[pontiacphil]

I'm at the point now of trying just about anything if it will help. The Summit catalog lists several 18 in. Flex Fans by Flex-a-lite and wondered which specific model you used. Is it the Flx-1818? Did you use it with the shroud or without? What brand water pump are you using?
A couple of posts here recommended the Derale #17018, 18 in. flex fan, but if the Flex-a-lite worked for you I'm willing to give it a try. Thanks.

[Tpower66]

Originally Posted by bobbyj1

I have been battling the idle problem since I got my car 3 years ago. Since my engine rebuild this past winter I have been expirementing with fan/shroud setups trying to find a combination that will solve this. I have a 67 GTO no/ac, with a Rodney Red Radiator. I have run without a shroud, with one, thermal fan clutch, non-thermal fan clutch. Yesterday I went with Rugrat's setup. I put a Flex-a-lite 18" 7 blade felx fan with a 2" spacer in and I was able to let my car idle in the garage for 15 minutes and the temp stayed around 190. Something I would never have been able to do before. I think you have to just keep trying different things until you hit on the one that works.

Bob

Where did you get your 7 blade flex fan. I don't know what Rugrat's setup is. Maybe you have a part number----Also where is the fan located in the shroud.----Thanks---WD

[Bill H]

This is the 18" 7 blade fan/ they also have a 17"

http://store.summitracing.com/partde...0&autoview=sku

[bobbyj1]

It is the Flex-a-lite FLX-1818 fan $44.95 in Summits Catalog. I have a 2" spacer that is putting my fan approx 1/2 in and 1/2 out or slightly more in than out. I am using a rebuilt stock water pump from Cardone, Partsamerica.com, that has a cast impeller and has had the divider plate clearance minimized. I am running a stock shroud that I got from Ames. I also have a 160 stat with 4 small holes drilled into it and a Rodney Red Radiator.

Let me know if you guys have any more questions!

Bob

[69*Goat]

Did you try the timing suggestion yet?

[kate`s67gto]

I have a Rodney Red with a 160* Mr Gasket stat, 11 bolt water pump cast impellor set at 1mm clearance to divider plate .Thank You George K . Steel fan shroud (not sealed) cadillac 18" fan, Hayden 2797 clutch , engine on second rebuild 60 over, run Sunoco 94 BIG$$$ for that. I can let that car sit all day at idol 750 rpms and the guage will not go over 175*. I have a infra red temp thermometer to take temps readings at different points on engine. i have no over heating issues at all at hiway rpms or idol . The engine is a 67 block WT code,auto trannsmission turbo 400 with 670 heads edelbrock rpm manifold edelbrock 1407 carb i use manifold vacum timing set at 10*.(stock HEI out of a 455 something) I use Ac r45s spark splugs gap set at 45thou, use mobil 1 15-50 oil with stp.Hopefully something in this will help your issue ?

[Tpower66]

Originally Posted by bobbyj1

It is the Flex-a-lite FLX-1818 fan $44.95 in Summits Catalog. I have a 2" spacer that is putting my fan approx 1/2 in and 1/2 out or slightly more in than out. I am using a rebuilt stock water pump from Cardone, Partsamerica.com, that has a cast impeller and has had the divider plate clearance minimized. I am running a stock shroud that I got from Ames. I also have a 160 stat with 4 small holes drilled into it and a Rodney Red Radiator.

Let me know if you guys have any more questions!

Bob

Do you run a clutch with it----does it bolt on without modifications---is it noisy---do spacers come with it.

[Bill H]

http://www.gtoalley.com/ttcool.html

When I said I screwed up my timing last week I was having one of my dumb A$$ days and set the initial timing with the vacuum advance connected, what a big mistake that was.

[Geoff]

pontiacphil,
Nowhere in your original post did I see 'vacuum advance' mentioned. Pretty sure '68 was the first year for Ported Vac Adv, so your '67 would have Manifold Vac Adv, MVA. If the stock vacuum advance can is connected, & connected to a manifold source as it should be for optimum cooling, performance & economy, then it may not be activating with that larger than stock cam. Bringing the rpm up to 1800 would increase vacuum enough to activate the vac adv, whether it was PVA or MVA, & would help bring down temps, as you found.
I would buy a Crane adjustable vac adv unit & connect to a manifold source, as Crane recommends. Then adjust the unit as per the instructions. It may not fix your overheating problem, but it could, & it will help. Good value for $25. You should also increase your initial timing to around 12 degrees & shorten the centrifugal curve to suit.

[bobbyj1]

I do NOT run a fan clutch with the Flex-a-lite fan. I drove the car extensively yesterday, 168 when cruising at 60mph, 178 when idling at lights. After driving for an hour car would idle in the garage at around 190 and steady. I do not find the noise to be any different from when I had the clutch fan installed.

[pontiacphil]

Geoff, I have tried both and the overheating stayed the same. I used the manifold by hooking into the small hole the factory used on a 68' intake just in the front rt. corner of the carb. Idle jumped up and I developed a flat spot or stumble when I gave it gas from idle to a faster speed. Overheating problem wasn't affected. I'm now running ported vacuum off the Quadrajet carb. It's so hot here in Tn., and guess that I'm too old, as the high temps. have kept me away from working on my car for a day or two. This Crower #60242 cam doesn't really seem radical enough to warrant using a vauum canister. I've got a 2,000 stall in the car and lack of vacuum sure isn't noticeable. I could be wrong however. I ordered a Cardone #58299 water pump form O'Reilley's
yesterday and plan to order a Mr. Gasket high flow 160 themostat, I'm running a 180 presently, and drill the 4 small holes that have been discussed here. I'm going to take off the new Hayden clutch fan & blade and go with a 18 in. flex fan with 2 inch spacer. I can't decide whether to order the Flex-A-Lite #1818 or the Derale #17018 as both get get comments here. I called Flex-A-Lite Tech. line and they weren't real optimistic about getting much more air flow at idle RPM's. Tried to call Derale but they didn't have a phone # and couldn't even E-mail them as the have a "spcecial" e-mail acct. that you have to register and sign up for. Too much of a pain to do. If anyone can help me with deciding between the 2 fans I'd like to hear your comments. Bobbyj1 has had such good luck with the Flex-a-Lite I'm swaying towards that one. Any other suggestions, tidbits, advice etc. will be sincerely appreciated.

[vidguy]

I have had a Flex Fan and spacer on my 67 GTO for 20 years and I have never noticed the noise... I guess:
I could be conditioned to it
The cam lope and exhaust more then drowns it out.
The Rhoades lifters distract me...

[455_regal]

if you have an airflow problem you shouldnt run a high flow stat, Ive been through this last month with my car, I ended up using a stock 160, keeps the water in the block longer, which takes more heat from the metal and stays in the radiator longer...cools more. my opinion at least. it worked for my car. just for safety, i mounted a cheap electric fan in front, i can turn it on if i ever get stuck in traffic. Some days i cruise and the gauge is at 160, I just did an hour cruise, bumper to bumper for about 4 miles, it never got over 190

[455_regal]

Ive seen where the trans cooler in the radiator was plugged a bit and the transmission was getting hot, over 260-280 mabye, heating the coolant

[pontiacphil]

At 5 pm today I pulled my GTO out of the garage and put it in the shade of the driveway. About 90 degree temp. Started it up, let it idle at 825 RPM for 6 minutes with a 20 inch box fan blowing through the grill. It hit 230 and I shut her down and let it cool down to 180.
Advanced my 7 degree at idle timing (plugged the vacuum advance off) and got it set at 12 degrees advance at idle. No box fan used. In 6 minutes it was back at 230 degrees. Everything in this motor is new or rebuilt. Hot tanked, dipped, cleaned by a very reputable machine shop. I'm at a loss as to what to do next. The 8-bolt timing cover was a bit pitted and corroded. Could this cause an overheating problem? The divider plates were in very good condition and I tweaked them to George's specs. for clearance. I can buy new stainless divider plates off E-Bay if anyone thinks that might help. I did get my Cordone #58299 water pump at O'Reilley's today ($24). Got a factory 160 thermostat and drilled the 4, three-sixteenths holes in the outer edge. I never got any responses here about which 18 in. flex fan, the Flex-A-Lite or the Derale is best so I think I will order the Flex-A-Lite from Summit with a 2-inch spacer and use my Ames shroud. along with the Rodney Red. If this doesn't solve my overheating I really don't know what else to do. Wish me luck. Any suggestions?

[70GS455]

"...The Derale heavy duty flex fan is a newly designed series that outperforms any clutch fan assembly and does not have the downsides of the old designs. It features full support blades, hardened metal centers and full rivot stainless steel blades (not aluminum or steel). They are good for over 8500rpms and will NOt fling blades and pull about 33% more air thru the system and use a fraction of the hp up top.

Fixed bladed fans can take up to 40hp+ to fling around and even 30ish with a clutch. The new technology Derale takes less than 7hp at full tilt because it gives up it's "biting" attitude at high rpms...."

One thing to consider, if you have enough room between the radiator and fan, and you can fit one, you might be able to put a slimline electric fan inside the shroud, between the rad and mechanical fan (my Dodge truck uses this setup). Spal or Derale make some 2" or 2.5" thick electrics that might help with the idle airflow issue.

[lust4speed]

After setting the initial timing to 12 degrees, did you go ahead and hook back up the vacuum advance? Try and set the timing by just listening to the engine RPM and don't worry about where it is actually at. Don't run it down the street, but I would really be interested to see if the heating problem is as bad if the engine gets to choose where it likes to idle.
Next, does the fan shroud match the fan diameter? an 18" fan in a shroud made for a 19.5" fan is just about like not having a shroud at all. Next check and make sure the shroud is not damaged. I had a chunk out of my A/C shroud that was only about 4" long and an inch thick, but the new shroud I put in for "looks" dropped 10 degrees off my running temp.

Somewhere you are generating way too much heat at idle - whether it is retarded timing, blocked water passages or even a stuck heat riser or some other problem. I had an engine that ran terribly hot. Finally traced it down to an HEI unit that the ground wire from the coil had broken, and it was seaking ground through the cap and firing plugs at odd times - you just don't know what you're going to find.

Also, while you could be at 9.48 compression, I come up with closer to 9.9 if you have taken much off the heads at all and had the block surfaced. It might be interesting to mix in a little race gas for a test and see if that helps the temperature. I would have the distributor redone to dial in an initial 14 degrees with a total of 34 degrees.

[slickman]

You stated you just had the engine rebuilt, is it a 455? I heard someplace that if you got too far with the boring (not sure if it was over .030 or .060) on a 455 you could have overheating problems. Can you expand on what was done with the over bore?

Originally Posted by pontiacphil

At 5 pm today I pulled my GTO out of the garage and put it in the shade of the driveway. About 90 degree temp. Started it up, let it idle at 825 RPM for 6 minutes with a 20 inch box fan blowing through the grill. It hit 230 and I shut her down and let it cool down to 180.
Advanced my 7 degree at idle timing (plugged the vacuum advance off) and got it set at 12 degrees advance at idle. No box fan used. In 6 minutes it was back at 230 degrees. Everything in this motor is new or rebuilt. Hot tanked, dipped, cleaned by a very reputable machine shop. I'm at a loss as to what to do next. The 8-bolt timing cover was a bit pitted and corroded. Could this cause an overheating problem? The divider plates were in very good condition and I tweaked them to George's specs. for clearance. I can buy new stainless divider plates off E-Bay if anyone thinks that might help. I did get my Cordone #58299 water pump at O'Reilley's today ($24). Got a factory 160 thermostat and drilled the 4, three-sixteenths holes in the outer edge. I never got any responses here about which 18 in. flex fan, the Flex-A-Lite or the Derale is best so I think I will order the Flex-A-Lite from Summit with a 2-inch spacer and use my Ames shroud. along with the Rodney Red. If this doesn't solve my overheating I really don't know what else to do. Wish me luck. Any suggestions?

[pontiacphil]

Had a reputable machine shop bore it 30 thousandeths over so it's probably about a 406 now. I'm sorry to say the new Rodney Red radiator did not solve my problem. Same temps. as my stock 4-core Harrison. I did replace the new Flow Kooler water pump with a Cardone and hammered the divider plate to such close tolerances that the impellers were just about dragging against the cover! Took off the new Hayden clutch fan and blade and replaced it with a 18 in. Flex-A-Lite fan using a 2 inch spacer like BobbyJ1 recommended. Removed the high flow, Mr. Gasket, 180 thermostat and put in a stock type 160 one with the 4 small holes drilled around the edges.Took Screamingchief's advice and used a VDV in my vacuum line after I went from port vacuum to manifold vacuum. Running 12 degrees at 825 rpm idle with a total of 38 degrees. After all this, the weather has dropped about 20 degrees here so I can't really compare apples to apples as to how much cooler it is running. I do think it has helped as it now runs about 170 at hwy. speeds and around 190 to 200 setting in my driveway. I have not let it idle for 15 to 20 minutes as I'm so gun shy, and tired of fighting this problem, that I just don't want to be disappointed if it should climb back up into the 220 to 230 range. Maybe I'll get over this and try an extended idle and hope for the best! Like I said, that's with an outside temp. of 70 degrees while back in the, Summer when it was running in the 220 to 230 range, it was 90 to 95 degrees. Everyone here has provided a lot of info. and suggestions which I am grateful for. I THINK my overheating may be solved by all of the things that I listed above. Seems that you just have to get the correct combinations of several parts and hope for the best. Sorry for such a long post but I just wanted to be specific in what all I had done to cure my problem. Thanx.

[Pontirag]

Its been said that overboring the later 455's can cause over heating. You stated that the Quadrajet appears to be set correct? Assume nothing. I had a small piece of teflon tape clog up a rebuilt carb. caused the engine to overheat and could not go over 55mph.

Check out your distributor for wear at the weight pivot points and check centrifugal weights for smooth operation. Rust, grease or other surface irregularities can cause the weights to stick. If they were rusty or dirty and you spritz them with WD-40. It may not be enought to loosen them up.

Have you checked the exuaste gas temperature or oil temp by any means. Evaluating these indicators will help locate the source of your heat. Are you using water? Detonation? Black smoke? what about power? is the car running strong? Gas mileage?

Really you must assume nothing. Even New parts can be defective