Author Topic: Bore/blueprint (Read 3405 times)

dillenger1 · « **on:** January 11, 2008, 06:43:06 pm »

I just dropped my block off at a new machine shop.Im having it cleaned and measured,then baked,bored,and honed.I tried to do a ridge reaming by myself and my tech tells me that i ruined the bore(standard)So now i have to bore .Question is :How much power does a 'oversive"bore give you?Are there any reasons not to go to 3rd oversize for more air/power reasons?How "dangerous" is 3rd oversize?I guess "is there any substantial power to be had from boring" :? ?

MaxHedrm · « **Reply #1 on:** January 11, 2008, 06:59:26 pm »

In my limited hunting I've seen 4th oversize (1mm over) pistons, so 3rd can't be too dangerous. I would think the disadvantage is that the more you remove, the fewer times you can redo it in the future.

2nd oversize (.5mm) adds like .02L to the displacement (if my math was right). So I wouldn't think a lot of power would be gained.

jimfoo · « **Reply #2 on:** January 11, 2008, 09:35:40 pm »

For an AAZ you go from 1896cc to 1944cc by going 1mm over.

rabbid79 · « **Reply #3 on:** January 11, 2008, 09:39:37 pm »

I think your math is right. On a 52 HP 1588cc engine that's about a 0.65 HP increase. The determining factor should probably be a matter of what pistons are available, and at what cost rather than how much HP can be gained.

I've seen some charts where the first oversize is only 0.25mm larger, then 0.5mm each oversize beyond that. So I think for the sake of clarity, it would be safest to refer to actual diameters since not everybody is on the same page.

Assuming you have a 76.5 mm bore and 86.4 mm stroke originally (i.e. a 1.6L), "punching it out" to 77.5 would increase displacement by 2.6% or about 1.4 HP on a 52 HP engine.

dillenger1 · « **Reply #4 on:** January 12, 2008, 04:22:49 am »

So is this gonna move anymore air?Im gonna need to pick up some lag on a big turbo.

stewardc · « **Reply #5 on:** January 12, 2008, 06:08:46 am »

Exhaust upgrade will make much more difference than bore. I bored mine to get to new engine specs, but don't expect that it added a great deal of power.

dillenger1 · « **Reply #6 on:** January 12, 2008, 07:13:16 am »

libbybapa,due you mean .5 for second instead of 5.0mm?

subsonic · « **Reply #7 on:** January 12, 2008, 10:35:58 am »

Quote from: "dillenger1"

libbybapa,due you mean .5 for second instead of 5.0mm?

Now that would be a Big Block VW :lol:

dillenger1 · « **Reply #8 on:** January 12, 2008, 02:53:28 pm »

You should of seen.I threw it up on the table and said"here it is"amongst all the v8s and inline 6s.It was belittled.Luckily he was a GTI freak in highschool.We talked for a good while and it was weird i was paying ,yet he still had to decide wether or not he was gonna work with me. :? or my engine for that matter.The whole deal (bake/blast,magnflux,measure,bore,hone,and any surfacing)for $175.00 not bad for piece of mind :lol:

stewardc · « **Reply #9 on:** January 12, 2008, 02:57:50 pm »

Quote from: "dillenger1"

You should of seen.I threw it up on the table and said"here it is"amongst all the v8s and inline 6s.It was belittled.

I had the same experience with my guy. He builds a pile of very successful race engines and when I went to pick it up, here it was on a stand in the middle of 6 bigblock Chevies, 3 smallblock Chevies, a 426 Hemi and a 428 Cobra Jet Ford. Humbling, but cool

dillenger1 · « **Reply #10 on:** January 12, 2008, 04:06:17 pm »

Yes,i saw a rack of HUGE cranks that make ours look like peanuts.He said "well this is an ahfull lot for 150horse",then he laugh and appologized :oops: I said "yah,but thats not what its about"

Thats when he agreed to work with me.

subsonic · « **Reply #11 on:** January 12, 2008, 05:45:18 pm »

My crank was polished and clear bagged at the machine shop that is doing my work. It has a big tag on it that say's " VW Super Turbo Diesel"
:lol: Yeah baby

dillenger1 · « **Reply #12 on:** January 14, 2008, 01:49:32 pm »

I just got a call from the shop.Hes ready to fit pistons ,but wants to know what im interested in.What are the differences between na & td pistons ,besides the cutout for jets?Is there a different coating on the td?My manual says first oversize is like ,25.Ive heard these are impossible to get correct?Some say the true first is ,5mm.

subsonic · « **Reply #13 on:** January 14, 2008, 03:28:40 pm »

Choose NA or TD.
What are you going to do with this? Is this going to be turbo'ed? If so than you have one option--TD.
TD comes with a hard anodized crown and cut outs for oil squirters.

Choose Diameter.
Depending on your bore spec's. If you can find a 1st overbore, go for it, if not get the second.

Choose a maker.
Most everybody goes OEM. Custom will cost you a kidney.
Kolbenschmidt, Mahle come to mind. I think there are more, but I can't name them off the top of my head. I chose Kolbenschmidt.

Additional options.
Are you going to run this hard? More fuel and boost? You may want to do some searching here about ceramic coating the piston tops. It will add some efficiencey and a bit of possible power.
You may also want to consider the Total Seal 2nd ring option. It appears to reduce blow by significantly.

Pick a vendor.
We have registered vendors on site that sell pistons. Check around,on site and off. You will find large price differences.

Hope this helps.

Jim

Author Topic: Bore/blueprint (Read 3405 times)

stewardc

stewardc