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Old 02-13-2006, 07:40 AM   #1
Aondor
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Cost of boring?

How much would it cost to do some moderate boring to my 351W?
I was going to ask this on the other thread but It turned into a flame post whore nightmare too quick.
What wall do you have to replace after a bore?
And also stroking and destroking were brought up in the other thread. So what exactly are those?
Im just trying to work on my ignorance and plan out my upgrade.
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Old 02-13-2006, 07:53 AM   #2
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Well here it's about A$8 per pot.

Usually you need to replace pistons and rings (and probably gudgeons, bearings, etc.)

Stroking just means you change the linear travel of the piston in the cylinder. If you increase the crankpin offset to crankshaft centreline you obviously increase the distance.

The idea in increasing the stroke is to increase the swept volume. You would normally try to at least maintain a desirable compression ratio and stop pistons colliding with headware, so you usually need to shorten the rods when increasing the stroke. On top of this you have to look at whether the piston skirts will foul on the rod, if the sidewall loading is too great, if the rod/stroke ratio is satisfactory, if the piston acceleration exceeds limits, if the crank can handle the stress, if the cam events suit, etc

If you are in planning stage and you are wet behind the ears, I would suggest you clearly define your objectives and copy someone else's success that mirrors your strategy if not your tactics.
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Old 02-13-2006, 07:58 AM   #3
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My objectives with the 351w I am going to be gettin soon look at several now just deciding which to buy and how to get it back to my little garage( engines aren't lite) Is to produce at least 300 horses on shear engine and cost me under 1700 dollars(total amount spent).
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Old 02-13-2006, 08:30 AM   #4
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300 net ponies from a 351W is not a big ask, but it will guzzle fuel so be aware that there is no such thing as a free lunch.

Also be aware that the figures people bandee about are usually highly inflated and based on dyno peaks rather than averages. Having a 225kW engine that only comes on cam at high revs is pretty hopeless for daily use and will mean a different stally if you have an auto.
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Old 02-13-2006, 09:03 AM   #5
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Its my weekesnd driver I have a 1997 jeep i drive daily. Guzzling gas won't hurt me much either since I don't drive it daily. There an engine specilaty shop beside my house so Im going to go there to talk with them about it. I would just like to have some basic info I have gathered before going to talk to them.
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Old 02-13-2006, 02:53 PM   #6
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Quote:
Originally Posted by Aondor
How much would it cost to do some moderate boring to my 351W?
I was going to ask this on the other thread but It turned into a flame post whore nightmare too quick.
What wall do you have to replace after a bore?
And also stroking and destroking were brought up in the other thread. So what exactly are those?
Im just trying to work on my ignorance and plan out my upgrade.
Depending on who does the work, what type of equipment they use, how good of a job they do, etc, you can expect to pay anywhere between $15 and $50 a hole to bore your engine. That being said, unless you intend to perform some fairly serious mods, don't bore the engine just for the sake of boring the engine. If it's well used and needs a re-bore because it's out of spec, just go to the next largest standard over bore and be happy with that. If you punch it to the biggest bore possible and end up hurting a cylinder in the future, you'll have no other choice but to sleeve the block or junk it.

Wally pretty well explained stroking/de-stroking if you can understand his jargon. And as he said, getting 300 hp (there we go again, being more interested in an arbitrary number instead of thinking big picture) out of a 351W is not a major task and can be done for well within your budget as long as you're turning all the wrenches and shop smart.
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Old 02-13-2006, 05:38 PM   #7
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Quote:
Originally Posted by vwhobo
Wally pretty well explained stroking/de-stroking if you can understand his jargon.
Uhm I found that difficult. Could I get a jargon-reduced explanation please?
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Old 02-13-2006, 10:41 PM   #8
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Simpler? Well I thought I had already simplified it, but.........

a crankshaft is a shaft with cranked arms, often referred to as throwers. The throwers have a round shiney thing that connects to a connecting rod (conrod). The shiney things are called bearing journals and aka as crankpins. The more cranked the pins the further away from centre of the crankshaft (i.e. offset) and therefore a greater arc of movement.

As the crankshaft rotates the connecting rod, being tied to the pin, will be forced to move up and down the cylinder (aka pot); this is known as the stroke. The bigger the crank offset of the pin the longer the stroke. But imagine that as you increase the crank offset:

1) the angle the rod makes when the pin is at right angles to the cylinder will become quite severe. This puts a lot of uneven load on the piston and supporting infrastructure. The angle becomes even worse if you are forced to use shorter rods.

2) because you have increased the stroke, the piston must travel further in the same time. This means it must accelerate faster and the average speed will also increase. The problem here is that there can be big problems with stability, lubrication, etc

3) the acceleration and speed characteristsics change through the stroke. Because the camshaft is designed to match these characteristics you need to revise the profiles. The general aim is to have maximum brake torque around the early teens ATDC, but if the kinematics are not in sympathy you can end up with a dog engine.

and so it goes, on and on.

If you guys aren't going to learn English and take an interest in automotive jargon, things will always be confusing.
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Old 02-14-2006, 06:56 AM   #9
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Hobo Im just looking for a small increase in bore size nothing serious. I say 300 hp because its a relative term Im not sure how other to gauge power than by hp.
I could say I would like to be able to run the quater in under 14s
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Old 02-16-2006, 08:50 PM   #10
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you can bore your own engine for free

just go to the parts store and borrow a boring tool and then use your drill

i have bored engines like this for years
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Old 02-16-2006, 09:11 PM   #11
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Quote:
Originally Posted by AutoPro
you can bore your own engine for free

just go to the parts store and borrow a boring tool and then use your drill

i have bored engines like this for years
WTF?
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Old 02-16-2006, 10:40 PM   #12
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You Americans are so lucky to be able to borrow such equipment from stores. Do they come complete with all the jigs?
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