[pontiacphil]

I'm finishing up a total rebuild of my 1967 GTO 400 motor. Tweaked it a little so it has a true 9.72 compression, 406 cu.in., Turbo 400, 3:55 gears, no AC. Factory Harrison radiator, 4-row, has had a complete new core installed. Fan is a factory 17 in. 7-blade. No fan shroud. I bought a new Flow-Kooler water pump and a high flow 180 degree Mr. Gasket thermostat. I bought these before I found this site and now realize that the Flow-Kooler pump may not be the way to go. I'm now at the stage of putting the water pump and accessories on the motor. I am trying to find the best combination of water pump, thermostat, fan, shroud, etc. to avoid overheating. I live in NW Tn. where it is warm and humid. GTO is used primarily for weekend "cruising". Should I go to a 19 and half inch fan? If yes, what brand? With a shroud or without a shroud? Will a larger shroud (19.5 in. fit my smaller 17.5 in. radiator)? Should I send the Flow-Kooler water pump back to Summit and buy some other water pump? I'm also a little unclear about the clearance issue on the divider plate in the water pump. Can someone pls. give me a little extra info. on that matter? Sorry to ask so many questions but I know people on this site have the experience and knowledge with Pontiacs that I respect. I'm just trying to avoid overheating and I'm at the stage of assembly where I can buy and install the best package/combination of parts that are recommended. I appreciate any and all help and info. you can provide. Thanks.

[george kujanski]

Welcome, and good idea on planning ahead.

Don't know about the specifics on the flow-cooler 8 bolt pump...some pics would be a help, but according to data collected on pumps, the impeller vane length and height are important (more is better), and the cast impeller seems to have these qualities more so than a stamped-sheet metal type of impeller.

Also, the clearance (gap) between the edges of the vanes and the mating surface of the internal housing (on a 8 bolt pump) has a major effect on coolant flow. Minimal gap is better.

Go to the sticky thread at the top of this forum "chalk up one more for the cast.....'

A ton of info and pics there to give you ideas.

Also use a shroud.

happy motoring!

George

[pontiacphil]

George, Thanks for the quick response and the info. you provided. I read all 40 pages of the thread you sent me to and must say I'm a bit overwhelmed and somewhat confused. Since my 67' water pump is an eight-bolt I'm just not certain what I need to do to the divider plate and what tolerances I should be shooting for. Can you pls. give me a condensed version of just what I should do to my divider plate when installing it. Is the Flow-Kooler water pump okay or should I consider buying another brand or type? Where is the best place to buy a fan shroud for my 67', no air (short radiator). Thanks again for all your help.

[george kujanski]

With the 8 bolt pump, the divider plate is not an issue, it's the "internal housing" that you need to check the gap on. If you go back and take a look at the figure from the manual showing the 8 bolt assy, you will see the divider fits around the perimeter of the vanes whereas the internal housing (has the large center hole) fits next to the edges (not tips) of the vanes, essentially enclosing the entire impeller.

Assemble the housing on the pump body and measure the gap from the inside surface of the housing to the edges of the vanes; it should be at a minimum without rubbing when you turn the impeller.

The main problem with the clearances seems to be in reman pumps, either the vanes are wrong for the application, (size, type), or the impeller is not pressed onto the shaft to the proper dimension.

If you can press the impeller onto the shaft to the necessary dimension, that's great, but most owners, (myself included), choose to "adjust" the gap by bending the flat surface of the housing (8 bolt, if it's a sheet metal housing) or the "divider plate" (11 bolt) to close up the gap to the vane edges.

If you can take some pics of your Flow cooler and post them so we could see.

Our host, PY, has fan shrouds for sale in their catalog; I'll be buying one, also. You may also find some for sale in the parts for sale forums.

[Geoff]

p/phil,
The shroud is veeeery important. I recently had a new crossflow radiator made for my 66 GTO, to replace the up/down original style. Both radiators were alum, same size tubes etc & core area of the c/flow was within 1% of the area of the old radiator core. In other words, virtually identical & since there is no difference in the cooling ability of c/flow & down flow of the same size, the cooling capabilty of the radiators was the same. Because of the different tank & hose placement, I could not use my original fan. So I installed the new radiator without the shroud; used the same fan, same position.
The engine ran noticably hotter. I knew a shroud was important, but I was surprised how much hotter the engine ran without it. I ended up making a shroud out of alum. The engine now runs cooler than it did with the original shroud, which I attribute to the new shroud, not the radiator change. I made sure that all gaps to the rad. were sealed, that the fan was half in half out of the shroud & that the shroud closely fitted the blades to optimise efficiency.
The best cooling fan I have found is the genuine Pontiac RAIV fan. It is a 7 blade flex fan, 19.5" diameter. I believe they aere now hard to get. I have also tried the Flex a Lite 6 blade flex fan, also 19.5" diam & it was also very good.

[pontiacphil]

Geoff, Thanks for the info. about the necessity of using a fan shroud. I knew they did a good job but after reading your post, and talking to a couple other GTO owners, I now realize a shroud does even a better job than I originally thought. I'm ordering one today! Thanks again.

[pontiacphil]

Took both of yours advice in trying to avoid overheating with my 400 total rebuild. Looks like the true compression of this rebuilt motor is right at 9.6. I did buy a Flow Kooler water pump and "massaged" it like George told me to do. Used a Robert Shaw 180 thermostat. Bought a fan shroud from Ames. Used my factory Harrison 4-core which has been recored. Fan is a 7-blade 17 in. flex type fan. During the 20 min. cam break-in car was in a garage without much air flowing to the front area. Highest the temp. got was a tad under 205. Today, after getting the HEI properly wired (thanks to George also) we took a short, slow ride. Outside temp. about 55, the highest the temp. got was 190. Looks like (fingers crossed) that overheating is NOT going to be a problem. Thanks again for your info. and suggestions.

[pontiacphil]

Well, Summer is here in Tn. as it was 91 degrees today and my new 400 is running hot! 200 to 205 on hwy. at 55mph and 220 to 230 after 5 min. of idling. Installed new Hayden clutch fan #2797 & Hayden 18 in. fan blade #220618 and that didn't help. Shroud fits good. Carb. doesn't appear too lean and timing is 10 degrees at idle with total of 37 at 3,500 rpm. Flow Cool water pump was tweaked. New recore in my factory 17.5 inch Harrison. What to do now?
I did notice when assembling the motor that the factory 8-bolt aluminum timing cover was "eroded" a little on the inside ports area. Could this cause a problem? Plates were okay.
The reason for the recore last Fall was that I let the engine idle for about 10 minutes in 80 degree weather, walked away from it, came back and temp. gauge showed 230 when suddenly-----Ka-boom. Loud explosion under hood. The Harrison 4-core radiator had split the seam along the edges of the top tank. Themostat was NOT stuck. New core time.
Block was dipped & hot tanked prior to the total rebuild this Winter. Rebuild has 150 miles on it now. Proper cam break-in done. Fresh oil after 30 min. run time. 100 miles on 15w-40 Rotella. Changed oil at 100 miles with Rotella T synthetic 5w-40 and some GM EOS.
What would cause this bitc# to run this hot? Would a Rodney Red solve my overheating problem? A new radiator appears to my only possible recourse at this point. Anybody got any better ideas or possible solutions? Thanx.

[67ramair4]

Just curious, are you using an external tranny cooler??

[pontiacphil]

No, I'm not running an external tranny cooler. I did have the stock Turbo-Hydramatic 400 totally rebuilt and filled it with Mobil 1 synthetic ATF. I just keep thinking, and hoping, that an aluminum aftermarket radiator would do a better job than the factory 4-core Harrison radiator. Just hate to risk spending big $ for one and it not solve my problem. I wonder if Rodney Red, Griffin, Be Kool, etc. have any type of guarantee or warranty that their radiator will lower your temps. or your money back? That would be nice. I'm really at the point of not knowing what else to try other than the aluminum radiator route. I'm open for suggestions!

[70GS455]

Original OEM Harrison 4-rows had 40 rows of 1/2" tubes, 4 tubes per row. That's a total of 160 tubes.

Your re-core (with a standard core, not a high-efficiency one) will have 29 rows of 1/2" tubes, 4 tubes per row. That's 116 total tubes.

An OEM Harrison 3-row has 120 total 1/2" tubes.

Your standard recore has less capacity than an OEM 3-row.

[pontiacphil]

Do you, or anyone else, know the Rodney Red compares to the factory Harrison as far as the number of tubes, size, etc.? I went to their website but didn't find specifics such as this listed. Is Rodney Red the best aftermarket aluminum radiator available or are there others that are as good or better? I just don't want to have do any fabrication to make it fit and seems like the Rodney Red is an easy "drop-in", no necessary fabrication, project. Is that a correct assumption? I'd like to hear from some Rodney Red users to see how they like theirs and if it really helped lower their temps.

[george kujanski]

Another thing to check is the gauge; is it accurate? Granted it shows an increase of 20 -30 degrees when idling but, if the gauge was reading high, that would put you into a nicer temp range.

george

[pontiacphil]

George, I wish it were the gauges! I have now tried 3 different temp. gauges, 2 mechanical and 1 electric. All show about the same figures. You have helped me on a couple issues before George and I repect your mechanical talents. I have rethought every step of this total rebuild trying to find a weak link somewhere. One thing I do recall is that my 8-bolt, aluminum, timing chain cover did have some erosion (sort of worn a little thin) on the 2 water port areas of this cover that match up to the ports in the block. Could this worn thin area possibly cause overheating? Since the water pump, fan, coolant, shroud, etc. have all been replaced, the radiator is about the last item left for me to focus on. I did have the Harrison 4-core radiator "recored" but GS455 says my "recore" probably is equivalent to less than a 3-core as the replacement core has much less coolant tubes. George, do you think an aftermarket aluminum radiator should be my next step in an effort to solve my overheating problem? If so, is Rodney Red the best approach or are there others that you would recommend? It's no fun to have to keep an eye on the temp. gauge the whole time you're driving. My biggest fear is spending $500 to $600 and it not solve the problem. If it would stop the overheating it would be money well spent. I look forward to hearing any suggestions or recommendations that you might have. Thanx!

[mike nixon]

out of curiosity, was the block checked for core shift before the overbore? it's not as prominent on 400's but i've seen a couple of times.

i'd try richening the fuel mixture up and see if that helps you. i'm not saying it'll fix your problem but it may help it.

also verify the ignition timing, not only at the base setting but also thru the advance curve. i've seen faulty advance mechanisms cause problems similar to yours.

also run the trans fluid thru an external cooler and then back thru the radiator before returning it to the trans. verify your trans temp and make sure it's not contributing to the problem with abnormally high temps. you may want to try rerouting the trans lines if they run close to the exhaust system.

fan placement also has an effect on cooling, you want the blades slightly over 1/2 way into the shroud, and as mentioned above, the shroud sealed so it's drawing air thru the radiator. use a fan with the full size blades so it pulls [ not pushes] the most air possible. if you go to an electric unit be sure to mount it on the inside of the engine comp so it doesn't block airflow.

in my opinion, the aluminum radiators are a last resort and are used as a band aid by many to cover up the real issues affecting their engine's temp issues. in a few instances they're a neccessity [mainly race], but in my experience the vast majority of street cars don't need them.

i've got a 65 gto with a 68 350, similar compression, mild cam, th 400, external cooler, a/c shroud and fan, 3:90 gears. before i tore it down for resto work i never saw the temp on it over 215 deg. the car was driven daily from spring thru fall.

if you've done all of the above then it may be time to upgrade the radiator but it never hurts to go over the basics again.

btw george gives sound advice,

mike nixon

[70GS455]

Do you, or anyone else, know the Rodney Red compares to the factory Harrison as far as the number of tubes, size, etc.?

RR has 43 rows of 1" tubes, 2 tubes per row. Thats 86 total tubes. Multiply that by the tube depth and you get 86 tube-inches, compare that with 58 tube-inches of your recore.

Some work was posted here from a few years ago:

http://forums.maxperformanceinc.com/...hlight=roundup

[pontiacphil]

I did not specifically ask the machine shop to check for "bore shift" as I am not familiar with that terminology. The machine shop I used is very competent, has a good reputation, and about 75% of their business is race motors, primarily Chevrolets. I dropped the block off with them and told to check everything out and then do the necessary machine work. I just can't speak as to whether it was checked for bore shift.
The timing and distributor has been checked and everything as it should be. Carb. and plugs show neither too rich nor lean.
Your question about the tranny lines close to exhaust opened up a new area of a possible problem. I replaced the factory exhaust manifolds with a set of Ram Air Performance HO exhaust manifolds. Yes, on the passenger side, where the factory automatic transmission lines are located, there is very little clearance between one of the lines and the exhaust manifold. Maybe one-quarter to three-eighths inch clearance. Could this cause my over heating problem? You opened my eyes to this potential problem area and now I'm wondering if this small matter could cause such high water temps. I don't think I can move or bend the lines to get them farther away from the manifold and may have to run new lines. Along this line of thought, would a transmission cooler be of benefit in trying to get my temps. down? If so, what is a good brand and model tranny cooler to use on a 67' GTO?
I agree that an aluminum radiator normally isn't necessary on my type motor. However, do you think a Rodney Red would get my temps. down into the 190 to 200 range? Thanks for yours, and everyone else's, input. I'm still open for suggestions as to what I need to do to resolve my overheating problems.

[70GS455]

Advance Auto sells an aluminum one with plastic tanks, $345:

http://www.partsamerica.com/ProductD...artnumber=9641

Doesn't look stock but is cheaper.

There are other universal-type all-aluminun ones for under $200 from Jegs, Summit, Northern, etc.

[mike nixon]

ok i'll type this a second time as the forum ate it. pmo!

core shift is what happens when the casting shifts at the foundry as the block is being poured. it leaves one part of the cylinder wall thinner than the rest causing heat transfer issues [hot spots].

any heat you can eliminate in a stacked headlight gto is a good thing. these cars had some issues when you could buy good fuel let alone the garbage we're forced to buy these days. at least you're not fight comp ratio issues also.

yes i've seen exhaust significantly increase trans temps which are then passed on to the cooling system.

i should have stated re-run the lines instead of move them, my bad.

i usually also increase the tubing size from 5/16 to 3/8 id if it's not been done already , including the fittings that screw into the trans. the larger lines will provide more volume and some additional cooling. try to find a cooler with the the same size tubing and the largest surface area that will fit in the space provided. i'd ask what a reputable local trans shop uses as far as brand name.

i've been using units that i aquired several years ago thru a source i had at the dealership i worked at when i was doing parts. they weren't automotive specific applications and came in plain boxes so i don't know the brand name. my 65 got the last one i had.

when re-running the lines keep them as far from the exhaust as possible. i like to see a couple of inches clearance if possible.

i also like to fab up brackets with at least and inch clearance in front of the radiator/ condensor so that the heat has a chance to dissapate a bit before crossing the radiator. this also reduces that chance of the cooler rubbing holes in the radiator if the cheesy zip ties that most mfgs send losen up. i use rubber in the mounts to minimize vibration / stress to the cooler.

run the trans fluid thru the external cooler, then back thru the radiator to maintain enough heat to satisfy the minimum heat reqiurements of the trans. this will extend fluid and trans life.

the radiator with the plastic tanks mentioned by 70gs455 will leak in time, that's guaranteed. the heat differential cause by the t/stat opening up will crack the plastic tank eventually.

if you're going to spend the money on an aluminum radiator buy one with aluminum tanks and minimal use of epoxy.

as mentioned above,cooling efficiency is affected by tube size / number of fins per inch on the tubes. generally the more the better unless it's a high dirt enviroment,which i assume is not the case here.

i have never installed a r/r radiator. i have installed a few of the generic summit units which required minor [in my opinion] modifications to the mounts to fit. they did decrease coolant temps.

if you're looking for a bolt-in unit spend the money.

i just hate to see someone use a bandaid fix instead of repairing the cause of the problem which may, in time, cause other issues that are generally more expensive to repair.

mike

[bobbyj1]

I have a 67 GTO with a Rodney Red NON A/C radiator and, at the moment, NO fan shroud, I also have the factory fan and a hayden fan clutch. The temps in all ranges were reduced by using this radiator and making the much mentioned impeller mods. At speed, even when it is over 100 degrees here in Illinois, my car never goes over 200. If it is remotely cool outside it barely goes over 180. However, on a hot day my cars temp WILL increase if left to idle. I am currenlty looking to find the right fan spacer so that I can install my new shroud and see if that helps the "idle creep". The other thing I noticed when I switched to the Rodney Red was that the temp "recovers" much faster than it did before. In other words after the temp goes up a little while idling, it takes very little driving to get it the temp to come back down.