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Author Topic:   ? for Engine Builders (Dart block deck height?)
OKC9
Dirt Full Roller

Total posts: 52
posted August 31, 2005 03:54 PM  
One local builder says zero deck it, use flat tops and milled heads to get desired compression with better flame travel. Another builder says leave it at +.025 and use dome pistons. 421 c.i. with 230 heads and dart intake. Is it worth the money to deck it and mill the heads? What are the pro's and con's? Thanks in advance.

akadirtracer7
Dirt Freak

Total posts: 217
posted August 31, 2005 05:36 PM  
I hear flat tops but opinions are like you know what.

leapinlizard
Dirt Freak

Total posts: 402
posted September 01, 2005 07:44 AM  
Domed piston are heavier than flattops. That limit's rpm before pulling a pin out or breaking a rod.

Domed piston also interfere with flame front propogation. You can make more power with a flat top but sometimes domes can make good power cheaper and easier. I would deck to 9.0000 and run a piston to zero deck and a .041 head gasket with angle milled heads. Shoot for about 13.0 and you'll make plenty of power.

rocket36
Dirt Freak

Total posts: 209
posted September 01, 2005 09:35 AM  
if you have the option. flat top or dished pistons are way better than the big, heavy lump sitting up on top in the way. personally i'm not a fan of angle milling. much better to purchase the right head with the right combustion chamber size and then the right piston design to achieve your desired compression.

Kromulous
Dirt Forum Champ
Total posts: 796
posted September 01, 2005 10:10 AM  
The problem is if you arnt going the SB2.2 route, your never going to find a cylinder head with a cobustion chamber small enough.

With a zero deck flat top your gonna need to be at 50cc or smaller to get them compression numbers.

If your on a budget, get the 49cc Darts, flat tops and call it a day at about 13 to 1.

There is a thread about this very subject on 4m.net, go check it out, its down at the bottom in the power train section.

Krom.

stockcar5
Dirt Forum Champ
Total posts: 578
posted September 07, 2005 11:01 AM  
with 49cc darts a 421 would be 14.6 to 1 with flat tops. i'd go the flat top route.

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