Drag Racing Discussions > Six Cylinder Drag Vehicles

New 6 cylinder Motor Idea For My SDRA Dragster

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Dolmetsch:
Nope I haven't. However might I be so bold as to suggest a set of custom made pistons. They are not particularly expensive. I use Ross for most of my special needs.
Having said that , what is wrong with 10.6 to 1? A bit of head and block planning will get close to 11 to1.
Once I get to 10 to 1 static ratio the only reason I look for more is so I can add camshaft duration.  Compression in and of itself is not the factor. When we increase duration the intake valve is held open longer into the beginning of the compression stroke. This effectively shortens the amount of stroke available to make cyl pressure so the only way to keep pressure up where we want it is to rise the static ratio of the engine so the end result  is where it was before. I work a lot with cranking compression. I can tell far more from that then anything else including forty pages of math. A good powerful bracket engine expected to be competitive and run  long time wants a cranking compression is about 175 PSI regardless of cam used. I do whatever I need to to get there. (My slant is there right now) This relationship between engine compression and camshaft duration is the biggest speed secret. Once one understands that everything changes and much of your competition becomes cannon fodder.  There is among us  North  Americans a real tendency to always think bigger louder longer is better when in fact right is better and often more is just more $ spent often paying back nothing but bragging rights. I spend a lot of time sorting this relationship out and have now my cams custom ground to my specs to match my motors needs. Duration is determined by needed RPM. Compression is determined from Duration required. Lift is determined from Cyl head flow testing (since I am on the subject.)
don

old28:

Don -- I sent you a PM today 11/13/2014

Serendipity:

--- Quote from: Hoss on October 04, 2013, 05:59:49 AM ---We have a pretty good class of SDRA cars that run here at Tulsa.
They need to change to slicks. They run a index so tires really do not matter.
The street tires really screw the track so they always have to run last.

Hoss

--- End quote ---

What effect do street tires have on the track?

Lenny

George:

--- Quote from: Serendipity on January 08, 2015, 11:41:38 AM ---
--- Quote from: Hoss on October 04, 2013, 05:59:49 AM ---We have a pretty good class of SDRA cars that run here at Tulsa.
They need to change to slicks. They run a index so tires really do not matter.
The street tires really screw the track so they always have to run last.

Hoss

--- End quote ---

What effect do street tires have on the track?

Lenny

--- End quote ---
Besides tracking junk onto the racing surface the treaded tires tend to tear up the good rubber. I try and make sure a slick tire class runs ahead of our group. I would prefer the street tires not run on the same day. George

old28:
Treaded tires on a SDRA or HA/GR dragster like mine with 250 HP or less don't tare up the so called good rubber like a 4000# door car with street tires. We have been running with the ANRA group out of Bakersfield, CA for over 10 years and have had no real problems. 9.60 index open wheel & 9.60 index gas door cars with slicks run right after use and have no problem hitting their index numbers. We do not use the water box so as to not pull any water up into the stage area.

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