well according to my electrical teacher who is a die-hard mopar fan they new "hemi" is a semi-hemi. he actually got to tear down one of the very first examples in one of his trainin classes. he said the head is slightly oval at the base to allow for a squish area. also it used flat top pistons instead of the old hemi dome pistons. is that enough proof?

 

So the 4V heads have all their valves inline??? Holy crap. Those valves must be tiny.
Dude of course we are talking about the 3V heads. Why would I want to bring up the 2V 5.4 heads? That's the ole tech. Would you want to talk about 5.9's??? BTW, the valves in both the 3V and 4V Ford are not inline. They are a pent-roof design, which is SUPERIOR to a hemispherical combustion chamber. The thing that made the hemi powerful (back in the day) was the fact that you could stuff large valves in there and could have valves canted toward their ports. It had nothing to do with the combustion chamber. As a matter of fact being truly hemispherical was detrimental, as it made it difficult to get a decent CR. Hence the new Hemi's have combustion chambers that are NOT hemispherical. Do you understand the definition of hemispherical???

 

Oh yeah, I still haven't heard you name the time and place where we can race. You tell me what to bring, my old school 460 (surely it's no match for a hemi), or my new 5.4 with 2V heads. LMK, I'll be there.

 

No shortage of mis-information and half truths here. Finally a couple people appear to be willing to race, but not with the 5.4L 3 valve, I wonder why?

Apparently some of you feel better about yourselves by calling the 5.7L a semi-hemi as if that discredits it’s 345 hp / 375 ft lb rating. Unfortunately for you, it doesn’t work that way. And in the interest of sharing knowledge with those on the forum, I’ll share the following tid-bit so you can better understand what a HEMI is and how the new one compares to the legendary HEMI powertrains of the 60s & 70s.

The new HEMI as well as the legendary 426 do not have true hemispherical combustion chambers, . . . shocking but true. However, the shape of the combustion chamber is close to being a portion of a sphere and is responsible for the popular HEMI name. BTW, feel free to explain why a pent-roof offers superior performance potential. The new HEMI also features twin plugs for improved combustion (better idle, emissions, and torque at all speeds through more repeatable and complete combustion events).

A key factor overlooked by many (not all such as bigsnag) out there is that the HEMI design features an elaborate valvetrain that places the intake and exhaust valves in-line with their ports (see picture below). The valves are canted to a near optimal position for high flow numbers and are huge (HEMI chamber coupled with canted valves allow for large valve size w.r.t. bore diameter). This is common on overhead cam engines, but unusual for pushrod engines. The new HEMI also features other goodies like cross-bolted main caps, 6 head bolts per cylinder, etc.

Left features common pushrod layout (wedge) while right features HEMI => http://www.hotrodsandhemis.com/mtr1.gif

Twin plug HEMI head => http://www.dvorakmachine.com/photos/PlungeCut1.jpg

The 5.4L 3 valve with it’s overhead cams should at least match the HEMI in specific output (power/displacement) but doesn’t. The Ford Engineers just fell short. Perhaps it was management’s fault for not setting appropriate goals, maybe marketing limited their freedom, perhaps handicapped by starting with the 5.4L 2 valve engine architecture, not enough money/time, who knows? Both engines reportedly make 80% of peak torque from 1000 rpm up. The 5.4L 3 valve doesn’t have much if anything in its favor. Can you explain “useful torque”? If the HEMI makes more torque at low (except perhaps 1000 rpm), mid, & high speeds, how does the 5.4L 3 valve make more “useful torque”? The HEMI simply owns the 5.4L 3 valve. Anyone who believes otherwise fails to grasp reality.

 

Torque, is having two spark plugs similar in effect to having a MSD ignition installed, except that you get two separate sparks instead of multiple sparks from one plug?

 

In saying that the pent roof is superior, I was referring to the fact that first off if your combustion chamber is hemispherical it is difficult to obtain a decent CR. Typically you would need a domed piston. It is difficult to get a good quench without inducing detonation in this circumstance. Pent roof designs allow for a decent CR with flat top pistons. Also a pent roof design is basically inherent to a 3, 4 or even 5 valve head. If you don't think a 4V DOHC design is superior to a hemi, then I have some swampland I can sell you.

 

I didn't say the HEMI was superior to a four valve did I? The hiearchy of designs with all else being equal usually follows the rule that the more valves you have, the better performance potential. But more valves also increase cost, usually requires more packaging space, increases friction, and gives you more components to fail (more lash adjusters, timing drive, more potential leaky valves, etc.).

In general, the two valve family varies considerably with designs such as the old flat head near the bottom and the HEMI at the top. The HEMI generally even outperforms the 2V OHC engines due to the exteme valve canting (more than you'll see on a SOHC engine). Again, there is a large variance in performance with various 2 valve designs, but the HEMI is King.

The HEMI design even eclipses the volumetric efficiency Ford has obtained with the more complex 3 valve design. If done properly, Ford should have been able to come closer to matching the HEMI's output (falls short of the HEMIs specific output - power/displacement).

I'd like to end this post again stating that the HEMI owns the 5.4L 3 valve. Anyone that disagrees, please step forward so we can hash this out.

 

Just as much or MORE canting can be obtained with a SOHC design. Ford put the valves inline on the SOHC for simplicity, however you could easily have cam followers similar to on the DOHC with them pointing opposit directions from the cam and allowing you to position the valves in a canted position inline with their respective ports.

As for the HEMI owning the 5.4, well first off it is a larger engine so it should, however in response to your obvious volumetric efficiency and hp/cid arguments, I will say that the HEMI owns the 3V 5.4L in its current configuration. Ford will easily be able to up the power output when and if they need to.

Personally, I wish Ford would stop F'ing around and go all 4V. A 4V 5.4 would stomp the hemi into a mudhole (See the 5.4 L Cobra R engine for an example). A 4V V10 would stomp Dodge's V10 and Chevy's 8.1 into the ground as well. You can check out several articles about a Ford prototype V10 mustang or the prototype 7 Litre for examples as to the power potential of a 4V V10.

 

The 5.4 in the new GT makes 500hp and 500tq, so the potential is there.

Torque, your argument is lacking. The 5.4 is SMALLER than the 5.7, therefore it SHOULD make less power. If Ford would bump the displacement to 5.7 it would equal or surpass the 5.7 Dodge, that I can assure you.

Therefore, since you are comparing apples to oranges, the 6.8 V10 OWNS the 'Hemi'.

 

[QUOTE]Originally posted by torque


The HEMI design even eclipses the volumetric efficiency Ford has obtained with the more complex 3 valve design. If done properly, Ford should have been able to come closer to matching the HEMI's output (falls short of the HEMIs specific output - power/displacement).

wow! thats alot of big words! get both motors at 100.000 miles and see who owns who.

 

Interesting that while I challenged a race to someone with a 3v 5.4, you want to race me with a 460? either way I'm game. Just curious, but what has been done to your 2v 5.4? Surely you don't need the advantage of a modified motor to beat the weak HEMI right?



Interesting. So you're saying that by increasing the 5.4's displacement by a mere 17 cubic inches or .3 litres and performing no other modifications, you can guarantee me an extra 45 horsepower and 10 ft/lb? Wow, a 14% increase in horsepower for only 17 cubic inches. I'm going to get the 470 in my race car bored an additional .010. That should be good for 30-40 HP right?

 

why can't we post attachments? i've got pictures of the 5.7,426, and boss 429 heads in my gallery (real hemi in a real truck) i don't know where you get "completely hemisphericle" from. because they ain't my freind. from left to right...boss 429, 426 5.7...

 

That's right.

Look at the difference between a 4.6 and the 2V 5.4:

4.6 231hp, 290tq
5.4 260hp, 350tq

That looks like 29hp and 60ft lbs of torque with .8 liter of displacement.

Interesting. Ford could do lots with .3 liter of displacement.

That was my point, you can't begin to make a fair comparison when the two engines in question don't have the same cubes.

If you are so into this 'Hemi'...why don't you sell that F350 and get a real truck...with a real 'Hemi'?

 

did you notice the real truck is a ford?

 

My 5.4 is a bone stock 2V motor. It happens to be a Lightning, but it is bone stock. Still want to race? Ha ha ha ha. Don't even think about challenging the old 460 as it will outrun the L.