She lives (again)! Finally got the new oil pump installed on the new engine, and drove her around for about 3 miles, her longest trip yet. Nice, strong 50 PSI of pressure. Here's hoping the lack of oil pressure didn't do much damage.

My next hurdle seems to be diagnosing some heavy detonation. I need to recheck everything, including putting a bright spot of white paint on the timing mark just to make sure, but I've adjusted the timing from about 2 degrees advanced all the way back to 10 to 12 degrees retarded, but no matter what, I still get heavy detonation at anything more than 1/4 to 1/2 pedal under load.

What worries me is, this is a long rod engine, with the dished KB Hyper pistons. Slantzilla insists that long rod engines are "incredibly resistant to detonation", and other reports that KB Hypers are "very brittle, and break like glass when subject to detonation". I used the KB dished pistons, and the machine shop said that they ended up 6 in the hole. The combustion chambers are 54 cc, I used a Fel-Pro head gasket, and the last time I calculated compression last year using an online calculator I came up with 9.37:1.

Which leads me to think it may be the distributor/advance curve. It seems I've almost always had some detonation issues with this car/engine. Even before the rebuild, I had to run premium to staunch the pinging, even though the timing was only 8 degrees advanced. It has the original distributor with the Pertronix conversion I made 6-7 years ago, and I'm thinking that the stock advance curve might be wack.

I'm currently using the extended tip NGKs on the new engine. I bought a new electronic distributor a year or so ago to make the HEI conversion, and now I'm thinking I should do that now and try a new distributor and so if that makes a difference. Any thoughts from the gang? Anything else I should try first?

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vm

A lot of the new Mopar Performance distributors come with a hyper-aggressive advance curve. If it's an MP piece, that may be the problem. At what RPM does it typically ping?

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

I'd say 1500 to 2000 rpm. I'm 99.99% positive that the distributor is the original. The previous owner was an older gentleman who kept the car well-maintained but totally stock.

As I pull away from a dead stop, I don't detect any detonation until it shifts to 2nd gear, then it pings badly if I'm not really, really careful.

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vm

It sounds lean to me.

.......or your new motor with unseated rings has a little blowby causing detonation at your peak firing pressure.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

I have never had any issues with detonation on one of my long rod motors. I have never broken a piston from it either. However, too much spray will break one in half I guarantee.

What is your total timing set at? Base timing means absolutely squat if total is going too high, especially with a vacuum advance hooked up.

I have my distributor that I spray on limited to about 10* total advance. I will run 15* intial and only 25* total.

As Sandy said, it may be way lean. What are you using for a carb and how is it jetted?

One other thing to remember, I run a very loose torque converter and a 3.91 gear. Your mileage may vary.

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Official Cookie and Mater Tormentor.

#2 Sounds better, of course. The car hasn't been driven more than 20 miles since the rebuild, so here's hoping.

A little update: Since I filled up the tank last Feb. right before the oil pump went south (with reg. unleaded, I think), I put in a shot of octane booster last night to see if it made a difference. I'm sure it takes some shaking around to mix it in well.

I've been out tweaking and tuning this morning. I've got most of the detonation eliminated with the timing reset at 6-8 degrees "After". I figure it might just be the octane booster getting mixed in completely.

I have noticed the timing mark jumps a bit, and the detonation kind of "pops" occasionally, rather than being consistent. The engine has a new double roller timing chain from Hughes. Does this indicate a worn distributor? Again, I think it's the original. I installed a new (stock) coil when I did the Pertonix conversion.

The carb is a '77 Super Six carb, rebuilt when I built the engine by a reputable local shop. I went ahead and backed out the idle screws 1/2 turn while tweaking. I need to become better at diagnosis and try one thing at a time. That detonation was just scary, though. Thanks for the help so far.

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vm

Detonation doesn't "pop". Are we talking about the same thing here?

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Official Cookie and Mater Tormentor.

Sounds like when they changed the oil pump your distributor is off one tooth.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Certainly it's worth checking for lean running (what do the spark plug tips look like?), but the more I read this thread, the more I suspect something like a broken advance weight spring in your distributor. You should definitely not have to retard the base timing to ATDC to "reduce" the pinging!

Which new distributor did you buy? (P/N)? I think my next step if I were wearing your shoes would be to put my own shoes back on. Then I'd swap distributors, since this dist seems to be a constant factor (before/after new engine) and you say you've always had pinging issues in this car.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yep. Like I said, THIS detonation just doesn't seem constant, like I'm used to when I've experienced it in the past. In the past, when I hear pinging, I've backed off the throttle and it stops. With this condition, it often pings once or twice but stops BEFORE I get off the throttle.

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vm

I installed the oil pump and distributor myself, and made sure the rotor was clocked identically. Plus, I had some detonation before the oid pump change.

I considered that the distributor might be one tooth off, but other than the pinging, it runs SO WELL. Nice idle, nice power across the powerband... and wouldn't that throw the timing mark way off? Does anyone else think this could be a possibility?

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vm

Well, now you mention it...have you checked your timing mark against actual TDC?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Haven't checked the plugs yet (laziness, that's one of my next steps). The P/N for the new distributor tag says " 28 6" on the top line, and "3874714" below. Got it from the guy on eBay who's been selling them for years.

Guess I'll find an HEI controller and the wiring, and maybe try to get another coil, and see if it makes a difference. I'm with you, Dan - Although there may be other issues going on (lean condition), I really think the current distributor is wack, and has been for a long time.

Any more insight would be appreciated, but in the meantime I'll work on switching the ignition and get back toy you guys then Thanks!

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vm

3874714 has a pretty good street-compatible curve on it right outta the box, according to Doctor Dodge. I am guessing your ping problem will probably be significantly reduced or eliminated when you put in this distributor and set the timing at something reasonable. Me, I'd start it out at 2½Â° BTDC to start out with, and if no pinging, nudge it to 5° BTDC.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I trust your word about long rods and detonation, 'zilla. That's why I know something funny must be going on...

Although I realize that it's critical, I admit, I haven't checked my total timing yet. I don't have a dial-back timing light, and no "helper" to rev the engine for me. Under the circumstances, I've disconnected the vacuum advance.

Don't know the jets on the carb, only that it was rebuilt by a reputable local carb builder who was recommended.

My new torque converter is a 2600 stall Edge, but my current ring & pinion are the stock 2.76's (I know, I know. One thing at a time! ).

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vm