PDA

View Full Version : Water pump pulley size? Does size matter



jeff5347
07-07-2006, 12:59 PM
Ok this is the short of it. I have a 68 camaro with a black magic 15" elec fan that i think moves 2600cfm. I have a 3 core rad and as of now a 180 tstat. Driving down the road the temp is at 180-185. Sitting in traffic it creeps up. This past weekend in 90* weather it got to 220. Not good. My question is i have a 7 inch v belt pulley on the wp. Someone said to get a smaller diam pulley to make the pump spin faster to circulate the coolant better. May be to slow. What donor car can i get v belt pulley off of that is smaller than 7" and do you guys think i even need to do this and will it help. Also i have the temp gauge (mechanical) in the driver side head between the 3 and 5 tubing of the headers.
Also to note my rad is from fin to fin about 23"long. The fan leaves about 3-4 inches of the rad uncovered on each side so sitting in traffic i have a total 6-8 inches not affected by the fan. Im sure this is not helping.

Randy67
07-10-2006, 07:05 PM
There is also a chance that the fan doesn't pull enough air when sitting still. Some Mustang owners have tried the 15" Black Magic fan and alot ended up taking them off due to running hot in traffic. If you can get hold of a mechanical fan and shroud, try it and see if the problem persists. If it is better, then you need more airflow.

ProStreet R/T
07-10-2006, 08:03 PM
What size crank pulley are you running?

Also what rpm does the motor redline at? Do you regularly spin it that high?

Reason I ask is that it IS possible to overspeed a waterpump which will cavitate the impeller and basically cease to pump any fluid at all. Be wary of it.

With no shrouding I would bet the problem lies in the fan more than the pump. For a cheap solution look into the stock 99-02' dodge viper fan. It comes with a full shroud (with rubber airflow baffles) and is setup as a 2 speed. On high it pulls a claimed 5500ish cfm, on low it should be more than adequate. For $150-200 (from a dealer) it's one of the best available.

Just my $.02

jeff5347
07-11-2006, 04:51 AM
Prostreet,
It is a 7 inch diam water pulley with a sigle groove. I have a th350 and on the street may cruise in second. Well i do have shrouding on all of my fans. The black magic is encased in itas own shroud a but i feel as it does not cover the whole rad there is some area that needs to be covered. The 2 fans i got from the junkyard have there own dedicated shrouds, i just modified them to fit flush against the rad fins. I was thinking that a 6 or 5.5 inch diam water pulley may help to get the water thru the block a little faster. The junkyard had pulleys but were 3 groove but were smaller diam.

engine
07-11-2006, 01:40 PM
You want a 1.2 to 1.35 :1 waterpump to crank speed ratio. I use a 6.25" wp pulley and a 7.75" crank pulley to get a 1.24:1 ratio. Both are Stock GM that I got from Pace Performance for LWP applications.

I used to have both a 6.25" wp and 6.25" crank pullies and got a 1:1 ratio. This was good with a flex fan and no AC condenser in front of the 4-row rad. As soon as I installed the AC condenser, it proved to be just enough of an air flow restriction through the rad, that it screwed everything up. I then changed to an HD clutch fan, which helped a little, but never solved the problem. Then I got the pullies, and everything worked out great...as soon as I got my timing in order as well. Now I'm all good.

jeff5347
07-11-2006, 01:52 PM
Engine,
i have been searching for a smaller than 7' wp pulley but none list the diam. I went to autozone and they couldnt give me an answer to save their lives. What donor could i get a wp pulley off of that is 6.25 or something smaller than 7 inch, so i can give autozone an idea what to look for. Also do you remember what the part # for the pulley is that you got from pace? is this their site? http://www.paceperformance.com/index.asp?PageAction=PRODSEARCH&txtSearch=water%20pump%20pulley&Page=2

engine
07-11-2006, 07:36 PM
Engine,
i have been searching for a smaller than 7' wp pulley but none list the diam. I went to autozone and they couldnt give me an answer to save their lives. What donor could i get a wp pulley off of that is 6.25 or something smaller than 7 inch, so i can give autozone an idea what to look for. Also do you remember what the part # for the pulley is that you got from pace? is this their site? http://www.paceperformance.com/index.asp?PageAction=PRODSEARCH&txtSearch=water%20pump%20pulley&Page=2

Mine are original GM pullies. I had the WP pulley off a donor car.
6.25" Double groove V-belt
# 367161BM stamped on it

Both grooves are the SAME diameter, NOT like this one where one groove is larger than the other:
https://static1.pt-content.com/images/noimg.gif

I called Pace, and gave them that GM part number, and the guy looked it up on the computer and gave me a matching 3-groove 7.75" crank pulley, in 2 seconds.
Since I'm adding A/C, I wanted the 2 grrove wp and 3 groove crank. If you want single groove wp and double groove crank, they can probably look it up. But you have to call them, I don't think you'll have much luck on the Internet.

But looking at their pulley pages, they have a Trans-Dapt steel pulley like it:
2-groove
http://www.paceperformance.com/index.asp?PageAction=VIEWPROD&ProdID=128802
1-groove
http://www.paceperformance.com/index.asp?PageAction=VIEWPROD&ProdID=128801
3-groove crank pulley
http://www.paceperformance.com/index.asp?PageAction=VIEWPROD&ProdID=128805

But I don't see and 2-groove crank pullies in 7.8". Only 6.9"
then they have chrome versions of these stamped steel pullies on page 5.

CarlC
07-11-2006, 08:08 PM
engine is spot on. For factory A/C cars (mine) the waterpump is overdriven. GM offered 1:1 ratios for non-A/C cars. Mine is currently 1:1 GM pulleys with a Victor Jr. pump, but the car has an overkill radiator and cooling fan system.

The 1:1 pulleys are still available from GM. Sorry, no P/N's, but if you ask for a non-A/C 1968 SS pulley arrangement you should be good to go. This is for a short waterpump only.

And as mentioned above, the overdriven GM A/C waterpump pulley is two-groove only, and uses an add-on pulley for the P/S. It's a strange setup, but works well as a stock system. I still have the stock GM overdriven A/C pulleys if you need pictures.

Sounds to me like you have a low-speed airflow problem.

TUBED
07-11-2006, 08:43 PM
If you have a short water pump, run an A/C double groove pulley from a 68 Chevelle. I believe it's 5" - 5 1/2"
Gerald

jeff5347
07-12-2006, 04:35 AM
thats what i was thinking to. A low speed airflow problem. At speed i dont heat up that much but in traffic and city driving with no flow coming thru the rad i get a creep up of the temp. I have ordered the DC controller and have a fan that i got from the junkyard pictured below. The fan as far as i know was off a lincoln continental. It is a 16" diam blade with a lot better shroud to cover the rad. I have no Ac. My wp pulley is 7 in" diam and my crank is 6.75in" diam. Is that a good ratio. Also i measured the WP and it is 2in" deep. Also how do i know if it a short or long water pump? I also have the taurus fan off a 95. This pic isnt mine but this is what it looks like. http://cgi.ebay.com/ebaymotors/MUSTANG-TAURUS-ELECTRIC-FAN_W0QQcmdZViewItemQQcategoryZ33600QQihZ004QQitem Z140005009490QQrdZ1 Which fan do you guys like better?

So maybe with getting a smaller diam wp pulley, adding the fan with the dc controller i may be in good shape.

engine
07-12-2006, 03:19 PM
thats what i was thinking to. A low speed airflow problem. At speed i dont heat up that much but in traffic and city driving with no flow coming thru the rad i get a creep up of the temp. I have ordered the DC controller and have a fan that i got from the junkyard pictured below. The fan as far as i know was off a lincoln continental. It is a 16" diam blade with a lot better shroud to cover the rad. I have no Ac. My wp pulley is 7 in" diam and my crank is 6.75in" diam. Is that a good ratio.
So maybe with getting a smaller diam wp pulley, adding the fan with the dc controller i may be in good shape.
If your water pump pulley is LARGER than your crank pulley, then your waterpump is UNDER DRIVEN, meaning that the water pump will spin slower than the crank. Being that the WP pulley is only .25" larger than the crank pulley, it is underdriven by 4%. You ALMOST have a 1:1 ratio. Like I said before, get the 7.75" crank and 6.25" wp pullies for the best wp OVERDRIVE ratio (wp spinning faster than crank)

When I had the 1:1 ratio pullies, and put the AC condenser in front of the rad, the car would be OK driving, but while idling it would go up to 220*. Yes, it did have a low-speed air flow problem because I stuck a condenser coil in front of the radiator, creating an air-flow restriction. The 1:1 wp speed ratio was also not enough for the air flow I was getting. It wasn't until I corrected the water pump speed that my low-speed engine temperature was good.

Remember you need good flow on BOTH sides of the heat exchange equation. You can give it all the air flow you can, but if you water flow is too low, your engine will heat up.

what year is the engine? Short wp engines were between '55 and '66 or '67, I believe. All small blocks after that were Long waterpump, except for Corvettes due to the space limitations of their engine bay. Also, correct me if I am wrong, SWP engines did not have cylinder heads with accessory bolt holes???

jeff5347
07-12-2006, 03:50 PM
the engine is a 4 bolt truck engine. I think it is a 73-75 or so. I think i have the long pump after looking at pics. So what i could do is since the crank is 7.125-.25 and the wp is 7. i could get a 5.75 in diam wp pulley and that would get me a 1.25-1 ratio. I never thought about the diam maybe not being enough.
ok just looked at pace and cant find a single groove or any groove 5.75 in diam wp pulley.
yuo are correct about the bolt holes. I know when they changed to lwp they needed the bolt holes but did not have them with swp. The engine is all aftermarket. Built it up about 4 yrs ago.

engine
07-12-2006, 04:13 PM
the smallest wp pulley I've seen, stock or aftermarket is 6.25". You'd have to get the larger crank pulley to get the right ratio with it.

HwyStarJoe
07-13-2006, 05:12 PM
Hi all, quick question.

Engine, will the pulley that you pictured here work for a power steering setup?
I'm in need of a two-groove water pump pulley for that reason and I think I can get one like is pictured here. I have a small block with long water pump, alternator on pass. side and power steering.

I'm assuming the smaller diameter inner groove would be used for the PS belt, and the outer for the Alt. belt. Correct? Or do I need a two-groove with both grooves being the same diameter?

Thanks folks!





Both grooves are the SAME diameter, NOT like this one where one groove is larger than the other:
https://static1.pt-content.com/images/noimg.gif

engine
07-14-2006, 01:15 AM
yes you can use that with PS.
the alt belt would go around the large groove and the crank. The PS belt would go around the small groove and PS pulley only. Not the crank .

HwyStarJoe
07-14-2006, 04:40 PM
Thanks!