Not exactly a science lab test but, I drove out from Vancouver Island to Alberta and return three years ago and did another trip this month. Both trips were about 3000 miles. Went to Calgary and did day trips from there. Not exactly, but close to the same trip. Same carb and carb tuning, tranny, rear gear, tires, etc. First trip I had my wife with me and her trunk full of luggage, second trip alone but more beer in trunk. Probably 130 pounds lighter the second trip. Only real change was the camshaft and lifters.
Interesting observation and gas mileage I've never heard of achieving with our cars, unless its a six banger (care to share your secrets?). The real question you should ask yourself is was the car more fun to drive in trip 1 or 2? Another point to consider is you only have 1 data point to compare. Its never a good idea to base your judgement on one date point only. Would recommend at least 3 ea (leave cam in place and just do 3 trips/same route and look for repeatability). Use shorter trips, but all the same route, get the same fuel, etc.
Car was actually more fun the first trip. During the second trip I didn't drive it at WOT enough to feel the benefit of the larger cam, but I did notice the lower quality driveability at lower rpm and idle. Not much, but better ride in first and second gear through parking lots and crowded streets stop and go with the smaller cam. I ran my car up island a dozen or so times with the 230/236 cam and the MPG averaged out to around 24 in the 1300 or so miles. I've had the car up there with the 236/245 cam a couple times but didn't record the mileage, only on the 3000 mile trip over the Rockies. Like I said not a laboratory experiment but that's about a14% drop.
Need more specs on car, the best you'll get with a 400 is maybe 18, tranny and rear gears and tire height all make major differences, your cams aren't that different.
My last long trip in my '68 400HO I got 17.5 mpg from Illinois to Colorado and 19.5 mpg returning. That is with everything factory original including the 2.56 rear and TH400. That is pretty consistent with what I remember it would get for highway mileage during its daily driver days.
I haven't checked for years, but I remember ballpark 10 -12 MPG. It was always "smiles per gallon"
I used to be indecisive. Now I'm not sure. I feel like I am diagonally parked in a parallel universe. 1968 400 convertible (Scarlet) 1976 T/A - 455 LE (No Burt) 1976 T/A New baby, starting full restoration. 1968 350 - 4 speed 'vert - 400 clone (the Beast!) 1968 350 convertible - Wife's car now- 400 clone (Aleutian Blue) (Blue Angel) 2008 Durango - DD 2008 GXP - New one from NH is AWESOME! 2017 Durango Citadel - Modern is nice! HEMI is amazing! 1998 Silverado Z71 - Father-daughter project 1968 400 coupe - R/A clone (Blue Pearl) (sold) 1967 326 convertible - Sold 1980 T/A SE Bandit - Sold
That makes all the difference, I only get 14 MPG driving around Pender Island. Speed limit is 30, no flat land anywhere, no straight roads anywhere, first gear is very low, a 373 rear gear and 464 cid doesn't add up to good gas mileage.
It's not the actual MPG numbers I was commenting on but the fact if was lower with the larger camshaft. Whether it was 25 MPG or 15 MPG wasn't the point, just that it was higher with one cam and lower with the other. Cars move due to the engine's torque, I got more torque with the shorter duration camshaft and more horsepower with the longer duration camshaft. Peak horsepower was higher with the bigger camshaft but at a higher rpm. I didn't drive 3,000 miles at 5,800 RPM which is where the higher horsepower was. The smaller camshaft had more overall torque and at a lower rpm than the other camshaft. I did drive 3,000 miles at an rpm mostly between 2,000 and 3,000 rpm.
I'd be interested to know what a bone stock 68 400 with a 066 camshaft would get for MPG and then what it would get with a 744 or a 041 camshaft, traveling the same 1000 miles or so at the same speed and conditions.
Just wonder, don't know why these things interest me but...
Ramair68: No secret, just an engine with a lot of torque and a five speed tranny with an 0.68 overdrive. 70 MPH is just over 2,200 RPM. One does have to have the torque to move the car at 70 mph over a 4,000 foot mountain pass at that low an RPM.
Last edited by Bluebird428; 09/01/1911:06 AM. Reason: typo
I will probably get some haters and non believers with this claim but I once changed a rear end for a long highway drive to a 2.56 from an automatic. Was running an M20 Muncie behind a .030 over 400 with a Holly 750. The cam had an advertised lift of 467 and duration of 313. The setup was completely incorrect for any normal stop ad go driving but was happy on the highway. Don’t be hating but, from PHX to Sacramento I figured that it achieved 22mpg. Mostly flat road, gears, gears, gears!
I'm not really sure why you have a muscle car and you care about gas mileage, other than making sure you reach your destination without incident. I understand the curiosity factor. Its good info to know and certainly an important part of understanding the machine. But honestly I'm much more concerned with horsepower and torque and whatever gas cost is involved. I don't want to waste gas unnecessarily and I want the car running correctly but I don't think you are commuting to work in this car? And if you are by the way... that is awesome... but you made poor economic choice so deal with it. Yes it cost money to go on a road trip. Stop swapping out the 350 2bls if its such an issue! :-)
I'm not really sure why you have a muscle car and you care about gas mileage, other than making sure you reach your destination without incident. I understand the curiosity factor. Its good info to know and certainly an important part of understanding the machine. But honestly I'm much more concerned with horsepower and torque and whatever gas cost is involved. I don't want to waste gas unnecessarily and I want the car running correctly but I don't think you are commuting to work in this car? And if you are by the way... that is awesome... but you made poor economic choice so deal with it. Yes it cost money to go on a road trip. Stop swapping out the 350 2bls if its such an issue! :-)
Wow, have you ever been west of the Mississippi? There are parts of Texas here where gas mileage is important. And this is with a daily driver that gets 32 miles per gallon highway at 75. (Yes, we have highways here posted at 80/85). I imagine BC is similar.
1968 400 Coupe, verdoro green, black vinyl top 1968 400 Convertible, verdoro green, black top 1971 Trans Am, cameo white, auto 1970 Buick Skylark Custom Convertible 350-4(driver)
I've got somewhat of a muscle car and it eats gas. 91 octane costs $7.84 a gallon on this island. I'm going to drive it whether I get 14 MPG or 44 MPG. That isn't the point I was getting at. I was just curious about the difference between mileage with the two camshafts. I wasn't complaining about it, just thought is was curious. I'm sorry I brought the subject up! If I wanted an economical choice I wouldn't have bought another 60s Pontiac with a large displacement. My GTO was lucky to get 8MPG. I would have spent my money on a new car with all the bells and whistles including a screen on the dash for all those guys who don't have a clue how to drive or how to get from point A to point B without electronic help. I'll refrain from posting "I wonder why" subjects in the future.
wovenweb; Not many posted that high here. We have a couple of highways posted 75 MPH. Of course all the tree hugging wingnuts are protesting. Telling us driving that fast is going to cause California to sink into the ocean. They may succeed in getting it lowered, who knows! They're slowly taking the fun out of driving.
Never stop wondering why... besides we love hanging out here spouting about such things. Some people love burning rubber and others think it wastes good tires, other people worry about gas millage and other people could care less. Some people don't read the posts correctly. That's what makes the world go around!
I like pulling up next to Prius in the Firebird. Generally 2 types of guys driving the Prius. One guy hates me. I hope he enjoys my exhaust. The other guy wishes he was me sooo bad.
wovenweb; Not many posted that high here. We have a couple of highways posted 75 MPH. Of course all the tree hugging wingnuts are protesting. Telling us driving that fast is going to cause California to sink into the ocean. They may succeed in getting it lowered, who knows! They're slowly taking the fun out of driving.
That's what I see when I go to Ontario. Painfully slow speed limits coupled with high gas prices. What I find strange is the speed limits in the cities (Toronto) go up but go down in the middle of nowhere. Somewhat opposite of the states.
Honestly I'm not buyin any of this without more spec's
never saw anything posted about the tranny, rear gears or tire height
I did have a 72 GTO that did achieve about 22mpg hiway, it had tall tires, from memory about 27" and a 4sp with a 3:55-1 rear, the quadrajet also helped, and I had done some WOT bursts in 4th blowing off 3 firebirds, 2 late 70's turbos and 1 early 80's turbo going uphill on 95S from Vermont, I let them try to catch me on the downhill, never downshifted, I had filled up in Ct driven to Vermont and back, refilled and calc'd mileage
Well I don't give a **** if someone buys any of this or not. I don't write stuff that isn't the truth to impress or piss off people I don't even know or will never meet. Still can't get across "it's not the gas milage number just the ratio between two trips!" Man, I gotta give this place a rest for a while.
Checked the price of gas today, now at $8.05 "Believe it or not! $4.50 in Calgary, but that's not the province (state) that is protesting the pipe lines.
I think of it as my duty to burn the back tires upon occasion.
I'm not sure about any of that mileage running around the country up there. No way gas is $8 per. Does the gas mileage change when the price goes up? LOL! Just bustin your balls Al. I know you don't care what the mpg is as long as the smiles per miles stays the same.
Actually our problen here is that the corporations own our government, they pay no taxes and our tax dollars are given to them in a variety of ways from R&D, write offs, BLM land use, etc etc, they not only pay no taxes they get a refund from all of their write offs and R&D (R&D we already paid for) and those refunds come out of our taxes, we have too many punk billionaires who are working the system, the entire left vs right thing is a show to divide and conquer, Pelosi and Boehner are both multi millionaires from taking bribes and pretending to care.
We could and should easily have free health care and more, when any corporation whether it's big oil or Rx or whoever....when they work the system all other businesses get hurt, people in the US are spending way too much on energy and healthcare when that money could be going in all directions and that's what makes an economy strong.........ours is about to crash again because we went right back to the trickle down crap.
It also hurts our hobby because people don't have the money to spend on cars and parts, etc,
There is no question that corporations use the tax laws to minimize their tax liability. Individuals do too, or they should be if they don't. Interestingly, 44% of Americans now pay no federal income taxes and the top half pay 97% of the taxes.
That said, in reality, corporations don't end up paying the tax dollars anyway. Consumers of the companies' goods and services pay it in the form of higher prices, investors pay it in the form of diminished returns (negatively impacting 401k, IRA, pension plans, and individual stock holders), and employees pay it in the form of lower wages. Worse, high corporate taxes (and oppressive regulations) on US corporations makes them less competitive in the global marketplace which pushes purchases to foreign competitors or the US corporations moving overseas which impacts jobs, stockholders, communities, and the US economy.
Although I may oppose some of them for other reasons, I do not begrudge "punk billionaires" who have legally earned their fortune building a successful business. I like the thought of new entrepreneurs.