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Maximum Overbore for a 350??

  
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Maximum Overbore for a 350??

 
Hoffy630 Hoffy630
New User | Posts: 11 | Joined: 03/08
Posted: 03/10/08
12:58 PM

I am just getting ready for a new motor to build for my '82 Firebird. I am going to get a 4-bolt main block, and I was wondering what the maximum Overbore is before the walls begin to crack. I am looking at a 350 block that was bored .040 over, and been magged and cleaned. Is this too much for comfort? also what does it become...383, some random larger number? I want to be able to drive this car daily to school, and every once in a while smash on it. Thanks everyone!! Cool  

race4life race4life
New User | Posts: 8 | Joined: 03/08
Posted: 03/10/08
01:10 PM

You will have difficulty finding rings for over .060. At .030 over you will have a 355ci, 357ci with .040, and 360ci with .060 over. the greater the bore is increased, so it the problem with over heating. I wouldnt reccomend over .040 overbore. What exactly are you trying to accomplish with a greater combustion chamber size?  

race4life race4life
New User | Posts: 8 | Joined: 03/08
Posted: 03/10/08
01:21 PM

Sorry, I missed the question of the 383. A stock 350ci block with a 400 crank (machine work required) will give you a 377. If you use .030 bore and pistons that will give you the 383ci. Again, what are you trying to accomplish? Horse power, tourque, what?  

Hoffy630 Hoffy630
New User | Posts: 11 | Joined: 03/08
Posted: 03/10/08
01:29 PM

i'm trying to get more power..I can grab a 4-bolt main block that is not bored or magged or cleaned, or I can get one that is .040 over that was magged and cleaned and is cheaper. I want the most I can get SAFELY from a 350 block. I'm trying to push for 400 plus Horsepower to my wheels. 400 is my MINIMUM.  

410hp355 410hp355
New User | Posts: 1 | Joined: 03/08
Posted: 03/10/08
03:17 PM

To get 400hp to the wheels is askin alot of your motor if your not wanting to spend alot of money.  But it can be done.  Now, Boring a motor over will increase your torque output, where as increasing stroke, and buying a good set of heads with a 64cc combustion chamber or smaller, will net you more horsepower.  The poor mans ticket to HP is compression, which is easily done by shaving the heads a few thousandths, or decking your block in the same manner.  Those are the cheapest and easiest ways to gain HP if you are building a motor from the ground up.  A decent porting job on the heads will yield even greater gains in horsepower and torque.  Some other things you can do are to go with a roller cam, roller lifters, and roller rockers.  The less friction there is on any rotating part of the motor, the more efficient it will run, and the more power it will willingly put out.  Just swapping out the cam and lifters on  a motor that used mechanical lifters and cam, along with roller rocker arms, will yield atleast 40-50hp if not more on a motor where everything else is stock.  I just finished building my 355, and it was dynoed at 410hp/483ftlbs of torque.  That was at the flywheel.  At the wheels, it would probably put between 330hp to 360hp down.  You lose up to 35% of the power by the time the power reaches the ground.  A set of 4.11 rear gears would put more power to the ground than a set of 2.14, which were used in the 80's olds cars like the cutlass.  There are many ways to net 400hp at the wheels, but the question isnt how to do it, but how much are you willing to spend,  

Hoffy630 Hoffy630
New User | Posts: 11 | Joined: 03/08
Posted: 03/10/08
04:45 PM

Money isn't a HUGE issue for me, and there is no way in hell i'm goin for a poor man's job on this. I'm just ticked because of all these damn tuners that are kickin my ass, and they don't even do anything to them except throw a cold air intake on them, and run a V-TEC motor!
I want this car to be scary fast, but still be able to drive it. Should I just say screw it and build a 427?

Bringing back my original question...Is a 350 block bored .040 over too much for comfort, and what is the risk of the cylinder walls cracking? Confused  

tomwicker tomwicker
New User | Posts: 7 | Joined: 01/08
Posted: 03/11/08
05:25 AM

I might be one of the lucky ones I guess listening to people post across different Boards. In my 4x4 I run a 350+60 and have for a few years without any heating troubles. Mind you know I also run a large five core radiator. Also here the temps reach over a hundred often here along the Gulf Coast.

I’m in the process now of building another for my Camaro same specs on the short block I’m trying to decide if I would benefit any by putting an Eagle 383 crank in it and still run 5,7 rods and flattops trying for a tad more ponies  

Rainman1986 Rainman1986
New User | Posts: 1 | Joined: 10/10
Posted: 10/20/10
06:47 AM

I know this reply is kind of late but have you considered throwing a 350 crank into a 400? Bored .030 over that is a 377. With the shorter stroke you can throw in some really long rods like up to 6.2" if you really want to shorten the compression height of the pistons. Throw in some gapless rings and with some port matching and good parts selection you should easily produce over 400hp.  

Dave632 Dave632
Addict | Posts: 2225 | Joined: 07/08
Posted: 10/20/10
01:00 PM

Having the walls sonic tested to see if there is enough metal there is the answer to your problem. This would allow a .060 overbore if needed and if the test is positive.
You can purchase a ready built 355 that will make 400hp for about 2700.
If you really have the bucks check out Reher and Morrison for one of thier killer SB with up to 800hp NA. This would make all rice cars look like the garbage they are.
I can't believe you have trouble with rice cars, I could beat them with my street car except some with turbos but my fast cars could beat the turbo ones by half the track.
I hate those cars and would always challenge/insult them but never once would one race me unless I pulled up next to one in staging where they could not get away.  
[[SUPPORT AMERICAN CARS, STOMP A RICE CAR TODAY.]]

gettnlarge01 gettnlarge01
Addict | Posts: 3330 | Joined: 09/09
Posted: 10/20/10
03:33 PM

First off boring the block is done to make the cylinders like new. Boring doesnt give any real noticable power gains and you'll only be wasting the block by boring it beyond what is needed. If it needs to be .030 over then why bore it .060?  
luck is when skill and opportunity meet

skyeking skyeking
Addict | Posts: 2738 | Joined: 08/09
Posted: 10/20/10
04:21 PM

Hi there,
 I would grab the 40/1000" overbore if it is in perfect
 condition.Mo worries with
 my past motors..past that then sonic test the block
 as suggested. No gain in power to speak of and getting
 too close for comfort when unnecessary.With the other
 block motor shops will go for 30/1000" over to clean up
 any very minor distortions...Skyeking  
skyeking

joseluis84 joseluis84
New User | Posts: 9 | Joined: 03/13
Posted: 03/24/13
09:02 AM

,,  

pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 03/24/13
12:28 PM

Joseluis84 welcome to CHP.

Can you do use all a big favor so we can help you?

Create your own post. This way we can stay with you and your build. Okay.Things will work a lot better for all of us. So we won't confuse your build and a build that is 5 years old....Thanks

Bob  

Dave632 Dave632
Addict | Posts: 2225 | Joined: 07/08
Posted: 03/25/13
02:10 PM

Getting 400 hp to the rear wheels is not that easy. There is a 20 to 30+ % drive train loss depending on transmission converter and rear used. I have seen several tenths of a second elapsed time lost due to the installation of a heavy-duty Ford 9 inch rear.
A dyno test of a big block Chevy that made 700 hp at the flywheel made only 496 at the rear wheels. This particular car had a high stall converter and heavy-duty drive train parts.
Getting 400 hp to the rear wheels with a little 350 is possible but expensive and generally out of the reach of most unless large amounts of money are available.
One of my big blocks, which had 488 cubic inches, made 526 hp at the rear wheels. This engine had 12 1/2 to one compression, full roller set up, tunnel ram with two 650s on it, and dart 360 heads. that car had a drive train that took a lot of power to turn I estimated it had over 700 hp at the flywheel.

Later on I installed that same engine in my Beretta and it ran high 4's at over 140mph in the eighth mile with a 350 shot of juice.  
[[SUPPORT AMERICAN CARS, STOMP A RICE CAR TODAY.]]

skyeking skyeking
Addict | Posts: 2738 | Joined: 08/09
Posted: 03/26/13
04:45 PM

Hi Agent 632  
skyeking

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