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#258987 - 07/09/05 05:11 PM better gas mileage with Vortec heads
kstagger Offline

Registered: 06/13/02
Posts: 647
Loc: Grand Rapids, MI
not a question - just an observation...

Ever since I threw in a 350 with Vortec Heads, I've been getting better gas mileage than the old 305. Don't know if it has to do with my old Quadrajet running so rich, or that I had to mash the pedal more with the 305 to get up to speed...

but I drive 15 miles to work and back, and the gas gauge is sinking down way less than it did before. Now I have to fill up once every two weeks - used to be almost once a week!

#258988 - 07/09/05 05:43 PM Re: better gas mileage with Vortec heads
Foompla Offline

Registered: 06/03/04
Posts: 931
Loc: North Bergen, New Jersey
that I had to mash the pedal more with the 305 to get up to speed...

that sounds about right \:\)
1987 Chevrolet Monte Carlo SS
Finally got the motor from the shop. Time to get to work!

#258989 - 07/09/05 05:43 PM Re: better gas mileage with Vortec heads
RW2003 Offline

Registered: 08/15/03
Posts: 362
Loc: Somewhere West of Newark, NJ
Nice.. esp. w/ today's rising gas prices. I have a similar length commute in the Monte and I'm filling up once per week. Maybe its time for a bigger engine!
1987 MCSS - 157k miles. Black w/ gray interior. T Tops. BF Goodrich Radial T/As. Stock except for TT 2.5" cat back w/ Super Turbos.

#258990 - 07/09/05 11:26 PM Re: better gas mileage with Vortec heads
RaGG Offline

Registered: 02/10/02
Posts: 340
Loc: Memphis, TN
Yea its nothing like filling up 2 times a week @ $2.25 for 89!

my vortec 383 has been guzzling, i just discovered the resistance in all my wires were fairly high while one wire wasn't passing through any spark!

No wonder it smelled a little rich @ idle. Just replaced them tonight, hopefully ill sneak through emmissions testing now. =)

even with my compression hovering around 9.8:1 89 works great.
gas guzzler

#258991 - 07/09/05 11:54 PM Re: better gas mileage with Vortec heads
SSScottSS Offline
10+ Year

Registered: 10/09/02
Posts: 2730
Loc: S/E Wisconsin
I run 89 octane in mine. I filled up tonight @ $2.54/gallon I'm not sure what my current milage is, but I'm going to keep an eye on it now with gas prices going through the roof.

A little off subject, but what should the resistance be for plug wires. I've never checked mine, and they're getting pretty old, actually really old.
88 SS

#258992 - 07/10/05 11:08 AM Re: better gas mileage with Vortec heads
lazygearhead Offline

Registered: 11/10/02
Posts: 5228
Loc: Atlanta, GA
if nothing else is changed, making a vortec head swap or similar should improve mileage in situations like this for exactly the reason you said. there is more power on tap, so you have to use less of it, and therefore you stay out of the throttle more.
Void where prohibited by law

#258993 - 07/12/05 12:05 PM Re: better gas mileage with Vortec heads
Damon Offline

Registered: 10/17/01
Posts: 1094
Loc: Philly area
If you used to have a carb that was running rich and have since gotten it running correctly THAT is 90% of the reason for your fuel mileage increase. Vortec heads might get you a little, but would be largely offset by the larger engine displacement. A properly running carb and a sharp ignition system (along with proper ignition timing) are where it's at for best fuel economy.
78 Malibu. Grandmother's old car with 33K original miles. Mild 383 with a Weiand 142 blower. New Redneck 2700 stall blower converter assures zero traction under all conditions.

1990 454 SS truck. All stock with a rod knock. Screwing together a nasty little solid lifter heavy-breathing big block to replace it.

#258994 - 07/13/05 04:24 PM Re: better gas mileage with Vortec heads
monte12345 Offline

Registered: 10/25/03
Posts: 738
Loc: Eastpointe, MI
I have to agree with Damon, getting the engine running right has a lot more to do with your milage increase than the Vortec heads.

I just returned from vacation and can now compare the fuel milage from my previous engine to the HT383 now in my Monte. The previous engine was a .060 over 350 with fully ported 186 castings (which got toasted when a valve seat fell out at on 30K miles). Cam in the older engine (210/216) was a lot hotter than the HT383 cam so I really expected to see a large gain with the HT383. BTW, these results are for a 1500 mile round trip pulling a 24 ft boat (5200 lbs total).

The previous engine had mileage ranging from 10 to 11 mpg when towing, depending on the fuel brand and it required at least 93 octane.

With the HT383 I got the best mileage using 89 octane, I tried 93 octance but it cost almost 1 mpg. I also saw more variation between brands of gas used and suspect that one tankful was actually 86 octane (beware of all the Sunoco's on the NY Thruway, octane cheating is really common with that shady outfit).

Sunoco, labled on the pump at 89 octane, mileage ranged from 9.4 to 10.2 mpg. Mobile 93 octane, mileage was exactly 10 mpg. Mobile 89 octane 10.5 to 11.2 mpg. Amoco 89 octane, mileage was an astounding 12.3 mpg.

That's at an average speed of 68 mph in overdrive for both engines. I tried running the HT383 a bit slower at 63 mph and the mileage didn't change at all, the engine also had a "tendency" to increase the speed to 68 mph. I think that 2500 rpm is a bit of a "sweet spot" for the HT383, that was were it seemed to run the best.

Bottomline, I think that at cruise the load on the engine requires "x" amount of gas to move the load. That means that, if the engine is running efficiently, it's going to yield the same mileage, no matter what the head or cam used. In my case I am comparing a 9.5:1 motor with a 210/216 cam to a 9.1:1 motor with a 196/206 cam. Despite the much milder cam in the HT383, the fuel economy was very similar to the engine with the "hotter" cam.

Note; most "full race" heads and cams don't allow the engine to really run efficiently at the low engine speeds for highway cruising. That's why I am always a bit conservative about cam choices.

PS, anyone who wants a great engine for towing, I can heartily recomend the HT383. This engine has a ton of torque down low and had no problem pulling the boat as long as the engine speed was over 1500 rpm. The previous engine was pretty good but it would "fall off the cam" at 1900 rpm which would then require a downshift. It's also a lot of fun to drive because the throttle response is terrific at low engine speeds, no waiting for a downshift, it just takes off when you goose it like an old SS396.
85 MC SS

#258995 - 07/14/05 01:57 PM Re: better gas mileage with Vortec heads
kstagger Offline

Registered: 06/13/02
Posts: 647
Loc: Grand Rapids, MI
yeah, probably mostly in the change of driving habits with more torque on the bottom...

and my last carb with a cc quadrajet - but apparently the previous hillbilly owner didn't have the computer hooked up. The carb ran really rich!

#932564 - 05/18/12 10:25 AM Re: better gas mileage with Vortec heads [Re: kstagger]
t8rtot Offline

Registered: 11/17/09
Posts: 46
Loc: KS
i'm sorry for dragging up an old thread but seeing these guys complain about gas then and seeing where the prices are now.. lol i can't help but laugh

#932572 - 05/18/12 11:24 AM Re: better gas mileage with Vortec heads [Re: t8rtot]
joyride Offline

Registered: 05/09/10
Posts: 678
Loc: Tacoma, Wa joke right!?!?^^^ damn 4.43/gallon here in tacoma wa for 92 down the street.

Had an 88 Monte SS in HS, sold that!
07' MC SS black, all stock (for now)
85' Monte SS project car. Flat Black, 305 w/ LT headers, drop spindles, CPP 2 inch A-body rear springs, 18" Boss 338s



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