[Old Goat 67]

Very, very interesting. I'm not sure I would have done what you did to help us out like this, but we are very grateful. Thanks,
Charles

[soupman]

It was easy. Been meaning to check how correded it was in there. Didn't look too bad.

[big_gto]

got mine back together. Decreased clearance to .055". not including gasket. Now it'll idle for 90 minutes between 180 & 190. Can't argue with that! Thanks.

[70GS455]

Anyone ever consider that the large gap might be an intentional design characteristic? I got the idea by reading the Stewart tech tips section. They mentioned certain pumps are not compatible with certain thermostats due to lack of bypass. Maybe it's possible the pump gap is a built-in bypass for coolant when the stat is closed.

[george kujanski]

Perhaps, but It will also bypass when the t-stat is open. Normally, with the tstat closed, the coolant is returned thru the heater core and/or the passage from the intake manifold. Obviously, with the tstat closed coolant must still circulate thru the block to keep cylinders and heads cool; My thinking tells me that increasing the clearance just circulates coolant around the impeller, not thru the engine, where it needs to be.

Not only that, members have reported different amounts of clearance; I would think that if it was designed in, it would be more consistent.

George

[wheelspin]

George,

While cruising the swapmeet @ the Phoenix Pontiac Heaven event I noticed a modified cast impeller pump for sale. Someone had braised a sheetmetal "skirt" onto the impeller's blades. Since the guy had a divider plate in his inventory, I took the time to compare the "gap" which appeared to be about .200. I informed him about this thread and he mentioned that he could have saved a lot of time if he had "tweaked" the divider clearance, per your suggestion. I performed the mod on the Goat, but low temps haven't allowed a proper test.

Les

[george kujanski]

Les, looking forward to your report.

I was in Arizona last week, but left on Friday. Next year I'll check the dates of the meet first, sorry I missed it.

George

[PMDRACER]

The one time I went racing with the stamped impeller, I'd get up to 180 degrees before I knew it, and 200+ by the end of the run. Never was able to get the car below 190 consistently that day.

Running around in Phoenix, even after two back to back hot-lap runs, the car never went above 190 degrees.
If I pulled into the waterbox at 160, I'd see less than 190 at the turn around. By the time I would idle back to the lanes, I'd be down to 180.

The only change to the car was the pump itself.

Ran my best times so far at Phoenix this past weekend. Many factors contributed, but getting the motor cooled down surely helped. According to my timeslips and notes, every +15 degrees of water temp cost me about a tenth.

[Old Goat 67]

Cool Dude, or is that a pun?

[Big Mike]

The by-pass is the small hole from the intake manifold to the back of the timing cover. The pump impellers could drag on the separator plate and you would still get the proper amount of by-pass flow through that small hole.

[Squidward]

My divider plate modifications originally got me about 5 degrees improved, but after I replaced my Tstat this weekend with a 160 cheapie from Autozone, I'm running 180-190 consistently whether I'm highway zooming at 70 mph or idling forever in the Del Taco drivethru, all of this with 90+ deg temps. I'm back to where I want and need to be. Right on!!!

Next demon to slay is A/C installation!!!

BTW, I got my proper clearances by leaving out the gasket and mashing on the divider plate at the opening until it contacted the impeller vanes. When I assembled it with a gasket, it gave me exactly the clearance I was looking for.

[george kujanski]

Squid, you sure get up early in the morn.

George

[1badgto]

Is there any advantage in changing to the newer timing chain cover rather than an original 67?

[GTOJOE228]

I just completed the task of reducing the clearance between the plate and impeller and the results were great. Let sit at idle for approx. 20 mins after reaching operating temperature and had consistant 180-190 degrees. I call this a major improvement. My thanks to all who shared and I'd like to compliment George for being so informative. You are a valuable asset to this forum. [URL=http://www.goodfe.la.com/gtojoe

[paulkx807]

Hi Joe,I'll talk to you tomorrow.Paul

[wheelspin]

1badgto,

Welcome to the Forums.

It is generally agreed that the later style water pump is a worthwhile improvement in cooling and the 11 bolt timing cover allows the use of aftermarket aluminum water pumps such as Flow Kooler and Milidon.

Les

[Hattmann68]

Been Reading the topic and thought i'd share my thoughts and results. Pulled my pump that I installed in 1994 and it was a stamped impeller ,my plate had some cancer around the two outer holes enough to not allow a seal. Bought my new pump with cast impeller, installed a extra plate I had, set clearance to .080. now it will idle for 1 hr at 180-190 deg.so simple Thanks George!

[george kujanski]

Show me the money! My account in the Caymans' could use some help. I was expecting to retire soon. We need some more success storeies!

George

[Squidward]

Actually, GK, I was at work. I work a 6pm to 6am shift. So, I guess you can say I go to bed very early (usually about 7am), depending how you look at it!!!

[kate`s67gto]

Here is another success George. Got car out after rebuild of engine stock except bored 60 over now. Run 160 stat rodney red rad it was 55 to 60 here yesterday car on hiway ran 160 tops. In town same . I consider this a success even if temps are not that high. This was first drive after rebuild I`m beginning to think i may have to boost to a 180 stat.