nhra_crazy

iTrader: (86)

Just wandering what the power difference is if you bore a block over 30 or just hone it out.. If it doesnt need to be bored?? Thanks Just wandering if its worth saveing the money somewhere else.

org

Virtually none.

Gen414

iTrader: (38)

Difference is cubic inches which equals more power. Now, just taking a block .030 over is NOT gonna make a huge difference, but it can and will make some You also have too look at say cylinder head's like my set of L92's. The L92's require a MININUM bore size of 4.00. Why? Because anything smaller and the valve's could hit the cylinder. So, that means at a 4.00 bore, the valve's are "shrouded" and can and will hurt flow characteristics which can hurt power. So, if you open up that bore size, like .030 over, you get more room in there, which "UNshrouds" the valve, and you have better flow characteristics, and power increases' and since you are adding cubic inches when you bore, you are gaining power there too. Most motor makes @ 1.25 to 1.50 HP per CI. Say you bore a motor .030 you gain around 6 Cubic inches and you can gain say 6-10 HP. Now, it is not much, and if you have a fresh motor, would it be worht it to tear it down and rebuild JUST to gain those few CI's? Heck no. but, when a motor is torn down, and needs to be rebuilt that is another story.

Busted Knuckles

.030 overbore is only going to unshroud the valve .015. That's a tenth and a half of a tenth of an inch, not enough to make any difference. Save your cylinder wall thickness, you'll have better ring seal which will make more power than the few cubes you'll get from an overbore.

nhra_crazy

iTrader: (86)

Thanks for the info guys... very helpful!!

Gen414

iTrader: (38)

Yeah, but it IS going to unshroud the valve. And like I said, if the motor is still together, it is NOT worth tearing down and punching out for the sake of gaining that little bit. However, IF the motor is apart, and you need new pistons, then I would punch it out. My motor is a prefect example. My 6.0 block was brand new straight from Scroggin with the 4.00 bore. All it needed was a hone and I would be good to go. However, I did not have pistons, I was starting from scratch. So, I had teh block sonic tested and we opened her up .060. I was able to gain roughly 12 CI's and got teh valves some room to breathe. All else being equal, by punching it out, I picked up roughly 15-18 HP.

nhra_crazy

iTrader: (86)

So if I do go .030 and still use my stock crank that gives me a 370 correct.... I am debateing on 408 or not right now.

Gen414

iTrader: (38)

Yes. A 408" you will need a new crank, and rods and pistons. So, if you want to save a step, I would do one of two things:

1) Keep teh motor as is, and wait until you are ready to build teh 408" that way you will save money in teh long run

2)Build the 408" now, and be done with it

If you say, bore your block .030 over now, and later on decide you want the 408", you will need to buy another set of pistons. The reason being is, when you add teh stroker (4.00") crank and rods, it will move teh pin location on teh piston, and then teh pistons you already have wiil NOT have teh pin in teh right location. Make sense?


Edit: A 370" motor CAN and WILL make power as well, so keep that in mind

99blancoSS

iTrader: (115)

+1 Very good point. ^^

Doing it once is a lot less money than doing it twice.

LSXmike01

Yes, with a stock 3.62 stroke!

Mr. Black

It's a 15 year old thread. Nice work.