392 piston shapes

[sdowney717]

My engines, one has this piston other has that piston.
What is the difference?
Which is better for economy?
Do they run any different?
I think I have seen another shape as well

 

[Robert Kenney]

The top is what is referred to as a contoured non emissions version. It uses a completely open, round at the deck combustion chamber.

The bottom one is a emissions styled piston. The combustion chamber has an overhang for quench.

The two combustion chambers will have a visible difference in size. If the flat top piston is used in the open contoured chamber the compression ratio will be reduces significantly.

 

[sdowney717]

There are different non ic heads? With different combustion chamber sizes?

On this picture, this engine has the contoured non emissions version.
Does it look like the correct head?

That must mean my other head would be different?

 

[Robert Kenney]

I stole your cc/head picture. Those are all open chambers and need to use a contoured piston..

I added the basic difference you will see on an emissions type of chamber that uses the flat top piston.

Open chamber

Emissions chamber. The red hatched area will be flush with the gasket surface. It provides what is called quench/squish that improved detonation resistance and a better quicker burn rate. Aids in emissions reduction.

 

[Michael Mayben]

And...obviously the long block that was produced for the palmer conversions is somewhat different in configuration compared to the engines designated for use in motor vehicles. That was common practice for industrial engine applications in order to effectively lower the compression in engines used in continuous service under heavy load (such as a marine application). That heavy load condition was aggravated by the use of fuel that was stored in bulk for long periods and also used entirely different chemical additive compounds at that point in time for establishing octane rating (such as tetraethyl lead).

Those engines were designed for fuels and lubricants common in the 60's and 70's. In 1972 the whole world changed thanks to the federal government and they certainly didn't give a shit about the marine/industrial industry then...and they certainly don't now with the forced conversion to using corn for gasoline.

 

[sdowney717]

Definitely gas today is pretty bad for carburetter engines.

I would like to be able to drain the carbs after shutting down. I was thinking you could turn off the tank valve and let it run dry but that still leaves some fuel in there and wont do anything for the secondaries.
My other thought was somehow adding a dip tube to the float bowl and suctioning out the fuel. Or some kind of tapped hole in the float bowl side. I would like the process to be fairly simple and robust.
I currently have an electric fuel pump in conjunction with the mechanical pump. This way I can prime it and it starts instantly. Before the electric pump lines were added (I tee'd off the output of the mechanical pump for the output of the electric and added one way valves) it would take forever to crank and start.

Todays gas does ok with sealed fuel injection systems, but that is likely to much work to install and likely too expensive. Now if it got more use and it got significantly better fuel economy, I might consider it.

 

[Robert Kenney]

And added one way valves

Why??? The mech pump has perfectly capable check valves in it already. Fuel can not flow back through a mechanical pump.

 

[Michael Mayben]

definitely gas today is pretty bad for carburetter engines.

I would like to be able to drain the carbs after shutting down. I was thinking you could turn off the tank valve and let it run dry but that still leaves some fuel in there and wont do anything for the secondaries.
My other thought was somehow adding a dip tube to the float bowl and suctioning out the fuel. Or some kind of tapped hole in the float bowl side. I would like the process to be fairly simple and robust.
I currently have an electric fuel pump in conjunction with the mechanical pump. This way I can prime it and it starts instantly. Before the electric pump lines were added (I tee'd off the output of the mechanical pump for the output of the electric and added one way valves) it would take forever to crank and start.

Todays gas does ok with sealed fuel injection systems, but that is likely to much work to install and likely too expensive. Now if it got more use and it got significantly better fuel economy, I might consider it.

Use stabil marine formula, it's been a marine industry standard for many years and is marketed under private label by all marine engine manufacturers. It is currently (and has been for many years, the only defense against the debilitating effects of gasoline cut with alcohol along with the stabilizing effect it has in long-term storage of any gasoline-base fuel supply.

Have you ever attempted to clean out twin 50 gallon marine gasoline fuel tanks that are impossible to remove from a boat without cutting it in half??...with the boat in the water where ya can't pump the trash, rot, sludge, algae, and shit overboard?

Never heard of a "sealed" injection system...and if you think that e10 doesn't fuck with modern efi then you haven't "worked on cars" much. Phase separation, non-stabilized fuel, oxidation, moisture absorption, and internal component corrosion caused by exposure to alcohol are facts of life, the evaporative emissions system on any motor vehicle is open to the atmospheric through some sort of vent anytime the vehicle is in operation.

Turning off a tank supply valve won't run a carb dry, it just allows the fuel in the bowl(s) to be pulled down to the point the fuel circuits are uncovered resulting in engine stall. There is still plenty of liquid fuel inside the carb and that aggravates the long-term storage issue.

 

[sdowney717]

why??? The mech pump has perfectly capable check valves in it already. Fuel can not flow back through a mechanical pump.

__________________
ok, 2 one way brass anti siphon valves are in a y splitter.
Fuel flow output from a single electric pump enters one leg of y
the other 2 legs of the y have the one way valves screwed in and those lines feed into both carbs.
Carbs inlet line has a flare tee. One input comes from mech pump, the other from electric pump. This way one electric pump can pump fuel to 2 carbs for priming and if one engine is running, it's mechanical pump can not pump fuel to the other carb or back thru the carter marine electric fuel pump.

I could have bought 2 electric pumps but why spend extra $100. One pump has plenty of flow and I can even close the fuel valve to the mech pumps and run both engines from one electric pump just fine.

It all works very well. I had to add a regulator to the electric pump as these rochestor 4g can not handle over 3psi.

Before doing this, you would go out and come back, shut down engines. Then next weekend go out and fuel bowls would be dry. So engine would have to crank and crank to bring enough fuel back in, which is tough on the starter. The starters on these engines are kinda slow to spin anyway and it was a pain wondering if they would ever start. They dont spin fast like my GM v8's. I went thru the system, new marine batteries 8d, twin banks, and rebuilt replaced starters, connections are all good. Made no difference at all. It has been like that all the time I owned it. About 10 years. Talked to the starter rebuild people and they told me they are high output torque, so it is what it is. The cables are beefy with the copper a good 1/2 - 5/8 inch thick. Nothing gets hot when cranking. It just cranks slower than I like.

Anyway when everything is as it should be, both engines start within 3 seconds of cranking, even with their 'slower sounding' crank speed.

 

[sdowney717]

Yes, the ethanol fuel issue has me concerned. The boat gets little use compared to a car. I looked into pri-g which has good reviews as a stabilizer and I can buy it at west marine.

This poor quality gas makes me wonder how viable a gasoline powered boat can keep functioning seeing infrequent use. If the carbs could be drained out between runs, I thing it would help a lot.
Plus these tanks are open to the air at the tank vent. I read that ethanol fuels evaporate quickly and can also phase separate. It is just all around bad news for gas powered boats.
I read the epa has passed new laws on gas boats requiring emmisions fuel vapor containment for the tanking. So I wonder if it could be retrofitted and would keep the fuel fresher and less likely to phase separate.

 

[Eric VanBuren]

yes, the ethanol fuel issue has me concerned. The boat gets little use compared to a car. I looked into pri-g which has good reviews as a stabilizer and I can buy it at west marine.

This poor quality gas makes me wonder how viable a gasoline powered boat can keep functioning seeing infrequent use. If the carbs could be drained out between runs, I thing it would help a lot.
Plus these tanks are open to the air at the tank vent. I read that ethanol fuels evaporate quickly and can also phase separate. It is just all around bad news for gas powered boats.
I read the epa has passed new laws on gas boats requiring emmisions fuel vapor containment for the tanking. So I wonder if it could be retrofitted and would keep the fuel fresher and less likely to phase separate.

Yes a closed fuel system will help. Ethanol is hygroscopic and will absorb moisture out of the air. Once the total amount of water exceeds 1% phase separation can occur. You May be unnecessarily worrying about it though. There are only about a dozen states that mandate e content. What state are you located in? Most of the states or areas that do require e10 or lower e$ allow fuel sold at marinas to be 100% gas. Check with your local marina fuel station or take a sample and test it for the presence of ethanol.

Edit I see you are in va so no you are not in a state that mandates e10, don't know if you are in a designated non-attainment area where the epa mandates a min 5.75% but again fuel for boats is exempt. Of course that doesn't mean you don't have ethanol in your fuel because the gas companies have quotas of the amount of ethanol they must blend and others blend at the max 10% to boost profits through higher margins and to sell credits to companies that don't have the blend equipment.

 

[Dealbreaker74]

So I'm guessing no pics of that adjustable valve train? If both engines are back together? Or did I miss it? I know its a bit off your thread topic, but that tease is killing me! I'm very interested to see what you described as "adjustable."

 

[sdowney717]

Next time I go out there I will post the pictures. Rockers and lifters along with cylinders etc...
The rockers are solid IH not boat style and has all the stand offs.
Each rocker has a lock nut and adjusting screw. The pushrods are ball and socket. I got one head cleaned up. Intakes were totally gummybut otherwise in very good shape.

The marina crushed an eggharbor with palmers and they gave me a pair of 392 ic heads which had been refurbished. They were laying loose in the boat. (all shiny and wrapped in plastic). The marine left those palmers laying around and I think they went for scrap. One of the engines looked fresh. I grabbed as much loose engine parts as I could. I got rockers and shafts, pushrods, gaskets, water pumps. The blocks would have been nice to get, but too heavy to grab and would have had to buy them, deal with moving, storage, my garage is full, etc....
I was looking at my head and noticed the exhaust valve guides had some wear. So I pull apart the refurbished head and what do you know, they were also loose feeling. Then I read some posts on how replacement guides are also loose and said ok, then it will just have to be what it is. I did read on some people going to a lot of trouble improving these.

When I boat, I never push my engines past 3000 rpm. Typically I just go about 1000 rpm. It goes slower but uses much less fuel. I have twin 150 gallon monel tanks and you can imagine what it costs to fill up.

I just have not been back to the boat and will go out there Monday and post pictures.

I would like to know where the block drains are. I will post what I think is the drain. It is not in the same position as the other engine.

 

[Dealbreaker74]

Sweet. I'm dying to see that, because if you've read any of the posts describing deck heights, head surfacing, etc., you'll see that compensating for those changes is a real pain with these non-adjustable shaft rockers. Maybe someone could re-pop a version of what you have down the road....?

As far as block drain, there are pipe plugs above the oil pan that run the length of the block on each side. Some are oil galley plugs and the others drain the water jackets. You seem crafty enough (your fuel system mods for instance) to plumb those jacket plugs together and terminate them into a petcock valve that would drain the water from the block. Kind of a pain. If the engines tilt fore or aft, you could probably just valve the lower of the plugs and call it good. My manuals don't show a pic of those plugs, but they are visible if you can see the oil pressure sender (on a truck app, not sure on a boat).