Anyone Tried a long Rod Stock Stroke Combo?
10-05-2010, 06:30 PM
#1
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Anyone Tried a long Rod Stock Stroke Combo? Ive been looking into getting a spare block and building a 355-357 using the stock crank and wondered about doing a long rod build.
I know mahle has pistons available for 6.125" rods but i found some Keith black pistons that are made for 6.200" rods. I have been told that the longer rod will help boost efficiency while squeaking out a bit more power. My only concern is that the rod will push the pin up into the ringpack which wont be a good idea on my daily driven vehicle.
Has anyone done a Gen1/2 build with 6.125"+ rods and kept the pin out of the ringlands?
I know mahle has pistons available for 6.125" rods but i found some Keith black pistons that are made for 6.200" rods. I have been told that the longer rod will help boost efficiency while squeaking out a bit more power. My only concern is that the rod will push the pin up into the ringpack which wont be a good idea on my daily driven vehicle.
Has anyone done a Gen1/2 build with 6.125"+ rods and kept the pin out of the ringlands?
10-05-2010, 06:49 PM
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I completely agree on the much better quality of product, but if im getting new pistons im getting new rods. I know 6.000" rods clear the ringpacks with room to spare but why stop there?
10-05-2010, 08:16 PM
#4
From the "Camfather" Iskendarian:
"The longer the rod, the closer your wrist pin boss will be to your ring lands. In extreme situations, 6.125" & 6.250" lengths for example, both ring and piston life are affected. The rings get a double whammy affect. First, with the pin boss crowding the rings, the normally designed space between the lands must be reduced to accommodate the higher wrist pin boss. Second, the rings wobble more and lose the seal of their fine edge as the piston rocks. A longer Rod influences the piston to dwell a bit longer at TDC than a shorter rod would and conversely, to dwell somewhat less at BDC."
Read more, about 1/2 way down the page, "Rod Lengths/Ratios"
http://www.iskycams.com/techtips.php
Particularly the extra flexibility you get with duration when using a shorter rod...
"The longer the rod, the closer your wrist pin boss will be to your ring lands. In extreme situations, 6.125" & 6.250" lengths for example, both ring and piston life are affected. The rings get a double whammy affect. First, with the pin boss crowding the rings, the normally designed space between the lands must be reduced to accommodate the higher wrist pin boss. Second, the rings wobble more and lose the seal of their fine edge as the piston rocks. A longer Rod influences the piston to dwell a bit longer at TDC than a shorter rod would and conversely, to dwell somewhat less at BDC."
Read more, about 1/2 way down the page, "Rod Lengths/Ratios"
http://www.iskycams.com/techtips.php
Particularly the extra flexibility you get with duration when using a shorter rod...
10-05-2010, 09:37 PM
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From the "Camfather" Iskendarian:
"The longer the rod, the closer your wrist pin boss will be to your ring lands. In extreme situations, 6.125" & 6.250" lengths for example, both ring and piston life are affected. The rings get a double whammy affect. First, with the pin boss crowding the rings, the normally designed space between the lands must be reduced to accommodate the higher wrist pin boss. Second, the rings wobble more and lose the seal of their fine edge as the piston rocks. A longer Rod influences the piston to dwell a bit longer at TDC than a shorter rod would and conversely, to dwell somewhat less at BDC."
Read more, about 1/2 way down the page, "Rod Lengths/Ratios"
http://www.iskycams.com/techtips.php
Particularly the extra flexibility you get with duration when using a shorter rod...
"The longer the rod, the closer your wrist pin boss will be to your ring lands. In extreme situations, 6.125" & 6.250" lengths for example, both ring and piston life are affected. The rings get a double whammy affect. First, with the pin boss crowding the rings, the normally designed space between the lands must be reduced to accommodate the higher wrist pin boss. Second, the rings wobble more and lose the seal of their fine edge as the piston rocks. A longer Rod influences the piston to dwell a bit longer at TDC than a shorter rod would and conversely, to dwell somewhat less at BDC."
Read more, about 1/2 way down the page, "Rod Lengths/Ratios"
http://www.iskycams.com/techtips.php
Particularly the extra flexibility you get with duration when using a shorter rod...
I will still probably run a 6.00" rod over the 5.70" being that mahle has more pistons for them.
10-07-2010, 10:16 AM
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With a stock stroke why go higher than a 6.0 rod on a street motor??? Yore adding price to something that will at most give small results.
Concentrate more on friction reduction with a better piston and ring package.
Concentrate more on friction reduction with a better piston and ring package.
10-08-2010, 10:50 AM
#9
What HP level are you looking to make?
If your going with the stocker cast crank....upgrading to better rods won't necessarily increase your power capacity by much.
The stock rods are pink rods if im not mistaken....if your building up for some N20...u could upgrade to forged piston and leave all the rest as is...it would be conservative shots tho.
If your not going to upgrade the crank...u wont gain much with just the rods alone.
That being said...if u need to upgrade any of these at all.
If your going with the stocker cast crank....upgrading to better rods won't necessarily increase your power capacity by much.
The stock rods are pink rods if im not mistaken....if your building up for some N20...u could upgrade to forged piston and leave all the rest as is...it would be conservative shots tho.
If your not going to upgrade the crank...u wont gain much with just the rods alone.
That being said...if u need to upgrade any of these at all.
10-08-2010, 02:10 PM
#10
What HP level are you looking to make?
If your going with the stocker cast crank....upgrading to better rods won't necessarily increase your power capacity by much.
The stock rods are pink rods if im not mistaken....if your building up for some N20...u could upgrade to forged piston and leave all the rest as is...it would be conservative shots tho.
If your not going to upgrade the crank...u wont gain much with just the rods alone.
That being said...if u need to upgrade any of these at all.
If your going with the stocker cast crank....upgrading to better rods won't necessarily increase your power capacity by much.
The stock rods are pink rods if im not mistaken....if your building up for some N20...u could upgrade to forged piston and leave all the rest as is...it would be conservative shots tho.
If your not going to upgrade the crank...u wont gain much with just the rods alone.
That being said...if u need to upgrade any of these at all.
Can I guess your "knowledge" is based on older applications?
In the LT1 the crank is good to a fair bit more power than the rods. Rod failures are documented once you turn the rpms up, but I am not aware of a single case of anyone overpowering a stock crank.
Frankly I would use it BEFORE a chinese forged/machined piece, based on my decade of experience and observation of THIS PARTICULAR ENGINE for what that is worth.
10-08-2010, 02:33 PM
#11
Can I guess your "knowledge" is based on older applications?
In the LT1 the crank is good to a fair bit more power than the rods. Rod failures are documented once you turn the rpms up, but I am not aware of a single case of anyone overpowering a stock crank.
Frankly I would use it BEFORE a chinese forged/machined piece, based on my decade of experience and observation of THIS PARTICULAR ENGINE for what that is worth.
In the LT1 the crank is good to a fair bit more power than the rods. Rod failures are documented once you turn the rpms up, but I am not aware of a single case of anyone overpowering a stock crank.
Frankly I would use it BEFORE a chinese forged/machined piece, based on my decade of experience and observation of THIS PARTICULAR ENGINE for what that is worth.
Its why I asked what he's looking to do. If he thinks he's going to need rods then he may in fact need a crank as well.
Here's a link to our stock rods....which in my opinion are fairly matched to our stock cast crank(of unfailing reputation):
http://www.gmpartsdirect.com/perform...CATID=847.html
Again if he needs more than these stockers can provide....it'd be worth his while to consider the crank as well.
You can ARP rod bolt the stockers and gain some insurance against failure...again depending on how what level he wants to go to. And keep BOTH the great stock crank and rods.
Last edited by License2Ill; 10-08-2010 at 02:44 PM.
10-08-2010, 08:22 PM
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Its Not that i NEED more rod strength, but there are more pistons available from better quality manufacturers with the longer rod lengths ie 6.000 and 6.125 and Scat has some quality forged rods for under 300$ that run a cap and bolt design versus the thru bolt design that is used on the stockers. I dont plan on any power adders but this engine will rev to close to 7000 when its all said and done. Im personally just not comfortable revving stock style rods that high, ive seen a few "pink" and "x" rods that have imploded at these rpms.
10-08-2010, 08:31 PM
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I've seen on stock crank break, from the snout being bent by a procharger.
As far as the rod length debate I put 6" Eagle SIR rods with some Mahle pistons on my stock crank rebuild. It wasn't any price difference and the longer rod has less rocking in the bore
As far as the rod length debate I put 6" Eagle SIR rods with some Mahle pistons on my stock crank rebuild. It wasn't any price difference and the longer rod has less rocking in the bore
