I don't know what cam you are using, but very often the manufacturer's specs for lash (on a perf cam) are not wide enough for a Slant. I sometimes open mine up 0.002 - 0.010" on one or both valves and find it idles and runs better.

Lou

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Put it back together today, took for test run. All is fine for now. I'll drive it and let you all know how it goes.

It runs solid, plenty of umph, good throttle response, idles smoothly. I'll just have to drive it for awhile and see how it goes, no signs of detonation that I can discern; at least I know that the air/fuel mixture is rich enough, not leaning out. It definitely pulls up hills more strongly, though I think the throttle response was way better with the timing more advanced. I have it at TDC; I'm circumspect about advancing it after all this. I had been running at 10 degrees advanced, it seemed to me to have excellent acceleration/response at that timing, but of course I had the detonation issue. It may be that I could bump the timing back up now that the fuel mix is richer, but...I'll take it slowly...

b

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[quote="'67 Dart 270"...It may be that I could bump the timing back up now that the fuel mix is richer, but...I'll take it slowly...[/quote]

Yup. I think you can do exactly that.

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I'll see how it goes.

b

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I drove it for about 20 miles and it started the rough running again on the highway. Drove it home and put it back in the garage. Now that the mixture is richer, I'm not sure what to try next. ECU?

DD had relayed to me that sometimes the ECU can go bad, run OK cold but once it warms up, crapola. BUT, I changed out my ECU (orange box) for another one during this testing phase, that didn't seem to make any difference.

I had checked my distributor, that seems fine; also swapped out for a newly rebuilt one (same setup, super six, same spring setup as before, total advance without vacuum is less than 30) that made no difference. Cap and rotor look good, no signs of arcing or carbon traces, clean as a whistle in there (vented cap).

I suppose it could be that this summer blend of gas is just not compatible with my engine.

Anyone else ever had a problem like this?

Brian

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Possibly you have your dist to ECU reluctor wires reversed? I did this once and it ran fine for 10-15 min, then rough...

Lou

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Seems I remember some problems with the orange boxes in the past. But not sure I remember what it was.

After all this work and still no resolution, I may hook up a $15 HEI module and eliminate the Chrysler box completely. Even if just temporarily to make sure your ignition box is not the culprit. I assume you are still running the ballast resistor too? I really feel sorry for all you done to try and get this fixed.

Rick

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12.70 @ 104.6

Hmm, that would be great if it were that simple. How would I mix them up, it has that plug that only goes one way? Please explain how these got mixed up in your case, thanks.

Maybe my ECU ground? I could check that as well.

Brian

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OK.....listen. FACTS.
1/ you have very high cranking compression
2/ You get the same failures again and again
3/ your engine is making metal
So, why is your compression so high? Like I've said many many times before you MAY have your valve timing a tooth out.
Your still using the Mopar ECU? Really? The 4 pin HEI is old tech,still does the job and is light years better than that crap if that's what your running.... I doubt the ECU will fix your engine making metal,just my opinion. I've mentioned in previous posts what I believe you should be doing.

I soldered a new ECU pigtail onto the directional plug and got it backwards. If you did not start with these parts, then probably you are fine there.

Lou

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I'm listening SlantSteve, I'm listening...

1/ you have very high cranking compression - TRUE
2/ You get the same failures again and again - TRUE
3/ your engine is making metal - TRUE
So, why is your compression so high? Like I've said many many times before you MAY have your valve timing a tooth out. COULD BE, MAY BE TIME TO PULL HER OUT AND CHECK THAT...


Your still using the Mopar ECU? Really? YES

... I doubt the ECU will fix your engine making metal,just my opinion. JUST BRINGING IT UP AS A POSSIBILITY, I DON'T THINK IT'S THE PROBLEM EITHER..

I've mentioned in previous posts what I believe you should be doing. YOU DID, AND I APPRECIATE YOUR FEEDBACK, YOU'LL GET THE CIGAR IN THE END IF YOU'RE RIGHT. I DON'T HAVE ANY OTHER IDEA WHAT IT COULD BE; YOUR PROPOSAL IS SOUNDING PRETTY SOLID.

Brian

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...so, if it were off a tooth, advanced, that would give higher compression numbers and explain the dieseling on shutdown, but wouldn't it also make it harder to start or make my intake vacuum weird or lower or jumpy? Maybe not, I'm a novice in this department. School me, Steve.

Brian

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Me too, but if it was way retarded wouldn't it be down on power?

Brian did you degree the cam on install? Sorry i can't remember

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

DD built this one, I'm pretty sure he would have dialed in the cam.

If it the cam were off by a tooth, it seems like it wouldn't run so well otherwise, but I suppose it could. I drove it for 5000 miles before that head gasket went, but now it's chronic/accelerated, whatever it is. I have read some anecdotes about high compression numbers when cam was off (advanced) a tooth, but usually there were other symptoms like vacuum was jumpy or off or something. I have been getting some fuzz on my magnetic plug, but a detonation issue unchecked would do that, even if it didn't come from cam being off.

That all said, I'm stumped. She's sitting in my garage and I have no idea what to do with her except pull the engine and see if the cam is off.

Any other suggestions?

brian

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Rick,

I think if it were retarded one tooth off you are correct, power would be down, but if advanced one tooth I think the fall off would be at high rpms. I've never cranked her past 4000 rpms, but she's strong all the way up to that point. I suppose I could rev it up past 4000 to see if it breaks up at high rpms....

brian

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