advance all of the plug wires by one tower, after installing it, and setting the initial timing, but I think that was to make up for the loss of the vacuum advance. I don't remember anything like that on newer electronic distributors. I can't think of anything in particular off hand that would cause that, unless something just isn't right. Please don't think I am being condencending or anything, I just don't know what to tell you other than to double check everything. Don't assume anything.

 

[PotvinGuy]

Lee, grasping at straws here, but does the new dizzy have vacuum advance? And what is make and which springs are in it?

 

[one finger john]

Go back to basic basics. Establish that you have a true TDC, as indicated by the balancer/timing mark.
Put the heaviest distributer springs in the distributer.
If the distributer has a vacuum advance can, plug it at the can and at the vacuum source.

Something sounds a tooth off cam (?) or distributer (?).

John

 

[Lee_in_KC]

It was 76* degrees here yesterday afternoon... today it's 33!!! Too cold to work on the car today. But I'll answer some of the questions from you guys.

Dave, I think it's more likely I have a vacuum leak now rather than before. Yes, there was a little coolant getting into the crankcase before, but never enough to discolor the oil. Yes, I had a bad seal between the intake and heads and oil got into the cylinders. May or may not have acted like a vacuum leak.

Fletch, I realize it's not reasonable to expect the "new" motor to behave exactly like the old one, but it seems like it ought to be closer. I'm not trying to match them up, I just want to understand why there's so much difference. Don't most SBCs idle in the teens to low twentys? If it really wants to idle in the low 30s, what am I going to do about the mechanical advance? With the blower, I certainly want to stay away from detonation!!

I did degree the cam very carefully, rechecking everything as I went. I have a video called "Understanding Cams and Valve Trains" by Wayne Partridge, who is a pretty well known engine builder and racer out of Wichita. I watched that thing so many times I pretty much have it memorized!! I set TDC with the cam in and the heads off, using a piston stop. With the timing gear dots lined up the cam came in 2 degrees advanced, which is fine with me as I want the oomph on the low end. After setting TDC on the compression stroke and marking the timing indicators, I never touched the crank again during assembly until cranking the motor for the first start. Unless Dave's gremlins snuck in and changed it, it should still be dead nuts, but I am going to pull a valve cover and check it again (when the weather warms back up!!).

I was able to get the lopey idle back by backing off the idle air screw and messing with the idle mixture screws. I did a partial overhaul of the carbs, mainly just cleaning all passages and replacing gaskets. I did remove the idle mixture screws to check the seating services and blow out the passages. I tried to count the turns when I took them out so I could put them back the same way, but I don't think I got them right. Once I got the idle smoothed out with the mixture, I could back down the ignition advance about 5 degrees to about 30.

Kerry and John, the distributor is a brand new MSD Pro-Billet magnetic trigger... MSD 85551 Chevy V8 Pro-Billet Distributor - MSD Performance. No vacuum advance installed. I used one strong spring and one medium spring to get the same curve I had before. I revved up the motor a bit and could see the mech advance was working. I didn't rev it very high, as it did not sound right. I'm running cheapo block-hugger headers with no mufflers while I tune on the motor because I just had my roadster headers re-coated and don't want to ruin them (again!). The exhaust is so loud and can't hear the mechanical noises from the engine. Might have gotten a little detonation for a a couple of seconds. I'm going to pull the plugs and see what they look like.

When temps come back up in the garage, I'm going to go back through all the basics, as you guys suggest.

 

[HenrysT]

Do you have records of your old motor? Maybe your old motor had it's cam retarded. Did you build that one too? Was the timing marks correct on that one?

 

[Lee_in_KC]

Henry, I had the short block built to my specs. The cam was installed with the short block. I did not degree the cam before completing the motor, so I don't know for sure where it came in. All I know is it ran really well upon completion. It idled at 18 degrees advance. The mechanical advance came in around 1800 and was all in by 3200 at 35 degrees. Never had a lick of trouble with the motor until I pulled it apart to find out why I had so much blow-by. Go back and read the thread that I linked in the first post in this thread.

 

[one finger john]

Lee, something does not sound right in your description of how the present engine is assembled and tuned.
It shouldn't be rattling right off idle (you said it hasn't been driven yet so I have to assume that the rattle is caused by jazzing the throttle from an idle.)
All descriptions of the "old" engine are moot, useless and a waste of time. Put it out of your mind and never refer to it again, ever.
You received the distributer and you just stabbed it in. Never sent it to a distributer shop and had all the "stock" settings verified. Was there a card included with the distributer that said what springs were in it? Did that card say how much total advance was built into it ? Was that verified ?
Also, please pull the plugs and show them to us.
The engine should idle at a steady 1200 rpms. It shouldn't hunt or cycle. It should not need as much advance as is in it at the present. Put some real mufflers on it so you can hear what it is doing. Quiet ones. Push it outside when diagnosing. It shouldn't have detonation, pre-ignition, or death rattles off idle. It shouldn't pop, rattle, bang, hesitate, or have pre-ignition. Something is wrong with the tune up of your brand new engine. Something very basic. And you are not diagnosing it properly.
Hell, pull the blower off and replace it with a four barrel. A four barrel that is a know good piece that you do not have to monkey with. And pray that you have not washed the cylinder walls down and ruined a set of rings.

It is just an engine with a RV cam with a supercharger on it. A supercharger that should not be building any boost at idle. A regular ol' stock engine with an RV cam. That, with a four barrel on it, could go into a tow truck.

John

 

[fletcherson]

Lee, something does not sound right in your description of how the present engine is assembled and tuned.
It shouldn't be rattling right off idle (you said it hasn't been driven yet so I have to assume that the rattle is caused by jazzing the throttle from an idle.)
All descriptions of the "old" engine are moot, useless and a waste of time. Put it out of your mind and never refer to it again, ever.
You received the distributer and you just stabbed it in. Never sent it to a distributer shop and had all the "stock" settings verified. Was there a card included with the distributer that said what springs were in it? Did that card say how much total advance was built into it ? Was that verified ?
Also, please pull the plugs and show them to us.
The engine should idle at a steady 1200 rpms. It shouldn't hunt or cycle. It should not need as much advance as is in it at the present. Put some real mufflers on it so you can hear what it is doing. Quiet ones. Push it outside when diagnosing. It shouldn't have detonation, pre-ignition, or death rattles off idle. It shouldn't pop, rattle, bang, hesitate, or have pre-ignition. Something is wrong with the tune up of your brand new engine. Something very basic. And you are not diagnosing it properly.
Hell, pull the blower off and replace it with a four barrel. A four barrel that is a know good piece that you do not have to monkey with. And pray that you have not washed the cylinder walls down and ruined a set of rings.

It is just an engine with a RV cam with a supercharger on it. A supercharger that should not be building any boost at idle. A regular ol' stock engine with an RV cam. That, with a four barrel on it, could go into a tow truck.

John

That was the point I was trying to kindly make, there are too many possible variables between the two engines, like the fact that we have no clue where the cam was degreed in the old one, different distributor, and he worked on the carbs. Those aren't small things to change when tuning an engine. I understand his thinking about what it should do based on what the old one did, good reference material, but all things aren't the same now. For all we know, whoever built the old engine may have retarded the cam to prevent detonation, expecting the blower to make up for the lag....(?)

 

[Lee_in_KC]

Here are my plugs. They are definitely sootier than when I put them back in on re-assembly. These plugs have a couple thousand miles on them and were nice and dry and tan when I pulled them on dis-assembly last fall.

Going out to check TDC right now.

 

[2old2fast]

You may be on to something , guy on another forum was having a problem similar to yours , [excessive timing/poor running , his turned out to be carb related....only other thing I turned up was that some timing lights can't "read" the MSD multi-spark correctly..
dave