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weakest link in the zetec motor

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bartlomiej

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Discussion starter · #1 ·
what's the weakest link in the zetec head? and what's the weakest link in the zetec bottom end?

the main reason i ask, is because i am getting upgraded components (eagle rods, je pistons, iirc flatlander main & rod bearings), but I am just getting new OEM main bolts. Will this pose a problem? I know it'd be wise to upgrade to asp, but is it necessary? at what rpm and/or power level would it become necessary?
thanks!

bartek
 
#2 ·
If your gona spend teh cash on getting strengthed everything else. Why not spend the cash and get the strength and security of APR main studs? TonyD sells APR...might as well get them and keep things uniform.
 
Discussion starter · #4 ·
thanks for the replies, i realize i should upgrade them, but is it necessary?
 
#6 ·
has anyone heard of a stock zetec crank or main caps failing? I've seen some pretty twisted up bent rods that stayed together. And some trashed out pistons. I'll be attempting 300-350whp on the bottle this season and feel fairly confident with rods and pistons. <knock on wood>

g
 
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Discussion starter · #8 ·
weakest link....tuning

-Ult
Click to expand...
That's already been addressed (thanks modular depot!!!
Image
)

anyone ever heard of the main bolts failing???
Image
 
Discussion starter · #10 ·
I have seen MANY cracked and broke stock main caps and talked to another guy that had 2 broke main caps in his engine

Tom
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at what point do the main caps fail? I'm planning 180-200 whp MAX, after all is finished. should i be worried?

bartek
 
#12 ·
I dont think you will have a problem below 250HP at the wheels

Tom
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Is it hp (or torque with you, Tom) that kills them, or is it RPM?
In other words, which is more likely to kill main caps:
A turbo car with 15 psi of boost and a 6000rpm redline
or
A non-boosted car with an 8000rpm redline?

Last thing I need is it to be the second one...
Image
 
#13 ·
I dont think you will have a problem below 250HP at the wheels

Tom
Click to expand...
Is it hp (or torque with you, Tom) that kills them, or is it RPM?
In other words, which is more likely to kill main caps:
A turbo car with 15 psi of boost and a 6000rpm redline
or
A non-boosted car with an 8000rpm redline?

Last thing I need is it to be the second one...
Image
Click to expand...
I would say torque. unless the engine isn't balanced right.
 
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#14 ·
Is it hp (or torque with you, Tom) that kills them, or is it RPM?
In other words, which is more likely to kill main caps:
A turbo car with 15 psi of boost and a 6000rpm redline
or
A non-boosted car with an 8000rpm redline?
Click to expand...
A non-boosted car with an 8000rpm redline puts more strain on the engine than a properly designed, intercooled, with wastegate, etc. forced induction at 15psi.

However, there are a lot more variables when doing a turbo that can easily blow your engine at boosts much lower than 15psi; improper tuning, for example. So there are probably more blown turbo'd engines, than there are blown high-redline engines.
 
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#15 ·
Is it hp (or torque with you, Tom) that kills them, or is it RPM?
In other words, which is more likely to kill main caps:
A turbo car with 15 psi of boost and a 6000rpm redline
or
A non-boosted car with an 8000rpm redline?
Click to expand...
A non-boosted car with an 8000rpm redline puts more strain on the engine than a properly designed, intercooled, with wastegate, etc. forced induction at 15psi.
Click to expand...
I know that this holds true for the reciprocating assembly (rods, pistons, etc) but I was wondering if it still holds true for the main caps since they don't move? Not saying you are woring, just letting you know why I ask.
 
#16 ·
I know that this holds true for the reciprocating assembly (rods, pistons, etc) but I was wondering if it still holds true for the main caps since they don't move? Not saying you are woring, just letting you know why I ask.
Click to expand...
I am not sure about the caps.

The loads that you worry about (in the absence of things like preingnition) are tensile (the piston rising during exhaust stroke) and compressive (power stroke). when the con rods are being pulled or pushed, that will transmit roughly equal force (newton's law) to everything connected to the rods -- including the crankshaft and the main bearings. You would have to look at the supporting structures for the main bearings and crankshaft, but I suspect some of this load is transmitted from the bearing to the bearing cap.
 
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#17 ·
I know that this holds true for the reciprocating assembly (rods, pistons, etc) but I was wondering if it still holds true for the main caps since they don't move? Not saying you are woring, just letting you know why I ask.
Click to expand...
I am not sure about the caps.

The loads that you worry about (in the absence of things like preingnition) are tensile (the piston rising during exhaust stroke) and compressive (power stroke). when the con rods are being pulled or pushed, that will transmit roughly equal force (newton's law) to everything connected to the rods -- including the crankshaft and the main bearings. You would have to look at the supporting structures for the main bearings and crankshaft, but I suspect some of this load is transmitted from the bearing to the bearing cap.
Click to expand...
OK, I have that, but if you think about the way that the crank is, for every piston going up, there is one coming down. So on the whole crank, the net reciprocal effect should be zero. The only force that would not cancel would be the force of combustion. This ignores that fact that the each bearing may see different reciprocal forces, but in my simple mind, that would entail the crank bending. Now that, I assume, would totally FUBAR the mains!
 
#18 ·
OK, I have that, but if you think about the way that the crank is, for every piston going up, there is one coming down. So on the whole crank, the net reciprocal effect should be zero. The only force that would not cancel would be the force of combustion. This ignores that fact that the each bearing may see different reciprocal forces, but in my simple mind, that would entail the crank bending. Now that, I assume, would totally FUBAR the mains!
Click to expand...
The crank does not need to bend to transmit forces in different directions.

Take a think strip of balsa wood or a something else thin and breakable, and secure it between two vices (not a bench vice, you need a C clamp style vice). With one finger, push down on the pencil hard about 1/3rd of the way from a vice, and with the other finger, push up hard on the opposite end of the pencil 1/3 from the other vice. If you push hard (with equal force), the pencil will break in one of the two places you are pushing on. The forces will not cancel out because they are in different places.

Similarly, if you put a newton-style force gauge on each end of the strip, you would see substantial forces at each end of the strip of wood (torque). This is where the forces would be transmitted to the main bearings.
 
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#19 ·
The crank does not need to bend to transmit forces in different directions.

Take a think strip of balsa wood or a something else thin and breakable, and secure it between two vices (not a bench vice, you need a C clamp style vice). With one finger, push down on the pencil hard about 1/3rd of the way from a vice, and with the other finger, push up hard on the opposite end of the pencil 1/3 from the other vice. If you push hard (with equal force), the pencil will break in one of the two places you are pushing on. The forces will not cancel out because they are in different places.

Similarly, if you put a newton-style force gauge on each end of the strip, you would see substantial forces at each end of the strip of wood (torque). This is where the forces would be transmitted to the main bearings.
Click to expand...
Image
Image
Image

Jeff - thanks for bringing some kick ass tech.
 
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