[vaccaraj]

i have a 67 gto that just will not cool down. it now has a 455 +.030" over. 9.9:1 cr. cam has 465"/.469" lift, 231/242 degrees duration @ .050", 112 degrees lsa. 1 3/4" headers. 800 cfm spreadbore holley. single point dist. w/36 degrees advance all in by 2400 rpm.Turbo 400 with a tci 11" converter. 12 bolt chevy rear w/3.73 gears. the cooling system is brand new for the second time. 4-core radiator,stock 7 blade 18" fan w/heavy duty clutch(thermal),repro fan shroud,brand new gm water pump w/new divider plates,180 degree t-stat(160 also ran hot). i have great flow through the radiator, but it always climbs to 220 and beyond if i let it.(which i dont)changed each cooling system part individually,looking for the problem. the only thing that made a difference was the new water pump and divider plates. temp dropped about 10 degrees to 220. the stock 400 rated @ 335hp never went over 185. new 455 rated at approx. 420hp,cooling system cant handle it.
nunzi romano told me to add another outlet nipple on the back of the driver side head and connect it with a hose to the one on the back of the passenger side head which also goes to the heater core.also to use a smaller water pump pulley. use only a restictor plate instead of a t-stat and also to slow the timing down. all in by 3300-to-3500 rpm. if this doesnt help, install an aluminum radiator.. if i do have to change the radiator, i would still like to maintain the stock look(down flow vs crossflow).
i would like to up the power level on this engine again but am afraid to because the system cant handle what it has now.can anyone comment on this long standing problem in this long letter.

[vaccaraj]

guys,
the spark plugs are a darker color even w/the msd ignition. this is why i dont think that the engine is lean.there are no vacuum leaks, i checked with a special tester that i have for detecting leaks.
the fan is half in- half out of the fan shroud.
i still would prefer a down flow radiator to keep looking close to what it is suppose to look like.
thanks for your replies. will try different things to the engine,and let you know how i make out. i might be finished for the year though.
tony

[mike nixon]

just a note on pulling the thermostat. in some cases this will cause the engine to run hotter due to the fact that the coolant flows thru the radiator too fast and doesn't get a chance to cool.[not enough heat transfer]. i've had better luck with a flat plate and a drilled orifice.
if the car is getting hot at idle and not going down the road the stat isn't the problem. it would be the opposite due to more heat being generated. i would say the problem is air flow at this point.[idle]
have you tried a good high cfm electric fan to pull more air through the radiator?
one last question; what is the compression ratio of this monster, and what fuel do you run? mike


[This message has been edited by mike nixon (edited 07-27-2000).]

[Tim Corcoran]

Vaccaraj

Sounds like you have done all the right things. I guess you have your hands full here. Have you checked to verify that the radiator in good shape? I mean are all the tubes clear internally and all flowing properly? If I were you I would go to an aluminum radiator or a Desert Cooler. The Deser Cooler provides a close to original look and has more cooling capacity than a factory Harrison. The aluminum is the most effecient. The Griffin is the best because of the large tubes in their cores that most other companies don't have. The Griffin does not have a direct drop in like a Be Cool but they cool better and are higher quality. Good luck.

Tim Corcoran

[vaccaraj]

last night i removed all of the anti-freeze from the engine. flushed the block through the t-stat hole for about 10 minutes.
i installed a restrictor plate with a 1" hole in it. filled the system w/straight water. temp still goes to 210 and slightly higher at idle, but cruising speed it comes down to 190-to-195 at a pretty fast rate. this proves that straight water does cool more efficienly than anti-freeze and this part of the cooling system,(cruising range) is working properly. i'm going to put in some red line water wetter next (for corrosion resistance and whatever other benefits)
compression ratio on this engine is 9.9:1 and i'm running 100 octane fuel.
the problem definately seems to be an air flow one. i'm going to look into sealing the fan shroud with an a/c gasket sealing set.
has anyone researched electric fans. from what i've read, i like the flex-a-lite black magic fan.
i've always been convinced that the stock 7-blade fan (18") and thermal clutch are better than a flex fan. this is my second clutch fan. it seems to work fine. but maybe its just not pulling enough air at idle.
will a good flex fan pull more air than this stock setup.(the new clutch unit is a heavy duty one)
thanks again for responding
tony

[This message has been edited by vaccaraj (edited 07-27-2000).]

[JSchmitz]

I have to question how much flow you will get by running the lines to the front cross-over. You get flow through the heater core because it goes to the intake side of the pump (ie., pressure differential). I would think the pressure across the block would be pretty even. There is a pressure drop across the thermostat however. I am thinking a "T" in the upper hose, or a bung on the radiator would work. Then have a heater control valve or thermostat to control the flow. Otherwise, you would be bypassing the thermostat when cold. My cooling system is working pretty good. I just need the "icing on the cake". I may try this myself. I will have to wait for hot weather to see if it works.

[vaccaraj]

tim,
i'm going to recheck a couple of things over again on my car to be absolutely sure that they're right.(timing & jetting). but the radiator is brand new. flows great. the old radiator was recored. i had that checked out by a radiator shop. that one flowed perfectly too. if i have to resort to another radiator, i want it to be a griifin. have you had any experience installing one. you said its not a direct fit. is there a lot of fabrication involved in getting it in.
tony

[RRF]

A 160 degree thermostat and new severe duty clutch fan solved my heating problems, not that this helps you...

Where is your thermostat connection?... on the intake or head? And are you sure it is reading correctly?
Of course there is a obvious difference when you raise the hood on a 160 degree engine than on a 220 degree one.

[Zimtok]

It seems to me that if you are cooling down when the car is moving then it would be one of two things.
1. not enough air is flowing across the radiator when sitting still. Make sure that you have good flow of air across the radiator.

2. The water pump is not circulating enough volumn at a slower speed. Make sure the pump is in good condition and the passage ways are open. if the aluminum casting is coroded and allowing the water to leak back into the pump cavity the pump will not push the volumn of water it needs to cool it down.

These are the two things that change in the cooling system when you start moving down the road.



------------------
A.S.D.Zimtok

[vaccaraj]

i have a 67 gto that just will not cool down. it now has a 455 +.030" over. 9.9:1 cr. cam has 465"/.469" lift, 231/242 degrees duration @ .050", 112 degrees lsa. 1 3/4" headers. 800 cfm spreadbore holley. single point dist. w/36 degrees advance all in by 2400 rpm.Turbo 400 with a tci 11" converter. 12 bolt chevy rear w/3.73 gears. the cooling system is brand new for the second time. 4-core radiator,stock 7 blade 18" fan w/heavy duty clutch(thermal),repro fan shroud,brand new gm water pump w/new divider plates,180 degree t-stat(160 also ran hot). i have great flow through the radiator, but it always climbs to 220 and beyond if i let it.(which i dont)changed each cooling system part individually,looking for the problem. the only thing that made a difference was the new water pump and divider plates. temp dropped about 10 degrees to 220. the stock 400 rated @ 335hp never went over 185. new 455 rated at approx. 420hp,cooling system cant handle it.
nunzi romano told me to add another outlet nipple on the back of the driver side head and connect it with a hose to the one on the back of the passenger side head which also goes to the heater core.also to use a smaller water pump pulley. use only a restictor plate instead of a t-stat and also to slow the timing down. all in by 3300-to-3500 rpm. if this doesnt help, install an aluminum radiator.. if i do have to change the radiator, i would still like to maintain the stock look(down flow vs crossflow).
i would like to up the power level on this engine again but am afraid to because the system cant handle what it has now.can anyone comment on this long standing problem in this long letter.

[mike nixon]

just out of curiosity what is the base setting of your timing with no advance? mike

[72LeMConvt]

On another thread on this same bulletin board, another user had good luck with his separate trans. cooler mounted away from the radiator. This might be an option for you - relocating your trans cooler. You mention above that it's hugging the front of your radiator.

[Old Man Taylor]

JSchmitz - I don't understand your point. Tapping into the heater core flow simply recycles hot water. Going through the thermostat cannot be too much of a restriction because that is where all of the return water flows. That is the whole point of the thermostat, to control the flow. I do not see a limitation by plumbing into the manifold water cross over. It returns the hot water the same as the rest of the water from the engine (except the heater). My connection is through a 1/2" pipe fitting. Am I missing your point?

------------------
Jim

[mike nixon]

when you built the engine did you check for rust in between the cyls? what i'm getting at here is a restriction in the block. another possibility could thin cyl walls due to core shift. i mention these possibilities because it sounds like you've been through all of the basics already. mike

[vaccaraj]

mike,
if you mean my static timing,it's now 8 degrees btdc. it was 12 begrees before. i changed it yesterday and it seemed to help somewhat. i'm going to go up slightly in the primary jet also. the plugs are slightly colored but maybe not enough.
tony

[Half-Inch Stud]

OK, I bit, so here's my response for STREET/Strip.

First, Are you getting the performance, responsivness, and ping-free operation that you expected? Then determine if your overheat occurs during steady-State Highway cruise, Thermal rise at a stoplight [Idle], or both. If both, you could have anything odd going on from notes threaded above to poor cam timing, or wiped rod bearings.

My problem was a thermal rise at stoplight.
Thus, insufficient airflow.

I researched using 2 electric fans..no good. Clutch fans...no good.
Back to the 5 or 7-Blade GM Flex.
Get the Aluminum Water Pump & Watch the impeller design!
Use fresh donut tubes within the Timing cover.

MEDICINE [see this at the GRove on Sunday]:
1. No more Tranny heat to Radiator cold-side. Parked a finned aluminum Tranny cooler at the passenger inner fender port at the Radiator support.

2. Radiator Shroud [duh], but installed smartly, Spaced the fan blade to be mostly-inside/kinda outside of the shroud and the mech fan blades fill the Shroud hole with minimal clearance [I forget - about 1"?].
Moreso, close-off upper area in front of Radiator from hot engine air recirculating forward [Back-to-Front flow]. Easy to do on GTO's not so easy with Firebirds. I used black headliner material and with nip and tuck got a decent air barrier.

3. Block the Exhaust crossovers. The better you do this [pour molten metal vs steel shim plates] the better the results.

4. Two heads of water meet at the Thermostat housing. One head flows while the other stagnates. That's one hot bank of cylinders. My favorite: Removed the water crossover and replaced it using a Y-connect to upper hose.

[JSchmitz]

I assume that, by running the heater outlets to the front of the engine, you are trying to route this water through the radiator instead of recycling it via the heater core. I was trying to figure out how much coolant would actually flow to the front through those lines. The thermostat provides a restriction that helps pressurize the block. If the pressure at the heater outlets is the same as the pressure at the cross-over (I don't know if it is), there shouldn't be much flow through a line that connects the two. I would like to see your setup. I also may be missing the point. :~) My whole thinking here is, it makes sense to connect both heads and go through the heater core. That way both heads are recirculating, not just one. I started thinking after reading this post that it would be better if that water went through the radiator. I hope this helps my point.

P.S. If you don't mind E-Mail me a picture of your set-up.

[This message has been edited by JSchmitz (edited 11-09-2000).]

[vaccaraj]

mike-the block was acid-dipped before all the machine work was preformed. hopefully that would eliminate any rust in the block.
as for sonic testing the block for thin walls and having the bores checked for shifting, i didnt have that done.
i hope this problem doesnt get to that point, or i'll be looking for another block.

[vaccaraj]

in the past couple of days i've done a couple of things to try to get my temp. down in my engine. first, i brought the timing back to 32 degrees. then i went up in the jets again. plugs are a light tan color. i also found a water pump pulley from a '66 gto. it measures 7" in diameter vs. the original which measures 8".what all of this did was make the cooling system operational at cruisig speed. but as soon as i stop at a light,the temp. still climbs. when i take off from the light and have a good steady road to go down the temp will start dropping.
drops to about 195. but after quite a few start and stops in alot of traffic,the engine gets a good heat soak and the cooling system has a harder time bringing the temp down. my next step,before considering an aluminum radiator,just might be straight water and water wetter???? i just dont understand this whole cooling system problem. i have a friend who has a '67 427 chevelle putting out 525hp. he has a downflow radiator and a 4 blade fan with no shroud. the car runs 190 degrees all day long. i've helped build many high perf chevies, buicks and mopars,all with know problem w/the cooling system. what gives with the pontiac engine.any more suggestions would be appreciated.
i talked to ken crocie of h-o racing specialties and he told me he thought he saw an advertisement for a book, something along the line of "how to cool a pontiac engine" i've looked all over for this book. has anyone ever heard of this.

[This message has been edited by vaccaraj (edited 07-25-2000).]

[MoJo]

vaccaraj,
A flex fan was the only way I cooled my 72 400 down in my bird. I fought all of the above options to no avail (except the alum radiator). I know it's not correcting the root cause but it keeps it on the road in this Texas heat. I run the stock fan setup in cooler weather.