340 Chugging instead of Reving

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Carnut68 said:
I'll bring it up again. Wiped cam? Have you rechecked your lash?
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Sorry, I did see your note on that earlier but got side tracked here. I did inspect the lobs when I replaced the intake gasket. They all appeared to be like new. No sign of being worn that i could see. I used lots of Lucas assembly lube originally and I coated the cam again before putting the intake back on. I rechecked the lash at that point and looked closely at the rockers movement. Did not see any of them with less movement. I guess I could put a dial indicator on them to verify.
 
That is exactly how my xr700 box acted. No amount of tuning could solve it.
 
TT5.9mag said:
Have the box checked out. A few degrees of retard from a. Box is normal. 14 degrees is not normal. I think you have a faulty box.
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I going to send it out in the morning. It's at least another verification and piece of mind of what's good or bad. The $100 for repair plus shipping is probably money well spent.
 
Haven't read all the posts but locking the dist & getting an improvement in how the engine runs does not surprise me at all. It nearly always does run better.
I do not think you have an ign problem. Looking like wiped cam lobes, bent valve, burned valve etc.
 
Is this car driven on the street at all? No way in hell would I lock out the distributor. That's a crutch and a band aid. Find the real problem. Have you tried another box yet?
 
In my process of elimination I chose to lock the distributor and in turn its reviewed a potential problem with the ignition. (Not to say I am ignoring a cam issue) but for the timing to be locked at 38* and see retard down to 24~27 range seems extrem. My understanding is 3* to 4* would be more common, so I'm going to have it checked out. I do not have access to a other box and this car will never be used on the street. However, I eventually plan on unlocking the distributor and set enough mechanical advance to cancel the the 3 to 4 deg that I might still see upon return of the box.

Meanwhile, I'll put a dial indicator on the each valve spring retainer and see if there is sign of a lift issue. This is a new build and I used a Oregon Cam with solid lifters. The lash was set to cam card specs and has been checked 3 times since break in and still holds the original lash settings. Although that would only indicate wear on the base line not the overall lift.

In the plan this week while the box it out, I'll have access to leakdown guages the check for other potential issues in each cylinder.
 
1969GTS340 said:
In my process of elimination I chose to lock the distributor and in turn its reviewed a potential problem with the ignition. (Not to say I am ignoring a cam issue) but for the timing to be locked at 38* and see retard down to 24~27 range seems extrem. My understanding is 3* to 4* would be more common, so I'm going to have it checked out. I do not have access to a other box and this car will never be used on the street. However, I eventually plan on unlocking the distributor and set enough mechanical advance to cancel the the 3 to 4 deg that I might still see upon return of the box.

Meanwhile, I'll put a dial indicator on the each valve spring retainer and see if there is sign of a lift issue. This is a new build and I used a Oregon Cam with solid lifters. The lash was set to cam card specs and has been checked 3 times since break in and still holds the original lash settings. Although that would only indicate wear on the base line not the overall lift.

In the plan this week while the box it out, I'll have access to leakdown guages the check for other potential issues in each cylinder.
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Let us know what Dave finds if you don’t mind. I’ll be interested to know. And I agree, it shouldn’t be backing up 14 degrees.
 
TT5.9mag said:
I love when people comment and don’t read the thread.
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It happens to me a LOT, because having only one eye has tremendous disadvantages when reading. Lines tend to run together and lots of things are missed. But I still get roasted on regular occasions and that's cool. I've dealt with it since 1973 nothin's gonna change now.
 
RustyRatRod said:
It happens to me a LOT, because having only one eye has tremendous disadvantages when reading. Lines tend to run together and lots of things are missed. But I still get roasted on regular occasions and that's cool. I've dealt with it since 1973 nothin's gonna change now.
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Wasn’t solely speaking towards you but I gotta say that’s a bogus excuse. You’ve proven time and time again that you are absolutely just as capable (if not more) than anyone here with two good eyes.
 
TT5.9mag said:
Wasn’t solely speaking towards you but I gotta say that’s a bogus excuse. You’ve proven time and time again that you are absolutely just as capable (if not more) than anyone here with two good eyes.
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You'd be surprised what happens after looking at print for a long time. Cover one eye up and try it. But that's no good, because you always have the option to uncover it.
 
RustyRatRod said:
You'd be surprised what happens after looking at print for a long time. Cover one eye up and try it. But that's no good, because you always have the option to uncover it.
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I had a sliver of metal from a carbide cutter drilled out of one of my eyes not that long ago. Wore a patch for a month like a damn pirate. It is much harder to read and your depth of focus is severely distorted. So I can say I’ve briefly had to deal with it.
 
TT5.9mag said:
I had a sliver of metal from a carbide cutter drilled out of one of my eyes not that long ago. Wore a patch for a month like a damn pirate. It is much harder to read and your depth of focus is severely distorted. So I can say I’ve briefly had to deal with it.
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Im glad you two guys now see eye to eye.

Sorry, I couldn't resist. lol
 
Cam lobe verification complete. Using a dial indicator with a magnetic base mounted to a .060 plate that I attached to the valve cover mounting holes. I measured lift with the probe on the flat surface of the spring retainers. Some fluctuation in the numbers are attributed to the various set up positions I needed to use. But I'm relieved to find no sign of a wiped lobe. With this set up all intake lobes were within .009 of each other and exhaust within .008. Taking lash into account the lift overall was very close to the cam card spec.

Ignition box is on its way back from repair. I highly recommend Dave Telling if you ever question the performance of a Mallory product. In addition to reducing the amount of retard timing greatly, Dave reprogrammed the micro processor to bring my early revision box up to the latest that was offered. Eliminating bugs that were discovered over the years and added some programmable options as well.

I expect to have everything back together this weekend and will provide another update.
 
Rat Bastid said:
If you think it’s ignition, you want to contact this guy and have him look at it for you. He is the guy who ran the R&D for Mallory for all the digital boxes. He’s retired now but he still does repairs for a decent price.

I don’t have any 685 boxes laying around or I’d send you one so you could test it.

[email protected]

Send Dave an email and he will hook you up.
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Thank you once again for connecting me with Dave Telling.
 
That is excellent news. So what was the overall diagnosis of the box? Was it a setting that was yanking the timing out or was it something faulty he found with the box?
 
TT5.9mag said:
That is excellent news. So what was the overall diagnosis of the box? Was it a setting that was yanking the timing out or was it something faulty he found with the box?
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Basically, yes. The box was a very early version of the 685 that was proceeded by a number of improvements over the following years. The retarding of ignition timing will still be present but at a much higher RPM and in the 3 ro 4* range instead of 10 to 14*. There were many other bugs in this version that were also addressed by updating the revisions in the microprocessor. Dave did not elaborate on the details of the bugs.
 
1969GTS340 said:
Basically, yes. The box was a very early version of the 685 that was proceeded by a number of improvements over the following years. The retarding of ignition timing will still be present but at a much higher RPM and in the 3 ro 4* range instead of 10 to 14*. There were many other bugs in this version that were also addressed by updating the revisions in the microprocessor. Dave did not elaborate on the details of the bugs.
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Thats CRAZY. I’ve personally never seen a box that would retard 10-14 degrees but yours did. That is WILD.

Thats why locking out ignition timing is so bad. You never know how much or at what RPM they retard. And they ALL have some retard in them.
 
Rat Bastid said:
Thats CRAZY. I’ve personally never seen a box that would retard 10-14 degrees but yours did. That is WILD.

Thats why locking out ignition timing is so bad. You never know how much or at what RPM they retard. And they ALL have some retard in them.
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That is wild yet sad at the same time. I reinstalled everything, checking connections and reluctor alignment with the pick up and firing order for the 8th time. Fired the engine and the problem is still there @#$^&...
The timing retard is very minimal, starts and idles good but begins popping stumbling around 2500.... same story. The popping increases in rhythm as I advance the timing. I checked the plug and coil wire resistance and all were around 25ohm per foot. I'm delayed to work on it for another day now but compression test and leakdown tests are next. I'd much rather have an ignition mystery then evidence of anything mechanical, but I'll know soon enough.

One last ignition possibilty I thought of is the pickup. I read that you should never hook up a battery charger without unplugging the distributor. Prior to swapping in a brand new battery and installing an alternator, I had to charge and jump the car a few times. I don't know if that causes an instant kill or weakens the pickup. So any info on how a pickup dies would be helpful, or how the test measure it.
 
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[1] Spark plug wire resistance is not the issue. I have a test where different wires with different ohms per foot resistance were used & the highest HP obtained was with wires that did NOT have the lowest resistance. The purpose of the test was to find out if wire res affected HP.
[2] You do not have to disconnect the dist to charge the battery.
[3] The pick up is obviously working because the engine runs; probably already stated earlier in the thread but air gap should be 0.008".
[4] Not aware of any reliable in-car test you can do on a p/up. They either work or they don't; long time use if VA is connected can break the wire[ s ] from flexing. Test with an ohmmeter, while flexing the wires. Reading should not change.
[5] Get the engine running & disconnect the alt wires. Then test drive. Test is to see if alt diodes are leaking/damaged & are producing AC ripple; transistors etc do not like AC.
 
Bewy said:
[1] Spark plug wire resistance is not the issue. I have a test where different wires with different ohms per foot resistance were used & the highest HP obtained was with wires that did NOT have the lowest resistance. The purpose of the test was to find out if wire res affected HP.
[2] You do not have to disconnect the dist to charge the battery.
[3] The pick up is obviously working because the engine runs; probably already stated earlier in the thread but air gap should be 0.008".
[4] Not aware of any reliable in-car test you can do on a p/up. They either work or they don't; long time use if VA is connected can break the wire[ s ] from flexing. Test with an ohmmeter, while flexing the wires. Reading should not change.
[5] Get the engine running & disconnect the alt wires. Then test drive. Test is to see if alt diodes are leaking/damaged & are producing AC ripple; transistors etc do not like AC.
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It depends on which system he has in the distributor. If it’s a Unilite it needs to be unplugged.
 
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