11.5 mpg 396? - Page 5 - Chevelle Tech
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post #61 of 79 (permalink) Old Sep 17th, 19, 4:04 PM
 
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Re: 11.5 mpg 396?

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Originally Posted by 69-CHVL View Post
I'll have to pull the 5.3 out of my Yukon and install that 572 for better mileage is what your telling me?
Sure can, and that was before a GearVendors overdrive!!! My diesel cams on average are worth a 22% increase in fuel mileage.

Chris Straub
Mfg Performance Parts

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Why is it we never have time or money to do it the right way in the beginning but we always have time and money to do it over again?
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post #62 of 79 (permalink) Old Sep 17th, 19, 5:00 PM
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Harry
 
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Re: 11.5 mpg 396?

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Originally Posted by McHaggis View Post
Get a wideband and start tuning. Donít be afraid to go beyond 14.7:1 at cruise. I ended up about 16.1 but I run an MSD 6AL ll programable with a map sensor so I was able to tune the vacuum advance as well.
10.5:1 355sbc in a 69 Javelin
3.73 gears 3600 rpm 9.5 lock up converter
750 DP Speed Demon on a Victor Jr intake
HR cam 228* 230g on 107* centres, 1.6 rockers
1-3/4Ē headers into 3.5Ē collectors.
TH200R4 trans
This was never setup to get mileage but after lots of tuning with an innovative wideband I get 22mpg highway cruise at 60-70. This is about 2200-2300rpm.

Yes itís a small block but the old set up was with a TH350 and 2.87 gears with a 2200rpm non-lock TC and a 650DP Holley and I typically got 13 before adding the OD trans but the big improvements came form leaning the carb as much as I could and getting the timing curves optimised. Driveability is very good too.
I agree, it can be done, and I did it - with big cam, 750 Holley Ultra HP double pumper , aluminum heads... You need a wideband and a great understanding on how to tune a carb.. The ultra HP was key for me because it has the "air bypass" that allows you to close the butterflys at idle and tune the carb without "tip in" stumbles with a big cam. With a big cam, you also need to run approx. 20 deg. of initial timing at idle and add a vacuum advance which is fully advanced at idle - giving you approx. 36 deg. of timing at idle. To also aid atomization, get a higher degree thermostat ie. 195, and run hotter plugs. All this will allow you to close the butterflys more which is one big key to improving gas mileage. Then, using jets and air bleeds, pump cams, and pump squirters to get cruise around 14.7 afr, 2 barrel acceleration around 13.2 to 1, and WOT at 12.2 AFR. Also, a high energy ignition like a MSD will burn more fuel at idle and allow you to lean out more. Overdrive is also a big plus on the fwy. I doubled my gas mileage on my 396 compared to a stock Holley 750 double pumper.

Harry
1970 Chevelle SS396 (408), Fathom Blue,
Original Block & Forged Crank, KB Pistons, Edelbrock 6045 Heads,Comp Cam 292H, March Serpentine, RPM AirGap,750HP,100hp Nitrous
A/F Wideband,Tremec TKO 600, 12 bolt,
30 spline Moser Axles, Richmond 3:73's, Hotchkis control arms, swaybars, springs, Wilwood 12" rotors D/S, 4 piston calipers

Last edited by hjdca; Sep 17th, 19 at 5:17 PM.
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post #63 of 79 (permalink) Old Sep 17th, 19, 6:26 PM
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Re: 11.5 mpg 396?

The '56 Chevy Bel-Air mentioned in my signature (below) here averaged 12+ MPG during this past week's Drag-Week event. Also ended up a winner!

This was with driving to the 5 tracks with the trailer tagging along and with some 3.20:1 rear gearing and weighing just above 3800#!

Thanks, Gary in N.Y.

P.S. This is a pump-gas ride (in our area anyway, E-85 from the nozzle) with above 2000 HP, give or take a couple! No overdrive, straight T-400.
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Sept. 2019 Drag-Week Winner - N.Y. Legal Streeter - 1956 Chevy Bel-Air 7.23 @ 196+ @ 3800#
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post #64 of 79 (permalink) Old Sep 17th, 19, 7:09 PM
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Darren
 
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Re: 11.5 mpg 396?

I'll share my experience with mpg's that I had today.

Went for a nice little drive for a couple of hours. A total of 72 miles were driven. About 15 miles were interstate. The remainder of the miles were "stop and go city traffic" and some back road driving. Interstate was driven at 70-75 mph (6th gear) and the back roads around 50-ish mph (5th gear). Hammered on it pretty good getting onto the interstate, the rest of the time was pretty normal driving, but not "babying" it. Topped the tank off and it took right at 6 gallons to fill it up to the spout. 12 mpg. I don't think that's too bad considering my combo.......496, 10.5 cr, Brodix rect port heads, solid roller (256/264, .660/.660, 108lsa), Vic Jr, Pro Systems Venom-VX 1050 carb, Tremec 6 speed, 4.56 rear gears with 30" tires.
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Darren
1971 Chevelle
496
CFM Ported Stage 5 Brodix Race-Rites 310cc
10.5 scr
Ultradyne Solid Roller 256/264 .660/.660 108 lsa
CFM Ported Victor Jr / Pro Systems Venom VX 1050
T-56 Magnum 6 Speed, DFX
12 Bolt TrueTrac, 4.56 gear 33 spline Moser axles
30x12.5 ET Street Radial
525++ rwhp
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post #65 of 79 (permalink) Old Sep 18th, 19, 1:52 AM
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Stew
 
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Re: 11.5 mpg 396?

Quote:
Originally Posted by hjdca View Post
....You need a wideband and a great understanding on how to tune a carb..
Thatís the secret. I drilled and tapped my Speed Demon so I could change the IFRís, all air bleeds, the PVCR and I played with the emulsion circuits. I have about 29* at idle and I run as much vacuum advance as possible. I also found using the HVC ll coil a must as a Blaster SS didnít work nearly as well.
The custom Straub Tech cam also helps a lot.

I found most of the info to do this on this forum.
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post #66 of 79 (permalink) Old Sep 18th, 19, 4:02 PM
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Re: 11.5 mpg 396?

12 is believeable and damn good from a low geared fine tuned big block.
BEsting a 5.3 no way not a chance...

Do wish I had some of the finer tuning skills wiht the ifrs etc some of you guys do.
I know theres a lot more power in mine just dont know enough...and dont know/trust anyone to let my car loose with
Wish I had the dough to rent Westech and their know how for a day.

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post #67 of 79 (permalink) Old Sep 18th, 19, 4:29 PM
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Vince
 
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Re: 11.5 mpg 396?

When my 502 had a 850DP, it was cruising around 12.8:1. Went to EFI, and now cruises at 15:1+. I was expected a HUGE change in mpg. Guess what - NONE! I found that when your engine speed is reduced, your engine is taking less "gulps" of air/fuel, so AFR changes aren't as significant.

I would imagine a non-OD car that's turning a lot more rpms would see a benefit to leaning out the AFR more so since its just flat out consuming so much more.

*69 SS 502 EFI /224* HR/9.8:1/T56/3.90/ 4000lbs RW 11.5/124mph
*11 C6, 6.2, 6spd
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post #68 of 79 (permalink) Old Sep 18th, 19, 8:14 PM
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Darren
 
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Re: 11.5 mpg 396?

Quote:
Originally Posted by cuisinartvette View Post
12 is believeable and damn good from a low geared fine tuned big block.
BEsting a 5.3 no way not a chance...
Last year I took a short all interstate road trip, about 100 miles, and was able to get 15.5mpg. In 6th gear at 70mph, the engine is turning a little over 2200rpm.

And you are correct, I cant compete with a modern LS motor as far as fuel mileage, but thats ok, I'd rather have my BBC.

Darren
1971 Chevelle
496
CFM Ported Stage 5 Brodix Race-Rites 310cc
10.5 scr
Ultradyne Solid Roller 256/264 .660/.660 108 lsa
CFM Ported Victor Jr / Pro Systems Venom VX 1050
T-56 Magnum 6 Speed, DFX
12 Bolt TrueTrac, 4.56 gear 33 spline Moser axles
30x12.5 ET Street Radial
525++ rwhp
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post #69 of 79 (permalink) Old Sep 19th, 19, 6:39 AM
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Guy
 
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Re: 11.5 mpg 396?

Quote:
Originally Posted by GOSFAST View Post
The '56 Chevy Bel-Air mentioned in my signature (below) here averaged 12+ MPG during this past week's Drag-Week event. Also ended up a winner!

This was with driving to the 5 tracks with the trailer tagging along and with some 3.20:1 rear gearing and weighing just above 3800#!

Thanks, Gary in N.Y.

P.S. This is a pump-gas ride (in our area anyway, E-85 from the nozzle) with above 2000 HP, give or take a couple! No overdrive, straight T-400.

Got any pictures of that "bad boy" Gary ??
Thats pretty good fuel mileage for that much HP...
Guy

'86 Monte SS,
513 Stroker,
AFR CNC'd 315 heads,
Custom Bullet solid roller,.706, 285/293-255/263 @ .050,110 LSA,UDHarold's lobes.
Isky .904 EZX Roll lifters,
Thanks to Mike "Wolfplace" Lewis,
Weiand Stealth intake,ported & gasket matched,
825 Mighty Demon,tuned by jmarkaudio,
2 inch Hooker Headers,(Coated),
Doug Nash 4+1 5 speed,w/a couple of cryo treated gears,
9 inch rearend,
Hurst Vertical Gate II In Line Shifter,
TC Member # 4921
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post #70 of 79 (permalink) Old Sep 19th, 19, 8:12 AM
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Eric
 
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Re: 11.5 mpg 396?

Quote:
Originally Posted by 69-CHVL View Post
When my 502 had a 850DP, it was cruising around 12.8:1. Went to EFI, and now cruises at 15:1+. I was expected a HUGE change in mpg. Guess what - NONE! I found that when your engine speed is reduced, your engine is taking less "gulps" of air/fuel, so AFR changes aren't as significant.

I would imagine a non-OD car that's turning a lot more rpms would see a benefit to leaning out the AFR more so since its just flat out consuming so much more.
A/F ratio is important, but apples to apples, cruise rpm trumps A/F ratio.
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post #71 of 79 (permalink) Old Sep 19th, 19, 9:59 AM
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Re: 11.5 mpg 396?

Quote:
Originally Posted by GuysMonteSS View Post
Got any pictures of that "bad boy" Gary ??
Thats pretty good fuel mileage for that much HP...
Guy
Hi Guy, you can catch his run if you follow the link here:

https://www.google.com/url?sa=t&rct=...j1heywmlfZTn3E

His run is located at 6:23 (hours) into the show, you can locate the actual run on the "time-bar" at the bottom of the screen.

I can add this here also, it takes quite an effort to make this thing live as a "real" street ride with that type of HP! We're figuring he's above 2000?? And has more in it, this isn't the end yet!

Thanks, Gary in N.Y.

P.S. When he first comes up to the line the announcer got his last name wrong but corrected it just before the launch, this was his 7.23 @ 196.7 run!
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Sept. 2019 Drag-Week Winner - N.Y. Legal Streeter - 1956 Chevy Bel-Air 7.23 @ 196+ @ 3800#
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post #72 of 79 (permalink) Old Sep 19th, 19, 11:32 AM
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Re: 11.5 mpg 396?

Quote:
Originally Posted by GOSFAST View Post
Hi Guy, you can catch his run if you follow the link here:

https://www.google.com/url?sa=t&rct=...j1heywmlfZTn3E

His run is located at 6:23 (hours) into the show, you can locate the actual run on the "time-bar" at the bottom of the screen.

I can add this here also, it takes quite an effort to make this thing live as a "real" street ride with that type of HP! We're figuring he's above 2000?? And has more in it, this isn't the end yet!

Thanks, Gary in N.Y.

P.S. When he first comes up to the line the announcer got his last name wrong but corrected it just before the launch, this was his 7.23 @ 196.7 run!
Thanks Gary,
that's a nice looking '56,and almost 200 MPH in the 1/4,not too bad for a street car !!!
Guy

'86 Monte SS,
513 Stroker,
AFR CNC'd 315 heads,
Custom Bullet solid roller,.706, 285/293-255/263 @ .050,110 LSA,UDHarold's lobes.
Isky .904 EZX Roll lifters,
Thanks to Mike "Wolfplace" Lewis,
Weiand Stealth intake,ported & gasket matched,
825 Mighty Demon,tuned by jmarkaudio,
2 inch Hooker Headers,(Coated),
Doug Nash 4+1 5 speed,w/a couple of cryo treated gears,
9 inch rearend,
Hurst Vertical Gate II In Line Shifter,
TC Member # 4921
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post #73 of 79 (permalink) Old Sep 20th, 19, 2:06 AM
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Rod
 
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Re: 11.5 mpg 396?

Quote:
Originally Posted by McHaggis View Post
........
10.5:1 355sbc in a 69 Javelin
......
Pics, please!
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post #74 of 79 (permalink) Old Sep 22nd, 19, 1:33 AM
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Re: 11.5 mpg 396?

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Pics, please!
https://www.chevelles.com/forums/att...1&d=1569130330

https://www.chevelles.com/forums/att...1&d=1569130330
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post #75 of 79 (permalink) Old Sep 22nd, 19, 9:28 AM
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Rod
 
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Re: 11.5 mpg 396?

Looks nice. Right hand drive. Were they factory built with a Chevy small block for the New Zealand market?
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