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View Full Version : Maximum overbore?


emarsh
09-13-2009, 03:43 PM
I'm working on the chassis for a nostalgia junior fueler and the motor is next. The rules limit engine displacement to a maximum of 410 cid and the weight break and minimum weight limit engine size to about 385 cid, if I can get the car that light.

I'm thinking of a 4.125" bore Dart block but would like to keep the stroke as short as possible. Since I can't afford a billet crank that pretty much means choosing between a 3.75" and a 3.5" stroke. In order to get the displacement up with the preferred shorter stroke the bore is going to have to get big.

In your literature I saw that even with your maximum .080 overbore the engine size would be about 389 cid. Not bad but it would be nice if I could get a little more that would be nice. I read that with an .080 overbore there is still a .250 cylinder wall. I'm wondering if you think that .080 is really the limit or if there is room to go further, especially with block fillers. If so, how much further?

Thanks,

Eric

Awesome Bill
09-27-2009, 01:00 PM
I have run them @ 1400 hp and 4.200 bore size, oringed and reciever groove ofcourse with blown applications. So 4.200 is very usable but I would only go 3.625 stroke and 4.185 bore and go with a 399ci engine. jmo