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Author Topic: ?? Bore and Stroke ??  (Read 3064 times)

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jlcpcnc

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?? Bore and Stroke ??
« on: December 12, 2013, 18:49:24 »

So, come taxes.......My Father in law has a 360 short block

I want to rebuild the motor and have it bored and stroked and built

I went here to do some number stuff - http://www.mindsciencemotorsports.com/graphics/tech.htm


I hear people talking about having a motor bored and blue printer and stroked.


So, the stoke bore and stroke is 3.58 by 4.00 = 360ci


Now I do not know what 30 over 40 over 60 over means but i plugged in some numbers to the calculator AND,


With a bore of 4.125 and a stroke of 3.58 I can get 400ci


Now, I am assume you can get 400ci with a combination of bore and stroke.......


My question is to get from 4.00 to 4.125 what does that mean as fare as boring a motor "over" ?


Example 30 over means.....how many ci ????


And so forth, is it even possible to go from 360 to 400 ---- i am sure i do not know what i am talking about.
« Last Edit: December 12, 2013, 18:55:44 by jlcpcnc »
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Re: ?? Bore and Stroke ??
« Reply #1 on: December 12, 2013, 19:53:11 »

in a stock 360 block, you really cannot expect to overbore it more than .040, maybe .060 if you have it sonic checked. If the 360 you have is a 93 or newer magnum, i wouldnt count on more than .020-.030 as they were all 'lightweight' castings.

If you want to get to over 400ci with a 360 block, you need  a stroker kit- crankshaft, pistons and maybe rods. it can be expensive, but any good engine rebuild is. i would check out mancini racing and blueprint engines... They both have what you need. I have not seen a good stroker kit sell for under $1200 anywhere, and that is with basic parts (cast crank/hyper pistons) -ebay parts

boring a 360 engine .030 will only get you 5 ci. Any power difference you felt from that would be from all the new parts, not the 2% change in displacement.

check out this calculator     http://www.csgnetwork.com/cubicinchdispcalc.html
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Sublime440

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Re: ?? Bore and Stroke ??
« Reply #2 on: December 12, 2013, 20:55:17 »

Boring an engine "over" means you are increasing the size of the bore by the amount you want to go "over"...so 30 over would be 0.030" over the stock bore. So on a 4.00" bore cylinder it will now equal 4.030" in bore. The over bore is always per 10 thousand (0.010" x 30, 40, 60, etc).

You can't go .125" over on a 360 and it wouldn't make sense to. The logical thing to do would be to keep the amount you bore to a MINIMUM as it really doesn't do much for you other than freshen the cylinders with cross hatch pattern that's probably been worn out through the years. So you don't add anything performance-wise by boring an engine. You only clean it up. Typically, a 0.030" over bore only adds ~5-6 cubic inches.

When you stroke it you're increasing the throw of the crank...or the "up and down" travel of the piston. That's where you gain the most displacement, torque, and compression which equals more power.

I just built a 408 (actually a 410) which is a 0.040 over 360 with a 4" crank. So it went from 4.00" x 3.58" to 4.040" x 4.00". So just by going the stroker route you can instantly surpass your 400 cid goal.
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79dodge4ever

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Re: ?? Bore and Stroke ??
« Reply #3 on: December 12, 2013, 20:58:28 »

Boring an engine "over" means you are increasing the size of the bore by the amount you want to go "over"...so 30 over would be 0.030" over the stock bore. So on a 4.00" bore cylinder it will now equal 4.030" in bore. The over bore is always per 10 thousand (0.010" x 30, 40, 60, etc).

You can't go .125" over on a 360 and it wouldn't make sense to. The logical thing to do would be to keep the amount you bore to a MINIMUM as it really doesn't do much for you other than freshen the cylinders with cross hatch pattern that's probably been worn out through the years. So you don't add anything performance-wise by boring an engine. You only clean it up. Typically, a 0.030" over bore only adds ~5-6 cubic inches.

When you stroke it you're increasing the throw of the crank...or the "up and down" travel of the piston. That's where you gain the most displacement, torque, and compression which equals more power.

I just built a 408 (actually a 410) which is a 0.040 over 360 with a 4" crank. So it went from 4.00" x 3.58" to 4.040" x 4.00". So just by going the stroker route you can instantly surpass your 400 cid goal.


I agree with sublime you can't get a 400CI out of a 360 without a stroker engine. stroker kits start at about $800 and machining takes it from there

if you can build a stroker engine for under $3000 from intake to pan with no assembly required your doing quite well
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spike

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Re: ?? Bore and Stroke ??
« Reply #4 on: December 12, 2013, 21:38:56 »

yup, I just built a 390 stroker not long ago for my ram, 4" crank and .030 over pistons

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Re: ?? Bore and Stroke ??
« Reply #5 on: December 12, 2013, 21:45:04 »

Usually .010 over is around 2ci.

For an example, I'm going to use a 340- 4.04 x 3.313 is right about 340", 4.04 x 3.58 is around 367", 4.04 x 4 is 410". Most 360s can go .040 over. A stock 4" bore 360 with a 4" stroke is about a 402".

Boring is not a very practical way to increase displacement. It should be reserved for cleaning up the walls if it's not a serious race effort. Over 4.1" on an A engine realistically means a siamese block- which the cheap ones (X blocks) sometimes go around $1500 bare with 3.9" bores ready to be punched out. Very few A engines should go to 4.1", and even few could be overbored after that if they ever needed to be rebuilt.

I think the cheapest stroker kits out there are around $1100. Muscle motors (racing?) sometimes has really good deals. Because strokers turn less RPMs, they can make more power with cast cranks. Of course, nowadays with the better mild cams, mild intakes, and better flowing low-lift heads there's a great potential for power at lower RPMs than there used to be- so usually it's taking more HP to really have to worry about cast cranks naturally aspirated.
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jlcpcnc

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Re: ?? Bore and Stroke ??
« Reply #6 on: December 13, 2013, 07:36:01 »

So, its stroking that gives it the power.....*thats what all the boys say* LOL
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Re: ?? Bore and Stroke ??
« Reply #7 on: December 13, 2013, 08:51:39 »

The engine is only part of the process.  You're probably going to have to upgrade the radiator, rebuild or replace the transmission to handle the increased power and then there's the rear axle.  If it's a 7.25" axle, you've got to replace it before the engine.  If it's an 8.25" it would probably hold up but really needs better gears (though the torque from a 408" stroker would sure help overcome those stock gears).
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jlcpcnc

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Re: ?? Bore and Stroke ??
« Reply #8 on: December 13, 2013, 09:55:05 »

The engine is only part of the process.  You're probably going to have to upgrade the radiator, rebuild or replace the transmission to handle the increased power and then there's the rear axle.  If it's a 7.25" axle, you've got to replace it before the engine.  If it's an 8.25" it would probably hold up but really needs better gears (though the torque from a 408" stroker would sure help overcome those stock gears).


screw all that i will just fix what is broken and drive it!



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Captain Caravelle

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Re: ?? Bore and Stroke ??
« Reply #9 on: December 13, 2013, 13:43:30 »


screw all that i will just fix what is broken and drive it!

Good plan.
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spike

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Re: ?? Bore and Stroke ??
« Reply #10 on: December 13, 2013, 17:27:31 »

but you know how much more fun it would be to drive? :p

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Re: ?? Bore and Stroke ??
« Reply #11 on: December 13, 2013, 17:40:39 »

but you know how much more fun it would be to drive? :p

Trouble maker.    :D
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jlcpcnc

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Re: ?? Bore and Stroke ??
« Reply #12 on: December 13, 2013, 19:18:33 »

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270SE

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Re: ?? Bore and Stroke ??
« Reply #13 on: December 14, 2013, 00:36:50 »

I'd go used on an intake- determine what'll be best for your goals, pick the size of carb you're going to need in the end, and get a new cheap Holley in that size.
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