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Discussion Starter · #1 ·
Hey all,
Just joined the forum after years of learning from you all.
I have a 67 LeMans with a '77 400.
So here's my issue. I have the typical HOT idle issue. All good any other time. I'm going to switch from ported to manifold vacuum and see if that helps. My Q-Jet only has 3 vac ports. One 3/16th ported at front way at the top, the PCV at front base plate and the rear center base plate that has the brake booster and Auto trans lines. That's it.
Can I just add a 3/16 to the rear baseplate "T" that has the brake booster and trans connections?
Thank you
 

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Yes agree with 052!….you can later also get a Vacumn manifold from summit or JEGS about $45 and mount it on your firewall for additional ease of Vacumn ease of Vacumn routing.

The Vac canister pulls so little vac it is barely noticeable compared to the brake booster or PCV draws, your intake has plenty of vacumn
 

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Discussion Starter · #5 ·
Yes agree with 052!….you can later also get a Vacumn manifold from summit or JEGS about $45 and mount it on your firewall for additional ease of Vacumn ease of Vacumn routing.

The Vac canister pulls so little vac it is barely noticeable compared to the brake booster or PCV draws, your intake has plenty of vacumn
Thanks, good to hear.
Now after switching from ported to manifold, will I need to adjust the timing or carb again? I would think so, but really don't know.
 

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Discussion Starter · #6 ·
Well shoot. 76 degree day, driving around for 25mins never got above 185 moving and 195-200 even at long lights. Pulled into a parking lot, put in park and 5-7 min later 225 and still climbing.
 

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First thing to check when car is hot at idle MSD cool when driving is the thermostatic clutch fan or electric fan system. All clutch fans are not like. Some are no thermostatic and look similar but cool poorly.

also even the right ones wear out. In addition in must be shrouded properly nd half in nd half out of the shroud. Timing will not fix other bd coolant system problems, a bad fan clutch will still make it run hot.

when you are running hot at idle is the fan fully engaged? Pulling strong? Or weak and free wheeling?
 

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Discussion Starter · #8 ·
First thing to check when car is hot at idle MSD cool when driving is the thermostatic clutch fan or electric fan system. All clutch fans are not like. Some are no thermostatic and look similar but cool poorly.

also even the right ones wear out. In addition in must be shrouded properly nd half in nd half out of the shroud. Timing will not fix other bd coolant system problems, a bad fan clutch will still make it run hot.

when you are running hot at idle is the fan fully engaged? Pulling strong? Or weak and free wheeling?
First thing to check when car is hot at idle MSD cool when driving is the thermostatic clutch fan or electric fan system. All clutch fans are not like. Some are no thermostatic and look similar but cool poorly.

also even the right ones wear out. In addition in must be shrouded properly nd half in nd half out of the shroud. Timing will not fix other bd coolant system problems, a bad fan clutch will still make it run hot.

when you are running hot at idle is the fan fully engaged? Pulling strong? Or weak and free wheeling?
I currently run a 17” non-clutch fan. I have just put a Cold Case rad in. My previous 4 row copper rad and the Cold Case are 1” narrower than the shroud I got from Ames 10+ years ago. I admit I didn’t put the shroud back on for these test. I just didn’t see any difference with or without it on previous rad. Using paper test, there is a lot of suction through the rad. I will put the shroud back on and see. Another thought is the transmission fluid in the radiator. Would that be a major factor? I’ve been battling this for going on 3 decades now. Use to run 210 driving, so I’ve made improvements, now just the idling to solve.
 

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So you are running a flex fan?… some may great luck with they. Start with Pontiac engineers.

The hottest running cars were AC cars as the condenser dumps all that heat right in front of the radiator. So for those they had a big shroud and a seven bladed thermos tic clutch fan. The shroud must have all side baffling in place, even small gaps will hurt cooling.

at idle the fan must suck with great velocity to ensure proper cooling, and that shroud provides the needed funnel, so the pull is strong. The wheel well rubberized covers are needed as well and often taken out on cars where many engine changes are made.

in addition even a slight coating of rust in the system reduces cooling, rust blocks thermal transfer. We all fall for well I rebuilt that block 5 years ago, does not have many miles since, I know it is clean Yama, Yama.

see my thread a sticky on spring/summer cooling system flush. You might be surprised what comes out.
 

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I have a friend who swears when he put a transmission cooler on his 69 GTO and it changed his cooling dramatically. You might try getting a trans temp gauge and see if your trans fluid is somehow way too hot. Not sure if this will work but he says it did.

The Shroud and flush definitely, with “thermocure” as in my sticky. I Still like the heavy duty thermostatic clutch fan, though with a seven bladed fan, like the engineers designed.
 

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Back up to an earlier question. when switching from ported to manifold vac your base timing won’t change, but your idle timing will. Shoot the timing light with vac disconnected and plugged and then with it reconnected to full manifold vac. The additional timing is the vac advance.

Yes, recheck your carb idle setting, by adding vac advance to idle your RPM’s will show a slight increase because of the added timing you can then adjust carb accordingly
 

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Discussion Starter · #12 · (Edited)
I have a friend who swears when he put a transmission cooler on his 69 GTO and it changed his cooling dramatically. You might try getting a trans temp gauge and see if your trans fluid is somehow way too hot. Not sure if this will work but he says it did.

The Shroud and flush definitely, with “thermocure” as in my sticky. I Still like the heavy duty thermostatic clutch fan, though with a seven bladed fan, like the engineers designed.
Thanks for taking the time to help. Really appreciate it.
Here are some pics of my fan. Not a flex fan. Also see the shroud on my old rad, new aluminum rad is even a bit narrower. B63D45BA-4CA8-4C65-9E1F-09A6425B5901.jpeg 3097ED4D-D63B-4DAA-AF95-9A1A1B27809E.jpeg 189AADEA-2FDA-4D19-A039-D2D37BDFDA3B.jpeg 4FAC1411-FD9A-4F73-B97E-2676406887B5.jpeg 62AB9F97-5710-4527-980F-8F9ADD09D67C.jpeg
 

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I can't really add anything more than Lemans guys good advice. Definitely run the shroud. On my 67 Tempest it made a night a day difference in the hot southwest. I prefer manifold vacuum for advance as well. Along with the advice given don't be afraid to play around with your idle or even base timing if you want or need to get the settings your engine likes. Also, some intakes will have spots that you can tap into for a vacuum source. I have one located behind my carb in the old Offenhsuser intake I run.
 

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NoGoat, I would expect poor idle cooling for sure from that wide open set-up. The shroud also has separarate rubberized panels called baffled panels. Ames sells them nd they block off the gaps all around the shroud. They were stock. But can be easily modified to fit almost any space.

Also that fan bolted solidly on there is RPM dependent, When the engine runs fast so does the fan. At speed it is no real help and it puts a drag on the engine.

A thermostatically controlled clutch fan runs on temperature only, at speed, with free air flow and coolant flowing fast, it free wheels. Once the car slows down to idle, coolant flow and RPM’s reduce, but then the clutch kicks in because temps rise, and your fan then starts to pull hard.


Here is a Hayden clutch with a taller neck than original OEM one if you need the height to fit in the shroud. Don’t be afraid to engineer a different shroud from a different car.. bigger Pontiac even. Get the fan blades half in and half out of the shroud.

Radiator look pretty stout. Good luck, think like the original Pontiac engineers who designed these coolant systems, that will guide you!
 

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Discussion Starter · #16 ·
Not sure that Hayden page loaded right, but they make a clutch with a taller neck than stock.
Lemans guy, again, thanks for taking the time. Not just for me, but for all your input on this forum. Great to be able to access your wealth of knowledge. OK, I will get a clutch fan and start working on this or another shroud. Overall I've really improved the cooling in all other scenarios. Fun fact...30+ years ago when I swapped the 326 for this 400, the pulleys didn't line up so I put the 8 bolt water pump from the 326 on the 400. I just did the plate gap to impeller adjustment and that helped 5* in overall temps. I know the 11 bolt pumps are better / more efficient, but I don't think that or a high flow will correct this issue. Thoughts are appreciated. Again, I will work on getting the shroud and clutch fan set up and I'll report back. If I had one complaint about this and every other forum, very few get back and report out on final outcome.
 

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Thanks for the kind word NoGoat, but Remember what Al Capone said;

“You get more with a kind word and a gun,
…than with a kind word alone”!

I think you have a good plan, yes 11 bolt WP’s are better but an 8 bolt can do the job. I use an 11 Bolt Flowkooler pump.

Hayden makes a fan clutch that is about 3 inches tall, may help your spacing.

you will get it!
 

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I too have been battling hot running issues and these guys have helped immensely, I'm running a Butler 461 and they talked me into a vacuum advance which has helped, I've tried different fan clutches and spacers to get it closer but it was to much drag and my serpentine belt kept slipping so I ditched the mechanical for a 16" electric puller. Now I don't have a very good shroud which everyone tells me to put on but I'm managing the temp pretty good with the addition of two 13" pusher fans when I'm stuck in traffic, also have the 11 bolt Flow Kooler pump, drilled some holes in the 160 high flow stat like suggested here and running 70% water 30% antifreeze because I read several articles about how antifreeze is not good at transferring heat don't know how true that is also running some water wetter for what it's worth. So maybe if you don't have to have your car truly stock you can run some electric fans.
144363
144364
144365
 

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Discussion Starter · #20 ·
I too have been battling hot running issues and these guys have helped immensely, I'm running a Butler 461 and they talked me into a vacuum advance which has helped, I've tried different fan clutches and spacers to get it closer but it was to much drag and my serpentine belt kept slipping so I ditched the mechanical for a 16" electric puller. Now I don't have a very good shroud which everyone tells me to put on but I'm managing the temp pretty good with the addition of two 13" pusher fans when I'm stuck in traffic, also have the 11 bolt Flow Kooler pump, drilled some holes in the 160 high flow stat like suggested here and running 70% water 30% antifreeze because I read several articles about how antifreeze is not good at transferring heat don't know how true that is also running some water wetter for what it's worth. So maybe if you don't have to have your car truly stock you can run some electric fans. View attachment 144363 View attachment 144364 View attachment 144365
Very nice setup!
 
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