is .040 to much bore or OK

[syclone]

OK,
first for the sharks here, yes I done a search, Yes, I read a lot but all the threads I could find were from 2005, granted there have been improvements in things such as headgaskets etc. so I am unsure that what stood true then, stands true now, not to mention I never found a "clear" answer and a lot of bad info that I was going to correct
but the thread was old and dead so why bother.

what I have is a 6 bolt block with nicks in the side where a valve broke off and beat up my block, piston, and head, a .030 bore I dont think will quite clean it up so I am looking at .040

will .040 live, I can upgrade the radiator if nessessary I do all my own work and am not afraid to cut and paste.


yes it will be raced,
yes it will be driven long distances (if it stays together)


Jamie Sanders
Searcy, Arkansas
MODS:
eagle stroker crank, wisco pistons, eagle rods 280 cams, dsmlink, plx device wideband, frontmount, FP3052 turbo, 780 injectors, fluiddampener harmonic ballancer, 3" exhaust.
ported polished heads, etc, etc, etc,

 

[T9S1i]

Personally, i dont think 40 over is too much. My friend's motor is built 40 over and he has no problems with it. Companies make 40 over pistons and head gaskets and everything so there is no problem. If my 20 over motor went out and i had to change pistons to 40 over i wouldnt have a problem doing it.

I think its all personal preferance. If i was going to build a motor the first time, id probably look for a better shortblock core to start out with, but if it already had been built once and everything was all good, and it needed to be freshend up with new pistons, then 40 over wouldnt be a problem. Starting with 40 over means that you really only have 1 more build left in the motor should anything happen.


What are your problems with going 40 over? or are you just trying to see the general concensus?

 

[wt71gas]

I think the best answer might be that it all depends on the block itself. All blocks are susceptible to casting flashes,core shifts etc..... What you need to do is use a sonic tester to test the thickness of the cylinder walls. Most machine shops have them. It would be nice if you had a few blocks you were willing to run and were actually trying to run .040 for the bigger power increase and wanted to use a block out of a few you had lying around to build a "junkyard" motor. When you measure the cylinder walls of a few different blocks you will get slightly different measurements and you could take you pick of the thickest. I think it could be done but it sounds like you have a lot of nice parts going into the motor and strictly for the piece of mind you might look into getting a better block core. The minor cost of that would be worth the savings of doing it later. Hope that helps a little.

Wayne

 

[syclone]

Wayne,
you are right, I am worried about all my nice stuff, crank, rods pistones, expensive ported polished head, high dollar valves, etc

and yes I am looking for the general consences, of what is out of the norm,

I can get a complete motor for 216.00 from the local u-pull-it, as a matter of fact they have one sitting on the ground in front of a 1st gen car.

I am also concerned about blowing headgaskets because of the reduced sealing distance between cylinders. has this been an issue? I will be running 25-26 lbs of boost.

James Sanders
Searcy, AR

 

[HIGHPSI4]

0.040" is fine. I have just gotten back my 4G64 that is bored 0.040" and there were no problems with that bore. Good luck.

 

[Defiant]

And, to counter, with that much cut I'd want to ultrasonic the jacket at the bores for thickness. Common word is that it's the maximum cut for a DSM, but you still wouldn't want to go that far on a block whose core had shifted.
But the blocks are too cheap to run the risk. The head gasket isn't where the failure threat is; it's in the ring seal integrity. I'd start with another block.
Over-boring is a power move, if you have enough cylinders for it to add up to something. Four isn't.
As for racing, and driving long distances, welp, good luck with that.

 

[1g_tsi_awd]

Yea, I would for sure find a new block for the peace of mind. As Defiant said, .040 still won't give you extreme displacement increases because you only have 4 cylinders. I say get a new block and then do whatever you want, whether it be .020 or .040 over.

 

[Guzman08]

i know this is an ole thread but why make a new one when i have the same questions. So i wanted to know is .040 over to much for a 6 bolt?? its my daily

 

[ziggo0]

It will be fine, it's just like the 7 bolt in that aspect.

 

[GRAVEDIGGER]

There are lots of .040" over cars running around out there without any problems at all including myself. It is possible to go .060" or even .080" as well.

 

[Guzman08]

yeah i was just wondering just because im building my engine right now. not by choice but i spun a rod.. the shop told me it was already .020 so they told me to try .040

fixed

 

[phunny]

yeah i was just wondering just because im building my engine right now. not by choice but i pun a rod.. the shop told me it was already .020 so they told me to try .040

Oh I hate when I pun a rod

I'm no machinist but .040 isn't that abnormal at all

 

[keltalon]

That's fine. I am running 60 over in mine with no ill effects