I have an 86 GXL, and last year I had the engine rebuilt and ported. While I had it apart, I took off most of the emmissions stuff - including the cats and air pump. Once I got the car running, the water pump had a rattle, and has done it ever since.

All last summer I had "replace water pump" on the top of my to-do list, but it never got done. Now, since I removed the air pump, I removed the air pump belt. So the question is:

Do I need the dual alternator pully in order for my water pump to run properly? If I put one on, will it stop the rattling that I have now? If I don't put one on, will it ruin the new pump I put in? If I do need one, where is the best place to get it? Any experience/advice you can give would be great.

Nick

 

You definetly do due to cavitation of the Lower Rad Hose at higher RPM's. Atleast I did. Do you experience high temps when your running high RPM's?

A dual Pulley solved my problem - Instantly.

 

A bit higher temps, but I try not to run really hard when it is really hot out, so it's hard to tell. Where did you get your dual pulley?

 

www.rotaryinnovation.com

 

Yep, I bought one from there. Some of my friends bought other ones that don't make both belts as tight, but mine works perfectly.

 

Dual alternator pulley will not stop cavitation. The cavation is caused by the water pump its self and stops flowing water right around 4000 rpms.

The dual belt is so it doesn't slip at higher rpms, nothing else. and if you have your belt tight enough, you would not this part.

I have seen several 11s RX7s without this mod and they have no problems.

The real fix for your cavation is a larger pulley for the pump this will make is turn slower as compare tpo the old at the same rpm.

However I found that the larger pulley is no good for street driving and causes the car to overheat in stop and go traffic as the water pump doesn't start working with the pulley till you hit about 3500 rpms.

 

http://www.rotorhead.ca/ sells them also.

 

I think the dually pulley is a good idea for drivers who get on the car alot when the air pump is off. You don't want the alt. belt to slip...

 

so the water pump doesnt pump anything till higher than 3500 RPM? so your saying just at idel its not pumping at all?

Cause im having an over heating problem in the 7 i just bought.. the prev owner has removed the air pump and im thinking possibly this could have something to do with it..

What if i was to put a smaller pully on the pump to in a sence trick it to think im running 35 grand?

 

i have the dual pulley too, i wanted to know, does it take away a lot of voltage to the engine? When it had a single one, it would always run at like 14 volts, now it runs at about 12.8-13.6.

 

First you should try tightening the belt. These things do stretch.

 

This is wrong. Cavitation starts at around 6000 RPM. You can prove this easily if you have an aftermarket temp guage.

Really, you SHOULD have the dual pully if you have removed the airpump. HOWEVER, you may find that you don't need it if you are running an electric fan. If you have the stock clutch fan, you definitly need the dual pully to prevent the belt from slipping.

Also remember to properly tension your belts.

Underdrive pullies are the solution to cavitation, but on the street will result in lower alternator output, lower A/C performance and slightly stiffer power steering. Also, it is doubtful that you have a cavitation problem when street driving.

 

With the stock fan's thermoclutch engaged (after sitting at the lights for example) the single belt doesn't have enough grip to accelerate the fan when you rev the engine as you drive off. If you overtighten the belt it stops slipping for a while but mine always started to slip eventually. The pulley stops the very annoying squealing.

 

 

http://www.1300cc.com/howto/how2/belt.htm