So here's the story.

About 3 years ago, I was on a deserted piece of asphalt, and layed into the Dart from a slow rolling start. Hit 6000 rpm right now. Nothing out of the ordinary.

Right away it started to pop, sputter, etc... WTH?? At this point in time, I didn't have a garage, just a rented storage unit. I was able to drive it there and park it. At low rpm cruising, it was fine. Get on it, and the sputter, popping and a rattling sound was there. Didn't have to get on it hard really, just a load on the engine and the symptoms came back .

Life then gets in the way.

Then a garage gets built.

Fast forward to now.

I drained all of the old gas out and pulled the carb. Cleaned out the bowls and passages, reset/rechecked settings, etc.

Next I pulled the intake. Nothing out of the ordinary to be seen, but decided to pull the valve train as well and check. No bent pushrods, broken rockers, or collapsed lifters (I was kinda hoping to find a collapsed lifter). Valve springs all look good and at the same height and alignment.

Buttoned it all back up and gave it an oil change. Pulled plugs to look for possible mechanical damage. Nothing.

Also checked the bolts on convertor. Nothing loose.

Car starts fine. Idles fine (ish). Rich alittle but oh well. The popping and sputtering is now gone. At low rpm, say up to about 2200rpm, with light load on the engine, everything seems ok. Get into a little or drive up a steep hill, and I can hear what I can only describe as a rattle. Definitely not a knock. To be honest, ALMOST sounds like detonation, OR a collapsed or damaged lifter. When I checked the lifters, I could not compress them at all by hand using a pushrod on the plunger.

Here's a general breakdown of the set-up.

493 RB
Stock RPM heads
Roller tip rockers
Smith Bros pushrods
MSD 6AL, and pro billet distributor
11.1-1 calculated compression
BIGS 850 DP

Now. The best gas to be found here is 91 octane. So I can see detonation maybe , but it was fine before this incident. Timing is 20 initial, and I think high 30s all in by 2500 rpm (forgot to check total timing ).

The only other thing that I can think of to check, are the springs on the distributor maybe??? Maybe one broke or fell off, and once the rpm gets to a certain point, the timing goes through the roof, causing detonation?? Or am I just grasping straws on this one.

I am currently working offshore at the moment, so I can't actually do anything for 2 weeks,but I am ALL ears when it comes to suggestions on what to check for next.

The noise sounds too "tinny" I think to tear into the bottom end. Is there any chance it could be transmission related?

Thanks for reading.

codfish

The popping/sputtering is gone after you changed the gas etc? For the ticking I'd run some race gas for a day to elim detonation. Otherwise just WAG ing I'd say bad lifter if your preload is acceptable tho I'd want to be sure of that before I got into a new lifter breakin or a new cam/lifters. There's no ticking at idle right?

What brand roller tip rockers , what's your quench and what is your compression ratio ? what is your lifter preload and did you inspect the bottom of the lifters ?

The springs in the distributor don't LIMIT advance , they just regulate it , so the only thing a broken spring would do is make it come in too fast.

I would still look inside your dizzy if it sounds anything like detonation, although detonation should go away by the point your timing was all in before. Those pro-billets get rusty inside easy and I've seen springs rot and break, just recently as a matter of fact.

If not I'd say its probably a lifter/valve train issue. Whats your oil pressure like?

There is no tick at idle that I can hear. Car isn't particularly quiet.

Rockers are Comps. Ductile iron type. Quench is .040. 11.1 compression. Lifter preload not measured. When installed, I went 1/2 turn on adjuster after contact. Bottom of lifter look good. You can see an even wear pattern on all. Turning in the bores.

Oil pressure is 60 ish during warm up, and around 20 at idle.

I may see if I can hunt down some race fuel once I get off the rig in 2 weeks, and give that a try for sure. Can't hurt.

Thanks
codfish

Cracked flex plate? That will give a rattling type sound on load. I had a pickup with a cracked flex plate. It drove fine up to a certain RPM and started to sound like detonation. It was horrible on load. I tried everything and nothing made it better. On a hunch I pulled the transmission. Everything looked fine until I removed the flex plate and really looked at it carefully. It had a couple hard to see cracks. I swapped the flex plate and never had another issue.

Dunno what brand the lifters are. They came with a cam I got from Scott Brown. I'll have to wait til I get home to look at the paperwork as far as recommended preload is. Built it 5 years ago lol.

I did check the exhaust at the collectors. All tight. Never thought about at the head though.

And a cracked flex plate never crossed my mind. Will certainly have a close look at that as well

All good suggestions fellers.

Thanks
codfish

Does it do anything in park reving it up or holding the brake and flooring it? Make sure the exhaust is not touching anything, check motor mounts, and fan, check drive shaft ,pinion and rear suspension since this started after a nice 6K tire melter.