DeTomaso Mailing List: January 98, Message #136
     



From: 	Cary Foster <cfoster@etcconnect.com>

Subject: FW: Waterpump pulley increased diameter

Date: 	Mon, 5 Jan 1998 20:33:05 +0000



I think that more than 6% reduction would be needed to see a change.

Most aftermarket pulleys that are sold to reduce speed and increase hp

is around 20% to 30%. Sounds like alot and might not work around town.

With 21 feet of 1 3/8" undersized water pipe, the car might run hotter

in traffic. I am going to go to a junk yard and find larger a  pulley

with the same or larger offsets with around 20%-30% reduction. With a

larger offset I can probably shim the pulley into alignment.



Cary



> ----------

> From: 	Andy Poling[SMTP:andy@globalauctions.com]

> Reply To: 	Andy Poling

> Sent: 	Wednesday, December 31, 1997 10:00 AM

> To: 	Multiple recipients of list

> Subject: 	Re: Waterpump pulley increased diameter

> 

> On Mon, 29 Dec 1997, Rick in Ca. wrote:

> > Cary Foster wrote:

> > > Has anyone messed around with increasing the diameter of the

> waterpump

> > > pulley to slow it down? Did it have any effect on the car water

> > > temperatures at track speeds? Does the Pantera have a unique

> pulley

> > > offset or hole pattern or is it the same as mustangs and other

> common

> > > Ford products?

> > 

> >   I tried this and it made no difference. Pulleys I found were from

> a

> > six clyinder ford. Doing the math, one pulley was 6 percent slower

> and

> > the other was 10 percent faster. No diff in operating temp. Go

> figure,

> > cause I don't know why neither made a difference.

> 

> If your engine wasn't running hotter than the thermostat wanted it to,

> then

> you're not going to see any improvement with an over-driven pump.  If

> it

> cavitated, of course, you might have seen a reduction in cooling

> system

> effectiveness...

> 

> On the other hand, the fact that you didn't have a problem with a 6%

> underdriven pulley seems to indicate that maybe Cary is onto

> something.

> Evidently you didn't need the full output of the water pump during

> your test.

> 

> On a related note, it is my understanding that centrifugal pumps are

> not

> good at generating a significant pressure differential (as opposed to

> positive displacement pumps).  It seems to me, therefore that an

> overdriven

> water pump will probably just cavitate at some point (at high RPM),

> having

> generated as much pressure as it can and being unable to move any

> further

> volume.  Then again, I have no idea what the back-pressure from the

> radiator,

> engine cooling passages and various hose/pipe joints etc is...

> 

> Just a random thought that decided to sneak out today, before I kill

> that

> brain cell tonight. :-)

> 

> -Andy

> #3822

> 

> 72 Pantera - Rocky         91 Miata - Steve (bionic)            96 A4Q

> - Rudolf

> 80 928 - Phantom               97 Miata - Nadia                84

> RZ350 - Sting

> 

> 

>