# Manifold Vacuum Advance Source?



## NoGoat (Jul 21, 2021)

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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## O52 (Jan 27, 2019)

Yes you can.


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## NoGoat (Jul 21, 2021)

O52 said:


> Yes you can.


Well all right! Thank you for the response. Fingers crossed this keeps me cool at idle.


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## Lemans guy (Oct 14, 2014)

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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## NoGoat (Jul 21, 2021)

Lemans guy said:


> 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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## NoGoat (Jul 21, 2021)

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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## Lemans guy (Oct 14, 2014)

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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## NoGoat (Jul 21, 2021)

Lemans guy said:


> 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?





Lemans guy said:


> 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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## Lemans guy (Oct 14, 2014)

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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## Lemans guy (Oct 14, 2014)

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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## Lemans guy (Oct 14, 2014)

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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## NoGoat (Jul 21, 2021)

Lemans guy said:


> 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.


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## AZTempest (Jun 11, 2019)

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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## Lemans guy (Oct 14, 2014)

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.






Ecatalog







www.haydenauto.com





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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## Lemans guy (Oct 14, 2014)

Not sure that Hayden page loaded right, but they make a clutch with a taller neck than stock.


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## NoGoat (Jul 21, 2021)

Lemans guy said:


> 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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## Lemans guy (Oct 14, 2014)

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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## Baaad65 (Aug 29, 2019)

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.


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## Lemans guy (Oct 14, 2014)

Very innovative! The bottom line is it cools…..how you get there can be many ways!


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## NoGoat (Jul 21, 2021)

Baaad65 said:


> 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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## NoGoat (Jul 21, 2021)

Small update. Turns out the vacuum advance was already on manifold vacuum, hence the lack of change when I moved it to another manifold source. So my Q-jet has no ported vac sources. Strange. Checked water flow after the t-stat opened, and it was very strong at idle. Now to work on that shroud and fan setup. More to come…


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## Baaad65 (Aug 29, 2019)

Thanks...the rest of the story.


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## Lemans guy (Oct 14, 2014)

Looks Great!,….I can see that ME Wagner dual flow PCV in the valley pan, smart move!


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## NoGoat (Jul 21, 2021)

Lemans guy said:


> 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.


So I'm looking at the Hayden 2747 HEAVY


















Duty fan clutch, and Derale 17118 18" Heavy Duty fan blade. Do you approve? There is a Hayden 2797 SEVERE Duty also.


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## Lemans guy (Oct 14, 2014)

Yes those are very good. Match the bolt patterns…with the WP, Fan, and Clutch. Those are the tall clutches which gives you some more reach.Hayden also matches their clutch with the fan pitch, so you might red derailed “pitch” and see if that matches. I think the Heavy Duty specs should be good.

note that some later 60’s Pontiac’s nd firebirds hd some deeper shrouds, and the factory shrouds are square where they meet the radiator, so pull air from the whole surface.

check the Ames catalog for shrouds and measure, you can also cutdown shrouds and check ames for baffling, talk to them they are very helpful.

you are on it now!


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## NoGoat (Jul 21, 2021)

Lemans guy said:


> Yes those are very good. Match the bolt patterns…with the WP, Fan, and Clutch. Those are the tall clutches which gives you some more reach.Hayden also matches their clutch with the fan pitch, so you might red derailed “pitch” and see if that matches. I think the Heavy Duty specs should be good.
> 
> note that some later 60’s Pontiac’s nd firebirds hd some deeper shrouds, and the factory shrouds are square where they meet the radiator, so pull air from the whole surface.
> 
> ...


The fan blade pitch is 27*. Is that pitchy enough?


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## Lemans guy (Oct 14, 2014)

Just make sure it matches the clutch….they recommend a pitch for the clutch


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## Lemans guy (Oct 14, 2014)

__





FAQ - Fan Clutches







www.haydenauto.com





Note the pitch here you made need the severe duty.
Make sure the bolt holes are right or change to another fam


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## michaelfind (Dec 14, 2018)

I think I got their severe duty and I'm happy with what it does for me in Texas summer heat!


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## AZTempest (Jun 11, 2019)

NoGoat said:


> ................... So my Q-jet has no ported vac sources. Strange......................


 I have a 69 Qjet from a Chevy according to the numbers. It only has one port and it's manifold. That's my reason for using the intake for vacuum.


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## NoGoat (Jul 21, 2021)

Baaad65 said:


> Thanks...the rest of the story.
> View attachment 144370
> View attachment 144371
> View attachment 144372
> View attachment 144373


What do you use on your exhaust manifolds? They look great.


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## Baaad65 (Aug 29, 2019)

I sandblasted them and used KBS extreme temp primer then KBS XTC paint and baked them on the grill, I had samples sent to pick the color.


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## NoGoat (Jul 21, 2021)

PLOT TWIST!! My vacuum advance diaphragm is shot. No wonder nothing changed when I pulled the line and then put it back. No idle change, no timing change. This could be the ticket to my hot at idle problem. Ordered replacement, fingers crossed. More to come soon.


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## NoGoat (Jul 21, 2021)

*SOLVED*!!! Replaced the 17” fan (2” pitch) and poor fitting shroud with an 18” fan (2 1/2” pitch) and sealing up the fan shroud has me running 190* at idle all day long. Thanks for all the advice. Having a functional vacuum advance helped smooth things out, but no help with cooling.
View attachment 144595


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