My block is at the machine shop!!

[boataddict26]

Me and my dad droped my block and heads off yesterday. I was originaly going to go with 40over but the guy and my dad talked me into going 60over!!
How much horse power increase shoud I have?

[1FaastC10]

very little if any. all overboring does is square up t he bore. if the block will clean up at .040, go that route, that way if you ever have to/need to rebuild it again, you've got plenty of room.

[Tom]

Originally posted by 1FaastC10
very little if any. all overboring does is square up t he bore. if the block will clean up at .040, go that route, that way if you ever have to/need to rebuild it again, you've got plenty of room.

Agreed 100%
The only time you overbore is to get the bores cleaned up or you have a massively powerfull motor and need the extra clearence for bigger valves.

Go .040, you'll still enjoy it

[MylilBowTie]

Yeah, what they said. I would have a block sonic checked before I went 60 over. I dont think you will be able to rebuild this block if it needs bored again. Possibley if its just a spare race engine, and doesnt need to be depended upon. Yeah you can sleeve it but who wants a sleeved block?

As for the extra hp? Im gunna guess and say 10 hp

[1FaastC10]

Originally posted by MylilBowTie
As for the extra hp? Im gunna guess and say 10 hp

that's air dyno, right? no measurable power gains from boring a block. besides, a smaller overbore will make for thicker cylinder walls. thicker cylinder walls mean better ring sealing, which leads to more dependable horsepower.

[N2TRUX]

You need to talk to the machine shop and tell them what you want from your motor. Since it's getting bored, you will have to replace the pistons. You should decide now what type of pistons, and more important, what compression ratio.

What heads are you running? If they are stock 350 small valve heads, you may be better off buying new heads rather than rebuilding those. If you want more power, consider the Vortec heads. They are fairly cheap, and create great hp/tq gains right out of the box. You will need a new manifold to go with them though.

Nows is the time to make these choices while you still can...

[MylilBowTie]

Originally posted by MylilBowTie
Yeah, Im gunna guess and say 10 hp

Justa guess nothing set in stone. You do make more if you have more displacement also everything else being equal.

[boataddict26]

I am getting SRP Forged pistons. Flat Tops. Was going to get JE but decided not to spend the extra 180.00 My heads have oversized valves and are ported and polished. So if it is not to late I should go with .040?

[MylilBowTie]

If it was mine I would try and go 40 over but thats if its not to late. If the mechinest thinks the block will clean up at 40 thats what I would do.

[79BIG10]

I agree with everyone and go 40 if possible. If the shop can clean it good and test it to make sure it's a good bore then go with it. I'd rather have 40 than 60 for sure.

On the pistons if you ever want to add anything more like NOS or a larger cam or heads that flow better make sure that you have the bottom end for it. This is where you can spend your money now and not have to redo it later. Get a great bottom end on it then later add a larger cam and heads. You don't need a shop to do this. Adding pistons later will cost you more than $180 for sure.

[MylilBowTie]

So do you have any new news about the block?

[boataddict26]

UPDATE....Block has to go .060. The machinest went .040 and said that wasent enough. I still havent made up my mind completly about what pistons to go with. I know I want forged because I plan on running nitrous. I have been told that anything other that forged will not hold up. Any sugestions on what brand of pistons and rings?

[AirMale]

SRP pistons are an excellent choice. Check with SRP for a special N2O piston.

[Tom]

What compression are you going to run and how much nitrous? Cause hyper pistons can take some power, just not a ton.

[76HighSierra]

Originally posted by 1FaastC10


that's air dyno, right? no measurable power gains from boring a block.

Not really true. Whenever you bore a block, the resulting larger cylinder size, causes an increase in compression due to more swept volume. The HP increase may be small (maybe 5hp...it depends on your engine combo), but it exists nonetheless. Naturally, the larger you bore your block, you can expect a higher comp. ratio (if all other parts are kept the same). When configuring an engine combo, one must be carefull to factor in the overbore. An engine configured for optimum perf. at a std. bore size, may have you in detonation city with a .060 overbore. Everyone is right about not boring your block to .060. It's one thing if you "have to". Even then, I would still have it sonic tested. Bore to the minimum size that your block will "clean up" at.

[Mike76251]

Yeah..........boring a block means more air and gas in a cylinder.
This results in a "larger" engine.
This also means more power.
As the old saying goes "There's no replacment for more displacement"

[boataddict26]

Tom just brought up a good question. What compresion ratio should I shoot for? I have 74cc heads and in all the mags the ratio for a 64cc head. So if it says 10.63 what will I have?
I am getting the Edlebrock Nitrous kit. It is adjustable from 50-100hp. Would that be to much for the hyper pistons?

[Tom]

Originally posted by boataddict26
Tom just brought up a good question. What compresion ratio should I shoot for? I have 74cc heads and in all the mags the ratio for a 64cc head. So if it says 10.63 what will I have?
I am getting the Edlebrock Nitrous kit. It is adjustable from 50-100hp. Would that be to much for the hyper pistons?

You drop "about" a point of compression going from 64cc to 76cc. As for the NOS, thats a very small amount, stock cast pistons should handle that much if you were carefull.

[79BIG10]

But best to go with forged. This way you wouldn't have to worry as much then. Besides after 100 shot you probably would want more.

[1FaastC10]

for a .271:1 increase in compression ratio, i'd much rather have the strength of a thicker cyilinder wall. if this was a racing engine, and not one for a street truck, i could see the slight advantage. on paper or the race track, going with the biggest bore is best. but in the real world, in your wallet, and in terms of durability in this case, less is definitely more.

[boataddict26]

Thanks for the advice. I will go with the lower ratio.

[76HighSierra]

1Faastc10 is absoloutley right. I was only making the compression comment earlier in the post, because it's a common misconception that an overbore makes no difference anywheres. Stick with the smallest overbore you can get away with. Not only will you be able to rebuild it again, it will most likely give you less trouble. .060 is most likely OK, but for God's sake, spend the extra few dollars and get it sonic checked. A few dollars spent on that test may save you alot of grief later. Good luck!