Still Problems with Scat Cranks???
Thread Starter
Racer
Joined: Feb 2005
Posts: 373
Likes: 1
From: Bayonne NJ
Still Problems with Scat Cranks???
Im going to start my 383 stroker motor soon. I've heard a lot of mixed reviews on the scat cranks. Some say that they are prone to failure.. Anyone?
Also what gains would i see by using either a 5.7" connecting rod as apposed to a 6.0"?
I have so many options and i want to build a strong bottom end that i want to put maybe a 150-200 shot of nitrous on...
I just want to do it right this time!!!!!!!
Also what gains would i see by using either a 5.7" connecting rod as apposed to a 6.0"?
I have so many options and i want to build a strong bottom end that i want to put maybe a 150-200 shot of nitrous on...
I just want to do it right this time!!!!!!!
Race Director
Joined: Sep 2002
Posts: 10,362
Likes: 5
From: San Diego - Deep Within The State of CONFUSION!
Originally Posted by BanGnGearS
Im going to start my 383 stroker motor soon. I've heard a lot of mixed reviews on the scat cranks. Some say that they are prone to failure.. Anyone?
Also what gains would i see by using either a 5.7" connecting rod as apposed to a 6.0"?
I have so many options and i want to build a strong bottom end that i want to put maybe a 150-200 shot of nitrous on...
I just want to do it right this time!!!!!!!
Also what gains would i see by using either a 5.7" connecting rod as apposed to a 6.0"?
I have so many options and i want to build a strong bottom end that i want to put maybe a 150-200 shot of nitrous on...
I just want to do it right this time!!!!!!!
As for the 6 inch rods: I am running 6 inch H-beam rods in my stroker. Theory is this: with a longer rod, you will have the piston at TDC longer. This gives her more power.
How much? How to quantify it? Who the heck knows
but that is at least part of the reason they are desireable.Also, more block notching is required. I had to relieve my block way deep inside under the camshaft too, not just the bottom of the cylinders.
Thread Starter
Racer
Joined: Feb 2005
Posts: 373
Likes: 1
From: Bayonne NJ
Originally Posted by SanDiegoPaul
I haven't heard about SCAT crank issues. I'm using a forged Eagle stroker kit myself and have no issues but I'm not pushing it with juice, either...
As for the 6 inch rods: I am running 6 inch H-beam rods in my stroker. Theory is this: with a longer rod, you will have the piston at TDC longer. This gives her more power.
How much? How to quantify it? Who the heck knows but that is at least part of the reason they are desireable.
Also, more block notching is required. I had to relieve my block way deep inside under the camshaft too, not just the bottom of the cylinders.
As for the 6 inch rods: I am running 6 inch H-beam rods in my stroker. Theory is this: with a longer rod, you will have the piston at TDC longer. This gives her more power.
How much? How to quantify it? Who the heck knows
but that is at least part of the reason they are desireable.Also, more block notching is required. I had to relieve my block way deep inside under the camshaft too, not just the bottom of the cylinders.
Safety Car
Joined: Nov 2005
Posts: 3,961
Likes: 573
From: Lompoc, CA. Santa Barbara County
Originally Posted by SanDiegoPaul
I haven't heard about SCAT crank issues. I'm using a forged Eagle stroker kit myself and have no issues but I'm not pushing it with juice, either...
As for the 6 inch rods: I am running 6 inch H-beam rods in my stroker. Theory is this: with a longer rod, you will have the piston at TDC longer. This gives her more power.
How much? How to quantify it? Who the heck knows but that is at least part of the reason they are desireable.
Also, more block notching is required. I had to relieve my block way deep inside under the camshaft too, not just the bottom of the cylinders.
As for the 6 inch rods: I am running 6 inch H-beam rods in my stroker. Theory is this: with a longer rod, you will have the piston at TDC longer. This gives her more power.
How much? How to quantify it? Who the heck knows
but that is at least part of the reason they are desireable.Also, more block notching is required. I had to relieve my block way deep inside under the camshaft too, not just the bottom of the cylinders.
Race Director
Joined: Sep 2002
Posts: 10,362
Likes: 5
From: San Diego - Deep Within The State of CONFUSION!
Originally Posted by BanGnGearS
I cut corners the first time that i rebuilt my bottom end and i've had nothing but problems with it.. Im going to do more research but im looking to put about 2-2.5 grand into the bottom end.
I did short sight myself on the heads, reworking cast iron GM heads and in retrospect, spent almost the same $$ on that waste of time as I could have on aluminum heads
I wound up with less than 300HP at the wheels, which was my goal. Missed it by 25HP and I know doggone well that the heads are the only shortcoming in my motor.
But with my bottom end as sound as it is, I also know that when I put heads on it, I won't be in for any more sticker shock on engine build costs
As mine sits, it cost me $5800 to build and it pains me because I know there's others on this forum with half that invested under the hood and they claim lots more than 275 RWHP.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Longer rods have a very minimal advantage in the horsepower department but allow you to run a lighter piston, less skirt.
With longer rods you do have to watch piston to valve clearance more since the piston actually lingers at TDC longer.
A long rod engine also shows a little more camminess if that is a word? It makes the engine sound like it has more cam then with a short rod length.
Lastly a long rod reduces scavanger effect at low speeds.
You can run less timing with a long rod, stay out of detonation a touch longer, reduces bore wear.
If is doesn't cost any more go with the 6 inch rod but if you need to spend extra money stick with the 5.7.
The angular change is about 1 degree. 17 vs 16 degrees.
Our speed shop hates scat cranks and only uses eagle but I personally have not heard anything bad and last night on pinks the winning mustang used a scat crank.
With longer rods you do have to watch piston to valve clearance more since the piston actually lingers at TDC longer.
A long rod engine also shows a little more camminess if that is a word? It makes the engine sound like it has more cam then with a short rod length.
Lastly a long rod reduces scavanger effect at low speeds.
You can run less timing with a long rod, stay out of detonation a touch longer, reduces bore wear.
If is doesn't cost any more go with the 6 inch rod but if you need to spend extra money stick with the 5.7.
The angular change is about 1 degree. 17 vs 16 degrees.
Our speed shop hates scat cranks and only uses eagle but I personally have not heard anything bad and last night on pinks the winning mustang used a scat crank.
Drifting
Joined: Feb 2005
Posts: 1,738
Likes: 2
From: San diego ca
I'm running a Scat Crank and Scat 6" rods in my .040 over 350. I've nad no issues with either. I've always heard that SCAT cranks and rods were excellent parts for the money, certainly the cast steel items arent the same as forged.
Have things changed recently and Scat is becoming considered less reliable?
As for the 6" rod question, its a perrenial argument over the value of them, frankly I think the greater value is less angularity to the cylinder walls which means less side loading on them from the pistons which hopefully will result in less wear to cylinder walls and rings.
other benefits which are often suggested but not reliably proven I think are the longer dwell at TDC resulting in more power and/or greater resistance to detonation. Reduced compression height on poiston can result in a lighter piston which in turn reduces reciprocating weight...tho I suspect that would easily be offset by the increased weight of a rod that is .3" longer
Have things changed recently and Scat is becoming considered less reliable?
As for the 6" rod question, its a perrenial argument over the value of them, frankly I think the greater value is less angularity to the cylinder walls which means less side loading on them from the pistons which hopefully will result in less wear to cylinder walls and rings.
other benefits which are often suggested but not reliably proven I think are the longer dwell at TDC resulting in more power and/or greater resistance to detonation. Reduced compression height on poiston can result in a lighter piston which in turn reduces reciprocating weight...tho I suspect that would easily be offset by the increased weight of a rod that is .3" longer
Safety Car
Joined: Nov 2005
Posts: 3,961
Likes: 573
From: Lompoc, CA. Santa Barbara County
Originally Posted by norvalwilhelm
Longer rods have a very minimal advantage in the horsepower department but allow you to run a lighter piston, less skirt.
With longer rods you do have to watch piston to valve clearance more since the piston actually lingers at TDC longer.
A long rod engine also shows a little more camminess if that is a word? It makes the engine sound like it has more cam then with a short rod length.
Lastly a long rod reduces scavanger effect at low speeds.
You can run less timing with a long rod, stay out of detonation a touch longer, reduces bore wear.
If is doesn't cost any more go with the 6 inch rod but if you need to spend extra money stick with the 5.7.
The angular change is about 1 degree. 17 vs 16 degrees.
Our speed shop hates scat cranks and only uses eagle but I personally have not heard anything bad and last night on pinks the winning mustang used a scat crank.
With longer rods you do have to watch piston to valve clearance more since the piston actually lingers at TDC longer.
A long rod engine also shows a little more camminess if that is a word? It makes the engine sound like it has more cam then with a short rod length.
Lastly a long rod reduces scavanger effect at low speeds.
You can run less timing with a long rod, stay out of detonation a touch longer, reduces bore wear.
If is doesn't cost any more go with the 6 inch rod but if you need to spend extra money stick with the 5.7.
The angular change is about 1 degree. 17 vs 16 degrees.
Our speed shop hates scat cranks and only uses eagle but I personally have not heard anything bad and last night on pinks the winning mustang used a scat crank.
Do you have less (fewer) clearance issues with the shorter 5.7" rod?
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Race Director
Joined: Nov 2000
Posts: 11,872
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From: Waterloo ontario Canada
Originally Posted by Bee Jay
So 5.7" rod good, 6" rod bad?
Do you have less (fewer) clearance issues with the shorter 5.7" rod?
Do you have less (fewer) clearance issues with the shorter 5.7" rod?
The things against the 6 inch rod is reduced piston to valve clearance, more cammy idle and reduced low end scavenger effect.
There are many many good things to be said about the 6 inch over the 5.7
From the horsepower point of view there is little difference.
Thread Starter
Racer
Joined: Feb 2005
Posts: 373
Likes: 1
From: Bayonne NJ
Originally Posted by norvalwilhelm
Longer rods have a very minimal advantage in the horsepower department but allow you to run a lighter piston, less skirt.
With longer rods you do have to watch piston to valve clearance more since the piston actually lingers at TDC longer.
A long rod engine also shows a little more camminess if that is a word? It makes the engine sound like it has more cam then with a short rod length.
Lastly a long rod reduces scavanger effect at low speeds.
You can run less timing with a long rod, stay out of detonation a touch longer, reduces bore wear.
If is doesn't cost any more go with the 6 inch rod but if you need to spend extra money stick with the 5.7.
The angular change is about 1 degree. 17 vs 16 degrees.
Our speed shop hates scat cranks and only uses eagle but I personally have not heard anything bad and last night on pinks the winning mustang used a scat crank.
With longer rods you do have to watch piston to valve clearance more since the piston actually lingers at TDC longer.
A long rod engine also shows a little more camminess if that is a word? It makes the engine sound like it has more cam then with a short rod length.
Lastly a long rod reduces scavanger effect at low speeds.
You can run less timing with a long rod, stay out of detonation a touch longer, reduces bore wear.
If is doesn't cost any more go with the 6 inch rod but if you need to spend extra money stick with the 5.7.
The angular change is about 1 degree. 17 vs 16 degrees.
Our speed shop hates scat cranks and only uses eagle but I personally have not heard anything bad and last night on pinks the winning mustang used a scat crank.
Race Director
Joined: Feb 2004
Posts: 12,518
Likes: 19
Inspect the thrust surface of the crank carefully. Scat has been leaving them too rough, thus chewing up the thrust bearing in 200 miles or less.
This is a big problem that I personally have seen more than 6 times in the past year. Scat is fully aware of the problem, but denies it whan asked.
This is a big problem that I personally have seen more than 6 times in the past year. Scat is fully aware of the problem, but denies it whan asked.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
I am using 5.7 rods in my 385 motor. The 6 inch rods would have required a spacer in the ring land at the piston pin. I take mine to 7000 rpm all the time. The machinist has an identical bottom end as mine in a drag car and runs it 7500 rpm and has 2 seasons on it with no failures. I am running and Eagle forged crank with 4340 rodswit h7/16s bolts made for stroker motors. There is some clearancing that was needed. HP difference, you will never feel any difference in drivingthe car. It might show up on the dyno but HP differences are very small. You can go either way and you won't go wrong. Just use quality parts.
Thread Starter
Racer
Joined: Feb 2005
Posts: 373
Likes: 1
From: Bayonne NJ
Originally Posted by Gordonm
I am using 5.7 rods in my 385 motor. The 6 inch rods would have required a spacer in the ring land at the piston pin. I take mine to 7000 rpm all the time. The machinist has an identical bottom end as mine in a drag car and runs it 7500 rpm and has 2 seasons on it with no failures. I am running and Eagle forged crank with 4340 rodswit h7/16s bolts made for stroker motors. There is some clearancing that was needed. HP difference, you will never feel any difference in drivingthe car. It might show up on the dyno but HP differences are very small. You can go either way and you won't go wrong. Just use quality parts.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Eagle ESP cast 383 internal crank P/N 10350375057I ... it's designed to Internal balance ... works with EITHER 5.7 or 6 rods (smaller OD counterweights than scat) ... about same price as scat cast.
*edit* BTW ... I had a 355" asphalt circle track motor w/ scat 9K cast 3.48", Manley I-beams & Ross pistons ... ran hard & fast for 2-3 seasons ... motor blew ... Hi$ Ross piston separated just above the pin boss ... not a rod failure ... not a crank failure. The piston failed solely because the bores were loose & made alota piston slap. That cheap scat cast crank caught hell & no problem.
Weights ... do the math ... compare like rods in 5.7/6 & like pistons for 5.7/6 ... invariably I've found the taller piston weighs more than the longer rod ... long rod combo is lighter ... result is lower recip weight & lower bobweight.
When CT racing in restricted class where heads, bore, stroke & cam lift is limited & everyone's at that limit ... the long rod sees the flagstand first.
Not everyone needs bulky (& typically heavy) H-beams or 7/16" bolts/screws ... plenty of sturdy I-beams that usually require less block clearancing regardless 5.7 or 6.
*edit* BTW ... I had a 355" asphalt circle track motor w/ scat 9K cast 3.48", Manley I-beams & Ross pistons ... ran hard & fast for 2-3 seasons ... motor blew ... Hi$ Ross piston separated just above the pin boss ... not a rod failure ... not a crank failure. The piston failed solely because the bores were loose & made alota piston slap. That cheap scat cast crank caught hell & no problem.
Weights ... do the math ... compare like rods in 5.7/6 & like pistons for 5.7/6 ... invariably I've found the taller piston weighs more than the longer rod ... long rod combo is lighter ... result is lower recip weight & lower bobweight.
When CT racing in restricted class where heads, bore, stroke & cam lift is limited & everyone's at that limit ... the long rod sees the flagstand first.
Not everyone needs bulky (& typically heavy) H-beams or 7/16" bolts/screws ... plenty of sturdy I-beams that usually require less block clearancing regardless 5.7 or 6.
Last edited by jackson; Oct 5, 2006 at 05:07 PM.
Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
Originally Posted by BanGnGearS
So it seems that i would be less likely to run into any problems with a 5.7? Considering that you would have to do some work in order for it to fit right. I just dont want any problems with this build. I want to be sure that I have a sound engine when i get on it
Melting Slicks
Joined: Dec 2001
Posts: 2,025
Likes: 1
From: Billings MT
I have had the SCAT 9000 series crank in my 406 for almost 4 years now. 200+ Passes at the drag strip, 7300rpm and nearly 20,000 HARD street miles and I have yet to have any problems... This is with a JE/SRP piston and SCAT 6.0" H-Beam Rods.
So yeah, they are prone to failure.
:
-Travis
So yeah, they are prone to failure.
:-Travis
Thread Starter
Racer
Joined: Feb 2005
Posts: 373
Likes: 1
From: Bayonne NJ
Originally Posted by VETDRMS
I have had the SCAT 9000 series crank in my 406 for almost 4 years now. 200+ Passes at the drag strip, 7300rpm and nearly 20,000 HARD street miles and I have yet to have any problems... This is with a JE/SRP piston and SCAT 6.0" H-Beam Rods.
So yeah, they are prone to failure.:
-Travis
So yeah, they are prone to failure.
:-Travis
Melting Slicks
Joined: Apr 2002
Posts: 2,337
Likes: 14
From: Norfolk VA
Originally Posted by Bee Jay
So 5.7" rod good, 6" rod bad?
Do you have less (fewer) clearance issues with the shorter 5.7" rod?
Do you have less (fewer) clearance issues with the shorter 5.7" rod?
The cast crank will be the weak link on the bottom end. One can get away with driving at 7000 rpm every now and than. I wouldn't do it too often. I have a block at the machine shop now that is being clearanced for an eagle 383 cast crank with 5.7 rods. Will upgrade to a forged unit when I'm able to afford one. However, with 6.0 rods, a 383 when coupled with the right parts, the engine can be a real stump puller.
Thread Starter
Racer
Joined: Feb 2005
Posts: 373
Likes: 1
From: Bayonne NJ
Originally Posted by Oldguard 7
5.7 rod allows you to rev the engine just a bit higher than a 6.0 rod.
The cast crank will be the weak link on the bottom end. One can get away with driving at 7000 rpm every now and than. I wouldn't do it too often. I have a block at the machine shop now that is being clearanced for an eagle 383 cast crank with 5.7 rods. Will upgrade to a forged unit when I'm able to afford one. However, with 6.0 rods, a 383 when coupled with the right parts, the engine can be a real stump puller.
The cast crank will be the weak link on the bottom end. One can get away with driving at 7000 rpm every now and than. I wouldn't do it too often. I have a block at the machine shop now that is being clearanced for an eagle 383 cast crank with 5.7 rods. Will upgrade to a forged unit when I'm able to afford one. However, with 6.0 rods, a 383 when coupled with the right parts, the engine can be a real stump puller.
Edelbrock carb
Performer RPM intake and cam
Dart Iron Eagle 180s 64 cc
Hooker comp headers..
Im hoping this will flow nice. Some say that the cam is too mild. I'll have to find out