[GTOJOE228]

I have been chasing my 1967 Ram Air GTO running hot ever since the body off restoration. I've done all the suggested tips mentioned in this forum with little or no results. I went to see Nunzi, yes the famous Nunzi from Brooklyn regarding something unrelated to this matter. After talking to him for the better part of an hour I brought up this problem of my GTO running hot. He then told me that he had a experimental pulley that was in the testing stage that may solve this problem. After some arm twisting he agreed to let me test one. He also gave me a thermostat with the inside removed......He had put an incredible amount of time developing this product. I went home and gave this awesome looking aluminum pulley a coat of semi gloss black paint. Installed it as well as the new thermostat piece.

Here are my initial results. It's 75 degrees outside and the sun is hot. The car normally runs 220 degrees or higher in this somewhat hotter weather.
I drove this car after it idled for 25 minutes and before the drive the temps were 170 degrees. I took the car on a 30 minute drive and it ran at 150 degrees and no higher. I stopped for 10 mins at an idle and it went up to 170 degrees. Drove to my final destination 10 minutes away and it was again down to 150 degrees. Parked in my garage and noticed that the front of the car was not near as hot to stand by as before. Another plus is that the car performed so much better. More responsive and it even sounded more throaty in the exhaust note.


My initial testing seemed to be extremely encouraging. I'm ecstatic to say the least. I'll be sure to report more results as I continue my testing.

Nunzi has always impressed me with his vast knowledge of the Pontiac motor and it's history.

These pulleys are going to be available through his website or you can call Nunzi at 718-837-1135

Tell him you read it here.......

Joe

[Bill H]

That sounds like good news for you and maybe others.

I don't have that overheating problem since I put in a Rodney Red radiator, a Q'jet that Cliff re-built and tuned and got my timing set right.

I have a flex fan, no shroud, and a 185 thermostat, the car will get up to 185 and drop like a rock when it (thermostat) opens. Most of the months here in CA and when it's in the 80's it runs about 170*, when it's in the high 90's and 100*> it will get up close to 200 when sitting in traffic. In the fall and winter months I'll be luck to get it over 160.

Hope your continued testing works out and solves your heating problem. I used to hate driving around looking at the temp gage all the time.

[GTOJOE228]

Originally Posted by Bill H

That sounds like good news for you and maybe others.

I don't have that overheating problem since I put in a Rodney Red radiator, a Q'jet that Cliff re-built and tuned and got my timing set right.

I have a flex fan, no shroud, and a 185 thermostat, the car will get up to 185 and drop like a rock when it (thermostat) opens. Most of the months here in CA and when it's in the 80's it runs about 170*, when it's in the high 90's and 100*> it will get up close to 200 when sitting in traffic. In the fall and winter months I'll be luck to get it over 160.

Hope your continued testing works out and solves your heating problem. I used to hate driving around looking at the temp gage all the time.

Bill,

Thanks for the encouraging words....I too went to a Griffin Aluminum rad...the one that resembles my stock Harrison. Zero improvement. This pulley has me really excited. I'm off to Raceway Park N.J. tomorrow which is about an hour away....I'll report back as soon as I get home.

Joe

[b-man]

Looks like the new pulley along with the gutted thermostat made a huge difference.

When I installed a new smaller water pump pulley (going from 8" to 6-1/2") my temps dropped by 10 to 15 degrees. My crank pulley is 7-1/4" in diameter.

What is the diameter of the new Nunzi water pump pulley?

For reference please tell us the diameter of your crank pulley too.

Thanks, Bart

[JSchmitz]

Originally Posted by b-man

Looks like the new pulley along with the gutted thermostat made a huge difference.

When I installed a new smaller water pump pulley (going from 8" to 6-1/2") my temps dropped by 10 to 15 degrees. My crank pulley is 7-1/4" in diameter.

What is the diameter of the new Nunzi water pump pulley?

For reference please tell us the diameter of your crank pulley too.

Thanks, Bart

Please, also include more of your setup details.

Bart, I also saw a big improvement going to "A/C" pullies. March sets come with a smaller than stock crank pulley (IIRC). You have to special order a large crank pulley. Something to watch out for.

[STVSHOBRD]

It would be interesting to know if it was the pulley or the thermostat or a combo of the two that made the big difference.Trying it with a normal thermostat would tell the story. Isn't 150 degrees too cold?

[ANDYA]

Yep, now that Nunzi is retired from working on customer cars it gives him lots of time to work on stuff that he always wanted to do. Keep your eyes open you never know what he's going to come up with next.

[chiphead]

Yes, please post the results and sizes of the pulleys.

What size crank and W/P pulleys were stock on '67 GTOs? It's likely that a lot of us having overheating problems have mismatched pulleys. The set I use are just whatever I could get to line up. No idea if they are a matched set. I think that's common, considering how easy it is to mix and match the timing cover components.

[GTOJOE228]

Today as I mentioned before was my trip to Raceway Park in NJ.....45 min to an hours drive away. Temperaure was 85+ degrees outside.....lots of sun, enough to give you a sunburn. Got on the road and carefully watched the guage. 150 degrees all the way down. Stopped for a period of time to line up and pay to enter Raceway Park grounds....temps went up to 170........Started my appraoch to the field and temps dropped down some. Spent 5 hours at the show and left when the temps outside felt like 90 degrees but was more in the 85+ degrees as I mentioned. Drove in slower traffic than the morning and the car never got above 170 degrees. Let the car idle in my driveway for 5 mins in direct sun with virtually no wind and the temps were a shade under 180....pulled the car in the garage and after the car was off for a few mins. the temps started to DECREASE....which never happened before.

I'm running a Griffin aluminum radiator......fixed 6 blade fan half in the stock shroud. The pulley setup are as follows: 5 1/2" Nunzi water pump pulley plus a standard 7 1/4" crank pulley.

Keep in mind that Nunzi's pulley has deeper groves which hold the belts perfectly with virtually no chance for slippage.

I also agree that 150 degrees is on the low side. So I may opt for putting the 160 thermostat back in.

After dealing with this problem for 5 years this comes as a relief that a pulley and a reworked thermostat core has given me these positive results.

I saw Nunzi at the track today and he again reiterated how long he experimented with this modification. How ever slight, this seems in these few outings to have solved this nasty problem.

Again, I am still going to keep testing the current setup. I will be changing the 6 blade fan to a stock Pontiac 5 blade fixed fan. I don't like the sound this fan makes. Hopefully things won't change for the worse.

Stay Tuned...

GTO JOE

[chiphead]

What timing cover setup are you using? The '67, '68, or '69-newer?

'67 had the hub balancer and 8 bolt water pump
'68 had larger balancer and 8 bolt water pump
'69-newer had larger balancer and 11 bolt water pump.

There is a lot of scuttlebutt here that the 11 bolt pump system moves water better. I'm running the '68 8-bolt setup in my '67, but you could be running either pump.

So, 8 or 11 bolt water pump on your car??

[GTOJOE228]

Running the 8 bolt standard Flow Kooler pump with the disc welded to the impeller.

[b-man]

Using the 5.5" water pump pulley and the 7.25" crank pulley turns the water pump & fan at 131.8% of the crankshaft speed. Pretty fast, that water is really pumping and the fan is pulling some air.

As a comparison the mid-'70s 455 engines with factory A/C used a 6.5" water pump pulley and an 8" crank pulley, turning the pump/fan at 123% of crankshaft speed.

Another comparison is the '64 389 engine (no A/C) with an 8" water pump pulley and 7.25" crankshaft pulley, pump/fan turning at only 90.6% of crankshaft speed. I had this combo on a 455 for a while, it ran too hot.

Spinning the pump and fan fast does work.

Any idea on the cost of the 5.5" pulley?

Thanks, Bart

[GTOJOE228]

The cost will be in the $225.00 range. When you feel the weight of this piece you'll agree as to how well it's made. Nunzi has done a great job with this one.....

I also believe that the combination that currently is working for me is the water pump and the fan's RPM's have increased enough to create an efficient process. I had a 6" pulley on before and the results were negative. The thermostat mod also helped....

Thanks Nunzi.......So far, so good!
More to come as the summer progresses.

GTO JOE

[rad400]

Wow thats nice my trans am only get to 200-205 would like to get a smaller pulley, I have a alumium water pump electric fan, 165 stat. aftermarket copper rad.

[chiphead]

Cool, that's the same pump I use.

When measuring pulleys, are you measuring at the OD, or the bottom of pulley grooves?

Is there any chance of spinning the pump too fast? What about cavitation? If I shift at 6K at the track, the W/P and fan clutch would be turning 7800. Is that kosher?

[GTOJOE228]

This is a good question.....Nunzi assured me that the pulley was one of trial and error.....My suggestion would be to give Nunzi a call and he'll be happy to address your concerns. 718-837-1135

[GOAT8U2]

Jesus, $225 for one water pump pulley, it doesn't take Nunzi to tell you that by making the water pump pulley diameter smaller it's spinning much faster and increasing flow out of the engine and through the rad.

Wow I should contact my CNC buddy and get him on this, he'd sell a crap load at $125 and make a ***** ton I guess.

[screamingchief]

Originally Posted by chiphead

Cool, that's the same pump I use.

When measuring pulleys, are you measuring at the OD, or the bottom of pulley grooves?

Is there any chance of spinning the pump too fast? What about cavitation? If I shift at 6K at the track, the W/P and fan clutch would be turning 7800. Is that kosher?

Some sources like Stewart components generally recommend a max water pump speed of 7000 RPM for racing applications.

For street use they generally recommend up to 25% over crank speed (125%).

Are these sources the "be all/end all" cooling system resources to follow,hard to say for certain,but those guys do have a lot of very good suggestions to follow as far as a general guidline sorta deal.

Your comments about pump cavitation are no doubt legitimate concerns,but even places like Stewart comp. bases most of their recommendations on chevy & ford cooling systems,so I would suspect there may be some "wiggle room" as far as our pontiac water pumps are concerned.

Also fan/clutch related issues may be a concern,but that's even harder yet to prove one way or the other.

[b-man]

Originally Posted by chiphead

When measuring pulleys, are you measuring at the OD, or the bottom of pulley grooves?

Measure the OD.

[GTOJOE228]

Originally Posted by b-man

Measure the OD.

5 1/2 inches O/D.......Nunzi made several versions and this version was the one he's confident about.

Joe