LS7 Titanium Connecting Rods
#41
Safety Car
#42
Le Mans Master
Thread Starter
Yes - I read post 5 and post 9 and all the posts in the thread. Let me see if I can put this another way. Look at the cost of the Ti Rods - about $1K - then we have the cost of the custom pistons - I don't know what that'll be but I think it's safe to say $500 more than an equivalent se of "off the shelf" HP pistons.
So let's look at some other numbers ... If you check out the Summit Racing site - you'll see a set of 6.0" Scat 4340 Forged H Beam rods with the ARP 2000 Rod bolts runs about $560. So - the Ti rods are about $400 more - plus the upcharge on the pistons.
OK - let's look at Crankshafts. The standard weight 4340 Forged steel Scat crank for a Gen 1 SBC weighs in at about 48 Lb and runs about $690. The lightweight 4340 Forged Steel Crank for the same Gen SBC is about 8 Lb lighter and runs about $950. So - for $300 more ($100 less than the lighter rods) you save about 8 lb of rotating weight.
If you look at the cost of a standard weight flywheel - it looks like a nice standard 168 tooth steel flywheel for a SBC weighs about 30 - 33 Lb and will run about $225. A lightweight flywheel will weigh in right around 15.5 Lb - 16 Lb and look like they run about $450 - $500.
So - for less than the cost delta between the Ti Rods and the custom pistons - you can upgrade to the lightweight crank and a lightweight flywheel, and save on the order of 22 Lb or rotating weight.
To me - if you're concerned about the weight of the reciprocating / rotating parts of the motor - the lightweight crank and the lightweight flywheel make a lot more sense than the lighter rods. Yes - if you're going to be revving the daylights out of the motor - the lighter weight rods do buy you some things - but not all that many street motors see the super high revs where the rod weight really matters. And remember - the valvetrain typically give you more problems with high revs than the reciprocating assy - so if you're going to spin the motor to the stratosphere - plan on spending lots more $$$ on valve springs, and either top of the line hydraulic roller lifters - or more likely solid roller lifters ...
So let's look at some other numbers ... If you check out the Summit Racing site - you'll see a set of 6.0" Scat 4340 Forged H Beam rods with the ARP 2000 Rod bolts runs about $560. So - the Ti rods are about $400 more - plus the upcharge on the pistons.
OK - let's look at Crankshafts. The standard weight 4340 Forged steel Scat crank for a Gen 1 SBC weighs in at about 48 Lb and runs about $690. The lightweight 4340 Forged Steel Crank for the same Gen SBC is about 8 Lb lighter and runs about $950. So - for $300 more ($100 less than the lighter rods) you save about 8 lb of rotating weight.
If you look at the cost of a standard weight flywheel - it looks like a nice standard 168 tooth steel flywheel for a SBC weighs about 30 - 33 Lb and will run about $225. A lightweight flywheel will weigh in right around 15.5 Lb - 16 Lb and look like they run about $450 - $500.
So - for less than the cost delta between the Ti Rods and the custom pistons - you can upgrade to the lightweight crank and a lightweight flywheel, and save on the order of 22 Lb or rotating weight.
To me - if you're concerned about the weight of the reciprocating / rotating parts of the motor - the lightweight crank and the lightweight flywheel make a lot more sense than the lighter rods. Yes - if you're going to be revving the daylights out of the motor - the lighter weight rods do buy you some things - but not all that many street motors see the super high revs where the rod weight really matters. And remember - the valvetrain typically give you more problems with high revs than the reciprocating assy - so if you're going to spin the motor to the stratosphere - plan on spending lots more $$$ on valve springs, and either top of the line hydraulic roller lifters - or more likely solid roller lifters ...
..... I used the LS7 rods because they were available , affordable , and made of titanium ... about as close to unobtainium as I will ever get ! ... the original build used off the shelf Mahle pistons #SBC000155D08 that I bought for about $550 (currently near $800) ... I need custom pistons now because I melted one of the Mahles ... the block cleaned up at 4.157" and no one has that bore size available as a normal stocking item ... the new slugs are JE's and will cost me about $1400 for TEN pistons and rings ... The heads have SS valves and Isky Tool Room springs with titanium retainers and a T&D shaft rocker system to fluctuate them ... these rods have been north of 8000 rpm on more than a couple of occasions but that wasn't my goal ... the solid roller cam is mild by some standards and only makes power to 7400 rpm ... no flywheel , instead I have a flexplate and 9.5" torque converter ... You seem to know your way around the guts of a performance engine ... tell us about your mill ? .....
Last edited by C409; 02-25-2018 at 09:56 AM.
#43
Le Mans Master
OK - let's look at Crankshafts...for $300 more ($100 less than the lighter rods) you save about 8 lb of rotating weight.
...A lightweight flywheel will weigh in right around 15.5 Lb - 16 Lb and look like they run about $450 - $500.
So - for less than the cost delta between the Ti Rods and the custom pistons - you can upgrade to the lightweight crank and a lightweight flywheel, and save on the order of 22 Lb or rotating weight.
To me - if you're concerned about the weight of the reciprocating / rotating parts of the motor - the lightweight crank and the lightweight flywheel make a lot more sense than the lighter rods.
...A lightweight flywheel will weigh in right around 15.5 Lb - 16 Lb and look like they run about $450 - $500.
So - for less than the cost delta between the Ti Rods and the custom pistons - you can upgrade to the lightweight crank and a lightweight flywheel, and save on the order of 22 Lb or rotating weight.
To me - if you're concerned about the weight of the reciprocating / rotating parts of the motor - the lightweight crank and the lightweight flywheel make a lot more sense than the lighter rods.
Last edited by MatthewMiller; 02-25-2018 at 11:11 AM.
#44
Le Mans Master
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Don't know where you get your .16/.28 numbers but the atomic weight of Ti = 48 and Fe = 56 while Al = 27.. Of course alloys change those weights but that's all I have to work with and those are the major constituents.
#45
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This has already addressed twice by me, and maybe also by others. So for at least the third time, crankshaft and flywheel masses have zero impact on reciprocating mass! They don't reciprocate - they only rotate. I don't know how to state that any more simply. Connecting rod mass is mostly important because it saves on reciprocating mass. It does very little to reduce total rotating mass, and nobody would spend big money for exotic rods just to reduce rotating mass. Stop equating reciprocating mass with rotating mass. You're trying to solve an apple shortage by planting orange tress.
As far as flywheel and crankshaft weight the lighter parts do help the motor accelerate/rev faster. That's important to some but others prefer a smother feel from a heavier flywheel on a daily driver/cruiser. Trade offs are made for performance.
#46
Le Mans Master
Well a large advantage of the lighter rods and pistons is the it greatly reduces the tesile stress on the rod as it changes directions. I'm not going to do the math here but tensile stress increases exponentially with piston/engine speed. Lighter rods and pistons significantly increase a racing engines life.
As far as flywheel and crankshaft weight the lighter parts do help the motor accelerate/rev faster. That's important to some but others prefer a smother feel from a heavier flywheel on a daily driver/cruiser. Trade offs are made for performance.
Originally Posted by Purple92
Supposedly NASCAR Monster Energy motors are running 4340 rods and cranks - and bottom end failures are quite rare - even though they are regularly turning 9,000+RPM (supposedly 10,000 RPM on the dyno is not exactly unusual.) Top end failures are a fair bit more common. Valve spring pressures are supposedly approaching 900 Lb wide open.
Almost any top-level racing category is like this. F1 had some teams using beryllium/aluminum alloys for pistons and brake parts (maybe other parts?) for a few years before it was banned due to weight and the health hazards of machining it. If cost and rules were no object, steel wouldn't be used in very many automotive parts at all.
#47
I just spent about an hour typing in a nice long reply - and something happened as I hit submit - and I had to log in to CF again - post was lost....
Bottom line - I get that reciprocating mass is different than rotating mass. Weight of recip assembly causes loads that increase with the square of engine RPM - so light weight rods lower those loads. I get it. The point I was trying to go to - was that typically the increased loads impact crank journals - piston pins, pistons and most importantly connecting rod bolts. I tend to think GM went to the Ti rods on their LS7 not because they were worried about rod bolt failures - but because the were worried about oil film strength with the 5W-30 oil they like to specify for fuel savings. 4340 steel rods have been proven to work in many pro racing applications where very high sustained RPM is the norm.
So - lighter weight cranks and flywheels will take less energy to spin up - so more energy will be available to accelerate the vehicle, and the results of losing 20 Lb of recip mass will be measurable. No way that results of lighter weight rods / pistons will ever be measurable on vehicle acceleration.....
Bottom line - I get that reciprocating mass is different than rotating mass. Weight of recip assembly causes loads that increase with the square of engine RPM - so light weight rods lower those loads. I get it. The point I was trying to go to - was that typically the increased loads impact crank journals - piston pins, pistons and most importantly connecting rod bolts. I tend to think GM went to the Ti rods on their LS7 not because they were worried about rod bolt failures - but because the were worried about oil film strength with the 5W-30 oil they like to specify for fuel savings. 4340 steel rods have been proven to work in many pro racing applications where very high sustained RPM is the norm.
So - lighter weight cranks and flywheels will take less energy to spin up - so more energy will be available to accelerate the vehicle, and the results of losing 20 Lb of recip mass will be measurable. No way that results of lighter weight rods / pistons will ever be measurable on vehicle acceleration.....
#48
#49
Le Mans Master
Bottom line - I get that reciprocating mass is different than rotating mass. Weight of recip assembly causes loads that increase with the square of engine RPM - so light weight rods lower those loads. I get it. The point I was trying to go to - was that typically the increased loads impact crank journals - piston pins, pistons and most importantly connecting rod bolts. I tend to think GM went to the Ti rods on their LS7 not because they were worried about rod bolt failures - but because the were worried about oil film strength with the 5W-30 oil they like to specify for fuel savings. 4340 steel rods have been proven to work in many pro racing applications where very high sustained RPM is the norm.
So - lighter weight cranks and flywheels will take less energy to spin up - so more energy will be available to accelerate the vehicle, and the results of losing 20 Lb of rotating mass will be measurable.
#50
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Yes, it's almost as if its sabotage sometimes. So I began to type in word, or word pad or note pad then cut and paste into the post box but most of my reply's are to short to bother. Problem is many times a short reply turns into a long one and its overlooked when its to late to save it. My tablet is worst culprit at killing my reply's.
#51
Team Owner
Pro Mechanic
#52
Safety Car
The mass of an object does not increase linear with its increase in atomic number, as shown below, it depends on the material.
Last edited by bjankuski; 02-26-2018 at 08:28 AM.
#53
lightweight flywheel
video is 5abi vt's
https://youtu.be/1zkEz59cZjM
https://youtu.be/1zkEz59cZjM
#54
Yes, it's almost as if its sabotage sometimes. So I began to type in word, or word pad or note pad then cut and paste into the post box but most of my reply's are to short to bother. Problem is many times a short reply turns into a long one and its overlooked when its to late to save it. My tablet is worst culprit at killing my reply's.
I was wondering if I went too long typing, and the server didn't see "activity" per se and just logged me off...
#55
..... The heads have SS valves and Isky Tool Room springs with titanium retainers and a T&D shaft rocker system to fluctuate them ... these rods have been north of 8000 rpm on more than a couple of occasions but that wasn't my goal ... the solid roller cam is mild by some standards and only makes power to 7400 rpm ... no flywheel , instead I have a flexplate and 9.5" torque converter ... You seem to know your way around the guts of a performance engine ... tell us about your mill ? .....
I have a couple of street legal Vettes and all but one has a stock engine. I also have a couple of dedicated track cars - one is a 1992 C4 with a LT1 based motor. It's a 383 with a forged 4340 crank and rods, and I believe Mahle pistons that run around 11.0:1. The motor was built by Golen Engine Service. The heads are heavily ported sock LT1 heads (done by Lloyd Eliott) and I have his middle of the road cam in that motor. The motor is PCM limited to 6250 RPM, and was dynoed right at 500 HP.
The other track vehicle started as a pile of steel tubing. It has a 415 SBC Chevy (3.875 stroke crank). World Block, forged 4340 crank, rods and I believe Wiesco pistons - it's running 10.5:1 compression. I am running Brodix Track 1 heads on that one, and it's fed by a good old fashioned Holley 750 DP (that was tweaked a good bit on the dyno). It makes 510 flywheel HP and the chip in the MSD Box is set to 6,100 RPM (so it starts pulling spark at 5,950). This is the motor with the Jessel shaft rocker system, and it's running a mellow solid roller cam. (I tend to think that even though the cam is one of the most mellow roller lifter cams available - it's acceleration rates were what killed the individual rocker arms I tried to use initially). But in a 3,000 Lb vehicle (wet - with driver) - it does a pretty good job - and it makes torque from about 3,500 RPM - and when you're playing on a road course - torque is a truly WONDERFUL thing !!! I've managed to run a sub 2:10 lap at Watkins Glen with that vehicle.
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#56
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But the advantage of Ti that I do see is with its lighter weight it doesn't need to be as strong.
Last edited by cardo0; 02-26-2018 at 09:40 PM. Reason: Stupid autocorrect!
#57
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So I did a google for Ti LS7 rods and on top of the links was Crower Ti rods for sbc. 6" Ti rods for the sbc from Jeg's at $750.. Can this be true?
Today's technology moves ahead a fast pace. Whew! Think of a good idea and it's there like now.
Today's technology moves ahead a fast pace. Whew! Think of a good idea and it's there like now.
#58
Le Mans Master
Thread Starter
..... That price is per EACH ..... Back a few years ago , the Chevy Parts retail price for new LS7 Ti rods was $778.00 each .....
Last edited by C409; 02-27-2018 at 10:19 PM.
#59
Le Mans Master
Thread Starter
..... Soooo , I think we can all agree that the substitution of lightweight internal components in an engine will NOT increase the horsepower output of that engine ? But will affect the acceleration in RPM/second ? ... the same for lightening external (behind the crankshaft) components ? ... BUT , Consider this : if 2 cars line up at a drag strip and we just imagine that scientifically all is equal between the two including the scale weights and horsepower/torque ... and the difference between the 2 cars is that one has extensive lightweight components vs the other with none ... will there actually BE a difference in acceleration as measured by the ET slip ? .....
#60
..... Soooo , I think we can all agree that the substitution of lightweight internal components in an engine will NOT increase the horsepower output of that engine ? But will affect the acceleration in RPM/second ? ... the same for lightening external (behind the crankshaft) components ? ... BUT , Consider this : if 2 cars line up at a drag strip and we just imagine that scientifically all is equal between the two including the scale weights and horsepower/torque ... and the difference between the 2 cars is that one has extensive lightweight components vs the other with none ... will there actually BE a difference in acceleration as measured by the ET slip ? .....