FYI: Carrillo Rods vs. Factory Rods
- Thread starter JimmyMac
- Start date
not hp but quicker to rev i believe . You have good point about rotaional mass
oaklandopen
Member
rod length doesn't change the compression ratio, it just changes the piston placement inside the cylinder. crankshaft, piston face design, head design, and gaskets can change the compression though.
Humor me on this please. If i use a thicker gasket i reduce compression because i have increased the volume at top dead center. If the rod is say shorter, doesn't that have the same effect. Like a flat top piston compared to domed might change compression or wrist pin location might also? I appreciate the dialogue
The rod has same stroke, it's just an illusion because the factory rod has more material at the top and bottom of the rod. So it appears longer.
A thicker gasket will lower compression, but will also affect timing because timing chain will be stretched/pulled more. A shorter rod will also lower compression because the piston will not go as high in the cylinder at tdc.
A thicker gasket will lower compression, but will also affect timing because timing chain will be stretched/pulled more. A shorter rod will also lower compression because the piston will not go as high in the cylinder at tdc.
hyperpasta
Member
Here's an explation for short vs Long connecting rod in a race motor and what is involved in making it run at peak performance levels.
You always want the piston at acceptable squish clearances at TDC.
Rod Length Relationships
In general, most observations relate to engines used for some type of competition event and will in general produce peak power higher than 6000 RPM with good compression ring seal as defined by no more than 3/16 CFM blowby per cylinder.
Short Rod is slower at BDC range and faster at TDC range.
Long Rod is faster at BDC range and slower at TDC range.
I. LONG ROD
A. Intake Stroke -- will draw harder on cyl head from 90-o ATDC to BDC.
B. Compression Stroke -- Piston travels from BDC to 90-o BTDC faster than short rod. Goes slower from 90-o BTDC to TDC--may change ign timing requirement versus short rod as piston spends more time at top. However; if flame travel were too fast, detonation could occur. Is it possible the long rod could have more cyl pressure at ie. 30-o ATDC but less crankpin force at 70-o ATDC. Does a long rod produce more efficient combustion at high RPM--measure CO, CO2? Find out!!
C. Power Stroke -- Piston is further down in bore for any given rod/crank pin angle and thus, at any crank angle from 20 to 75 ATDC less force is exerted on the crank pin than a shorter rod. However, the piston will be higher in the bore for any given crank angle from 90-o BTDC to 90-o ATDC and thus cylinder pressure could be higher. Long rod will spend less time from 90-o ATDC to BDC--allows less time for exhaust to escape on power stroke and will force more exhaust out from BDC to 90-o BTDC. Could have more pumping loss! Could be if exhaust port is poor, a long rod will help peak power.
D. Exhaust Stroke -- see above.
II. Short Rod
A. Intake Stroke -- Short rod spends less time near TDC and will suck harder on the cyl head from 10-o ATDC to 90-o ATDC the early part of the stroke, but will not suck as hard from 90-o to BDC as a long rod. Will require a better cyl head than long rod to produce same peak HP. Short rod may work better for a IR or Tuned runner system that would probably have more inertia cyl filling than a short runner system as piston passes BDC. Will require stronger wrist pins, piston pin bosses, and connecting rods than a long rod.
B. Compression Stroke -- Piston moves slower from BDC to 90-o BTDC; faster from 90-o BTDC to TDC than long rod. Thus, with same ign timing short rod will create less cyl compression for any given crank angle from 90-o BTDC to 90-o ATDC except at TDC. As piston comes down, it will have moved further; thus, from a "time" standpoint, the short rod may be less prone to detonation and may permit higher comp ratios. Short rod spends more time at the bottom which may reduce intake charge being pumped back out intake tract as valve closes--ie. may permit longer intake lobe and/or later intake closing than a long rod.
C. Power Stroke -- Short rod exerts more force to the crank pin at any crank angle that counts ie.--20-o ATDC to 70-o ATDC. Also side loads cyl walls more than long rod. Will probably be more critical of piston design and cyl wall rigidity.
D. Exhaust Stroke -- Stroke starts anywhere from 80-o to 110-o BBDC in race engines due to exhaust valve opening. Permits earlier exhaust opening due to cyl pressure/force being delivered to crank pin sooner with short rod. Requires a better exhaust port as it will not pump like a long rod. Short rod has less pumping loss ABDC up to 90-o BTDC and has more pumping loss from 90-o BTDC as it approaches TDC, and may cause more reversion.
III. NOTES
A. Rod Length Changes -- Appears a length change of 2-1/2% is necessary to perceive a change was made. For R & D purposes it appears a 5% change should be made. Perhaps any change should be 2 to 3%--ie. Ignition timing, header tube area, pipe length, cam shaft valve event area, cyl head flow change, etc.
B. Short Rod in Power Stroke -- Piston is higher in the bore when Rod-Crank angle is at 90-o even though at any given crank angle the piston is further down. Thus, at any given "time" on the power stroke between a rod to crank pin angle of 10o and ie. 90-o, the short rod will generate a greater force on the crank pin which will be in the 70-o to 75-o ATDC range for most engines we are concerned with.
C. Stroke -- Trend of OEM engine mfgs to go to longer stroke and/or less over square (bore numerically higher than stroke) may be a function of L/R. Being that at slower engine speeds the effect of a short rod on Intake causes few problems. Compression/Power Stroke should produce different emissions than a long rod. Short rod Exhaust Stroke may create more reversion--EGR on a street engine.
D. More exhaust lobe or a earlier exhaust opening may defeat a longer rod. I am saying that a shorter rod allows a earlier exhaust opening. A better exhaust port allows a earlier exhaust opening.
E. Definition of poor exhaust port. Becomes turbulent at lower velocity than a better port. Flow curve will flatten out at a lower lift than a good port. A good exhaust port will tolerate more exhaust lobe and the engine will like it. Presuming the engine has adequate throttle area (so as not to cause more than 1" Hg depression below inlet throttle at peak power); then the better the exhaust port is, the greater the differential between optimum intake lobe duration and exhaust lobe duration will be--ie. exh 10-o or more longer than intake Carbon buildup will be minimal if cyl is dry.
IV. DEFINITIONS
Short Rod -- Min Rod/Stroke Ratio -- 1.60 Max Rod/Stroke Ratio -- 1.80
Long Rod -- Min Rod/Stroke Ratio -- 1.81 Max Rod/Stroke Ratio -- 2.00
Any ratio's exceeding these boundaries are at this moment labeled "design screw-ups" and not worth considering until valid data supports it.
Contributors to Date: Bill Clemmons, Jere Stahl
oaklandopen
Member
maybe my extremely crude mspaint representation can help...
i tried to make the one on the left twice as long as the one on the right. and here you can see that changing rod length alone only changes the piston position in the cylinder. and even though the longer rod looks like the compression is higher than that of the shorter rod, its also starting higher than the shorter piston, so the ratio is the same
hyperpasta's post is excellent stuff too, but if we're only discussing rod lengths, givin everything else remains constant, simply changing the length won't change compression
but like hyperpasta posted, different length of rods are used for different applications, like one gives you more hp at higher rpms, another gives you better torque at lower rpms, etc
hyperpasta
Member
True! Although the static compression will remain the same, through cam and ignition timing, dynamic compression can be increased and be used to create more HP with a much shorter rod. Not torque.....
lots of info and a clarification.
Absolutely. Now i get it. about static compression. I was confusing myself thinking about too many things happening such as spark event and valve control. Thanks you guys, alot of help. and now more stuff to think on. How about nodular iron and shot peening your rods?!maybe my extremely crude mspaint representation can help...
i tried to make the one on the left twice as long as the one on the right. and here you can see that changing rod length alone only changes the piston position in the cylinder. and even though the longer rod looks like the compression is higher than that of the shorter rod, its also starting higher than the shorter piston, so the ratio is the same
hyperpasta's post is excellent stuff too, but if we're only discussing rod lengths, givin everything else remains constant, simply changing the length won't change compression
but like hyperpasta posted, different length of rods are used for different applications, like one gives you more hp at higher rpms, another gives you better torque at lower rpms, etc
JimmyMac I am curious as to which rod bent in your motor. I was just on the 6club and a lot of people mention that the Balance Shaft might be related to bent rods. They say the Rod 3 (or whichever is connected to the balance shaft) is the most commonly bent...
axisboldaslove
Member
- :
- 07 MS3 GT Heavily Modified
price listings from jscspeed
Description Part # MSRP Price Inventory
Pro-SA Rods 3/4 WMC bolts MA-23DISI $964.00 $877.00 Ships in 7-14 Days
Pro-H Rods 3/4 WMC bolts MA-23DISI>-65927H-04 $1,112.00 $1,012.00 Ships in 7-14 Days
Pro-H Rods 3/4 CARR bolts MA-23DISI>-65927S-04 $1,350.00 $1,229.00 Ships in 7-14 Days
Description Part # MSRP Price Inventory
Pro-SA Rods 3/4 WMC bolts MA-23DISI $964.00 $877.00 Ships in 7-14 Days
Pro-H Rods 3/4 WMC bolts MA-23DISI>-65927H-04 $1,112.00 $1,012.00 Ships in 7-14 Days
Pro-H Rods 3/4 CARR bolts MA-23DISI>-65927S-04 $1,350.00 $1,229.00 Ships in 7-14 Days
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- :
- 06 LS MS6
07 BM GT (shell has been struck from the roll)
SCRREEEEEEECH
you can't pull the flywheel, without pullin the block ???
should be able to get it wiht the transaxle out, unless, unless, I can;t really imagine, what would stop u
Curious, cuz someday, when the stock clutch goes, I will def drop the bux on a fidanza wheel
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Whats the quality of K-1 rods?..........These are 445.95 at pt performance......just carious. Carrillo rods Ive alwas heard good things about...another thing on making big power..is pistons,rods,gasket,arp bolts be good enough..or would a new set of bearings be in order as well?
http://www.pt-performance.com/showProduct.php?vID=3&cID=4&pID=310
http://www.pt-performance.com/showProduct.php?vID=3&cID=4&pID=310
justanothermp5
Banned
- :
- Rust Bucket
you can pull the trans on a p5 without pulling the engine, you have to really angle the engine a little bit to get it to slide out but you can do it
so i cant imagine why you wouldnt be able to with the MS3's
absolutely replace the bearings.
axisboldaslove
Member
- :
- 07 MS3 GT Heavily Modified
PG charges $1K to drop and install a motor
I am having my mechanic do it for $500
List and Prices of What You Might Need:
ARP Head Studs- $200
Main Bearings- $71.02
Rod Bearings- $68.41
Cometic Head Gasket (or use oem)- $83.50
Carillo Rods- $400-$900
K1 Rods - $405
Pauter Rods- $800
Arias Pistons/Pauter Rods - $1200
MT90-$14.00 X 3
Thrust Washer- $64.05
Arp Main Studs- $126.14
OEM Crank Pulley Bolt- $14.90
Clevite Main Bearing/Thrust Washer Set- $85.00
Labor or DIY = $$$$$
I am in the middle of a rebuild so I have done the researching
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Was your head damaged after you blew? I strangely had 1 burnt intake valve, which was probably burnt before mine blew. No other head damage though.
Good information guys 
....Think ill just be happy running with what I am. Rods-Pistons-bearings-gasket-head bolts&studs-and couple misc stuff and your looking at 1700.00 ish...........then say 500 bucks if your lucky to drop the motor..plus how many hours to build the engine while its out of the car...wild ass guess-10-12 hours??..typical mechanic rate 80-hour..but that could be different wherever you go..but were talking about grand prabaly...your at least @ 3000.00 to have a built motor in the car minus the big turbo kit..so nice turbo manifold with ewg and 30 series turbo from atp...and a fmic from PG..so thats another 3000.00..so now im @ 6000.00....how close is that fellas? I "THINK" my upgraded ptperformance cdfp is good enough for the 3071-3076 turbos..could be wrong..botton line..alot of money..gotta pay to play though
....Think ill just be happy running with what I am. Rods-Pistons-bearings-gasket-head bolts&studs-and couple misc stuff and your looking at 1700.00 ish...........then say 500 bucks if your lucky to drop the motor..plus how many hours to build the engine while its out of the car...wild ass guess-10-12 hours??..typical mechanic rate 80-hour..but that could be different wherever you go..but were talking about grand prabaly...your at least @ 3000.00 to have a built motor in the car minus the big turbo kit..so nice turbo manifold with ewg and 30 series turbo from atp...and a fmic from PG..so thats another 3000.00..so now im @ 6000.00....how close is that fellas? I "THINK" my upgraded ptperformance cdfp is good enough for the 3071-3076 turbos..could be wrong..botton line..alot of money..gotta pay to play though axisboldaslove
Member
- :
- 07 MS3 GT Heavily Modified
I have two heads..the motor is coming out on moday i will make a rebuild thread...so starting on monday i get closer at getting this b**** ass motor out of the car...and that is my biggest stress right now is stock k04 or 30 series...
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