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Author Topic:   Dome Piston Vs. Small Chamber
d4490
Dirt Maniac

Total posts: 113
posted April 16, 2003 11:41 AM
Knowing that a flat top/dished piston give a better flame travel than a dome piston, how much hore power is gained by going with the flat top/dished piston. I am looking at a 347 Ford small block with around 15:1 compression.

towmandan
Dirt Maniac

Total posts: 110
posted April 16, 2003 01:06 PM
If you hope to achieve 15to1 compression your not gonna get it with a flat top piston unless youve come up with a cyl. head Ive never heard of .....towman

outlawstock17
Dirt Forum Champ
Total posts: 620
posted April 16, 2003 02:34 PM
i hope you have an svo block. 15 to 1 will blow the crank out of the bottom of a production ford block.

The Rascal
Dirt Roller

Total posts: 13
posted April 16, 2003 06:01 PM
Think of the piston top as the "floor" of the chamber...so...it really doesn't matter...the "flat-top & airflow/power" deal is really just a general rule...or no brainer way of doing it "right"...now moving parts don't like additional weight...so in general we try to do things with a smaller chamber to keep piston weight...but to be honest I aint married to that...small chambers shroud the valves but in most restricted motors the biggest choke lies elsewhere...with our stuff anyway...can't offer anything on the Ford motors in particular...a good compromise with our stuff has been a closed yet shallow chamber with a quench pad we can work together with a pad on the piston...in essense a mini-dome...Rascal

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"blessed mother of acceleration don't fail us now!" Elwood Blues

sdhnc29
Dirt Freak

Total posts: 467
posted April 16, 2003 10:32 PM
It is actually very possible to get your 15:1 with a flat top , depending on which head your trying to use . If your speaking about using the N351 steel head , then it is possible . I'm doing a limited late model engine right now , that is a 3.335" stroke X 4.125 (357ci), using the N351 head and flat top piston's , and it is 15.1:1 . You must understand though , that there is a lot of work that goes into a combo like this . This combo is also due to the track rules that are designed to save money for the racer (HA! HA!) , by not allowing domed piston's .

You are correct in your thought's about the flat top vs. dome piston . In every case , a flat top piston engine with the same compression ratio , and the same air flow number's from the head's , will produce more power than a dome piston engine . So generally you will find "little" race engines with the smallest dome possible to achieve the correct compression ratio . In most every situation using a modern racing cylinder head , the dome on a piston will only be large enough to displace the loss in CC's from the valve pocket . Basically , the day of the 15cc domed piston's is long since past , for any combo that you want to produce a lot of power in .

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

towmandan
Dirt Maniac

Total posts: 110
posted April 16, 2003 10:42 PM
What cc is the combustion chamber on these heads when you get them done?

outlawstock17
Dirt Forum Champ
Total posts: 620
posted April 17, 2003 11:58 AM
hey steve. i have a question for you. i'm running the "N" head and i was wondering how much can you safely angle mill them. 1996 casting, never been cut.

sdhnc29
Dirt Freak

Total posts: 467
posted April 17, 2003 12:25 PM
towmandan ,

This particular combo uses 40cc chambers .

outlawstock17 ,

We don't actually angle mill the N351 head , we flat mill it . Due to the spark plug location , this limit's the angle milling and you don't lose as many CC's as you think you would . We flat mill the one's that we do up to .180" . I would not suggest going this route unless you absolutely have to . This type of combo is labor intensive and it gets very expensive .

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

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