Is the s65 a Hemi?

[luxbmw]

As stated, does anyone know if the s65 uses hemispherical combustion chambers?

THX

[Someone?]

Yup

[luxbmw]

Yeah just found a pic, I guess pretty much all modern engines use a pentroof design to accommodate four valves

[W Cole]

Yes of course.

[regular guy]

Photos of S65 cylinder head.





More cylinder head photos:
http://www.rcollins-home.org/photobu...s.php?album=85

Full engine build photos:
http://www.rcollins-home.org/photobu...dex.php?cat=35

[luxbmw]

That is just sexy.

[blankstar43]

I had no idea, learn something new everyday

[kenwelch]

But not an real "old school" HEMI

[M3-S65]

Confused, I thought that pentroof design was more efficient and used almost exclusively in all performance engines today.
Hemi being outdated....yet picture that was posted seems to say that they are one of the same thing...??????

[M3-S65]

Okay I pulled out "Automotive Technology A Systems Approach"
It states the following:

"Many of today's engines have a pentroof combustion chamber. This design is a modified hemispherical chamber."

So technically do we have a pentroof combustion chamber or some sort of combination?

[M3-S65]

More information ....from Google search...It appears we have a "Pentroof" like everyone else not a true "Hemi" too inefficient and outdated...if this is not correct I would like to know...mechanical gods please explain.

Hemi breakdown:

1. They were NOT invented in the US. They were in use by some Europeans early as the 30's
2. Theoretically they should be the most efficient design. But due to their surface area they end up soaking up alot of the heat produced in the cylinder. heat is power
3. The valves have to go somewhere, this also throws a wrench in the works. This throws of the shape and puts the valves at weird angles.
4. The classic American HEMI chamber was so big that the size of the dome ended up being inefficient. It was however better than the other american heads of the time.
5. European cars had already ditched the HEMI and moved onto the pent roof by the time it came out.
6. The modern HEMI isn't a HEMI at all. It's a pent-roof like ours.
7. The HEMI is an obsolete design no longer in use except in classic cars. So it has no relevance to us or any other discussion of modern engines.

Pentroof:
1. Provides many of the hemispherical benefits but it allows:
-4 valves per cylinder
-More thermodynamically efficient
-Better valve angle
-Easier manufacturing
-Comparable burn efficiency
-Better flow in/out of the cylinder
2. Everyone uses a pent roof these days.

[Jonjt]

There are no modern memis. Hemispherical combustion chambers were shown to be inferior to pentroof designs a while ago.

[kenwelch]

The Welch Brothers used Hemi combustion chamber design in 1901. Their 1909 model vehicle was expensive at $7000.00

http://theoldmotor.com/?p=13724