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.020 overbore : Approx hp/tq gains on 4.6

Old 11-04-2006, 01:17 AM
  #11  
Armydad
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Default RE: .020 overbore : Approx hp/tq gains on 4.6


ORIGINAL: droptoppony


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ORIGINAL: JD1969

You don't bore an engine for added HP. Boring is done to true the cylinder walls and provide a good seal for the rings.
thanks for the response, I agree that perhaps.020 is more of a trueing of the cylider walls, but why then would someone need to go bigger? To increase displacement and make more power. if you need to overbore .040-.060 just to true the walls, you should look for a new block.
some will do a .020 over on an engine rebuild then if they make a change take it out to .030 over...modular blocks shouldn't be taken out much more then that thus the reason for resleeving them when going with a big bore. Now a big bore will add some power.

yeah, Ive been reading up on those big bores, they seem to be more race oriented than daily driver. I don't think busting out the walls will buy me anything, so i'll prolly do staight rebuild.
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Old 11-04-2006, 05:04 AM
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FDNYBullitt
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Default RE: .020 overbore : Approx hp/tq gains on 4.6

It all depends on how worn the cylinders are. If there only .001-.002 over stock you can just flash hone it and re-ring it. If its any more then that then you'll have to bore it .010 or .020, depending on what pistons are available. Boring it .020 would give you about 1-2 HP as stated before, good luck.
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Old 11-04-2006, 06:18 AM
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Default RE: .020 overbore : Approx hp/tq gains on 4.6

Check my sig.... The block that I'm getting is a 281 bored over .20 to get me to 283 which will give me a better seal for the Forged pistons.
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Old 11-04-2006, 08:23 AM
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Default RE: .020 overbore : Approx hp/tq gains on 4.6


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ORIGINAL: JD1969

You don't bore an engine for added HP. Boring is done to true the cylinder walls and provide a good seal for the rings.
Why do you think guys take 350s and stroke them to 383s? More power! More potential! You don't bore out a 350 30 over and put a 400 block crank and pistons in it to seal rings. Don't know where you got your information from.
A stroker kit is adding much more CI than a simple bore job

No way no how, on any engine, that you are seeing any significant power increases with a .20 overbore, modular OR 350 chevy. The only way you could/would see a power increase is if the original engine is running so badly that you repair compression loss etc.

People overbore to a .40+ because the cyl ARE that damaged, or because they have already done so once to .20 and need more. A modular block without sleeving will not do this anyway.

In a single sentance: Completely worthless as a power mod.
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Old 11-04-2006, 08:44 AM
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Default RE: .020 overbore : Approx hp/tq gains on 4.6


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Well actually I will be having ported SVO heads a Crower blower cam and probably the FRPP s/c. Also headers full exhaust, CAI, TB, I probably should have mentioned all that, sorry.
ORIGINAL: 2000GT4.6

A .20 will add virtually nothing to your 2v car, espcially with stock heads/cams/intake. Even most of the stroker kits do not add alot of power on built cars.
BTW, in case nobody told ya yet, the FRPP blower sucks. Putting a FRPP blower on a car with ported heads and blower cams is like putting slicks on my old stock 88 bird. I am sure it would be faster than without the slicks, but its still silly.

Also, unless you plan on running an aftermarket shortblock the heads are a waste of time and energy. The proper supercharger setup along with a set of blower cams will have the factory shortblock on the limit without spending 1500 bucks on heads.
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Old 11-04-2006, 11:56 AM
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Default RE: .020 overbore : Approx hp/tq gains on 4.6


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ORIGINAL: Armydad

Well actually I will be having ported SVO heads a Crower blower cam and probably the FRPP s/c. Also headers full exhaust, CAI, TB, I probably should have mentioned all that, sorry.
ORIGINAL: 2000GT4.6

A .20 will add virtually nothing to your 2v car, espcially with stock heads/cams/intake. Even most of the stroker kits do not add alot of power on built cars.
BTW, in case nobody told ya yet, the FRPP blower sucks. Putting a FRPP blower on a car with ported heads and blower cams is like putting slicks on my old stock 88 bird. I am sure it would be faster than without the slicks, but its still silly.

Also, unless you plan on running an aftermarket shortblock the heads are a waste of time and energy. The proper supercharger setup along with a set of blower cams will have the factory shortblock on the limit without spending 1500 bucks on heads.
Hi and thanks

I am sorry I thought I had mentioned earlier that, Yes I am going to forge the bottom end (SHM has a nice kit for $1500). You are absolutely correct, putting those heads on a stock bottom end would not be optimal, but it can be done along with some other mods and should get you around 320-340 hp. Adding a blower to this combo (stock bottom) would eventually grenade the motor .

As far as the blower, what makes it silly if I get 100hp out of it and I am happy with that hp level? 400 ponies is nothing to sneeze at.

I am not glued to any of my plans, things change, oportunities present themselves, i will stay flexible. I might have a good deal on a Vortech that I am negotiating, for the right price I will scap it up and replan the rest of the build.

Again thanks for all the good responses/info

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Old 11-04-2006, 12:14 PM
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JD1969
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Default RE: .020 overbore : Approx hp/tq gains on 4.6


ORIGINAL: Stang9946

ORIGINAL: JD1969

You don't bore an engine for added HP. Boring is done to true the cylinder walls and provide a good seal for the rings.
Why do you think guys take 350s and stroke them to 383s? More power! More potential! You don't bore out a 350 30 over and put a 400 block crank and pistons in it to seal rings. Don't know where you got your information from.
I highlighted the part that gives you the power. The question he asked was about boring NOT stroking. Next time you think I don't know what I am talking about, go do some research on your own before you make yourself look like an ***.

ORIGINAL: 2000GT4.6


ORIGINAL: Stang9946

ORIGINAL: JD1969

You don't bore an engine for added HP. Boring is done to true the cylinder walls and provide a good seal for the rings.
Why do you think guys take 350s and stroke them to 383s? More power! More potential! You don't bore out a 350 30 over and put a 400 block crank and pistons in it to seal rings. Don't know where you got your information from.
A stroker kit is adding much more CI than a simple bore job

No way no how, on any engine, that you are seeing any significant power increases with a .20 overbore, modular OR 350 chevy. The only way you could/would see a power increase is if the original engine is running so badly that you repair compression loss etc.

People overbore to a .40+ because the cyl ARE that damaged, or because they have already done so once to .20 and need more. A modular block without sleeving will not do this anyway.

In a single sentance: Completely worthless as a power mod.
Thank you 2000, at least somone else here has a clue
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Old 11-04-2006, 12:39 PM
  #18  
GodAmGT00
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Default RE: .020 overbore : Approx hp/tq gains on 4.6

Maybe people don't know math, or measurements very well, since .020" is 2 HUNDRETHS of an inch, or roughly .51mm..

Although compounded over all 8 cylinders, it won't make a difference, especially when there are 25.4mm per 1 (length/width not volume/displacement.)



JT


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Old 11-04-2006, 12:41 PM
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Armydad
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Default RE: .020 overbore : Approx hp/tq gains on 4.6

Thanks,

Being as how I'm doing the bottom end either way, would it be worth a little extra to stroke it? I have no experience as far as a stroked 4.6, some people say good some say worthless, are there any gains?
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Old 11-04-2006, 01:40 PM
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Default RE: .020 overbore : Approx hp/tq gains on 4.6


ORIGINAL: Armydad

Thanks,

Being as how I'm doing the bottom end either way, would it be worth a little extra to stroke it? I have no experience as far as a stroked 4.6, some people say good some say worthless, are there any gains?
If you have the extra dough, go for the extra cubes . Just do some research on which kit to go with. Code might be a good one to ask about that one.
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