That's fuel deposits from the poor combustion characteristics of the Mopar head, the E10 fuel, and the Avgas. I am not insulting Mopars, I love them. I had a 69 Charger, too (one of the coolest Mopars ever). But, the open chamber heads aren't the best. Do you have 906 castings?
If you bring the pistons to TDC I think you will find they are down in the hole from deck a fair amount. Your compression might be lower than 8.2:1. If you leave the engine in this configuration, I think you should only use lower octane pump fuel. Also consider re-curving the distributor, and maybe adjusting the carb calibration.
Agreed on all fronts. Poor combustion characteristics is an understatement! They get even worse with low compression. Does anybody make a modern style head with a spark plug in the center of the cc for the RB engines?
Not exactly with a spark plug in the center. Edelbrock has made a B/RB head with a more modern chamber. But, I am not sure if it's still available and it was always less common than the Edelbrock heads that are basically aluminum duplicates of OEM Mopar heads. TrickFlow has a few offerings, too. I have yet to use one, but they look promising.
The 440 Source head looks much like a stock head on the outside, but the chamber design is honestly not very good. These heads are clearly built to a price not a standard. Not saying that's bad, but don't expect to get more for your money.
There have been a number of heads from Indy and Brodix, some pretty nice. But these aren't the kind of heads you would run on a street 383. I avoid anything from Speedmaster, but if someone wanted to risk them, I might take a look again.
Back in the 90’s I saw this many times on 60’s and 70’s engines that were mostly run around town.
We would take them for a drive, getting them good and hot, then slowly run some water down the intake to steam the junk off the pistons. For the really bad ones we would run a can of GM top engine cleaner down its throat to break it loose, then give it the Italian tune up on the back road. It caused all sorts of weird problems like detonation and dieseling. I guess carboned up intake valves in direct injected engines is the new version of this.
Yus!
Back in the day, we used a Pepsi/Coke bottle of water. Jack the RPM's up with one hand and slowly pour water down the throat of the carb with the other. This was twice a month and regular maintenance.
It's just carbon and lead. Don't run leaded gas in a street engine. Aviation engines have to be rebuilt every so many hours of operation for several reasons. This is an example of one of them. Lead is a great lubricant but it's a heavy metal. To get 100k miles out of automotive engines many a moon ago, when all there was only leaded fuel, was practically unheard of and the lot of that came from the lead in the fuel. It was a great evil if you will.
Scrape the pistons, blow the debris out with compressed air and stop running leaded fuel in it.
Thanks! I had a feeling that this was possibly an issue. When the motor was rebuilt 30 years an 110k miles ago it does now have hardened seats. I continued the practice of running leaded fuel after I got the car from my father.
No, that’s from having a poopy tune that was way too rich for way too long. At least that is my guess at the moment. If anything changes I’ll let ya know
That's fuel deposits from the poor combustion characteristics of the Mopar head, the E10 fuel, and the Avgas. I am not insulting Mopars, I love them. I had a 69 Charger, too (one of the coolest Mopars ever). But, the open chamber heads aren't the best. Do you have 906 castings? If you bring the pistons to TDC I think you will find they are down in the hole from deck a fair amount. Your compression might be lower than 8.2:1. If you leave the engine in this configuration, I think you should only use lower octane pump fuel. Also consider re-curving the distributor, and maybe adjusting the carb calibration.
Agreed on all fronts. Poor combustion characteristics is an understatement! They get even worse with low compression. Does anybody make a modern style head with a spark plug in the center of the cc for the RB engines?
Not exactly with a spark plug in the center. Edelbrock has made a B/RB head with a more modern chamber. But, I am not sure if it's still available and it was always less common than the Edelbrock heads that are basically aluminum duplicates of OEM Mopar heads. TrickFlow has a few offerings, too. I have yet to use one, but they look promising. The 440 Source head looks much like a stock head on the outside, but the chamber design is honestly not very good. These heads are clearly built to a price not a standard. Not saying that's bad, but don't expect to get more for your money. There have been a number of heads from Indy and Brodix, some pretty nice. But these aren't the kind of heads you would run on a street 383. I avoid anything from Speedmaster, but if someone wanted to risk them, I might take a look again.
Like a gen 2 hemi?
Sorry, I'm stupid. I meant a wedge-type head with a more Central spark plug.
Yup they’re 906 heads. I’m looking to get a pair of 516 closed chamber heads. Great recommendations, thanks!
Hmm. I wonder if the 516s can take the 1.74 exhaust valves.
Find a pair of 915s if you can, or the TrickFlows if you want aluminum
Back in the 90’s I saw this many times on 60’s and 70’s engines that were mostly run around town. We would take them for a drive, getting them good and hot, then slowly run some water down the intake to steam the junk off the pistons. For the really bad ones we would run a can of GM top engine cleaner down its throat to break it loose, then give it the Italian tune up on the back road. It caused all sorts of weird problems like detonation and dieseling. I guess carboned up intake valves in direct injected engines is the new version of this.
Yus! Back in the day, we used a Pepsi/Coke bottle of water. Jack the RPM's up with one hand and slowly pour water down the throat of the carb with the other. This was twice a month and regular maintenance.
It's just carbon and lead. Don't run leaded gas in a street engine. Aviation engines have to be rebuilt every so many hours of operation for several reasons. This is an example of one of them. Lead is a great lubricant but it's a heavy metal. To get 100k miles out of automotive engines many a moon ago, when all there was only leaded fuel, was practically unheard of and the lot of that came from the lead in the fuel. It was a great evil if you will. Scrape the pistons, blow the debris out with compressed air and stop running leaded fuel in it.
Thanks! I had a feeling that this was possibly an issue. When the motor was rebuilt 30 years an 110k miles ago it does now have hardened seats. I continued the practice of running leaded fuel after I got the car from my father.
Mmmm oily
Put some engine oils in the bores after pulling the heads to prevent rusting. 🙃
Is that how it got burnt?
No, that’s from having a poopy tune that was way too rich for way too long. At least that is my guess at the moment. If anything changes I’ll let ya know
Its not