New Engine, Hard starting, Likes Lots of Advance

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PocketAces

PocketAces

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I recently fired my 273 for the first time. The engine is difficult to start but starts best with the distributor set at approximately 60 degrees advance all in. Once running above idle speed, I can time it back to around 35-40 all in and it will keep running. But when it quits it's hard to get it started again.

I just checked the valve timing and found that the cam is 4 degrees advanced from spec. Spec is intake centerline at 108 degrees ATDC, but I'm measuring 104. Exhaust centerline should be 108 degrees BTDC, but I'm measuring 112.

From what I'm reading, 4 degrees advance should not be a problem, and might actually improve the bottom end. But I wanted to rule it out as a potential source for my hard starting.

Here's the build:

273 with stock heads
Isky E4 cam
9.6:1 static compression
factory AFB carb which was running good when removed 2.5 years ago.
pro comp distributor which was also running good when removed.
 
Did you check to make sure the harmonic balancer "zero" mark is actually correct? When I was a kid I had a Pontiac that was the same as you described and I found that when the position was at TDC the harmonic balancer mark was no where near zero.

BTW: does it run right when you leave the timing advanced? When you check the timing you are doing so with the vacuum advance unhooked, correct?
 
fishy68 said:
Did you check to make sure the harmonic balancer "zero" mark is actually correct? When I was a kid I had a Pontiac that was the same as you described and I found that when the position was at TDC the harmonic balancer mark was no where near zero.

BTW: does it run right when you leave the timing advanced? When you check the timing you are doing so with the vacuum advance unhooked, correct?
Click to expand...

I used a degree wheel and a piston stop in the #1 spark plug hole. The timing mark on the balancer is within 1 degree of actual TDC, but my cam timing measurements were based on the degree wheel which was correctly set at TDC.

My ignition timing numbers are with both vacuum and centrifugal advance and running well above idle (maybe 2000 RPM).

It runs at high speed OK but when I try to slow it down it dies. And it's very hard to start.
 
You are either reading something wrong or something is put together wrong or the balancer has slipped.
 
RustyRatRod said:
You are either reading something wrong or something is put together wrong or the balancer has slipped.
Click to expand...

I've confirmed that the mark on the balancer is correct within 1 degree as I also did when I assembled the motor. I was using degree tape on the balancer so I could measure the full ignition timing. When we turned the distributor to where it would finally start, the all in timing measured around 60 degrees.
 
I am telling you as sure as I am sittin here, something is wrong. I have even put them together myself out of time and bent every intake pushrod. lol It happens. Almost sounds like maybe you have the wires on the cap retarded. You have something wrong somewhere.

Maybe the wrong timing cover?
 
What timing set you have, i have seen two times when crank sprocket was uncorrect, for example, if you use comp 2103 ,there is three "dots" what you can use,○ should be 0-timing(crank key groove top is round ), □ is 4 deg retard( crank key groove top is square), and triangle is 4 degree adv(crank key groove top is triangle,or it should be, but it looks like round). Mopar crankshaft key is square and those two times what i have seen, they put crank sprocket a 4 deg retard, because crank key is square and there is square groove in that sprocket,and it's fit perfectly, so it goes 4 deg ret. This doesn't solve your problems and doesn't fit your discriptions but could that timing set be wrong?
4 deg off is a lot in performance engines(high lift engines without measuring), shouldn't be a problem in stock engine.
Wrong timing cover?, broken balancer (outer ring?)
Hopely you can underdtand what i mean:)
 
What ignition are you running? MSD EG is well known for initial timing LIGHT trigger problems EG
 
Also reverse polarity on the magnetic pick-up will do that, if you are running the Orange box.If you reverse the polarity from what it is now, you will have to reset the dizzy to get the base timing back.
Yes on the MSD.
Your cam timing is not a problem.
The carb might, I say Might, have a low speed issue.
 
dartswinger84 said:
What timing set you have, i have seen two times when crank sprocket was uncorrect, for example, if you use comp 2103 ,there is three "dots" what you can use,○ should be 0-timing(crank key groove top is round ), □ is 4 deg retard( crank key groove top is square), and triangle is 4 degree adv(crank key groove top is triangle,or it should be, but it looks like round). Mopar crankshaft key is square and those two times what i have seen, they put crank sprocket a 4 deg retard, because crank key is square and there is square groove in that sprocket,and it's fit perfectly, so it goes 4 deg ret. This doesn't solve your problems and doesn't fit your discriptions but could that timing set be wrong?
4 deg off is a lot in performance engines(high lift engines without measuring), shouldn't be a problem in stock engine.
Wrong timing cover?, broken balancer (outer ring?)
Hopely you can underdtand what i mean:)
Click to expand...

I have convinced myself that the balancer and the timing tab are correct to within 1 degree.

The timing set is Cloyes True Roller. It has the symbols you've described and if I recall correctly it was installed so the circle marks were aligned when #1 was at TDC. But I guess those marks could be made to line up no matter which key way was used.

Regardless of why, the fact remains that the cam is advanced 4 degrees. The question is whether it's causing my problems or if I should look elsewhere.
 
67Dart273 said:
What ignition are you running? MSD EG is well known for initial timing LIGHT trigger problems EG
Click to expand...

I'm running the eBay distributor that is also sold under the Pro Comp brand name. Not MSD.

The ignition worked well before I removed it from the car. I can't say what the all-in timing was before I took it apart.

By "timing light trigger problems" do you mean that the timing is correct, but the light doesn't give the correct reading?
 
Please dont take this wrong but is your timing lite hooked to #1 wire. I mean 360/8 + 15 = 60. Could be coincidence but I gotta ask.

Also; rotor phasing. If the rotor is too far off the tower axis, the spark can jump to the wrong tower. Then when the advance starts coming in it can jump to the correct tower.

The MSD capacitive discharge system doesnt to like a lot of timing lites. My dial-back lite seems to work on it above 3000rpm. But below that the readings are ambiguous.My old-fashioned non-inductive,non d-b, lite seems to work ok.
 
Btw, sorry , i made a mistake, it is only 2 deg off when you use 3-keyway sprockets, not 4deg.
 
65DartGTConv said:
I have convinced myself that the balancer and the timing tab are correct to within 1 degree.

The timing set is Cloyes True Roller. It has the symbols you've described and if I recall correctly it was installed so the circle marks were aligned when #1 was at TDC. But I guess those marks could be made to line up no matter which key way was used.
Click to expand...

Yes, you can , but obviously it changes crankshaft/piston positions. If you take apart your timing cover, check that crank keyway position, it should be set correct.

If your timing is +/-1degree off, it is ok, but if you have +/-2 or more off, you should fix it. Depending engine type/usage.

check your distributor too, check your wires again,again and again
 
I'm guessing that you installed the timing set yourself. Did you install the gears with the dots facing each other with #1 at TDC? If you did then it is 180* out. Seen this many times also.
 
Hey dartman,............. think about that for a minute

And dart swinger,....... That cam will run anywhere from at least 6 or 8* advance to the same retarded. It just moves the torque peak around some.The cam timing is not the issue here.

65Dart
To my way of thinking,at this point, here are the most likely cause of your issues; 1)idle timing, 2)lifter preload, 3)vacuum leaks, and 4)carb issues,such as low speed circuit issues.
Forget about the cam timing.Forget about the balancer mark.You have thoroughly bugged those out.And by this time, I, at least, am confident that you know a thing or two about what you are doing. So, lets go to the less obvious stuff.
1)idle timing
"My ignition timing numbers are with both vacuum and centrifugal advance and running well above idle (maybe 2000 RPM)"
This is ambiguous at best.
Disconnect the vacuum advance,and plug the carb port.Set the power timing to 34ish degrees, at 3500rpm,or higher.Then report back.Leave the v-can disconnected for now.
2)lifter preload
Do you have adjustable rocker arms? If yes, are you sure the lash is set right? If no, do you feel the lifter preload was set right. Now dont go ripping the manifold off yet for a look-see.A simple compression test will tell you a bunch.
3)vacuum leaks
And finally, vacuum leaks. Im sure you know about the obvious places.But what about the not-so-obvious; Put a vacuum gauge on the crankcase(disable the PCV for a bit) and see if the intake is sucking air from the bottom.And speaking of the PCV, is it functioning properly. Or the brake booster. etc.
4)carb/.low speed circuit
I put this last, for a couple of reasons. Firstly I doubt this is the issue.Secondly,I believe the issue is among the first three. Thirdly, even with a non-functioning low speed circuit the engine could be made to sorta idle,well below 2000rpm.Now, a leaking PV, or a too high(flooding)float level, I could see. But the symptoms of those are almost overwhelming, and Im confident enough in your abilities that you would have recognized them.
Now, go check this stuff out.Starting with #1.Until the idle timing is set, no accurate diagnostics can be made.
 
AJ/FormS said:
Also reverse polarity on the magnetic pick-up will do that, if you are running the Orange box.If you reverse the polarity from what it is now, you will have to reset the dizzy to get the base timing back.
Yes on the MSD.
Your cam timing is not a problem.
The carb might, I say Might, have a low speed issue.
Click to expand...

I agree with AJ/FormS, this timing issue is what it sounds like when the polarity is reversed. Have you changed anything with the wires or distributor?
 
65DartGTConv said:
I recently fired my 273 for the first time. The engine is difficult to start but starts best with the distributor set at approximately 60 degrees advance all in. Once running above idle speed, I can time it back to around 35-40 all in and it will keep running.

My ignition timing numbers are with both vacuum and centrifugal advance and running well above idle (maybe 2000 RPM).
Click to expand...

Let's back up the bus a minute. 50° timing is quite common at 2000+ rpm when it's all in (including vacuum). Set your timing at idle (mine likes 12° before) and check the total at 2000+. The total can only be adjusted inside the distributor by lengthening or shortening the slots in the bar on top of the shaft. There are many threads here about tuning your distributor. 10° initial with 20° mechanical and 15 or 20° vacuum gets you around 50° at 2000+ rpm. You never include the vacuum advance in the total degrees when you're trying for 35°.
 
65DartGTConv said:
I'm running the eBay distributor that is also sold under the Pro Comp brand name. Not MSD.

The ignition worked well before I removed it from the car. I can't say what the all-in timing was before I took it apart.

By "timing light trigger problems" do you mean that the timing is correct, but the light doesn't give the correct reading?
Click to expand...

I meant trigger issues known to MSD

AJ has posted some good stuff which I nearly mentioned. Rotor phase and or reversed pickup wire polarity might be an issue. Google "rotor phasing"
 
AJ/FormS said:
Hey dartman,............. think about that for a minute

And dart swinger,....... That cam will run anywhere from at least 6 or 8* advance to the same retarded. It just moves the torque peak around some.The cam timing is not the issue here.

65Dart
To my way of thinking,at this point, here are the most likely cause of your issues; 1)idle timing, 2)lifter preload, 3)vacuum leaks, and 4)carb issues,such as low speed circuit issues.
Forget about the cam timing.Forget about the balancer mark.You have thoroughly bugged those out.And by this time, I, at least, am confident that you know a thing or two about what you are doing. So, lets go to the less obvious stuff.
1)idle timing
"My ignition timing numbers are with both vacuum and centrifugal advance and running well above idle (maybe 2000 RPM)"
This is ambiguous at best.
Disconnect the vacuum advance,and plug the carb port.Set the power timing to 34ish degrees, at 3500rpm,or higher.Then report back.Leave the v-can disconnected for now.
2)lifter preload
Do you have adjustable rocker arms? If yes, are you sure the lash is set right? If no, do you feel the lifter preload was set right. Now dont go ripping the manifold off yet for a look-see.A simple compression test will tell you a bunch.
3)vacuum leaks
And finally, vacuum leaks. Im sure you know about the obvious places.But what about the not-so-obvious; Put a vacuum gauge on the crankcase(disable the PCV for a bit) and see if the intake is sucking air from the bottom.And speaking of the PCV, is it functioning properly. Or the brake booster. etc.
4)carb/.low speed circuit
I put this last, for a couple of reasons. Firstly I doubt this is the issue.Secondly,I believe the issue is among the first three. Thirdly, even with a non-functioning low speed circuit the engine could be made to sorta idle,well below 2000rpm.Now, a leaking PV, or a too high(flooding)float level, I could see. But the symptoms of those are almost overwhelming, and Im confident enough in your abilities that you would have recognized them.
Now, go check this stuff out.Starting with #1.Until the idle timing is set, no accurate diagnostics can be made.
Click to expand...

This^^^^^^^^^^^^^^^^^^^^times 2

My bet, is the the vac advance disconnected, and then setting timing, will be the answer.
 
Thanks everyone for all your suggestions.

I think, based on what I'm hearing and also reading elsewhere, that the cam timing is not a problem. Many people believe that advancing the cam 4 degrees is a good idea if the goal is good low end torque. I think I will leave that alone for now and concentrate on other things. I may change it if I have problems with detonation, or if I'm not happy with the way it runs once dialed in.

I was under the mistaken impression that when people say things like "38 degrees all-in" they meant 38 degrees with both centrifugal AND vacuum advance. But if that term only includes the centrifugal advance then maybe I'm not so far out of the ball park.

I took the carb off and brought it home with me. I'm thinking I will open it up and have a look inside. I gave it a thorough rebuild 3 years ago and it was running good when I put it on the shelf 2 1/2 years ago. I tried to get the fuel out of it before I shelved it, but who knows. I think it's worth a look. Hopefully I don't destroy the gaskets.

As far as vacuum leaks, I did notice that the PCV hose fits kind of loose on the carb. I also don't know for sure if the PCV valve is good. So I think I will remove that and plug it. Ditto the source for the HVAC controls.

Then I will try harder to get it to idle and set the initial timing with vacuum advance disconnected and plugged.
 
Does it run smooth at idle, at any degree? forget the timing tab and marks, you baselined those when you taped it with your TDC tool, good. Id put it on tape TDC and see where rotor is pointing. Cam dots up or down doesnt matter on cam timing, crank could care less where it is, but you have to get distributor timing down. Id plug all vacuum and check distributor with cap off, IIRC @#1 TDC, dizzy slot points to #1 intake bolt if oil pump drive is installed to factory spec (just so you dont have vacuum pot pointing to firewall)
 
this is like a thriller movie..... i want to know the final determination....let us know....as soon as you find out...
 
Definately not the engine if everything you've done you did right (of which i have no doubt). It's got to be the distributor or wiring.
 
I just read my thread above and added a few words to be more clear. Don't add the vacuum advance in when checking advance totals. As suggested, disconnect and plug the vacuum advance at the carb and set your total around 35° at 2500 rpm. Check your initial and let us know what it is. I am guessing it will be 12-15°. I always start out with 10° initial and tune from there. You have a E4 advanced 4°. It should be happy at 12-15° initial. I advanced my E4 2 degrees and it likes 12° initial. I tuned my dist. to limit the total to 35° and switched the heavy advance spring to a light one out of a Mr. Gasket kit so I had full advance at 2000.
 
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