Hemi vs. Wedge

[A/Fuel]

I have been in a discussion here, and i think i need a dose of reality at this point.
the problem is, i have begun to doubt my beloved Hemi.
what we are talking about conserns N/A applications only (well maybe nitro, but thats a different story, well maybe not)
lets say we are most concerned with 5000-7500rpm what do you guys think would be better?
here are some of my points.
1) i think its easier to make more compression in a wedge style head than a hemi.
2) cams....try to go crazy with the lift on a hemi and you end up slaming the valves into each other.
3) i'm thinking that smaller ports, and smaller valves, shrouding wouldn't come into play much. 4.375 bore. and it might acually flow better in this rpm range. 2.45 x 1.94 valves vs. 2.30 x 1.88.
4) smaller combustion chambers might be better for use with a slow burning fuel. you could even cut a grove in the quench area and angle it toward the spark plug(s) if dome type pistons are used.
at what rpm would a hemi pull away from a wedge? opinions please.....
thanks

[SpiderGearsMan]

Re: Hemi vs. Wedge

2) cams....try to go crazy with the lift on a hemi and you end up slaming the valves into each other.

WHAT ?

[A/Fuel]

Re: Hemi vs. Wedge

i deserve that. i guess thats what i get for talking on the phone at the same time, and not re-reading before i hit the post button.
but really, no one else has any thoughts on this?

[BigBlockMopar]

Re: Hemi vs. Wedge

lets say we are most concerned with 5000-7500rpm what do you guys think would be better?

Ok, with my limited amount of experience when it comes to Hemi's, I am still under the impression Hemi-heads combust fuel and breathe better then wedge heads.

here are some of my points.
1) i think its easier to make more compression in a wedge style head than a hemi.
2) cams....try to go crazy with the lift on a hemi and you end up slaming the valves into each other.
3) i'm thinking that smaller ports, and smaller valves, shrouding wouldn't come into play much. 4.375 bore. and it might acually flow better in this rpm range. 2.45 x 1.94 valves vs. 2.30 x 1.88.
4) smaller combustion chambers might be better for use with a slow burning fuel. you could even cut a grove in the quench area and angle it toward the spark plug(s) if dome type pistons are used.
at what rpm would a hemi pull away from a wedge? opinions please.....
thanks

The last sentence reminds me of an old magazine article where they put a 440-Roadrunner on the strip next to a Hemi-Roadrunner.
As expected then, the 440 took the lead by a carlength and at 3/4 track the better breathing Hemi (stock) pulled in front and beat the 440.
We're talking stock motors here of course.
Then again it's 'easier' (cheaper) to buy Wedge motor performance parts then Hemi-parts so I don't think it's that strange that the Wedges have more potential these days.
On the other hand, if Wedges were really better engine-heads to begin with, wouldn't a TopFueler be the first to benefit from this?

[A/Fuel]

Re: Hemi vs. Wedge

well my thinking right now is that a top fuel car benefits from boost, and it makes up for the lack of compression, and large valves and runners.

[Ron Ward]

Re: Hemi vs. Wedge

Let me sum this up....


In the NMCA, the only head's up classes in which Hemi-headed engines are allowed to compete are Pro Street and Super Street. The reason, I have been told, is that because the Hemi-head configuration is so far superior to others there would have to be a substantial weight penalty imposed on the Hemi cars. So substantial, in fact, that the weight of the vehicle would surpass the maximum allowed per the SFI chassis certification for the classes. Go ahead and talk about big block Chevys being superior, but the fact remains, Hemis are outlawed for a reason: they dominate the competition.

Ron

[Brian Lohnes]

Re: Hemi vs. Wedge

Ron....well said and nearly impossible to deny.

IHRA Pro Stock is another great example.

Dodges competes with a Hemi headed motor
Fords compete with a (say it with me now) Hemi headed motor
The top running Chevys compete with Sonny Leonard "Next Generation" Hemi heads.

Here's a shot of the Sonny's heads with some machine work remaining...

http://www.superchevy.com/technical/engines_drivetrain/completebuilds_testing/0404sc_hemi_copy/photo_09.html

Brian

[CTX-SLPR]

Re: Hemi vs. Wedge

I think the new metric "Hemi" has a better chamber design than the original. The original hemis were pure domes, that gives you a very nice place to put a central plug and big valves that clear one another but to put a dome on the piston big enough to get the compression up you end up with a block to the flame travel though with the central plugs its not as big of a deal. I think you see twin plug TF hemis to combat this issue by kicking off the flame travel on both sides of the dome and thats why the twin plugs came back on the metric "Hemi". The new metric "Hemi" is actually a pent roof of sorts, all the benifits of having the valves on opposing sides of the chamber and the central spark plugs but you get reduced chamber volume, more quench and I'm still a believer till proven otherwise that smaller head chambers and bigger piston dishes are more efficient than the reverse which is exactly what the old Hemi was.
Throw into the argument that Ford made the "shotgun Hemi" and the SOHC Hemi heads for its motors, GM developed a few that never went anywhere, Toyota made Hemi's, and just about every DOHC motor uses a pent roof or hemi chamber ads to the fuel for its design merits.

Of course, I'm a Buick guy and not a thermodynamicist so I'm just making a decent WAG at this question.

[SpiderGearsMan]

Re: Hemi vs. Wedge

is it the hemi or the crazy cubes that the ford shotgun motor can be built for ?
I am not sure if sonny's chev hemi is legal in ihra pro stock
NHRA they run comp eliminator

[Brian Lohnes]

Re: Hemi vs. Wedge

Spider...not only legal, it's the only thing that saved the "Chevy" in that class. Before those heads came out the Chevies were a dying breed. Now they can really hang with the Fords. Ironically, the Dodges are on the outs

Spent the last two seasons calling IHRA Natl events.

Vinny Decigle's (butchered spelling) A/A Corvette ran a 600 inch "Next Gen" headed version of the 815 monsters the IHRA PS guys run. That car was flat nasty.

Brian

[Matt Cramer]

Re: Hemi vs. Wedge

The Hemi has better breathing but a worse combustion chamber when you try to turn up the compression. It's less of a factor in low compression motors, which is what makes them so devestating in blower applications.

[SpiderGearsMan]

Re: Hemi vs. Wedge

Spider...not only legal, it's the only thing that saved the "Chevy" in that class. Before those heads came out the Chevies were a dying breed. Now they can really hang with the Fords. Ironically, the Dodges are on the outs

Spent the last two seasons calling IHRA Natl events.

Vinny Decigle's (butchered spelling) A/A Corvette ran a 600 inch "Next Gen" headed version of the 815 monsters the IHRA PS guys run. That car was flat nasty.

Brian

I don't pay much attention to IHRA pro stock , the last IHRA race I went to was the Epping race the saturday before 9/11/01 . NHRA pro stock was getting to be a bit of bore until jeggy stole the championship from inevitable KB framers . I don't like the 5.0 bore center blocks and common template bodies - the grand am becomes the cobalt becomes the gto becomes the gxp
real hemis are cool and a super stock crowd pleaser