Cam Sprocket Position

[madkaw]

When you checked the mark on the cam sprocket at TDC - was the #1 mark on the sprocket where it should be ?

Id say your valve timing is retarded by the pic , but doesn’t explain running issues . Don’t be shy about advancing the sprocket - it will help low end torque .

4.5 turns seems way too much . Sure you have the needle jets seated correctly ?

Verified good strong spark from the plugs ?

Verified no vacuum leaks ? Taken a vacuum reading ? 
 

Compression test ? 
 

 

Was Pertronix set up properly based on ballast resistor used or not ? 

[Jughead]

Here are my answers to @madkawquestions:

Q: When you checked the mark on the cam sprocket at TDC - was the #1 mark on the sprocket where it should be ?
A:  I didn’t check, but I will.  Where should it be?

Q: Sure you have the needle jets seated correctly?.  
A: I think so.  I set up per the ZT video, hear  good “thunk” sound from the piston drops.when I remove the damper pistons

Q: Verified good strong spark from the plugs ?
A:  What’s the best way to do this?

Q: Verified no vacuum leaks ? Taken a vacuum reading?  
A:  Not yet. Where’s the best place to get a reading on a ’72, & what should I look for? 

Q: Compression test ? 
A: Not yet, but will do & report back,
 
Q: Was Pertronix set up properly based on ballast resistor used or not?
A:  I paid a shop to do it.  The ballast resistor is still wired in.  Should it be?

BTW:  I hear "whistling" & a ticking sounds coming from between the carbs.  Could this be a intake or exhaust manifod gasket?  Both are original-looking - especially the exhaust. COuld my issues be manifold gasket-related?
 

Thanks Gents!!!   JH

[Zed Head]

On 3/14/2021 at 1:54 PM, Jughead said:

Ignition is new Pertronix electronic setup from MotorSport with a 3.0 Ohm coil. 

Which Pertronix do you have?  There are two.

I don't think that you need the ballast if you're using a 3 ohm coil.  With either of them.  That's going to give you weak spark probably.

https://cdn.shopify.com/s/files/1/0247/6913/4628/files/1741.pdf

[Zed Head]

On 3/14/2021 at 1:54 PM, Jughead said:

Still the car backfires under load when driving.

How about a description of a normal cold startup, warm up, then the driving experience?  It's hard to tell what is really wrong.  Make sure you distinguish between tailpipe "backfire" and carburetor popping.  Does it just not "go", or does it go with a lot of bucking and back or front firing?

A video would be great.  You can tell a lot by how an engine sounds.

[Jughead]

I got the Pertronix set up from Motor Sport for Christmas (2.5 months ago), so whatever Motorsport was selling then, that's what I have.  I chose the 3.0 Ohm flame thrower coil with it, and I just realized/remembered that the 3.0 Ohm coil has a built in resistor.  The shop that installed it to left the Ballast resistor installed, so maybe that's the issue...?

Regarding the experience:  It starts with a bit of effort with full choke.  Once it gets warm, it runs without any choke.  I start the mixture nuts at 3 turns, and adjust using piston-lifter pin method and/or Colortune.  It needs to be around 4+ turns to sound good.  Then I take it on a ~ 1.5 mile test spin.  It'll run "OK-ish", until I put the pedal to the metal. Then, I'll get exhaust backfire.  If I then lean out the mixture, I get "front-fire" out of the carbs.  I check the plugs when I get back to my place' and they're all sooty.  I've done this test repeatedly - always with same results (and yes, I'm going crazy!!)

See prior notes in this thread and you'll see I've rebuilt carbs with ZT kit (set floats, installed new jets & needles), adjusted valves, checked for cam chain stretch....  The next steps I was gonna take were 1) verify ignition set up is OK, then 2) replace intake & exhaust manifolds.  What do you think?  Am I getting close?  Could it be as simple as bypassing the ballast resistor?!

   

Edited March 28, 2021 by Jughead
clarification

[madkaw]

Sounding like a vacuum leak . You need to spray something around that gasket while running . That would answer why you need some many turns out if you are sucking extra air . The wrong impedance on your coil would answer the sooty plugs .

Pull a plug out with the wire attached and turn over the motor - preferably in low lighting - and see if the spark is blue or more yellow . 
 

Don’t worry about the cam sprocket for now - get the basics first 

[Zed Head]

Like madkaw says, vacuum leak probably.  You're tuning at idle for the leak, then when you get on the throttle the leak has less impact and your tune is wrong.

Motorsport has good advice about the Pertronix and coils.  Lose the ballast.

https://www.thezstore.com/page/TZS/PROD/classic11g/12-4020

Coil Notes:
The only performance coils that should be used with the PerTronix Ignitor, the 40,000 volt Flame-Thrower canister coil's higher voltage allows larger spark plug gaps for added power, smoother response and better fuel economy. They are oil filled for great heat control, and internally resisted. Legal in all 50 states and Canada (C.A.R.B. E.O. #D-57-10). The 3.0 Ohm coil is not for use with the factory (or any other) ballast resistor. If your setup requires you to keep the ballast resistor, please select the 1.5 Ohm coil above (see Related Items below for more information about the 1.5 Ohm PerTronix coils).

[AK260]

I haven’t fully read all the comments above, so this may be a dumb suggestion/ repetition. The only time I’ve had back-firing when on the power was when my Magnecore 8.5mm plug leads failed and there was unburnt fuel in the exhaust, popping as it hit the silencer / fresh air. A cheap set of Accuspark 8mm leads at a fraction of the price of the Magnecores fixed the issue and there was no performance drop over the more expensive leads.

So check your leads / plugs or swap them out for new given how little they can cost to fully eliminate them. Also the vac leak hypothesis works here too, especially if you are setting up over-rich for idle and with a weak spark. Also check your break booster hoses / connections and any other vacuum take off from your balance bar. Again, brake booster hoses can get brittle and leak + I’ve found loose connections on mine too. Check any blanking bolts and the gaskets on the balance bar too.

On my 123 ignition dizzy, I can see coil voltage/current. When I connected the ballast resistor to my 1.5ohm flamethrower as an experiment, the voltage didn’t even register on the gauge and the current was minuscule compared with where it should to be. So just bypass the ballast resistor for a while to eliminate it (if you haven’t already) while trouble shooting.

I’m sure someone has said this already, check all your manifold nuts are torqued up properly - I’ve found that even a 1/6 or 1/12 of a turn tighter made my life so much better - also all the carb to insulator nuts. Again, my carbs had rattled themselves loose in 300 miles of being put back on.

Using the spray something around potential leak points, I found even on my ZTherapy carbs (after 7 years of hard use) the throttle shaft cap on the rear carb needed re-sealing (probably due to a HUGE carb pop and exhaust backfire I had when I once got the leads 1 position wrong and tried to start the car on WOT)!!!!

Do you have a vacuum gauge to connect to the balance bar on the manifold (or vac advance nipple if not ported vac) to see what is happening at idle? It’s one of the essential trouble shooting tools for these situations IMHO!

Something like this ....
https://www.ebay.co.uk/itm/Gunson-Vacuum-Pressure-Tester-Engine-Fault-Petrol-Pump-Lo-Gauge-LSR5-/123731949087?_trksid=p2349624.m46890.l49292

The only time I’ve had intake popping was when the timing was way out. But I see you’re on that now.

Good luck - these are simple engines and with a systematic approach you WILL find the gremlin(s).

[Mark Maras]

14 hours ago, Jughead said:

 

Regarding the experience:  It starts with a bit of effort with full choke.  Once it gets warm, it runs without any choke.  I start the mixture nuts at 3 turns, and adjust using piston-lifter pin method and/or Colortune.  It needs to be around 4+ turns to sound good.  Then I take it on a ~ 1.5 mile test spin.  It'll run "OK-ish", until I put the pedal to the metal. Then, I'll get exhaust backfire.  If I then lean out the mixture, I get "front-fire" out of the carbs.  I check the plugs when I get back to my place' and they're all sooty.  

   

At 4+ turns down you got backfire out of the exhaust during acceleration, then you leaned out the mixture and got backfire from the carbs. How many turns did you lean it out?

[Jughead]

Update: 

 1) Today I bypassed the ballast resistor.  (I disconnected the wire from one terminal resistor and connected it to the other terminal along with the other wire.)  It helped a little.  I set mixture with lift pin method. It still backfired out of exhaust,  but was better.  Then I adjusted with Colortune, and it “front-fired” out of carbs right away.  Same ol’ same ol’

 2) Then I took the plugs out, cleaned them (once again) and looked at the sparks.  They were all pretty much the same.  The color is "white-ish blue" – almost purple.  I really had to look hard to see blue. Not sure how to tell if sparks are strong, as I have nothing to compare them with. (Is there a way to measure this? If so, what should the reading be?

 I’m running new NGK BRR6ES plugs and new NGK leads (the blue ones).

 3) Checked the compression in all cylinders. Here are the readings.  Seems like a wide variance…thoughts? 

 Cylinder         PSI

1                152

2                149

3                154

4                179

5                152

6                179

 BTW: I have sprayed starter fluid on the manifold/gaskets and carb bodies.  The manifold/gaskets don’t seem to be affected.  When I spray in on the carb bodies near the shafts it decreases the RPM by a few hundred RPM.

Edited March 30, 2021 by Jughead
clarification

[7tooZ]

10 hours ago, Jughead said:

When I spray in on the carb bodies near the shafts it decreases the RPM by a few hundred RPM.

This sounds like an issue I experienced last summer. It was a vacuum leak at the throttle shaft on my rear carb. The shaft seal was compromised (leaking). At the standard 2.5 turns down and a hot engine it wouldn’t idle and back fired when off the throttle at speed. Seemed to run better at 2500 rpm and above. 
my solution was to send my carbs them back to ZT after 20 years who replaced the shaft bearings, throttle shafts and seals. They replaced  and adjusted the floats. Came back in a week and All I had to do was bolt them on. Best $$$ I have spent since buying them in 2001. 

[Jughead]

Update: 

1) Yesterday I bypassed the ballast resistor.  (I disconnected the wire from one resistor terminal, and connected it to the other terminal along with the other wire.)  It helped a little.  I set mixture with lift pin method again & test drove.  It still backfired out of exhaust,  but was better.  So I adjusted with Colortune, and as soon as I left the driveway, it “front-fired” out of carbs right away.  (Same ol’ same ol’...)

2) Then, I took the plugs out, cleaned them (once again) and watched them all spark.  They were all pretty much the same.  The color is "white-ish blue" – almost purple.  I was in a dark garage & I really had to look hard to see BLUE. Not sure how to gauge the strength of the spark. (Is there a way to measure this? If so, what should the reading be?  I’m running new NGK BRR6ES plugs and new NGK leads (the blue ones).  Plug Gap = .8 MM (Is that correct for Pertronix set up?)

3) I also checked the compression in all cylinders. Readings are below.  Seems like a wide variance…thoughts? 

Cylinder         PSI

1                152

2                149

3                154

4                179

5                152

6                179

BTW: I did spray starter fluid on the manifold/gaskets and carb bodies.  The manifold/gaskets don’t seem to be affected.  When I sprayed starter fluid on the carb bodies near the shafts, it decreases the RPM by ~ two hundred RPM at idle speed.

Is the consensus still leaning toward the manifold? 

Is there a recommended thread on testing/interpreting vacuum on a '72 a40 anywhere on the board?

I have ZT Carbs on order...are they likely to help?

Thanks much for hanging in there with me...keep those thoughts & ideas coming!!

JH

Edited March 30, 2021 by Jughead
clarification