Engine rods have 450 rwhp Limit?
4/28/08, 05:02 PM
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Engine rods have 450 rwhp Limit?
Hey all,
I was in a conversation with some local gear heads and they warned me that the engine in my 05 GT should not be pushed over 450 rwhp. They said anything over that was a gamble with the rods and such, even tho people still do it. This is the first I've heard of this and was curious to it's validity. Anybody have any insite about this?
I was in a conversation with some local gear heads and they warned me that the engine in my 05 GT should not be pushed over 450 rwhp. They said anything over that was a gamble with the rods and such, even tho people still do it. This is the first I've heard of this and was curious to it's validity. Anybody have any insite about this?
4/28/08, 05:23 PM
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Have you ever seen a stock 4.6L 3V connecting rod? They are about as big around as a toothbrush. Not sure I'd be comfortable pushing much over 400 rwhp with them! I, too, have heard rumors of this weakness, but have no proof to back it up.
4/28/08, 05:35 PM
#3
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450 seems to be the general consensus however many people have pushed beyond that successfully and others have made less power and encountered failures..... luck of the draw.
4/28/08, 10:41 PM
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Everything seems to point to the fact that the rods are the single weakest link in the rotating assembly from the factory. The block is VERY tough. The crank is pretty tough. The pistons are a bit of an unknown quantity. But only because the rods fail before the pistons can.
About the only way I would push 450 hp on the stock rods would be if I had a VERY conservative tune AND I only hit full power on rar occasions. If I could make those conditions, then I would wait until I could put better rods (and, I have to admit, pistons) into the block before I started getting happy at 450 or above.
About the only way I would push 450 hp on the stock rods would be if I had a VERY conservative tune AND I only hit full power on rar occasions. If I could make those conditions, then I would wait until I could put better rods (and, I have to admit, pistons) into the block before I started getting happy at 450 or above.
4/29/08, 06:32 AM
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I do most of my mods myself with the help of a friend, but I've never done rods/pistons before. Rods are fairly inexpensive, but how extensive or difficult is the install? Might be worth it for peace of mind for future mods.
4/29/08, 06:40 AM
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It is certainly all with the tune. A lot of STOCK MOTOR GT's get tuned out of Brenspeed with over 450 rwhp. A local shop here has a 05 GT as their shop car with a KB. Puts down 475 rwhp, over a year now...no problems. Within reason, it's all in the tune, always.
4/29/08, 09:44 AM
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Is that a piece of Hypereutectic cast piston or a Cracked powdered metal rod? 
But I can just about guarantee you that the rod failed first and that took out the piston. Once you have a rod failure, all kinds of nasty things happen. Every engine failure analysis I have seen so far on a stock rotating assembly has always started out with a rod failure. Just about anything that could cause a piston failure will generate enough pressure spikes to cause the rods to fail first. That was the reason that I said we don't really know what the pistons can handle because the rods always fail before we find out.
When you rebuilt, what rods and pistons did you go with?
Last edited by RRRoamer; 4/29/08 at 09:44 AM. Reason: I still can't spell...
4/29/08, 09:48 AM
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I'm pushing 500+ RWHP for a good 18 months and it is fine. My tune is not conservative but not too aggressive.
The rods are the only real weak point. They will disintegrate at any HP level above 425 with the slightest detonation or if you over-rev them.
If you dont get detonation and keep the RPMs down they are fine.
The rods are the only real weak point. They will disintegrate at any HP level above 425 with the slightest detonation or if you over-rev them.
If you dont get detonation and keep the RPMs down they are fine.
4/29/08, 09:51 AM
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I have NO idea what that piece is! But I can just about guarantee you that the rod failed first and that took out the piston. Once you have a rod failure, all kinds of nasty things happen.
Every engine failure analysis I have seen so far on a stock rotating assembly has always started out with a rod failure. Just about anything that could cause a piston failure will generate enough pressure spikes to cause the rods to fail first. That was the reason that I said we don't really know what the pistons can handle because the rods always fail before we find out.
When you rebuilt, what rods and pistons did you go with?
But I can just about guarantee you that the rod failed first and that took out the piston. Once you have a rod failure, all kinds of nasty things happen. Every engine failure analysis I have seen so far on a stock rotating assembly has always started out with a rod failure. Just about anything that could cause a piston failure will generate enough pressure spikes to cause the rods to fail first. That was the reason that I said we don't really know what the pistons can handle because the rods always fail before we find out.
When you rebuilt, what rods and pistons did you go with?
4/29/08, 12:52 PM
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Chalk me into the Failure Club. 
I can tell you first hand that the weak link is first rods, then pistons.
Is that a piece of Hypereutectic cast piston or a Cracked powdered metal rod?
I can tell you first hand that the weak link is first rods, then pistons.
Is that a piece of Hypereutectic cast piston or a Cracked powdered metal rod?
When did that happen? How much were you putting down? Who did the tuning?
I musta missed that post!
Last edited by Rebel73; 4/29/08 at 12:55 PM.
4/29/08, 01:02 PM
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Generally everyone agrees with the 450rwhp mark, but MANY people are pushing the limit at right around 500rwhp and everything is fine...I personally think its really in the tune, but even then I would be very 'iffy' about pushing over 475 on the stock block.
But if/when you are talking about superchargers I believe Centri's are generally safer because they will build boost as the RPMs rise, and only hit full boost and peak power right before you would shift to the next gear, unlike Positive Displacement blowers which can make a BOAT load of torque right off idle, and peak HP well before centrifugal blowers...None the less, if I had my choice I would still go with a Whipple #1, then Novi2200 following close behind.
But if/when you are talking about superchargers I believe Centri's are generally safer because they will build boost as the RPMs rise, and only hit full boost and peak power right before you would shift to the next gear, unlike Positive Displacement blowers which can make a BOAT load of torque right off idle, and peak HP well before centrifugal blowers...None the less, if I had my choice I would still go with a Whipple #1, then Novi2200 following close behind.
Last edited by SlamMan02; 4/29/08 at 01:07 PM.
4/29/08, 01:17 PM
#17
New shortblock being built by MMR as we speak. 
I kept this on the down low.. not my proudest moment.
Death ocurred on April 15th.
I screwed up... motor went waaay lean and went poof. Nuff said about that.
- New production Ford aluminum block
- 4340 Forged 3.543 stroke Cobra Crankshaft w/micro polished journals
- 4340 5.933 MMR 800HP H-beam Rods w/ARP rod bolts
- Forged Manley pistons 3.552 Bore size (9.0:1)
- Coated Pistons (ceramic dome/teflon skirt)
- Speed Pro file fit rings
- Clevite tri-metal Rod Main bearings
- ARP Mainstuds
Death ocurred on April 15th.
I screwed up... motor went waaay lean and went poof. Nuff said about that.
4/29/08, 01:51 PM
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4/29/08, 03:20 PM
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Wow, so sorry to hear about that, Bill. That truly sucks. Hey, I know it must be hard to talk about, but if you could shell out a few details maybe you could save some fellow Stangers from the same fate...
again, sorry bro'
again, sorry bro'