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Old 07-08-2008, 03:08 AM   #1
86ray86
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Default Brian crower 2.71 stroker kit ??

Hey Guys

im from australia and looking for some opinions from you guys that have used this kit and have pushed big hp with it. im looking to push 500-550kw atw with this kit, will the pro rods be able to cope. as there my main concern, any advice and feedback would be great...
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Old 07-08-2008, 10:35 AM   #2
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1 KW is approx. 1.34 HP. So 670HP to 737HP. not bad expectations.
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Old 07-12-2008, 04:19 AM   #3
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anyone have any feedback on this kit, im looking at buying very soon as my 2.5 has been sold...
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Old 07-12-2008, 02:57 PM   #4
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I have one and its a great setup, just rather expensive to get fully going. The main reason is that not only is it a stroker setup but also a big bore. This requires the darton big sleeves for the 102mm bore. This alone adds about $1600 to the setup on top of the actual stroker kit.
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Old 07-12-2008, 03:04 PM   #5
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why not go with and axxis 2.65l stroker
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Old 07-12-2008, 04:50 PM   #6
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why? reasons ?
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Old 07-12-2008, 05:04 PM   #7
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Quote:
Originally Posted by Sinister redlines View Post
I have one and its a great setup, just rather expensive to get fully going. The main reason is that not only is it a stroker setup but also a big bore. This requires the darton big sleeves for the 102mm bore. This alone adds about $1600 to the setup on top of the actual stroker kit.
what kind of power you putting through it ? did you use the rings that cam with the kit or sorce your own ?
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Old 07-12-2008, 10:06 PM   #8
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i think the problem with stroker kits this big is the piston speed. to me it seems that you are bound to break, i remember seeing titainium rods, cobb i believe,
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Old 07-13-2008, 12:55 AM   #9
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Quote:
Originally Posted by SniperSVD View Post
i think the problem with stroker kits this big is the piston speed. to me it seems that you are bound to break, i remember seeing titainium rods, cobb i believe,

Stroker having piston speed issues? No, in fact they are actually slower. However the main debate is rod ratio not speed. Not to mention the amount of stroke increased is small compared to other applications (79mm - 83mm = 4mm = .157" roughly 5/32")

A small block chev is 3.480" stroke vs a 383 is 3.750" = .270" a little over 1/4" big difference....

Last edited by Sinister redlines; 07-13-2008 at 01:21 AM.
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Old 07-13-2008, 06:02 PM   #10
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Long rod kits would really help our subie boxers. Anybody make a long-rod kit? The short search I did came up wanting....
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Old 07-14-2008, 01:09 AM   #11
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not in a stroker setup due to the assembly process on subies making the rods hang from the crank then after the case is together you install the piston and wrist pin. This makes the fact that the oil ring cannot cover the wristpin and theres no more room to push the pin higher on the skirt.
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Old 07-14-2008, 10:09 AM   #12
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Quote:
Originally Posted by bcblues View Post
Long rod kits would really help our subie boxers. Anybody make a long-rod kit? The short search I did came up wanting....
yup, someone does...
If I say more than that, I will definately get in trouble.
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Old 07-14-2008, 10:15 AM   #13
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Quote:
Originally Posted by Sinister redlines View Post
Stroker having piston speed issues? No, in fact they are actually slower. However the main debate is rod ratio not speed. Not to mention the amount of stroke increased is small compared to other applications (79mm - 83mm = 4mm = .157" roughly 5/32")

A small block chev is 3.480" stroke vs a 383 is 3.750" = .270" a little over 1/4" big difference....
a stroker motor at the same RPM as a long rod, will have higher instantaneous accelerations in a subaru because you have to shorten rod ratio to stroke. Might want to rework your "slider crank model" again.
My long rod setup is 1.8:1 and the 2.71 stroker is 1.57:1

You can also assemble the block quite easily with a long rod setup. There is also room to push the ring package up without much sacrifice to the ring lands...
I KNOW this for a fact. I spent a few years designing and modeling my package.

Last edited by Homemade WRX; 07-14-2008 at 11:52 AM.
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Old 07-14-2008, 10:43 AM   #14
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Quote:
Originally Posted by Sinister redlines View Post
Stroker having piston speed issues? No, in fact they are actually slower. However the main debate is rod ratio not speed. Not to mention the amount of stroke increased is small compared to other applications (79mm - 83mm = 4mm = .157" roughly 5/32")

A small block chev is 3.480" stroke vs a 383 is 3.750" = .270" a little over 1/4" big difference....
Yes but MOST small block chevy engines dont rev to 8500rpm. The forces acting on the rod increases geometrically with rpm.
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Old 07-14-2008, 07:25 PM   #15
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Quote:
Originally Posted by MS WRX View Post
Yes but MOST small block chevy engines dont rev to 8500rpm. The forces acting on the rod increases geometrically with rpm.

Yes you are correct the forces do climb with rpm, and yes sb can rev to 8500 with lots of work. What you failed to see what I was saying is that the BC stroker doesnt gain all of its displacement from stroke but rather bore/stroke combination. My relation was just to show that there wasnt a huge change in stroke and that was all. So on....
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Old 07-14-2008, 07:32 PM   #16
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Quote:
Originally Posted by Homemade WRX View Post
a stroker motor at the same RPM as a long rod, will have higher instantaneous accelerations in a subaru because you have to shorten rod ratio to stroke. Might want to rework your "slider crank model" again.
My long rod setup is 1.8:1 and the 2.71 stroker is 1.57:1

You can also assemble the block quite easily with a long rod setup. There is also room to push the ring package up without much sacrifice to the ring lands...
I KNOW this for a fact. I spent a few years designing and modeling my package.

Maybe I showed what I was getting at incorrectly, but I was totally agreeing with the stroker not having the best rod ratio. And yes the blocks can be assembled the other way as I have had to disassemble one this way also. Its just not as easy with setting the rod bolts otherwise it is a other method and yes theres nothing wrong with the wrist pin in the ring lands (I have had different platforms like this in the past).

I have watched your build and you are playing with some neat ideas, but you are not the only one. I too have 12 years playing with built engines (that I have built not bought) so theres no reason to get defensive or agressive. I realize just about anything can be done but I was more getting at the norm as far as assembly and not the exotic. My next big build is going to be a short stroke, long rod, huge bore oddity.

Last edited by Sinister redlines; 07-14-2008 at 07:39 PM.
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Old 07-14-2008, 07:33 PM   #17
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In the end we are interested in forces applied to the various components in the system. A BC 2.71L stroker kit will yield higher forces than a standad 2.5L engine at any given RPM due primarily to three factors.
1. Extended stroke. A longer stroke means that the average piston speeds (and by definition average loading) will go up at any given RPM. 2. the extra stroke alters your rod stroke ratio, increasing the rate of acceleration the rod/piston see. 3. the 2.71L displacement is arrived at via an 83mm stroke and 102mm bore. Generally going from a 102mm piston from a 99.5mm piston will add some weight, further increasing rod/bearing etc loading at a given RPM.
Quote:
Originally Posted by Sinister redlines View Post
Yes you are correct the forces do climb with rpm, and yes sb can rev to 8500 with lots of work. What you failed to see what I was saying is that the BC stroker doesnt gain all of its displacement from stroke but rather bore/stroke combination. My relation was just to show that there wasnt a huge change in stroke and that was all. So on....
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Old 07-14-2008, 08:34 PM   #18
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Quote:
Originally Posted by Sinister redlines View Post
I have watched your build and you are playing with some neat ideas, but you are not the only one. I too have 12 years playing with built engines (that I have built not bought) so theres no reason to get defensive or agressive. I realize just about anything can be done but I was more getting at the norm as far as assembly and not the exotic. My next big build is going to be a short stroke, long rod, huge bore oddity.
Sorry, I did not mean to come off as agressive but rather wanted to straigthen out the facts. Also, my wrist pin is not in my ring lands...I just chose my components wisely
same reason it is easy to assembly my long rod setup...others it would depend on how they did things.

Sounds like you are following in a similar path to mine
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Old 07-14-2008, 08:38 PM   #19
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Quote:
Originally Posted by MartinSTi05 View Post
3. the 2.71L displacement is arrived at via an 83mm stroke and 102mm bore. Generally going from a 102mm piston from a 99.5mm piston will add some weight, further increasing rod/bearing etc loading at a given RPM.
also might add increased friction and decreased ring life
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Old 07-14-2008, 09:18 PM   #20
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Quote:
Originally Posted by Homemade WRX View Post
Sorry, I did not mean to come off as agressive but rather wanted to straigthen out the facts. Also, my wrist pin is not in my ring lands...I just chose my components wisely
same reason it is easy to assembly my long rod setup...others it would depend on how they did things.

Sounds like you are following in a similar path to mine

Its all good, just wanted to be clear And I have been mistaken before and will be again for sure. LoL
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Old 07-15-2008, 10:55 AM   #21
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Sinster, i was not flamin ya dude, just made that face to show what a chevy sbc would look like at 8500 LOL
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Old 07-15-2008, 10:04 PM   #22
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Another thing to consider regarding high RPM stroker operation.
Harmonics. Considering the fact that the 83mm Stroker crank uses oem bearing journals, by definition you have 1.5mm less overlap of the rod journal/main journal cross section as compared to a standard 79mm ej25/7 crank, and 4mm less overlap than an ej20/7 based setup. Material choices aside, this would make a crank that is less torsionally rigid. Losing rigidity generally accompanies a reduction in resonant frequency. Theoretically this would lower the RPM at which potentially damaging torsional vibrations can manifest themselves.
How much the above is really worth worrying about is still up in the air. I have a 2.71L crower kit now, and hope to get it running soon, i will let you guys know how it fares.

Last edited by MartinSTi05; 07-16-2008 at 07:33 AM. Reason: Homemade WRX caught a screwup;-)
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Old 07-15-2008, 11:40 PM   #23
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also to add to the cons of the 2.7L is the clearancing of the block for the kit...so adding more loading on the block, increased harmonics and a weakened block...I'd say they start to run into issues at in the high-7k to low-8k rpm range

also you had a typo martin...the EJ25 is 79mm
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Old 07-16-2008, 07:07 AM   #24
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Quote:
Originally Posted by Homemade WRX View Post
also to add to the cons of the 2.7L is the clearancing of the block for the kit...so adding more loading on the block, increased harmonics and a weakened block...I'd say they start to run into issues at in the high-7k to low-8k rpm range

also you had a typo martin...the EJ25 is 79mm
Oops, my bad, your right, i was thinking ej20.
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Old 08-25-2008, 02:18 AM   #25
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Is anyone else having clearance issues when they are putting this motor together?
Last week I got back the block and started the rebuild, but when I finished connecting the first 2 pistons I found there was “knock” and an obvious metal on metal drag when I turned the engine over. Aver some careful inspecting and the help of a sharpie I found one of my con rods was hitting the block at BDC.
For this kind cash I thought it should be a no mod’in rebuild,
Going at a re-sleeved sti block with the dremel, That just seems wrong
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