Icon IC 743 piston weight incorrect

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72DMag

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Building up the 360 and purchased the icon ic743 pistons to significantly up the compression to run e85.

According to icon pistons catalog the piston should weigh 492 grams and the wrist pin should be 118 grams. After getting the pistons in and weighing them they are much much heavier than advertised!! On average the piston alone weighs 563 grams and the wrist pins average out to 125 grams.

Does anyone have experience with these pistons?? I am going to call icon on Tuesday but 71 grams heavier than advertised is crazy and can't be used with my stock balanced magnum 360.

Before any responses yes the scale is correct and zeroed out. I place some connecting rods on it to verify. Thanks
 
did you get the right pistons? Sounds like you got sent the wrong ones.
 
Nope they are the correct ones. Engraved on the side of the piston is ic743 std. Sorry I should have mentioned that in my original post that I checked that.
 
Pics

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Factory weight for a 'LA' 360 is 584 grams for the piston only. Pin and rings weights can change the overall weight. A magnum 360 may be different.
 
I have 469 grams for a stock Magnum piston. If the OP's numbers are correct, then he would be over 80 grams heavy compared to the stock bobweight. It ID odd that a domed piston would be lighter than the equivalent flat top piston in the same series and size. (IC741)

OP what weight did you get for a single Magnum con rod with cap and fasteners, no bearing shell? My data shows 744 grams + or -.

You can check your scale for incremental accuracy if you an accurate cc measuring device like a burrette used for checking head chamber volumes. Put a glass measuring cup on a see the weight then start adding water with the burrette, each cc is 1 gram. Add 100 cc's and see if the scale weight goes up 100 grams.

BTW, I have the same scale as one of my 2 and they are accurate if used right; I checked them against the local machine shop scale. But this still could be a scale problem. These type of inexpensive scales need to be PERFECTLY level or they can read off. If tilted, any sideways loading of the scale's platen will throw off the cheap strain gauges used in them.
 
@nm9stheham I agree with your logic that it makes little sense that a dome piston would be lighter however thats what icon themselves advertises the weight as. Hence why i bought them cause wanted to keep the stock external balance.

As for the connecting rods out of my magnum I got the following. All rods made sense except one was a hair on the lighter side but still doable in my opinion.

Rods:
1. 744
2. 741
3. 743
4. 741
5. 739
6. 743
7. 741
8. 738
 
Those con rod numbers all make sense, so your scale looks to be accurate.

Well, with the bobweight going up around 80+ grams, you sure will be out of balance. Options:
  • Add more external weight, but may not be possible to add enough up at the damper. Then again, if some was drilled out of the damper ring, you might get there.
  • Add heavy metal to crank throws
  • Change to SCAT rods which are going to move your bobweight to around 150 grams UNDER stock. That ought to balance out with 1 not-too-deep hole in each end crank throw (based on past experience). With SCAT rods (and Eagles too), they are weight matched in sets, for total weight as well as big and small end weights; the end weights come with the set documentation for the SCATS (and I am pretty sure for the Eagles too). So for a 'very good' balance job (better than with the stock rods), you don't have to work over the rods. You just need to compute up the new bobweight (not hard as you seem to be able to work with numbers, or I can help show you how), and have the shop balance the crank to that bobweight with just your crank and external weight parts. A lot less pricey that way.
  • Change the piston plan but IDK what you will get that is lighter. Even the KB hypers weigh in the same range as what you have. (And they are advertised to not fit in the stock Magnum head chamber anyway....)
 
@nm9stheham Yep those are the options that I see at this moment too.

Is there a way to calculate how much weight needs on the damper and flywheel based on the bobweight? I bought the blueprint damper that comes with 3 different weights. Maybe there is a way I can utilize them to add weight at the damper. Will be interesting to see what Icon says when I call them tmrow. My guess is they will just say its a misprint in their catalog. Hopefully they refund me for the return shipping from summit.

Thanks!!
 
Yes, but it requires some very accurate dimensions and computations of centers of mass, etc.. I have not ever worked that all out. IIRC, on those sets, the Magnum takes the middle sized weight, and the LA360 took the largest and the cast crank 340 the smallest. So there probably is some weight to be added in that largest weight. Tacking weight on at the back is easier. IIRC, the Magnum flexplate has a pretty wide weight under the starter ring.

I can tell you that with a 230 gram bobweight drop on an engine, the shop had to drill 81-82 grams out of the crank throws. (Or was it 82 in-oz??? The shop was not clear if it was grams or in-oz, and I did not measure it.) That was about a 1-1.25" deep hole in each end throw of an LA cast crank.

So with an 80 gram bobweight increase, it will not take a lot of physical mass.

Oh one more option:
  • Drill out weight inside the crank journals for 1-2 and 7-8 journals. That was done on 340's and is done on SCAT 4" cast cranks; it effectively cancels out some of the bobweight, and is the equivalent to adding heavy metal to the throws. I don't think 80 grams of cast iron is a big hole, but it is not hard to compute. And if it is off-centered a bit towards the outside, it can be smaller.
 
@nm9stheham Thank you. I appreciate the info and ideas. Was really good to bounce ideas off of you. Yes I have never calculated the math do do external weights nor do I know the equation unfortunately. yes you are corrcet on the magnum flexplate. I am contacting to contact icon tmrow then make a decision based on their response. (I'll post here what happens)

Gonna see if I can negotiate and get some style of a dome piston that is reasonably close to their advertised weight. Probably will need to be custom. Their response will determine which way i will go with this. wasn't there an icon rep on this forum? I know brian was on here a few years ago.

Thanks again and yeah you are correct on the weights for the engines. Have a great memorial day!
 
You're welcomed! Helps to bounce things around... unusual problem there. I am sure I woulda fallen into the same trap...
 
72D; I was snooping around and I found your pistons listed under 'UEM Pistons'. That part number [IC743] is listed for a 'LA 360' engine. The Magnum 360 pistons are much lighter, about 470 grams. The piston listing for Magnum 360's was confusing and for stroker motors.
 
UEMP is a major piston manufacturer. They make at least 3 piston lines, and pistons for other sellers.

Being 'for the LA360' has no real meaning for aftermarket performance pistons; everyone makes the same pistons to fit either LA and Magnum and you work with the piston to deck height that results for the 2 deck heights. On many of the KB and Icon pistons (both lines are from UEMP), the same pistons will end up nominally .003" above deck on a Magnum block and .012" below deck on the slightly taller LA block.
 
Welcome to engine building.

If you look you'll notice different sites have different listed weights. Pins as well.

They moved manufacturing around too.
They moved some to mexico, maybe all lines.. KB for sure. They weighed more after the move. Ex...us made kb243 from 2000 weighs 7 grams less than one from 2004 made in mexico.

Sloppy. The markings look like stick in the dirt drawings by a child. No more stamps at the that time..just doodles.
 
This is the response from Trevor at Icon. Kinda disappointed that he insisted I pay return shipping. Luckily Summit who I will shop with again gave me a prepaid return label at no cost to me. So hats off to them and not so much to ICOn.

I ordered the IC741 pistons that hot rod magazine used as a direct replacement weight. Sounds like their forging got heavier so i am curious now if these flat top pistons will even work. @MOPAROFFICIAL you are right moving to mexico added alot of weight. I'll let you guys know what the ic741's weigh when they come in. Thank all!!

Response from Trevor at ICON:
"What looks like happened is the forging was revised and strengthened, which not only increase the weight made it a more robust piston, at that time the pin was also changed with a slightly heavier wall unit.

While I understand your frustration with this weight change, UEM is constantly and consistently looking at ways to improve the product. Since this piston is not considered a replacement product (OE replacement part) the product weight and design is subject to change at our discretion, and may not reflect some published weight data . If you are still unhappy with the pistons they can be returned through summit, unfortunately since these are still perfectly usable pistons return and restock fees may apply."
 
I've read and heard worse.
We always weigh the pistons, balance guy doesn't just take numbers from a catalog.
It's just one of those variables in building.
Understandably if you wanted a lighter the lightest piston and it turned out to weigh more or even more than others...that sucks.
They better get caught up with their literature, covid or not
 
72DMag said:
This is the response from Trevor at Icon. Kinda disappointed that he insisted I pay return shipping. Luckily Summit who I will shop with again gave me a prepaid return label at no cost to me. So hats off to them and not so much to ICOn.

I ordered the IC741 pistons that hot rod magazine used as a direct replacement weight. Sounds like their forging got heavier so i am curious now if these flat top pistons will even work. @MOPAROFFICIAL you are right moving to mexico added alot of weight. I'll let you guys know what the ic741's weigh when they come in. Thank all!!

Response from Trevor at ICON:
"What looks like happened is the forging was revised and strengthened, which not only increase the weight made it a more robust piston, at that time the pin was also changed with a slightly heavier wall unit.

While I understand your frustration with this weight change, UEM is constantly and consistently looking at ways to improve the product. Since this piston is not considered a replacement product (OE replacement part) the product weight and design is subject to change at our discretion, and may not reflect some published weight data . If you are still unhappy with the pistons they can be returned through summit, unfortunately since these are still perfectly usable pistons return and restock fees may apply."
Click to expand...
Well sorry to hear it did not work out.

BTW, I do not think the IC741's are in any way shape or form actual replacements. Yeah, I know what the article sez and what has been discussed here.... but even with the slightly lighter ring pack, I get numbers that show the bobweight going up by 35 grams. That is not awful but is getting beyond the factory tolerance as I understand it.

Now... one thing you could do is gradually try to grind about 10 grams off the bottom pad of each rod. That is straightforward work and you can do that consistently. That would claw back 20 grams off of that increase. It is not properly balanced but at least you are getting within shouting distance of factory balance.
 
@nm9stheham Yep the ic741 pistons aren't exact replacement for stock weight. However I did order the lighter icon wrist pin (saves 18 grams) and that should only put me at 27 grams heavier per cylinder. For the most part the consensus on here is 30 grams is max heavier you can safely go.

I like your idea of rounding out the connecting rods!! Correct me if I am wrong but since this is above the wrist pin that would affect the reciprocating weight. Which is good because that is what i am trying to lighten due to the heavier piston/pin setup.

How much weight do you think can be shaved off by doing the following pictured below? Also even though these are press fit pins maybe drill an oil hole on the top to reduce weight too? Like they do for floating wrist pins. Any thoughts on that. Thanks!!

Magnum Rods.PNG
 
72DMag said:
@nm9stheham Yep the ic741 pistons aren't exact replacement for stock weight. However I did order the lighter icon wrist pin (saves 18 grams) and that should only put me at 27 grams heavier per cylinder. For the most part the consensus on here is 30 grams is max heavier you can safely go.

I like your idea of rounding out the connecting rods!! Correct me if I am wrong but since this is above the wrist pin that would affect the reciprocating weight. Which is good because that is what i am trying to lighten due to the heavier piston/pin setup.

How much weight do you think can be shaved off by doing the following pictured below? Also even though these are press fit pins maybe drill an oil hole on the top to reduce weight too? Like they do for floating wrist pins. Any thoughts on that. Thanks!!

View attachment 1715536387
Click to expand...


Help me understand the issue here. If you are going to balance the crank, why is piston weight an issue? FWIW lighter pins are almost always a bad move. The load on the pin is incredible at crossover and if the pin flexes and goes out of round it will grab the rod and rip the pin right out of the rod.
 
72D; WOW! The company rep said 'perfectly usable pistons'. Yeah, for a LA-360! The IC741 , like the IC743 is also listed for the LA-360. They should both weigh the same. [factory spec is 584 gms.] ---- Magnums around 470 gms.
 
OP, if you take 1 gram off the small end of each rod, then that drops the total bobweight by 1 gram. If you take 1 gram off of the big end of each rod, then that drops the bobweight by 2 grams; the numbers I suggested were for taking it off the bottom.

So that is why I suggested taking the weigh off the pad... by which I meant at the bottom. You get 2x the bobweight removal there. It does not matter if you take it off of the reciprocating or rotating weight. BTW, the beam is almost 100% part of the small end if you think of taking it off there.

When you grind it off, just do a small bit at a time to avoid heating the metal. You don't want to distort either end. Have the rod cap bolted and torque in place, and I personally would check the big end bore before and after. And the hole in the top shouldn't hurt....since it gets done regularly.

YR, he is trying to not do the balance work but to stay within the factory tolerance.
 
nm9stheham said:
OP, if you take 1 gram off the small end of each rod, then that drops the total bobweight by 1 gram. If you take 1 gram off of the big end of each rod, then that drops the bobweight by 2 grams; the numbers I suggested were for taking it off the bottom.

So that is why I suggested taking the weigh off the pad... by which I meant at the bottom. You get 2x the bobweight removal there. It does not matter if you take it off of the reciprocating or rotating weight. BTW, the beam is almost 100% part of the small end if you think of taking it off there.

When you grind it off, just do a small bit at a time to avoid heating the metal. You don't want to distort either end. Have the rod cap bolted and torque in place, and I personally would check the big end bore before and after. And the hole in the top shouldn't hurt....since it gets done regularly.

YR, he is trying to not do the balance work but to stay within the factory tolerance.
Click to expand...


Ok, then piston weight is fairly critical. IIRC the only pistons I’ve ever found that were close to OE weights were cast stuff, and some of those were actually light by a bit.
 
@nm9stheham Sorry didn't get back to you sooner been away from computer. I see what you mean now. When you said pad of the rod I thought of the small end since alot of guys grind those when doing a stroker.

Actually you have me thinking that I could possibly make the ic743 dome pistons work. I have them boxed but didn't return yet. I think I would need to grind both the top and bottom end though. I would grind the top as pictured above and might get like 20 grams off of it If I had to guess. Then I will grind the big end of the rod to a round shape like pictured. I bet I can get 10 grams off of it which would be 20 total bobweight. Again these are just numbers I am tossing out but that takes off 40 grams and only puts me 31 grams heavier than stock. So it will be close.

I could also use the 18 grams lighter wrist pin but with high compression sounds like a bad idea to me and not going to consider it.

I will be at the shop tmrow and I have some scrap magnum rods I can use for testing. Will measure cap weight by itself too and see what my final weights turn out to be. Thanks!

942-25700716_1.jpg
 
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