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Discussion Starter #1
I noticed in the "stroker" forum that a lot of folks talk about building 460 strokers utilizing 4.5" pistons! What is the advantage of the big bore versus a .030 or .060 0ver piston with a longer (4.5) stroke?

I am building a 545 by utilizing a .030 over(4.390) piston and a 4.5 stroke with 6.7 H-beam rods.

You all have me wondering...
 

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The advantage of using a bigger bore rather than more stroke is to decrease the internal mach speed of the motor. If piston speed is less, the engine will last longer. And not blow up
 

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Theoreticaly speaking it will last longer, I haven't seen it. Boring a production block .140 is iffy even if you have a good early block. Most of us can't afford a MS block. I like the 6.7 rod, 4.5 stroke, .030 bore. You can rebuild the engine without finding another block & for me, I can still use my tapered ring compressor.
 

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That's a nice stroker combo Tom, same I'll use on mine. A lot of folks (not me) who build strokers feel they must spin it the same rpm as the stock motor. Me thinks it kind of defeats the purpose of a stroker, ie more torque at lower rpm's.
 

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Years ago, telling my age now, you use to hear the terms "Under square" and "Over Square" They basically refer to the relation ship of the bore to the stroke, btw, square would be the bore and stroke are the same, i.e., 400M has a 4" bore and a 4" stroke.

Generally the under square engine was thought and is build to be high rpm motor since the bore was larger than the stroke.

The over square motors were built for torque with the stroke being greater than the bore.

Most of this applies to the old flatheads when the cam technology wasn't as advanced as it is today. But, in some cases, these terms still apply.

BTW, give me torque anyday over high rpm HP. You might catch me in the long haul, but in the short distance, the torque will get me moving and gone.
 

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I think there are a lot of different answers to why the massive overbore. Pick one-
1)Because they can
2)More is better, too much is just right
3)Heard someone else did it
4)Cheap extra cubes
5)Trying to use a specific piston
6)Theoretical stuff (see Mike's post)
I think a modest overbore with the thought that you can run the thing practically forever by freshening it up makes perfect sense.
 

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Discussion Starter #8
Thanks for the replies. I guess I'm on the right track with what I committed to.
Rcode, thanks for the technical reply!!(Hey Paul!)

<font size=-1>[ This Message was edited by: a1320tom on 4/18/02 6:29am ]</font>
 

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Discussion Starter #9
Greg Cook,
Do you have any idea of what cam and carburator he ran on that?
I am planning on using a Comp Cam, 256/266, .589/.615, 108*
Tom

<font size=-1>[ This Message was edited by: a1320tom on 4/19/02 7:53am ]</font>

<font size=-1>[ This Message was edited by: a1320tom on 4/19/02 7:56am ]</font>
 

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Well, Tom I don't know anything about 545 Mike's cam specs, but the HP calculator says with a 3500lb car and 750fwhp, 9.99 is the perfect world ET. Droolin' yet?
 

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cr is 13.-1, 1240 dominator, 4.5 stroke, 3.390 bore(.030 over) cam is 650I, 643E, 250/260 duration at .050 and 108 centerline. alot of people said the cam was to small center line, ill give them a ride and change their minds. 510.5 hp and 475 tq at rear wheels, 6500rpm and i stoped it, it wants more, car is 3190lbs, at 200lb for me
, if you need more info, let me know , im not nasa im willing to tell
 

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Discussion Starter #12
YIKES!!!!!!!!!!!!
Thanks for the replies Mike and Greg!
Music to my ears!!
I don't think I have the heads to support those big cams...yet.
I'm using stock '69 75cc(+/-) heads with basic match-port and slightly larger exhaust valve. Based on that head do you think a 800cfm carb is enough for now? Obviously at such time I get better heads I'll need to step up the carb cfm's...
Tom
 

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Discussion Starter #13
Hah!!
Yeah the heads are C9VE's. Sounds like they'll be similar to the heads on your fairlane.
And yes, I'm with you, set it up with what I've got and see what it does. I expect it to meet my expectations for this year. It'll be primarily raced (hoping to run low 11s), with perhaps 2x a year runs to the hamburger stand or the infamous New Years Day Hot Dog, Hot Rod, Street Rod, Rod Run!
 

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Now you got to spend a lot on the chassis to take advantage of that 545. Hopefully you won't wear that 545 out before you finally get the tires to stick
Mike, you are CRAZY!
 

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Discussion Starter #16
OK, I finally made some passes on the 545. Went like this...the three times that I actually hooked, it went 11.31, 11.31 and 11.32. That on the 800 double pumper, shifting at 5500 and going through the lights at 5900, 119.6MPH with 3.70 gears. I have a 1050 dominator coming. Can't wait to see if that makes a dif. I don't have all the safety stuff for tens, in fact I am not sure what's needed. I am running a 67 mustang fastback, and I hear that if you have the stock firewall (I do) you don't need the window net and maybe not the 10 pt rollbar...If anyone knows for sure let me know. I run summit series (NHRA).
Tom
 
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