32v bbc heads with 561cfm flow at .700 lift!

[robertisaar]

i think the pushrod angle comment was refering to these OHV 4 valve/cyl heads, not the DOHC ZR1...

[Raffaelli]

I got a article in a box at home(Hot VWs), a 16V air cooled bug. Has twin turbo, four carbs and the coolest looking intercooler ever. Point is, pushrod 4V/cyl is not totally out of reach.

Latemodels right, there are few REAL hemis. And the new ones are overrated anyway. My 82 Toyota pickup shatbox has a hemi style chamber. Its the crossflow that matters.

[no_doz]

if the hemi design was so great how come its not used on squat-other than big monster v8s?

[robertisaar]

its actually used on a few motors, it just never gets advertised.

kind of like the hemi slant-6 thats was made a while ago... technically it wasn't a hemi, it was actually a more efficient design.

[no_doz]

what i mean is, compared to the old flatheads, many engines nowadays could be classified as "hemi" but why is it only marketed on big v8's?

[robertisaar]

why is it only marketed on big v8's?

CAUSE IT GAT A HIMI!!!

probably more of a nostalgia thing...

[geoffinbc]

if the hemi design was so great how come its not used on squat-other than big monster v8s?

Because they are only do one thing good. Flow air. Their cross flow valve arrangement and splayed valves with a straight shot to the valves from the ports on both the intake an exhaust lend very well to flowing air. So whats wrong with the head then?

The Hemi head has a very large combustion chamber volume. Which requires a large dome piston in order to get a reasonable compression. This large dome is the shits for promoting a good flame front and burning all the fuel up quickly. So naturally the emissions are high and detonation now becomes a major factor. Not a problem on leaded gas engines from the late 60's. But today with 87 octane and tight emissions it doesn't work so well. So when the new Hemi came out Dodge cast the chambers with a quench pad on each side and dual plugs to start two flame fronts and make sure the combustion process was completed. A lot of people say it is not a true Hemi but really it is much better than the old one and still has what made the Hemi great in the first place.

The best example of a modern combustion chamber started with the Ford Cleavland and Oldsmobile and continues with todays LS Series head. The chamber is very flat and small and the plug is centrally located. This promotes a great, fast burn which results in low emissions and more power with less chance of detonation. Plus you can run much less ignition lead which means less pumping losses. Heads like these are so good in fact that the Oldsmobile was used well into the 90's with a Carb and it still passed emission standards and got great fuel economy. Most engine by then had fully switched to fuel injection. The Cleavland was killed by Ford in favor of the less desired Windsor motor which was later reduced to an 8.2" deck height 5.0L for use in the Mustang. Breathing is no longer a problem with modern port design so the Hemi really has no distinct advantage in that department anymore.

A 400M Ford (which is a 400 CI Clevland used in trucks) was the winner of this years Engine Masters challenge. But next year they are allowing modern motors. So who do you think will take it? Chevy LS, Ford MOD, or Dodge Hemi. Or will the old iron still take the prize?