40 over

[vietnam]

Ok all of you old guy's (don't be offended I am over 50!)ha Any ways My 65 that I bought a few years back was i need of a piston slap repair so I just figured rebuild the whole thing cause it just makes sense. Now I found block is .40 over standard bore. There was in the day a way to figure how much HP was given by the bore? Have a Hi Po cam. C90z-6250-C

 

[none67]

well i'm not 40, actually i'm not even half way there yet. but, i can tell you that depending on your set up you can get about 5-10 extra hp from a .40 bore. but boreing isn't just ment for gaining extra hp, the cyl. walls could have been damned ect, thus needing the bore.

 

[GaPonyFarm]

You're not getting any substancial, if any, additional power from the bored cylinders. Once the piston comes to the top, its the cylinder head's area that determines the compression ratio in its relationship to the cam.

 

[HistoricMustang]

My 289 is 40 over and I am over 55 so you are in good company here.

Seems like I did some research several years ago and the 40 over adds about 4 cubic inches. Guys/Girls, does this sound about right? I am sure this info is out on the www somewhere - how many cubes you pick up with a 30, 40, 50 or 60 over on a 289.

HistoricMustang
www.historicmustang.com

 

[none67]

well depending on what block you have: 289(bore: 4.005), or 302(bore: 4.004) you have a 289.25, or a 289.10, respectively. when most people bore them out they just go to a 4.030 or a 4.040.

so if your bore is a 4.040 you have a 294.32.

Hope that helps.

 

[vietnam]

Thanks to all of you every piece of info builds to a answer. The prof will be in the dyno.

 

[DAZ]

well depending on what block you have: 289(bore: 4.005), or 302(bore: 4.004) you have a 289.25, or a 289.10, respectively. when most people bore them out they just go to a 4.030 or a 4.040.

so if your bore is a 4.040 you have a 294.32.

Hope that helps.

So I assume that would make a 302 @ .030 a 305?

 

[LMan]

another boreout will take you to .060, which is the block's practical limit. watch out for overheating, or, get another block.

 

[SandSprite]

So I assume that would make a 302 @ .030 a 305?

a 30over 302 is a 306. i'm pretty sure on that.

 

[67coupe351w]

Cubes = bore^2 * (pi/4) * stroke * # of cylinders.

 

[DAZ]

a 30over 302 is a 306. i'm pretty sure on that.

Thanks! I am having my 1966 Mustang delivered this weekend. The engine
did not have any knocks or valve taping and it seemed to run very smooth.
Engine compartment barley reacted when it was reved up.
There was a little bi of black smoke when first starting, then it tunred white then turned normal mist. So I don't think there will be any problems... I'll keep my fingers crossed.

 

[none67]

A 302 stroke with a 4.03 bore is 306.13, its a good engine.