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Wiseco piston balancing limit / location

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willyp42

Proven Member
60
9
Sep 28, 2016
Windsor, ON_Canada
Hey guys I just finished up weighing my pistons, wrist pins, and rings and found I have a 1.5 gram weight difference max to min.

do you guys think it’s safe to take the 1.5 grams of the inside of the pin boss?

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I was going to put a gentle chamfer there.
Thanks,
-Will
 

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It wouldn't be a problem if not too much. I always take some material from there. You can combine the heaviest piston with the lightest rod (or vice versa) to make the weight difference minimum. Also you can remove some material from rods and wrist pins to make the total weight equal to avoid removing too much material from the same location on the same part.
 
Yeah I get you, I wouldn’t feel concerned if it was a half gram, but 1.5 seems excessive I wonder if anyone else has experience here?
 
If you would remove 1.5g material from only the boss where you marked then it may be too much. Just making chamfer on the boss would probably reduce only approx. 0.1g~0.3g. But how much material you can safely remove would depend on your setup though. Please see the pic below, I removed material most from the #2 piston, the removed weight was approx. 0.5g, now you can guess how much material would be 1.5g.
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You are fine with a 1.5 g difference, but it won't hurt to try and get it closer.
What is the combined weight of the 1-4 throw compaired to the 2-3 throw?
Add 1 and 4 together and add 2 and 3 together to see what the total throw weight difference is.
I have a 1.5 gram spread but only a .5 gram difference in throw on my motor and she runs fantastic.
You can open and look at these last 3 builds for reference if you want. The last 4g motor (MW2) is a 7 bolt and has super close weights, so close that I suspect the lower end was balanced at one point, I just rebuilt it for my son.
 

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#1 482.69
#2 481.30
#3 482.10
#4 481.33

1&4 984.02, 2&3 963.40

i still haven't weighed my rods yet, but i am looking to take full advantage of my Kelford 276HL cams. i plan on spinning it to 8500. its the reason why id like to be tight on my reciprocating mass.
-Will
 
#1 482.69
#2 481.30
#3 482.10
#4 481.33

1&4 984.02, 2&3 963.40

i still haven't weighed my rods yet, but i am looking to take full advantage of my Kelford 276HL cams. i plan on spinning it to 8500. its the reason why id like to be tight on my reciprocating mass.
-Will
So you haven't weighed the rods yet... then don't take any material from the pistons yet. As I said above that how you combine the pistons and the rods would change the weight difference. After you weigh everything and calculate all combination weight should be the moment to start thinking how much material you need to remove.
By the way, the Kelford 276HL is a bit peaky but a good set. I used to run them for some years and I liked them.
 
You would want your small end weights close to each other and the same with thee big ends, not necessarily the overall weights but the ends are more important and in doing that you would get the overall weights pretty close by default.
 
so optimized rod weight tolerance stack for total recip mass wieghts.
1103.97
1103.44
1103.60
1103.43
i dont disagree with motomattx, however i dont have access to a rod weighing apparatus.
i tried calling 2 of my local machine shops but they arent able to get to it.
i think im just going to take 3 tenths off heavy cylinder and run it.
thanks guys,
-Will
 
You probably won't notice the difference but you are getting it as close as you can.
Those cams will take you to 9k, BTW.
 
Thanks for response,
I’ve had this apart for so long I don’t remember the hardware limitation reason I believe it’s my rod bolts.
-Will
 
It's ideal but it's not super necessary to run. As @1990TSIAWDTALON Marty said you wouldn't probably feel any difference. But if you believe to build the engine often and want to properly weight balance each time you build, get a rod balancer would be a good idea.
BTW, to run those cams, just make sure that you have Kiggly high pressure springs or Kelford springs.
 
Thanks for reminding him about the springs Hiroshi, nice catch. :thumb:
 
So that you know, my motor in my car is the MW1 spec motor. It has a gram and a half spread across the 4 cylinders. I have hit the 8800 limiter a hand full of times and she seems to want to keep going a bit further. No odd vibrations or worries. Good springs and Kelford 264s with 9:1 Manleys and now on E!!! OMG :)
 
Thanks for looking out to my guys.
I just have set of 8.3:1 weiscos with eagle rods and crank (2.0)
Yes I have kiggly high pressures and evo rocker arms to match.
I’ve never met anyone else run these cams, have you notice any rocker arm wear?
That’s one of my major concerns.
-Will
 
My son is running the high lift Kelfords and we haven't noticed any.....yet. I will keep an eye on it tho.
 
That’s great to hear, Thanks everyone.
Any turbo insight or recommendations?
I have a gen 1 pte 6262 and going to see what she got.
 
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