Slant Six Forum
https://www.slantsix.org/forum/

How much to bore block, .045 or .084 power gains?
https://www.slantsix.org/forum/viewtopic.php?t=42255		 Page 1 of 2
Author:  dustertech2000 [ Wed Oct 13, 2010 4:27 pm ]
Post subject:  How much to bore block, .045 or .084 power gains?
i have my motor out and apart going to switch to weisco forged pistons, off-the-shelf size pistons are .045 or .084 over bore. my block was bored .030 8 years ago and is still good but custom pistons are way more money. i can get the machine work done and self pistons cheaper. Will going to .084 give me anymore power than a .045 bore.
Author:  Reed [ Wed Oct 13, 2010 4:33 pm ]
Post subject: 
Not that you would notice.
Author:  dustertech2000 [ Wed Oct 13, 2010 4:41 pm ]
Post subject: 
any reason to go to .084 instead of .045
Author:  Doc [ Wed Oct 13, 2010 4:52 pm ]
Post subject: 
A 5.4 cubic inch difference...
Do you have 7 inch long connecting rods to go with those pistons?
DD
Author:  Reed [ Wed Oct 13, 2010 4:54 pm ]
Post subject: 
You have lots of money you want to spend?

Quoting from Doctor Dodge's "No replacement for Displacement" article:

"boring a 225 0.060" yields a total of 232 cubic inches, not enough to make a noticeable difference."

Yes, boring to .084 instead of .045 will make a smidgeon more power, but not enough that you would notice. Lots of cost in machine work and oversize parts to net a gain you won't notice. It isn't worth it.
Author:  dustertech2000 [ Wed Oct 13, 2010 5:01 pm ]
Post subject: 
well the .045 and .084 pistons are both the same price and the block is going to be sent to machine shop either way and that will still only cost me 50 bucks. Why the question about 7 inch long rods??
Author:  ceej [ Wed Oct 13, 2010 5:53 pm ]
Post subject: 
The Wisco piston is part of a package that works with the K-1 long rods if your talking about the ones listed in the K-1 build. The pin height is different than a stock piston, and would produce extremely low compression with stock rods.
If your looking to run white gas, it'll get you down there! :lol: I compute around 5.8:1 with some basic assumptions.

Make sure your looking at the right piston pin height for your build. :wink:

CJ
Author:  dustertech2000 [ Wed Oct 13, 2010 7:32 pm ]
Post subject: 
i was looking at the wiesco protru pistons on cambell enterprise website, they say use with stock rods for 10.5:1
Author:  dustertech2000 [ Wed Oct 13, 2010 7:44 pm ]
Post subject: 
Nope your right... my bad, i didnt realize that those compresson numbers where with 7.005 rods, i can have custom made pistons for 200 bucks more, which probly in the long run would be about the same as having the block bored and decked .400".
Author:  66aCUDA [ Thu Oct 14, 2010 3:33 am ]
Post subject: 
In for a penny in for a pound. They make .105 over as well. The slant block can take it with no problems.
But on a more serious note between .045 and .085 the only reason that you might NEED to go the larger size is for big valves like the 1.78/1.50 Ford 300 valves. Then you NEED to be at .060 over or more.
Frank
Author:  Dart270 [ Thu Oct 14, 2010 4:56 am ]
Post subject: 
As said above, you can gain a little valve diameter too. 0.085" is still a fairly mild overbore on a forged-crank (pre-76) 225.

Lou
Author:  Reed [ Thu Oct 14, 2010 7:21 am ]
Post subject: 
Quote:
In for a penny in for a pound. They make .105 over as well. The slant block can take it with no problems.
But on a more serious note between .045 and .085 the only reason that you might NEED to go the larger size is for big valves like the 1.78/1.50 Ford 300 valves. Then you NEED to be at .060 over or more.
Frank
My brother's van is running a head with Ford 300 valves and has only been overbored .030. No problems for more than 5,000 miles.
Author:  66aCUDA [ Thu Oct 14, 2010 7:39 am ]
Post subject: 
Quote:

My brother's van is running a head with Ford 300 valves and has only been overbored .030. No problems for more than 5,000 miles.
Hey Reed have you had that head off? I had one on a 30K mile engine and it ran fine??? But it did wear off the side of the valve and notched the bore. Both CJ and I have had problems with .040 or less. I also cant see you being able to deshroud the valves.
Just my 02.
Frank
Author:  Doc [ Thu Oct 14, 2010 8:51 am ]
Post subject: 
The last time I purchased a set, the K1 / Wiseco package was right under $1000.00 total for custom pistons with pins and rings along with super-strong con rods, set-up for floating pins... and that package gets you 10 to 1 compression, without head or block "milling".... That's a pretty good value.

Or hunt around for some factory 198 con rods.
DD
Author:  Reed [ Thu Oct 14, 2010 9:18 am ]
Post subject: 
Quote:
Quote:

My brother's van is running a head with Ford 300 valves and has only been overbored .030. No problems for more than 5,000 miles.
Hey Reed have you had that head off? I had one on a 30K mile engine and it ran fine??? But it did wear off the side of the valve and notched the bore. Both CJ and I have had problems with .040 or less. I also cant see you being able to deshroud the valves.
Just my 02.
Frank
Head has been off several times, and no wear or notching on the bores or valves. I will agree that shrouding probably is a problem, but this is in a daily driver van, so (a) it doesn't really matter for the intended purpose of the vehicle and (b) you don't really notice when driving. I am in no way saying you and Ceej are wrong, but for me, so far so good. :shrug:
Page 1 of 2 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/