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#21
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I agree there are other pontiac owners with cooling issues... but at 75° it should not be overheating at idle or when moving, especially with an aluminum radiator..
Ive read the 1st gen firebirds dont have ideal air flow, do you have the full shroud and fan is positioned right in the shroud? Are there other pieces that go around the core support ive read about? Ive also heard that electric fans can restrict air flow and cause cooling issues compared to just the stock fan. One member on here has a 700hp gto that said he tried electric fans & other combos of parts but the best was a stock fan & shroud. Just some suggestions & things to consider, hope you can figure it out. |
#22
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#23
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Just a quick question, do you have the small water pump pulley to overdrive the waterpump? Not only does that speed up coolant flow, and increases fan speed, it pressurizes the system after the water pump to help eliminate steam pockets in the upper recesses of the water jackets. It was a HD cooling, as well as an A/C factory change.
And one other option is to do the 421 modification that opens a blind hole in the cylinder heads to improve water circulation. Done by the factory back in the mid 60s to factory 421 engines to help with steam pockets. The factory hole in most engines was not drilled when the blocks were machined, but drilling it out helps aleviate heat buildup. If you lay a head gasket on the block, and head, the hole is in the gasket, but never drilled by Pontiac. Of course this isn't an easy modification to make, simply because it requires engine disassembly to execute. |
#24
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#25
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#26
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His father started the radiator shop, and he was the second generation owner. My father also preceeded me, owning and operating his own auto repair garage, and our fathers knew each other very well. The material the fans are made from is a fiber reinforced injection molded piece, so they are strong, but a little more forgiving in a crash when they get in contact with the radiator, such as what frequently happens in short track racing. The blades have a tendency to break, rather than saw a hole in the radiator core, like a metal fan does. You'll never probably test that property, but I had occasion to a few times. You could still repair the tubes with a composite fan, whereas a metal fan would completely trash the radiator. The blades also tend to flatten out slightly at speed, but when coming back to idle they go back to the nearly 90 degree pitch and pull a huge amount of air at low speeds, and idle. Hopefully this, along with overdriving the waterpump with a smaller A/C style pulley, and the fan will get you where you'd like to be as far as engine temperature, when the ambient temp, and humidity are on the high end. |
#27
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So here's where I ended up with my fan situation. To summarize, I have been trying to find a fan that works better than my stock 5-blade flex and here is a list from best to worse:
1. Derale 6-blade flex 2. Stock 5-blade flex 3. Flexalite 6-blade flex 4. Nylon 6-blade flex 5. Pontiac 6-blade clutch fan 6. 428 Pontiac clutch fan So the Derale is the winner and it's what I will use. |
#28
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Idle timing is critical to keep idle temps down. You need a minimum of 12 degrees initial, 14-16 is better, and 8 vacuum helps when on top of that (vacuum can on manifold source, not ported). Obviously, you need to curve the distributor accordingly to control total timing.
Look at the service manual on how to set initial timing for cars before about 1970, they tell you to remove the vacuum hose to distributor and cap it off. What happens to the initial timing when you plug the hose back in? Yeah. As a loose example, newer cars run 22-26 idle timing. Or more. * The 5 blade (and 6 blade) OE clutch fan with shroud and a good clutch and AC pulleys should cool even the hardest to keep cool cars/engines. .
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. 1970 GTO Judge Tribute Pro-Tour Project 535 IA2 http://forums.maxperformanceinc.com/...d.php?t=760624 1971 Trans Am 463, 315cfm E-head Sniper XFlow EFI, TKO600 extreme, 9", GW suspension, Baer brakes, pro tour car https://forums.maxperformanceinc.com...ght=procharger Theme Song: http://www.youtube.com/watch?v=7zKAS...ature=youtu.be |
The Following User Says Thank You to HWYSTR455 For This Useful Post: | ||
#29
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. 1970 GTO Judge Tribute Pro-Tour Project 535 IA2 http://forums.maxperformanceinc.com/...d.php?t=760624 1971 Trans Am 463, 315cfm E-head Sniper XFlow EFI, TKO600 extreme, 9", GW suspension, Baer brakes, pro tour car https://forums.maxperformanceinc.com...ght=procharger Theme Song: http://www.youtube.com/watch?v=7zKAS...ature=youtu.be |
#30
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IE; I tried a aluminum flex fan to replace stock steel and fan clutch. It sounded like a blower, and sucked a bunch of HP to run. Went back to stock setup. Working in a speed shop you'd be amazed how often people would waste money on upgrades [cooling]that don't work because they were trying to cover up another existing problem. Timing,lean jetting etc.
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https://www.flickr.com/photos/197745168@N07/ "There's nothing more unsatisfying than watching an electric car go down the dragstrip." |
#31
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Resurrecting this as I still need to address it...what spacer are you running with the Derale fan?
It looks like the previous owner put in a two inch spacer but I read that the fan is supposed to stick out of the shroud (facing the injun) about a half inch - this does not. Should I switch to a one inch spacer? Thanks in advance. https://1drv.ms/i/s!Au-5lZp5WKEl5ehM...3rCog?e=9aYNvV
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Esquire '74 T/A 455 Y-code SD clone previously on Dawson's Creek: '74 T/A 400 '81 AMC SX/4 '69 FB 350 |
#32
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I hear the half-in, half out thing a lot but I don't believe it. Look at a fanjet engine...there is a cowling all around the fan. I therefore believe that should also be the case for our engine fan and shroud. in my case, ('67 GTO) I can't do it because the fan would be too close to the radiator, so it actually is about half-in, half out...one of these days i can experiment by addinng a shroud extension, but that won't be soon.
Works ok, tho. George
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"...out to my ol'55, I pulled away slowly, feeling so holy, god knows i was feeling alive"....written by Tom Wait from the Eagles' Live From The Forum |
#33
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Update:
Ok, after installing the derale fan it sticks out about a half inch with the spacer I have so that's all good... Finally got some seat time in 90F weather and SHE WAS COOL AS CUCUMBER 🥒 for the first time....ever! Thanks again @sirrotica for your sage advice as the clutch fan from Franks was going to be $175US and this was fifty bucks...no difference in noise afaict neither The true test will be cruise nite this Sunday but the early results are looking great.
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Esquire '74 T/A 455 Y-code SD clone previously on Dawson's Creek: '74 T/A 400 '81 AMC SX/4 '69 FB 350 |
#34
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Glad I could help you out, making the air move through the radiator as the composite fan does makes a lot of difference, especially at low speeds.
The radiator shop owner that first made me aware of the composite fans, actually used a lit cigarette and held it in front of the radiator as the car idled to demonstrate how much air those fans pull at idle. Seeing the demonstration made me a believer. I've been using those fans since the late 70s on street, and oval track cars with great success............ |
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