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Re: vacuum advance? yes or no.. [Re: RapidRobert] #2659171
05/25/19 07:41 PM
05/25/19 07:41 PM
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middle Tennessee
mopower440 Offline OP
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Didnt mess with it much today but i did hook the vacuum up to the rear port of the thermoquad. I sure dont like the way it sounded or acted! The lumpy idle from the fairly large cam smoothed out to sound like it was a stock cam. Also, when sitting still in drive with my foot on the brake and stomping it really quick with the brake on then letting off, when i drops back to idle it tries to quit, where as WITHOUT the vacuum hooked up, it drops right back down smooth and steady! With the vacuum hooked up it idles at around 28 degrees BTDC. Thats about all i did today just out of curiosity..didnt have much time to do any other stuff with it..

Re: vacuum advance? yes or no.. [Re: mopower440] #2659196
05/25/19 08:48 PM
05/25/19 08:48 PM
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Lincoln Nebraska
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RapidRobert Offline
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Stay with it, we ain't going anywhere. We love the toughies!


live every 24 hour block of time like it's your last day on earth
Re: vacuum advance? yes or no.. [Re: RapidRobert] #2659314
05/26/19 10:29 AM
05/26/19 10:29 AM
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moparx Offline
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if i'm not mistaken, the rear port on the T-quad is manifold [full time] vacuum. try one of the front ports that is ported vacuum [no vacuum at idle].
having full time vacuum at idle will advance the can, making it idle as if it were going down the road.
beer

Re: vacuum advance? yes or no.. [Re: moparx] #2659343
05/26/19 12:36 PM
05/26/19 12:36 PM
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mopower440 Offline OP
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Originally Posted by moparx
if i'm not mistaken, the rear port on the T-quad is manifold [full time] vacuum. try one of the front ports that is ported vacuum [no vacuum at idle].
having full time vacuum at idle will advance the can, making it idle as if it were going down the road.
beer


ah, ok..i thought it was supposed to be vacuum advanced at idle also..my mistake..That explains why it acted crappywhen doing the brake torque test..Thanks!

Re: vacuum advance? yes or no.. [Re: mopower440] #2659431
05/26/19 06:49 PM
05/26/19 06:49 PM
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Originally Posted by mopower440
What i have is a 1972 dart swinger with a .030 over, cast crank 440. It has the TRW 2355 six pack pistons with compression height of 2.062. Open chamber stock 452 heads. Compression ratio is right at 9.4:1. It has the mopar performance 284/484 cam installed 4 degrees advanced. Stock intake and a built thermoquad. 1 7/8 hooker fenderwell headers. I have the distributor dialed in at 18 degrees initial and 32 total. I have not been running the vacuum advance..but should i be? I didnt think cammed up engines were supposed to run the vacuum advance but been hearing conflicting things about it..

Whether or not your motor wants vacuum advance will depend on the compression ratio, quality of the gas, the shape of the combustion chamber, and a whole bunch of other variables.Generally speaking, the sooner you can ignite the fuel air mixture and not cause detonation, the more efficient the motor will be and the more power it will make. Vacuum advance really becomes advantageous at crusing speeds, steady state running at highway speeds where additional advance over mechanical advance amounts can gain more fuel economy. Learning how to tune your advance curve for your motor takes time. It sounds like you are 1/2 way there, with learning how to limit total mechanical advance and changing springs and such, and if you can grasp the concepts around tuning mechanical advance you can grasp tuning vacuum advance. Whether your engine wants or likes it can only be determined by trial and error, and a lot of testing.

This is separate to your vacuum advance questions but I need to ask - Lumpy cams and T Quads do not mix well in a stock configuration. I have to ask how the idle quality is. The metering rod set up in a TQ is controlled by engine vacuum, and if you do not have sufficient at idle to pull the metering rod piston down against the spring, the metering rods will dance up and down, doing a real number on the idle mixture, richening and leaning with every vacuum pulse. This can happen in a Holley too, when the vacuum is lower than the power valve setting, allowing it to open at idle and causing the car to run real rich. The solution in a Holley is to put in a power valve with a lower vacuum opening setting - on a TQ the solution is to clip 1/2 a coil at a time off the power piston spring and reinstall it and watch it at idle, stop clipping coils when the vacuum can keep the rods down at idle.. YMMV...

Re: vacuum advance? yes or no.. [Re: Sixpak] #2659439
05/26/19 07:03 PM
05/26/19 07:03 PM
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middle Tennessee
mopower440 Offline OP
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Originally Posted by Sixpak
Originally Posted by mopower440
What i have is a 1972 dart swinger with a .030 over, cast crank 440. It has the TRW 2355 six pack pistons with compression height of 2.062. Open chamber stock 452 heads. Compression ratio is right at 9.4:1. It has the mopar performance 284/484 cam installed 4 degrees advanced. Stock intake and a built thermoquad. 1 7/8 hooker fenderwell headers. I have the distributor dialed in at 18 degrees initial and 32 total. I have not been running the vacuum advance..but should i be? I didnt think cammed up engines were supposed to run the vacuum advance but been hearing conflicting things about it..

Whether or not your motor wants vacuum advance will depend on the compression ratio, quality of the gas, the shape of the combustion chamber, and a whole bunch of other variables.Generally speaking, the sooner you can ignite the fuel air mixture and not cause detonation, the more efficient the motor will be and the more power it will make. Vacuum advance really becomes advantageous at crusing speeds, steady state running at highway speeds where additional advance over mechanical advance amounts can gain more fuel economy. Learning how to tune your advance curve for your motor takes time. It sounds like you are 1/2 way there, with learning how to limit total mechanical advance and changing springs and such, and if you can grasp the concepts around tuning mechanical advance you can grasp tuning vacuum advance. Whether your engine wants or likes it can only be determined by trial and error, and a lot of testing.

This is separate to your vacuum advance questions but I need to ask - Lumpy cams and T Quads do not mix well in a stock configuration. I have to ask how the idle quality is. The metering rod set up in a TQ is controlled by engine vacuum, and if you do not have sufficient at idle to pull the metering rod piston down against the spring, the metering rods will dance up and down, doing a real number on the idle mixture, richening and leaning with every vacuum pulse. This can happen in a Holley too, when the vacuum is lower than the power valve setting, allowing it to open at idle and causing the car to run real rich. The solution in a Holley is to put in a power valve with a lower vacuum opening setting - on a TQ the solution is to clip 1/2 a coil at a time off the power piston spring and reinstall it and watch it at idle, stop clipping coils when the vacuum can keep the rods down at idle.. YMMV...



yes, its been clipped and idles great! If you remember demon sizzler that used to be here that built race thermoquads, he taught me a lot about them. I have this one tuned very good and love it! I have a 750 holley i want to try out but i know NOTHING about them..Not how to build them or tune them, so..The only reason i want to try it out is because the intake i want to get wont accept a spread bore thermoquad without an adaptor and it will be too tall to fit under my hood with the adapter.

Re: vacuum advance? yes or no.. [Re: mopower440] #2659570
05/27/19 09:07 AM
05/27/19 09:07 AM
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north of coder
moparx Offline
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could you use the small [3/4" thick] adapter and a drop base aircleaner ? i have that setup on my charger with the stock, flat hood.
beer

Re: vacuum advance? yes or no.. [Re: moparx] #2659578
05/27/19 09:39 AM
05/27/19 09:39 AM
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middle Tennessee
mopower440 Offline OP
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Originally Posted by moparx
could you use the small [3/4" thick] adapter and a drop base aircleaner ? i have that setup on my charger with the stock, flat hood.
beer


I didn't know they had a 3/4 adapter! That possibly could work..? Its a 440 in a dart, so..I really want a performer RPM intake for it with my thermoquad.

Re: vacuum advance? yes or no.. [Re: mopower440] #2659589
05/27/19 09:52 AM
05/27/19 09:52 AM
Joined: Sep 2003
Posts: 20,536
north of coder
moparx Offline
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i have seen those 3/4" adapters in cast, as well as "billet". also, i "think" i remember seeing a 1/2 or 5/8" cast [kinda chintzy] adapter that needed a little "tuneup" to clear the secondary throttle blades.
another thing you may consider, would be to space your K member from the front rails like the 68 hemi darts. those spacers were what, 3/4 or 1" ? shruggy that would give you extra room under your hood for sure, and would not be hard to fab up those spacers if a guy knew what the dimensions were.
beer

Re: vacuum advance? yes or no.. [Re: moparx] #2659655
05/27/19 01:17 PM
05/27/19 01:17 PM
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middle Tennessee
mopower440 Offline OP
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Originally Posted by moparx
i have seen those 3/4" adapters in cast, as well as "billet". also, i "think" i remember seeing a 1/2 or 5/8" cast [kinda chintzy] adapter that needed a little "tuneup" to clear the secondary throttle blades.
another thing you may consider, would be to space your K member from the front rails like the 68 hemi darts. those spacers were what, 3/4 or 1" ? shruggy that would give you extra room under your hood for sure, and would not be hard to fab up those spacers if a guy knew what the dimensions were.
beer


Put spacers between the frame rail and cross member at the front? it wont hurt anything with the torsion bars or anything?

Re: vacuum advance? yes or no.. [Re: mopower440] #2659687
05/27/19 04:05 PM
05/27/19 04:05 PM
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Lincoln Nebraska
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RapidRobert Offline
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^^^ that's what I was wondering, how much play to you have there. I guess that "hole/tube" they could be relocated higher in the K.


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Re: vacuum advance? yes or no.. [Re: RapidRobert] #2659903
05/28/19 08:51 AM
05/28/19 08:51 AM
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north of coder
moparx Offline
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must not have screwed anything up, because it was done to all of those. of course those were drag cars, so i don't know how they handled.
i need to google them about those spacers, or maybe someone familiar with those cars will chime in ?
beer

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