25 MPG!!!!!!

I just took a 100 mile trip in my 68 Cutlass and pulled down 25 MPG.    I was soo shocked at how little gas it took to fill up once getting into town I tried again...and again it clicked off   .  This is a 350 Olds bored to 4.155" with big block heads, 750 Holley carb, a cam with 204/216 degrees duration and .456/.484" lift, a 200-4R trans, 3.73 rear gears, stock exhaust manifolds, and a 2.5" Flowmaster exhaust.

I was averaging around 70 MPH on the trip.

And it was raining...now thats a daily driver for ya!  
68 Olds Cutlass ~ 350 Rocket
85 Delta 88 ~ 425 Rocket
02 Silverado 4X4 ~ 5.3L

The cooler denser air from the rain helped, along with your smallish cam, leaned out Holley, and overdrive tranny.

Can you tell that I am jealous?    

Hey C, this is good. Not only is good MPG an economic issue but also a sign of overall efficiency. Good job and fill us in on tune and maintenance issues.  

Sweet, I am not surprised with a 200R4. I had a '69 Firebird daily driver with a Pontiac 400 and a 700R4 that got 25-28mpg @80mph on the highway and minimum 18mpg around town.  It had an unknown cam that pulled a lot of vacuum, a Q-jet, points and 2.73 gears.  It was a little bogged down on the highway and always suspected with 3.23-3.42 gears the mileage would go up.

I am gunning for 30mpg on the highway for my '77 Skylark.  It has a 455/TKO-600 w/.67 OD and 3.23 gears.  It has a CompCam with .469 lift.  I'm looking at getting a Holley TBI unit for it too.  I figure when I get the car on the road it will get around 25mpg highway (HEI&Q-jet).  It's 2.5 hours from here to anywhere so mileage is important to me  

Can't beat a classic daily driver that can pull new car mileage.

I know I keep going on b u t ...... (stupid filter)
The 200R4 I pulled out of the '77 Skylark I'm going to rebuild with the best parts I can buy to put behind the 455 in my 5000lb Centurion...it'll be an endurance test on the trans to say the least.  
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The Silver Buick- '77 Skylark coupe w/ a Fuel Injected Buick 455&TKO-600, '72 Centurion Conv't - 455w/TH400, '67 T-bird 4Dr (suicide) w/428&C6. Needing to replace a '69 Firebird 400.

http://www.bangshift.com/forum/index.php?topic=6189.0

Actually I'm looking at switching to a Q-jet to see if there is any more mileage there (those small primaries are great).  But I used to have 3.08's out back and with the overdrive got about 21 on the highway.  Switched to 3.73's and the mileage went up. Probably due to Missouri's hills...it would have to downshift with the 3.08's (or at least disengage the lockup) to climb a hill...with the 3.73's it just cruises.  RPM were around 2300...sometimes higher sometimes lower...

Rebldryvr...you caught me...I did lean out the primaries on the carb 2 jet sizes (from 70 to 68).

I built the 200-4R that is in that thing right now...I did save some money...basically everything I did to it and to the car to get it in (rebuild trans, new servo, new boost valves, new pump, hardened stator support, hardened intermediate drum assembly, new aluminum pan, shift conversion kit, torque converter, trans cooler, and lockup kit)  cost about as much as a brand new TCI unit...but in hindsight...I wish I just would have bought one.  Actually, as soon as funds allow, I'll either switch to a manual overdrive, or get a BUILT 200-4R from someone like CPT, or Art Carr, or TCI.  Good luck with that 455 SilverBuick...that'll be a true test to the transmission's strength.  
68 Olds Cutlass ~ 350 Rocket
85 Delta 88 ~ 425 Rocket
02 Silverado 4X4 ~ 5.3L

My Impala gets about 17-18 if I drive the speed limit, but I'm usually driving with traffic. About 80-85 mph. Thats with a 383 sbc, iron heads, XE274 cam, 750 DP Holley with 80 jets, NP440 trans(think GM version of NP883OD) and 3.36 gears. I pull about 1900 at 70 mph, 2600 rpm at 85 rpm, and about 3000 at 100 mph.  

That's awesome! I have a 355 with a Comp XE268 (.477", .480", 224/230 at .05"), a Saginaw 4-speed with, of course, 1:1 final drive, and 3.08's out back, and it knocks back about 23-24mpg on the highway if I can keep my foot out of the secondaries on the Q-jet! Plus, it's very street friendly, even though it's kind of a dog below 2000 rpms! My daily driver was down, so I had to commute back and forth from  Portland, Maine to Boston daily to train for my new job, and even with the bumper-to-bumper rush hour traffic, the Cutlass madeit there and back on just under a half tank of gas.  

Hey TheSilverBuick I changed the gears in my caprice wagon with a 200-4r, from 2.73's to 3.42'a and the mileage did go up. I went from about 7mpg (had just got the car and it didn't run that great yet) to about 10mpg around town and about 12 on the highway.  The true dual exhaust (and some tuning) brought it up to 12mpg around town and upwards of 16mpg on the highway cruising around 75-80.  
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It may not be the fastest or prettiest, but i can pretend

 
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The Silver Buick- '77 Skylark coupe w/ a Fuel Injected Buick 455&TKO-600, '72 Centurion Conv't - 455w/TH400, '67 T-bird 4Dr (suicide) w/428&C6. Needing to replace a '69 Firebird 400.

http://www.bangshift.com/forum/index.php?topic=6189.0

Alot of ppl tell me you can't get 25-28 MPG out of these old cars and tune them to be fast at the same time. I try to tell them that I read about it all the time. How many ppl can say they got 400+ HP and get 25 MPG???? Don't let your head swell too much      
Guzzling gas and hauling ass, the true American way.

I'm shooting for 400-450Hp and 30mpg N/A on a Buick 455. Going to attempt computer controlled timing on my car tomorrow, if sucessful I expect a 3-4mpg increase to 25+mpg. Multiport EFI hopefully this summer. A v-6 turbo would be a walk in the park to get those numbers.  
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The Silver Buick- '77 Skylark coupe w/ a Fuel Injected Buick 455&TKO-600, '72 Centurion Conv't - 455w/TH400, '67 T-bird 4Dr (suicide) w/428&C6. Needing to replace a '69 Firebird 400.

http://www.bangshift.com/forum/index.php?topic=6189.0

Hey Silver,  I have a Centurion too and have recently aquired a 7OOR4.  I hope the tranny can handle the slightly warmed over 455.  My goal is to have 30 mpg, when its all said and done. Maybe a stretch, but it'll be fun tryin'.  I just want to be able to laugh at fullsize SUVs on the road as I out-tow, and out-run em.  And what of this REAR gear change you say?  Will fixing the highway bog give better mileage over less RPM's? Enlighten me.  Thanks  

TheSilverBuick:
I'm shooting for 400-450Hp and 30mpg N/A on a Buick 455. Going to attempt computer controlled timing on my car tomorrow, if sucessful I expect a 3-4mpg increase to 25+mpg. Multiport EFI hopefully this summer. A v-6 turbo would be a walk in the park to get those numbers.

Good luck buddy...definitely keep us updated here.  At the very least I wanna know how things are going!

Eventually I'll try to get my 425 powered Delta 88 in the mid 20s range.  Right now I'm handcuffed trying to finish my masters (Dec 08...can't freakin wait)...so everything is on hold.  
68 Olds Cutlass ~ 350 Rocket
85 Delta 88 ~ 425 Rocket
02 Silverado 4X4 ~ 5.3L

hey all im new to this message board but i have 1 important question here? I have a 1971 Olds Cutlass 2 Door Sport Coupe which i was told by the pres. of the Oldsmobile Car Club of America that it was 1 of 4,339 made back in 1971. While workin on it at 1 point I found the original build sheet between the foam and the wire frame of the back seat, this was about 15-20 years ago though, and it was in good shape back than. I took it out of there and put a plastic cover to protect it. and it eventually got put in the attic of the garage.since it was put there we moved around 3-5 times and everything that was in the attic at the old house got put into the attic at the new house or in a storage unit. Short story part now is that im not sure i still have it or if it got left behind at an old house. now for the BIG QUESTION. Where can a person get another copy of that original build sheet. I sure do need everyones help ro find out and i thank ya for givin me the time to ask this and thank all of your fro your information.  

I wasn't successful with my 7-pin HEI bench test, so that's for another day. I ordered a new vacuum advance though, one suited to bring a lot of timing in by 10"Hg. Hopefully this helps since I am not getting anywhere near maximum advance out of the mechanical at 2,000rpm cruising speed. And the low inHg is important because I drive a lot above 6500' elevation so engine vacuum is less due to our thinner atmosphere.  
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The Silver Buick- '77 Skylark coupe w/ a Fuel Injected Buick 455&TKO-600, '72 Centurion Conv't - 455w/TH400, '67 T-bird 4Dr (suicide) w/428&C6. Needing to replace a '69 Firebird 400.

http://www.bangshift.com/forum/index.php?topic=6189.0