What is the deal with lower pulley's breaking cranks?

[gtmustang00]

I have had a metco 4lb lower for 8 years now. Never had any problems. Now have 2.9 whipple with 3.5 upper pulley. 24lbs of boost. Stock tensioner. Am I in danger of breaking the crank? When I install longtubes the boost should drop a couple pounds.

How many documented failures have their been and what were the engine mods?

 

[GodStang]

Most of the breaks have been on the bigger Whipple 4.0 and 3.4 on noncaged lower do to added stress. I have been on a 6lb lower for 8 years and a 2.8L with zero issues. Modfords has a bunch of info on these.

 

[chipmonk]

how many miles are you guys putting on these cars? Years doesnt mean squat if its a garage queen! lol but just curious as im gunna have to do a lower and put about 5k miles a year on my car.

 

[SlowSVT]

I've never heard of anything smaller than a 3.4 breaking a crank snout. I remember a garage owner who posted the progress on a customers 4.0 installation. Soon after the job was complete the thread went "dark" and we never heard about the outcome. I suspect something like this occurred soon after the installation.

That's the handy work of a 3.4

The Metco pulley system that does away with the caged lower put all that lateral load on the #1 main bearing 8" back from the blower pulley ........... not a good idea.

 

[GodStang]

how many miles are you guys putting on these cars? Years doesnt mean squat if its a garage queen! lol but just curious as im gunna have to do a lower and put about 5k miles a year on my car.

If you are talking about on a 2.3L I would not worry. I know many many people on 10 of thousands of people with 2.8L and lower with zero Crankshaft failures.

I've never heard of anything smaller than a 3.4 breaking a crank snout. I remember a garage owner who posted the progress on a customers 4.0 installation. Soon after the job was complete the thread went "dark" and we never heard about the outcome. I suspect something like this occurred soon after the installation.

That's the handy work of a 3.4

The Metco pulley system that does away with the caged lower put all that lateral load on the #1 main bearing 8" back from the blower pulley ........... not a good idea.

This right here. I know one of the 4.0L broke 3 lowers. Not sure if caged or not. I know of a few 3.4Ls that have broke. I know of zero smaller blowers not saying it has not been done. I am pulling my Metco Lower when I go to the bigger blower in a few weeks just to be safe.

 

[gtmustang00]

how many miles are you guys putting on these cars? Years doesnt mean squat if its a garage queen! lol but just curious as im gunna have to do a lower and put about 5k miles a year on my car.

I'd say the lower pulley has been on for 8000 miles or so. 18k total miles on vehicle. Couple hundred on the 2.9 whipple 3.5 upper 4lb lower. Just installed it last summer.

 

[R.D.P.]

Even if it doesn't grenade, you know it's putting additional stress on the crank and thereby on the mains. And it's constant stress, not just in boost. I want no part of it, even with my little 2.3.

 

[Woody6799]

There is a lot of debate on the lower crank pulley. I have been looking into it for my car as I want to have the torque onset earlier and there are some heated and technical discussions on whether or not the lower pulley does anything at all. Some guys say "boost is boost" other claim they make more torque than an upper only car. That being said, most of them do agree that there is additional strain on the crank that may cause premature failure... even the 2.3, 2.9, and Eatons. I am no expert, but something about the tension from the belt causing the crank to flex slightly under pressure which throws the tolerances off enough to grind/rub/scrape whatever. This can cause damages although it may not snap the snout off completely.

 

[cj428mach]

This can cause damages although it may not snap the snout off completely.

I've also heard that some engine builders can tell if a car has had an uncaged lower just by looking at the internals of an engine. I've also heard an uncaged lower is harder on the oil pump as well and can cause failures there. Its not worth it to me.

 

[01yellercobra]

I think it's a combination of not having a cage and then people running the smallest belt possible. They don't seem to realize when you put a belt on that requires putting the tensioner against the stop something has to give. And there's only a few thousandths clearance for those bearings. The first time I pulled my BB/S apart the front main was chewed up. And I had been running a small belt that required two people to put it on. I've never run a belt that tight since.

 

[ti-force]

I know this thread is a couple years old or so, but I'm curious as to why you really only hear about this happening with the Terminator engines? What about the thousands of other engines (without forged cranks) that run centrifugal superchargers? You know they don't have a crank pulley support. Is it because the blower belt doesn't have as much tension as people are applying to the Terminators? Maybe because people are more likely to try and make bigger power because the Termi's are factory forged? Just curious.

Casey

 

[DSG2003Mach1]

I know this thread is a couple years old or so, but I'm curious as to why you really only hear about this happening with the Terminator engines? What about the thousands of other engines (without forged cranks) that run centrifugal superchargers? You know they don't have a crank pulley support. Is it because the blower belt doesn't have as much tension as people are applying to the Terminators? Maybe because people are more likely to try and make bigger power because the Termi's are factory forged? Just curious.

Casey

There are a lot of factors at play, the bigger PD blowers are a whole different animal than the centris are. The forces in turning that big blower, especially with the rpm change on shifts are pretty drastic. There are some good posts both here and on modular fords that discuss crank design issues etc... that all contribute to it.

 

[Soap]

The large blowers do put a lot of stress on the crank but what is unique to the Terminators is the undercut filet at the back of the crank snout. Major weak point.

--Joe

 

[ti-force]

Thanks for the replies. That makes sense. I wasn't aware of the 03/04 Cobra OEM crank design change.