I prefer champions, but I'm running 5224s because I could get them at the parts store. I feel like the extra electrode length helps unshroud the plug.
Speedmaster spark plug holes improvement??
- Thread starter 318willrun
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I prefer champions, but I'm running 5224s because I could get them at the parts store. I feel like the extra electrode length helps unshroud the plug.
I believe the RC12YC should be available and any parts store. At least I've not had a issue. It's basically a magnum plug (just smaller hex socket than the original RN12YC)
The RC12YC is definitely available like you said. I wanted to get the electrode further into the chamber, without having to do any blending on the plug hole (I forgot about it until I had the heads together).
Champion RC12MC4 and autolite 5224 have a .875 reach vs the .750 of the RC12YC. But the champions aren't available in the parts stores local to me.
I had to go back and look, but I took photos of the 5224s and the RC12YCs installed, it seems minor, but the extra .125 moves the electrode from flush with the chamber to exposed.
My home inspection of Speedmaster heads
My home inspection of Speedmaster heads
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That spark plug hole depth is atrocious. Can you get an extended tip plug so that the threads finish at the chamber wall and the tip is actually in the chamber? Otherwise you will be starting the flame kernel in the boundary layer so its gonna be slow to develop and need lost of ignition lead and most likely you will need to run it really rich to get it to start not to mention the fact it's surrounded buy metal which as the flame gets underway will stop its expansion.
You need to fix that quick.
You need to fix that quick.
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This will explain it:
Experiments showed that cyclic dispersion in spark ignition engines is inevitable because the turbulence of charge within the cylinder varies from cycle to cycle, the fuel-air mixture is not homogeneous and the exhaust gas residuals is not fully mixed with the unburnt charge. In particular, the formation of the first highly active constituents and the early flame development have a profound effect on the subsequent combustion. The formation of the flame kernel depends on the local fuel-air ratio, the mixture motion, and the exhaust gas residuals in spark plug gap at the time of ignition, which are not stable, but randomly fluctuated. This causes variations in duration of delay period of combustion and affects the early stage of flame propagation
In the early stage of flame growth, the flame is small and very sensitive to mixture conditions. If the flame nucleus is moved into the thermal-boundary layer surrounding the combustion chamber, then it will burn slowly. In addition, at a given flame radius, the greater contact with the wall will reduce the flame front area. Conversely, if the flame is moved away from the combustion chamber surfaces, it will burn more quickly. Therefore, it can be concluded that cyclic dispersion is increased by anything that tends to slow-up the combustion process, for example, lean mixture operation, inhomogeneous mixture, exhaust gas residuals, and low load operation.
In other words get that spark plug out into the chamber where it belongs!
Experiments showed that cyclic dispersion in spark ignition engines is inevitable because the turbulence of charge within the cylinder varies from cycle to cycle, the fuel-air mixture is not homogeneous and the exhaust gas residuals is not fully mixed with the unburnt charge. In particular, the formation of the first highly active constituents and the early flame development have a profound effect on the subsequent combustion. The formation of the flame kernel depends on the local fuel-air ratio, the mixture motion, and the exhaust gas residuals in spark plug gap at the time of ignition, which are not stable, but randomly fluctuated. This causes variations in duration of delay period of combustion and affects the early stage of flame propagation
In the early stage of flame growth, the flame is small and very sensitive to mixture conditions. If the flame nucleus is moved into the thermal-boundary layer surrounding the combustion chamber, then it will burn slowly. In addition, at a given flame radius, the greater contact with the wall will reduce the flame front area. Conversely, if the flame is moved away from the combustion chamber surfaces, it will burn more quickly. Therefore, it can be concluded that cyclic dispersion is increased by anything that tends to slow-up the combustion process, for example, lean mixture operation, inhomogeneous mixture, exhaust gas residuals, and low load operation.
In other words get that spark plug out into the chamber where it belongs!
I wish they hadn’t edited out the exhaust stroke so we could see what was happening during overlap, but its interesting to see what’s going on there.
[EDIT] If you pay attention, all the work and effective flame front happens with the blue fire. Most of the orange fire you see (especially at the end of the burn) is only converted to “dead heat“, as it’s burning during the pressure loss caused by the piston outrunning the combustion gas.
[EDIT] If you pay attention, all the work and effective flame front happens with the blue fire. Most of the orange fire you see (especially at the end of the burn) is only converted to “dead heat“, as it’s burning during the pressure loss caused by the piston outrunning the combustion gas.
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TrickFlow spark plug hole
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Great none the less!
Speedmaster and Edelbrock is just as bad.
That's why I did what I did. I made it look "semi" like TF. And there is a plug that extends further down, TurboGLH posted it above
I look at it this way, I ran 9.74 on alcohol with my Edelbrock heads like that. I run an AR3911 plug and I’m not switching so now every head Edelbrock, speedmaster type of head I touch will be relieved around the plug and radius’s. It can only help.
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What timing made best power?
One of my greatest achievements in life will be having called attention to this little detail, I’ve made my mark in the Mopar world!
I put it at 35-36 and never touched it.
locked?
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Flat top with quench?
no Sir.
flat tops in the hole with the 340 open chamber style Edelbrock heads. 1008 fel pro gasket.
How much compression?
The diamond pistons were 11.4-1 advertised but like I said the block was never cut and I did a fair amount of chamber work. I didn’t really want the open chamber heads but someone hurt one and I got them for 350 dollars. Easy chamber work fix and a couple valves. I ended up going with 2.08 valves anyway. On alcohol I fairly calculate final compression numbers. If anything I’m to low. Lol. This 408 I’m doing for 2021
Oh nice! I'm guessing Cometic head gaskets?
yes Sir. .040 or .045 but it’s been awhile since I’ve looked at them. Lol
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