Super Stock Hemi Engine Build

Discussion of the 426 Street / Strip HEMIs.

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scottm
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Super Stock Hemi Engine Build

Post by scottm » Wed Jan 27, 2010 8:59 am

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Super Stock Hemi Engine Build - All The Tricks
http://www.moparmusclemagazine.com/tech ... index.html
Whether you're a Mopar enthusiast or not, the dominance of Hemi-powered A-Bodies in Super Stock drag racing is indisputable. As seemed to be the norm back in the heyday of musclecars, Chrysler set their sights on dominating the ranks of a racing class and did just that with their Hurst-built Barracudas and Darts. Fortunately, rather than banning Chrysler's winning combination like NASCAR later deemed appropriate, drag racing sanctioning bodies simply modified class rules to accommodate the quicker cars, eventually leading to the Pro Stock class. After many years of ruling the SS/AA class with no real brand-X contenders, the NHRA made a class exclusively for the Hemi-powered Super Stock A-Bodies, and SS/AH racing was born.

When the Super Stock Darts and Barracudas hit the track in the late '60s, drag racing was a different world. These were not purpose-built chassis, rather they were street cars converted for race use. Racers hauled their cars on open trailers with station wagons and pickup trucks, not semis and motor coaches; chassis, engine, and tire technology were in their youth. A racer could literally purchase one of these cars from the factory, then with very few modifications race the car competitively. Elapsed times in the 10-second range were considered extremely quick, but the Hemi Darts and Barracudas clicked off 10-second passes with apparent ease. As the class evolved over the years, racing technology helped these cars get quicker and quicker, and sanctioning bodies were forced into rule changes for the safety of the sport.

As the Darts and Barracudas became more powerful thanks to improving engine technology, and traction got better thanks to improving tire technology, the wheelies got higher and elapsed times kept getting lower. Ultimately, the NHRA was forced to allow wheelie bars and suspension upgrades for safety reasons, but as a side effect, the cars again got quicker. Cars running deep in the 9-second range were common during the '90s, and the 8-second barrier was quickly broken as well.

Modern engine technology has again given this class a boost with engine builders getting more and more power from the factory 426 powerplant. Currently, if you plan to be competitive in the SS/AH class you'd better run in the 8s, deep in the 8s!

To get a full-bodied Barracuda to run deep 8s takes power and a lot of it. Charlie Westcott Jr. and his team have been making enough power in their "War fish" Super Stockers to not only be competitive, but also to set several class records. Making this kind of power is serious business, and requires many hours of hand massaging each part for maximum performance.

Though engine builders in this class are typically a very secretive bunch, Charlie Westcott Jr. and his team allowed us to look at what goes into their Super Stock Hemi engines. in case you don't think Charlie Westcott and his crew are the right guys to show us what's inside one of these things, guess again. In the last Hemi Super Stock race, seven of the twelve top qualifiers were running an engine built by Charlie and company. We'd say that qualifies him.
Follow the link to get all of the build details. Not a new article, but good stuff.

Goran
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Re: Super Stock Hemi Engine Build

Post by Goran » Fri Feb 05, 2010 11:57 am

I have tried to find someone who has knowledge of the hemispheric combustion chamber, but it
seems difficult to find. I'm trying to find out the significance of the combustion chamber shape
to incineration, not the function of the Hemi engine in its entirety.
Goran
I am a 69 years old sportscar freak living in Sweden with a Hemi equipped Pantera.

mart
Posts: 536
Joined: Tue Mar 22, 2005 2:06 pm

Re: Super Stock Hemi Engine Build

Post by mart » Tue Feb 09, 2010 4:05 pm

Goran wrote:I have tried to find someone who has knowledge of the hemispheric combustion chamber, but it
seems difficult to find. I'm trying to find out the significance of the combustion chamber shape
to incineration, not the function of the Hemi engine in its entirety.
Goran
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There are several advantages of a hemispherical combustion chamber, both for breathing and for combustion efficiency. First,
the chamber design allows for much bigger valves for a given bore
size than with a wedge type chamber. Secondly, the valves, besides being bigger than would otherwise be possible for a given bore size, are also completely unshrouded. Large valves in a wedge chamber end up being shrouded and flow-limited by valve's close proximity to the chamber walls and with a high-lift camshaft, by the cylinder walls too. Thirdly, because the valves in a hemi chamber are inclined *in the direction of gas flow*, the ports end up being very short and straight, giving the a nice, straight shot into the combustion chamber.....or in the case of exhaust, a nice straight shot out. Beyond the breathing advantages, combustion efficiency is very high with a hemi too. First, a hemi chamber gives the minimum amount of surface area for a given chamber volume - less 'surface area to volume' than any other design - so heat loss is kept to a minimum. Secondly, the usual central or near central spark plug location and the smooth, half-round 'increasing radius' shape of the hemi chamber tends to give very smooth and even combustion and smooth, steady flame propagation, allowing for more compression - and hence, more power and eficency - on a given fuel octane, than other chamber designs.

mart
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