Ram 5.7L Hemi Heads

[Danno]

Came across these in our shop.
Things I noticed, all probably discussed before, but here we go.

1. Combustion chamber isn't hemi but oval
2. The valves are large, which made dual plugs necessary. Center mount plug not an option.
3. Spark plugs are not indexed, not sure if that's possible or if it would help combustion. and if so, what would the indexing play be?

 

[Nessism1]

The "bath tube" shaped combustion chamber leads to lower emissions and more efficient in general. I remember seeing that on motorcycle heads back in the early 1980's.

Dual plugs is another efficiency thing. Center spark plugs on a two valve head?

Does indexing spark plugs provide verifiable benefit?

 

[benjy]

HEMI is typical MARKETING BUT reading notes the technology is BETTER! manufacturers only care about PROFITS but modern engines are generally BETTER making more power + lowering pollution BUT typical cost cutting with inferior parts is the PROBLEM IMO + as engines continue to get more COMPLICATED PROBLEMS will continue to rise $$$$

 

[OVERKILL]

Came across these in our shop.
Things I noticed, all probably discussed before, but here we go.

1. Combustion chamber isn't hemi but oval
2. The valves are large, which made dual plugs necessary. Center mount plug not an option.
3. Spark plugs are not indexed, not sure if that's possible or if it would help combustion. and if so, what would the indexing play be?

View attachment 250426

The size of the valves doesn't dictate the requirement for dual ignition (could have used an offset single plug), that was added (it's phased) to aide in low speed emissions performance as the design has poor swirl and flame front propagation characteristics at low port speed, which tends to lead to incomplete combustion. Igniting two flame fronts, one after the other is designed to mitigate this.

This is actually a very old technique originally used on big bore engines back in the 1920's (I've seen it on a few antique boat engines).

The Mazda 4-cylinder used in the Ranger also had dual ignition for this reason.

The addition of quench areas on the sides of the chambers (why they are oval rather than round) was done to improve low speed manners and performance, again, due to the low swirl at low speeds inherent to a hemispherical chamber, which performs best with high volumes of air being ingested at a high rate of speed. The BOSS 429 suffered from the same issue, which was why Ford added a quench area to the chambers on those heads.

I got into some of this in a previous thread, which I can link you to if you are interested.

 

[BrianF]

What he said^^

I had read about this in some Mopar magazine back when the gen 2 or 4 or 5 or whatever gen came out in the 2009 trucks. They went over the changes from the previous iteration and mentioned the dual quench areas as a big improvement.

@OVERKILL whether the OP is into it or not, I would gladly read the link.

Thanks

 

[clinebarger]

The size of the valves doesn't dictate the requirement for dual ignition (could have used an offset single plug), that was added (it's phased) to aide in low speed emissions performance as the design has poor swirl and flame front propagation characteristics at low port speed, which tends to lead to incomplete combustion. Igniting two flame fronts, one after the other is designed to mitigate this.

This is actually a very old technique originally used on big bore engines back in the 1920's (I've seen it on a few antique boat engines).

The Mazda 4-cylinder used in the Ranger also had dual ignition for this reason.

The addition of quench areas on the sides of the chambers (why they are oval rather than round) was done to improve low speed manners and performance, again, due to the low swirl at low speeds inherent to a hemispherical chamber, which performs best with high volumes of air being ingested at a high rate of speed. The BOSS 429 suffered from the same issue, which was why Ford added a quench area to the chambers on those heads.

I got into some of this in a previous thread, which I can link you to if you are interested.

Not that much different than the Ford 6.2L combustion chamber.

The dual plug 2.3L & 2.5L SOHC engines used in the Ranger was a Ford design.

 

[OVERKILL]

Not that much different than the Ford 6.2L combustion chamber.

The dual plug 2.3L & 2.5L SOHC engines used in the Ranger was a Ford design.

For some reason I thought Mazda had a role in the dual plug head development for the Lima 2.3L but it's been a few decades lol.

And yes, the 6.2L looks like a "twisted" HEMI:

 

[OVERKILL]

What he said^^

I had read about this in some Mopar magazine back when the gen 2 or 4 or 5 or whatever gen came out in the 2009 trucks. They went over the changes from the previous iteration and mentioned the dual quench areas as a big improvement.

@OVERKILL whether the OP is into it or not, I would gladly read the link.

Thanks

OK, this one has some neat pics, but not a lot of history:

Post in thread 'Engine oil for brand new 6.4 Hemi in Charger?'

Oct 26, 2022

If you are talking about the street hemi 426 from the mid 60s to the early 70s....they were ALL a true HEMI head....

I should probably have noted that I'm using HEMI here in the colloquial manner, referring to anything using hemispherical-style chambers, kind of like how most facial tissue gets called "kleenex" despite both being brands from specific companies.

I was referring to Ford's pursuit of using HEMI chambers too, which started with the 427 SOHC, which had true hemispherical chambers:

and the Can-am and competition versions of the BOSS 429 also had fully...

• OVERKILL

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This one has more history, but not as diverse pics:

Post in thread 'Fram Ultra XG2 (OG) C&P (9,584km)'

Oct 5, 2021

I never knew this. Well, had I ever been involved with building a Hemi engine I would have known.
Nothing against todays Hemi engines, but I have always thought that the TRUE/REAL Hemi engines were built from 1950-1971. The 426 being the KING OF THE HILL!
And, yes it's true, MOPAR/Chrysler still uses the same hemispherical cylinder head ("hemi-head") design for it's current Hemi engine equipped vehicles. Which I applaud very loudly for.
But, why is it so dirty? You state because of its big bore? You would think that with all of the history of the Hemi the engineers would have figured...

• OVERKILL

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