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Re: thermoquad VS. Holley 750 DP [Re: Performance Only] #1031724
07/14/11 01:33 AM
07/14/11 01:33 AM
Joined: Jul 2008
Posts: 26,197
Florida STAYcation
dOc - 3.0 ! Offline
still the village idiot
dOc - 3.0 !  Offline
still the village idiot

Joined: Jul 2008
Posts: 26,197
Florida STAYcation
Quote:



if ther A/F ratio is the same for either carb, can you please explain why one will get better mileage over the other? same amount of air, same amount of fuel.








BECAUSE the TQ does a BESTer job mixing air and fuel on the primary side than any other carb out there. Just-like EFI does a better job than any carb.

Re: thermoquad VS. Holley 750 DP [Re: dOc - 3.0 !] #1031725
07/14/11 07:15 AM
07/14/11 07:15 AM
Joined: Jan 2003
Posts: 6,329
nielsville, minn.
Q
quickd100 Offline
master
quickd100  Offline
master
Q

Joined: Jan 2003
Posts: 6,329
nielsville, minn.
Holley use a power valve, it's either on or off, there is no inbetween. A thermoquad uses vacuum controled spring loaded metering rods. This alone if tuned properly gives the mpg edge to the thermoquad. Dave

Re: thermoquad VS. Holley 750 DP [Re: DaytonaTurbo] #1031726
07/14/11 08:10 AM
07/14/11 08:10 AM
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck Offline
Not enough dumb comments...yet
Mr.Yuck  Offline
Not enough dumb comments...yet

Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Quote:

Quote:

Quote:

The TQ or QJ will still win over a squarebore carb, smaller primary bores get better mileage if the AFR is the same on both carbs. & you can make a 750dp get right at the same mileage as a 3310.




if ther A/F ratio is the same for either carb, can you please explain why one will get better mileage over the other? same amount of air, same amount of fuel.

the one thing i could never get used to on a spread bore carb is how much further you need to push the gas pedal in normal driving to get the same acceleration as a square bore carb.




The smaller venturis are supposed to be more responsive to small changes in vacuum/load during normal driving, so they should respond more precisely to fine changes in throttle position as you would encounter during daily driving. FWIW I always found spread bore carbs to be more responsive when driving around town than square bore carbs.




just here but since the TQ has much smaller primarys wouldn't that make the secondarys open faster? As mentioned before by me and others, a tuned carb is going to use the fuel/air it needs to push the car. What about a 6-pack? It runs off a small 2bbl most of the time.
Anybody got andy real world numbers?

Re: thermoquad VS. Holley 750 DP [Re: Performance Only] #1031727
07/14/11 09:53 AM
07/14/11 09:53 AM
Joined: Feb 2005
Posts: 5,221
Branson, Mo.
J
joedust451 Offline
super gas
joedust451  Offline
super gas
J

Joined: Feb 2005
Posts: 5,221
Branson, Mo.
Quote:

Quote:

The TQ or QJ will still win over a squarebore carb, smaller primary bores get better mileage if the AFR is the same on both carbs. & you can make a 750dp get right at the same mileage as a 3310.




if ther A/F ratio is the same for either carb, can you please explain why one will get better mileage over the other? same amount of air, same amount of fuel.

the one thing i could never get used to on a spread bore carb is how much further you need to push the gas pedal in normal driving to get the same acceleration as a square bore carb.




Its not really the same amount, i'm only talking on the primary side, Who drives around at WOT all the time, you have less air/fuel being drawn in on the smaller primary carb staying on the primaries, but yhou can still adjust the AFR to where you want it, now why wouldn't you think if the AFR was the same on both carbs, that the larger throttle bores would get the same mileage, The engine is able too pull in more air at the same throttle possition as the smaller primary carb,, lets say 1/4 on both carbs, so the larger throttle bodied carb lets the engine draw more air, more air needs more fuel, resalting in more consumption, its not a brain teaser.

But i do agree with you on how the larger primary carb feels better under moderate throttle (more responsive) then the smaller primary carb


75 Duster, 451 10.87 @ 123.58 NA 97 Z28 6sp., 12.01 @ 115 on a 100 shot 71 Swinger. 360 magnum. 12.58 @ 105 78 cutlass, 469 BBC. 12.70 @ 108 on street tires. http://www.youtube.com/watch?v=Z2kqNmMfheU
Re: thermoquad VS. Holley 750 DP [Re: joedust451] #1031728
07/14/11 10:41 AM
07/14/11 10:41 AM
Joined: Sep 2003
Posts: 1,465
Carson City, NV
B
babarracuda Offline OP
pro stock
babarracuda  Offline OP
pro stock
B

Joined: Sep 2003
Posts: 1,465
Carson City, NV
Thamks guys! I wantr to take some trips of 300-400 miles. The better gas mileage is important. Once I have the carb setup, I will need less gas. I havwe the money now, but may be tighter in a year or two. I hqave an Innovate A/F setup so I will know what my mix is. So far the DP is not good on gas. We'll see after I get it runnung with my new master cylinder, cam and power steering. Aging is not for sissies.

Re: thermoquad VS. Holley 750 DP [Re: Mr.Yuck] #1031729
07/14/11 11:13 AM
07/14/11 11:13 AM
Joined: Nov 2004
Posts: 2,825
Sk. Canada
RemCharger Offline
master
RemCharger  Offline
master

Joined: Nov 2004
Posts: 2,825
Sk. Canada
Quote:

Quote:

Quote:

Quote:

The TQ or QJ will still win over a squarebore carb, smaller primary bores get better mileage if the AFR is the same on both carbs. & you can make a 750dp get right at the same mileage as a 3310.




if ther A/F ratio is the same for either carb, can you please explain why one will get better mileage over the other? same amount of air, same amount of fuel.

the one thing i could never get used to on a spread bore carb is how much further you need to push the gas pedal in normal driving to get the same acceleration as a square bore carb.




The smaller venturis are supposed to be more responsive to small changes in vacuum/load during normal driving, so they should respond more precisely to fine changes in throttle position as you would encounter during daily driving. FWIW I always found spread bore carbs to be more responsive when driving around town than square bore carbs.




just here but since the TQ has much smaller primarys wouldn't that make the secondarys open faster? As mentioned before by me and others, a tuned carb is going to use the fuel/air it needs to push the car. What about a 6-pack? It runs off a small 2bbl most of the time.
Anybody got andy real world numbers?


I thought the center carb on a 6 pak was like a 500. Same as a 67 and down carter 4 bbl

Re: thermoquad VS. Holley 750 DP [Re: RemCharger] #1031730
07/14/11 11:40 AM
07/14/11 11:40 AM
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck Offline
Not enough dumb comments...yet
Mr.Yuck  Offline
Not enough dumb comments...yet

Joined: Jan 2003
Posts: 24,562
Brookeville, Md
"I thought the center carb on a 6 pak was like a 500. Same as a 67 and down carter 4 bbl"

It is but I've heard of people unhooking the oputboards for long drives...

Re: thermoquad VS. Holley 750 DP [Re: Mr.Yuck] #1031731
07/14/11 12:16 PM
07/14/11 12:16 PM
Joined: Jan 2003
Posts: 14,600
Not2farfromNashville, TN
R
Rug_Trucker Offline
I Live Here
Rug_Trucker  Offline
I Live Here
R

Joined: Jan 2003
Posts: 14,600
Not2farfromNashville, TN
Quote:

"I thought the center carb on a 6 pak was like a 500. Same as a 67 and down carter 4 bbl"

It is but I've heard of people unhooking the oputboards for long drives...




350.

TQ's are great if you fix the throttle shaft slop in the rebuild. Also buy an air door tool off of Doc.

My 511 '67 Cuda got 14mpg combined with the 6pak.























































































7 in the city, 7 on the highway!


"The only thing to do for triumph of evil is for good men to do nothing"

"NUNQUAM NON PARATUS!"
Re: thermoquad VS. Holley 750 DP [Re: Rug_Trucker] #1031732
07/14/11 12:31 PM
07/14/11 12:31 PM
Joined: Sep 2004
Posts: 6,900
IL, Aurora
A
ademon Offline
master
ademon  Offline
master
A

Joined: Sep 2004
Posts: 6,900
IL, Aurora
I've had a bunch of t-quads, none needed the shafts redone, but these were off performance cars that i bet were removed early on in favor of a holley

Re: thermoquad VS. Holley 750 DP [Re: ademon] #1031733
07/14/11 12:47 PM
07/14/11 12:47 PM
Joined: Jan 2003
Posts: 16,375
D
dogdays Offline
I Live Here
dogdays  Offline
I Live Here
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Joined: Jan 2003
Posts: 16,375
The Holley 500 two-barrel is rated as a two-barrel, with more vacuum across it than the four barrel rating. I believe the four barrel rated at 1.5" depression and the two-barrel is rated at 3" depression. The correction factor is the square root of 2. So rated like a four-barrel, the 500 Holley is really a 354.
R.
This comes up about once a year.

Re: thermoquad VS. Holley 750 DP [Re: dogdays] #1031734
07/14/11 01:18 PM
07/14/11 01:18 PM
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck Offline
Not enough dumb comments...yet
Mr.Yuck  Offline
Not enough dumb comments...yet

Joined: Jan 2003
Posts: 24,562
Brookeville, Md
"TQ's are great if you fix the throttle shaft slop in the rebuild. Also buy an air door tool off of Doc.

My 511 '67 Cuda got 14mpg combined with the 6pak."

I noticed on the 1st 6-pack build (mild 440 w/ 528 solid) I was getting pretty good milage. This build is much more agressive and on the last trip to the track (22 miles) I avg'd about 13-14. Not bad considering I got on it a few times. This is mainly backroads (45mph) stopping in 4 small towns.

Re: thermoquad VS. Holley 750 DP [Re: dogdays] #1031735
07/14/11 01:18 PM
07/14/11 01:18 PM
Joined: Jan 2003
Posts: 2,931
P
Paul_Fancsali Offline
master
Paul_Fancsali  Offline
master
P

Joined: Jan 2003
Posts: 2,931
The TQ takes a lot to tune and is absolutly no comparison to a DP Holley. I tried to run a TQ and succeeded but in the end the Holley won out hands down in Performance. When you are talking tenth's of a second I will now stick with Holley.
PS in mileage try a Q jet easy to tune and reliable and with Chrysler linkage from 1985 up to 1988

Re: thermoquad VS. Holley 750 DP [Re: Mr.Yuck] #1031736
07/14/11 01:22 PM
07/14/11 01:22 PM
Joined: Jan 2003
Posts: 14,600
Not2farfromNashville, TN
R
Rug_Trucker Offline
I Live Here
Rug_Trucker  Offline
I Live Here
R

Joined: Jan 2003
Posts: 14,600
Not2farfromNashville, TN
Quote:

"TQ's are great if you fix the throttle shaft slop in the rebuild. Also buy an air door tool off of Doc.

My 511 '67 Cuda got 14mpg combined with the 6pak."

I noticed on the 1st 6-pack build (mild 440 w/ 528 solid) I was getting pretty good milage. This build is much more agressive and on the last trip to the track (22 miles) I avg'd about 13-14. Not bad considering I got on it a few times. This is mainly backroads (45mph) stopping in 4 small towns.




Read down lower in my post. I got 7mpg. 3:23's .538-.5?? Crane solid cam.


"The only thing to do for triumph of evil is for good men to do nothing"

"NUNQUAM NON PARATUS!"
Re: thermoquad VS. Holley 750 DP [Re: Rug_Trucker] #1031737
07/14/11 01:44 PM
07/14/11 01:44 PM
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck Offline
Not enough dumb comments...yet
Mr.Yuck  Offline
Not enough dumb comments...yet

Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Quote:

Quote:

"TQ's are great if you fix the throttle shaft slop in the rebuild. Also buy an air door tool off of Doc.

My 511 '67 Cuda got 14mpg combined with the 6pak."

I noticed on the 1st 6-pack build (mild 440 w/ 528 solid) I was getting pretty good milage. This build is much more agressive and on the last trip to the track (22 miles) I avg'd about 13-14. Not bad considering I got on it a few times. This is mainly backroads (45mph) stopping in 4 small towns.




Read down lower in my post. I got 7mpg. 3:23's .538-.5?? Crane solid cam.




I'm running .030 over 440 w/ a 588 solid roller, ported stage VI heads, 3800 stall and 3.91's. I think my good milage was do to a nice slow steady drive of 40-45mph. Not much stop/start and not much outboard action...

Re: thermoquad VS. Holley 750 DP [Re: babarracuda] #1031738
07/14/11 09:36 PM
07/14/11 09:36 PM
Joined: May 2005
Posts: 2,295
dark side of the moon
D
Dougsmopars Offline
top fuel
Dougsmopars  Offline
top fuel
D

Joined: May 2005
Posts: 2,295
dark side of the moon
My GTX had a 780 DP on it when i bought it. Made good power but didn't stay in tune. It was old and leaked and had other isues but over all not a bad carb. Milage was poor. Went with an 800 eddy thunder series. Good carb, took a little to get the stumble out as car has a big cam. Milage was decent, throttle responce was good but lacked that kick in the pant's you get when you open up a spread bore and those big secondaries come in. Just switched to an 850 TQ and love it. Milage is a tad better, throttle responce is crisp and at WOT hold on. Over all i prefer the TQ to any other street carb.

Re: thermoquad VS. Holley 750 DP [Re: Dougsmopars] #1031739
07/14/11 10:14 PM
07/14/11 10:14 PM
Joined: Jan 2003
Posts: 1,180
Willoughby Hills, Ohio
gd9704 Offline
super gas
gd9704  Offline
super gas

Joined: Jan 2003
Posts: 1,180
Willoughby Hills, Ohio
A well-tuned TQ is fun to drive. Demonsizzler worked his magic on mine and I'm very happy with it.

Re: thermoquad VS. Holley 750 DP [Re: gd9704] #1031740
07/15/11 11:29 AM
07/15/11 11:29 AM
Joined: Jan 2003
Posts: 3,616
Millinocket, Maine
J
JonC Offline
master
JonC  Offline
master
J

Joined: Jan 2003
Posts: 3,616
Millinocket, Maine
I have a 850 TQ on my warmed 340 ebody and headers. When the secondaries kick in it feels like a passing gear. Have never compared it to anything else, gas mileage I have never checked. Don't care, it's not a daily driver.

Re: thermoquad VS. Holley 750 DP [Re: Paul_Fancsali] #1031741
07/16/11 04:16 AM
07/16/11 04:16 AM
Joined: Jul 2005
Posts: 383
Australia
M
Mcode69 Offline
enthusiast
Mcode69  Offline
enthusiast
M

Joined: Jul 2005
Posts: 383
Australia
Quote:

The TQ takes a lot to tune and is absolutly no comparison to a DP Holley. I tried to run a TQ and succeeded but in the end the Holley won out hands down in Performance. When you are talking tenth's of a second I will now stick with Holley.
PS in mileage try a Q jet easy to tune and reliable and with Chrysler linkage from 1985 up to 1988




If the holley won hands down in performance it means your TQ was WAY out of tune. I've had a 750DP and a TQ on the same engine and the difference was 11 mpg from the holley and 17 from the TQ around town.
Never saw any track times but the TQ had the holley by the butt dyno. And apart from that [and here's a name from the past] Ed Hamburger insisted that a TQ will have 2 tenths over a similar sized double pumper all day. As someone stated previously holley tend to cover up deficiencies in their design by making it rich, they CANNOT meter fuel properly at part throttle apart from all their other problems.

Re: thermoquad VS. Holley 750 DP [Re: Mcode69] #1031742
07/16/11 04:23 AM
07/16/11 04:23 AM
Joined: Feb 2004
Posts: 4,501
Gainesville,FL
G
goldmember Offline
master
goldmember  Offline
master
G

Joined: Feb 2004
Posts: 4,501
Gainesville,FL
A holley DP is not calibrated for fuel mileage.If you tune it properly it wins hands down. TQ's have their place,and I have some in a box on a shelf.

Re: thermoquad VS. Holley 750 DP [Re: goldmember] #1031743
07/16/11 04:31 AM
07/16/11 04:31 AM
Joined: Jul 2008
Posts: 26,197
Florida STAYcation
dOc - 3.0 ! Offline
still the village idiot
dOc - 3.0 !  Offline
still the village idiot

Joined: Jul 2008
Posts: 26,197
Florida STAYcation
Well goldy ....don't let them take-up ALL that shelf-space ... I will help-you get rid of them ...no problemO.

I might be rolling through on I-75 sooner than expected !

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