• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Gas Mileage

Share this page

B

Bobbee44

Guest
Guest
Offline
I am well aware that no one, in their right mind, necessarily keeps meticulous records on Healey gas mileage; however, the shop where I had my BT-7 tuned asked me to keep track of the mileage for a few tanks to ensure the the car was not running too rich. Anyone out there have any idea what mileage I may be looking for (combined town and highway)?
Thanks,
Bob
 
Bob, I just did a run to the coast, and got 23 mpg. Mostly highway at 55 mph. I have HS6's on a BJ8 motor.
 
I know it doesn't answer your original question- but spark plugs are a much better indicator of mixture strength.

Pull out a plug for each carb after a run and the insulators should be dull white on unleaded fuel. If any are grey or black then the corresponding carb is not set right. This works best with good valve stem seals as oil burning will mean the plugs are always slightly brown. Andy.
 
I get 20 mpg in mostly town driving and 22 mpg freeway driving at about 65 mph. I have a 64 BJ8 PH 1 with HD 8's. Have a good day!
 
I would think the shop would have him come back in after a couple weeks and check plugs and exhaust and pull a vacuum check, timing and etc. Rather than have customer do all the figure checks. Can't enjoy car if you have to keep tabs for the mechanic.
 
Good advice all, thank you. I will give the car a highway spin thisweekend and pull plugs. The compression checked out excellently, as did the leak down test. I think I am looking at a carb rebuild early in 2014. Could be worse, I guess.
Bob
 
I am impressed with the mileage all of you seem to be getting. Since new, I have not been able to get more than 17 mpg on premium. But there was one occasion.

In the process of moving West of Philadelphia during the winter of 1970, I had an occasion to drive up to NE Penn., then to NYC, and finely back to Philly. Cold and snowy, the trip was no pleasure and, since almost all was Turnpike-style high speed driving, I had little reason for stopping.

Somewhere along the trip the car started to balk down after stopping, especially in the city, and occasionally required a little clutch work to get moving. However, since it still could exceed 80 mph, and the weather had deteriorated to sleet, I had no intention of pulling over and investigate unless absolutely necessary.

While cursing at 60 mph on my home trip, I had a flash … I hadn’t stopped for gas and the trip odometer was registering about 350 miles! Although I had a full tank when beginning the trip, my gas gauge was still registering over a quarter of a tank? Anxious and questioning the gas gauge reading, I pulling into the next station and refilled the tank. Startled at the amount of fuel still in the tank, I did a rough calculation to find I had gotten more then 40 mpg. Totally confused at this result, I entertained myself at the cause and possibilities for the rest of the trip.

At home, the next 3 days were spent with a friendly Master Mechanic, identifying my (questionably) good fortune. A cursory review of the fuel system showed no obvious problems but dismantling the rear carburetor disclosed something I had not experienced before or since.

It turned out there were 2 issues that, in coincidental combination, caused the issue/benefit. First, the rear carburetor pin had loosened and vibration would cause it to fall from the piston and block the fuel supply. This condition combined with a lack of damper oil to allow the piston to drop with sufficient force to occasionally reseat the pin when stopped and, for a brief period, allow for normal start-up operation.

Unlike most other engines, the Healey 6 is nicely balanced into two 3 cylinder engines and never showed much displeasure idling on 3 cylinders. This balanced condition was one condition that initially directed us to other possibilities before centering on the carburetion. Over the years, I occasionally thought of causing this condition purposely but, as the Healey passed from everyday to occasional use, the thought passed.

All the best,
Ray (64BJ8P1)
 
Cylinder deactivation circa 1960. Had the same issue with my BJ8 once, but symptom was sometimes good running, sometimes running like it was fuel deprived.

I don't think the dashpot damper prevents the piston from dropping much if at all (the spring is a much stronger factor). It's there to prevent the piston from rising as fast as it would like when you open the throttles quickly, which would otherwise cause lean running and stumbling. I studied these ingenious little buggers when I had to cobble together two similar ones from a collection of parts for our BN2. They vary from carb type to carb type, but all the ones I've seen have a small disk above the (brass) damper piston which closes when the vacuum piston rises and opens when it falls (sort of a flapper valve).
 
Mmmm my BJ7 used to return mileage up in the high 30's but would not go more that 65 - 70 MPH. that was until I unblocked the fuel line from the float chamber to the jet on one of the carbs. been all down hill since. :wall:

My old 100/6 returned 13 round town and 22 on a run after a John Chatham rebuild.

I am just finalising the engine rebuild on the BJ7 so we will see what comes of that regarding mileage.

:cheers:

Bob
 
HI Bob,

You are correct in describing the purpose of the oil fordamping the withdrawal of the pin with the rise of the piston. However, without the oil, the piston, in myexperience, will rise and fall more aggressively and, in this situation the setscrew must have been positioned sufficiently to allow it to occasionally catch and holdthe pin for a brief time.

All the best,
Ray (64BJ8P1)
 
I have two problems,mileage and fuel gauge, but the bigger problem is the mileage. In short trips around town, I am getting 8-10 mpg. Since my second problem is a non-working fuel gauge, I ended up running out of gas on a fun-run yesterday. The car runs great, except for some hesitation around 4,000 rpm. It does take it a while to get started, and there is always a strong fuel smell (especially when warming up). I don't have any puddles of gas below the car. Should I be looking for a leak somewhere in the fuel system?
 
Re your fuel gauge- I just got mine working perfectly last week and it felt like overcoming a life long illness. It is surprising how satisfying a properly functioning and accurate fuel gauge is.

The problem was that it worked for some of the time then would go on random trips into lala land, wavering gradually about the dial as if possessed and then return a week later as if nothing was wrong. I did the wire onto the sender arm mod, checked the grounding of the tank/sender, checked the grounding of the gauge, checked the resistances across the gauge terminals, moved the coils to recalibrate it, hurt my back bending backwards upside down under the dash all to no avail. Then I took it apart and found one of the nuts inside that connect the tiny coil wires to the terminal posts was fractionally loose and would make only partial contact some of the time.

That's one small step I don't need to take again and I can thoroughly recommend fixing the fuel gauge to anyone.

Andy.
 
( It does take it a while to get started, and there is always a strong fuel smell ) Steve- check your timing, mine was way out and I had trouble starting for 8 years, then I got the timing checked -and adjusted WOW! what a difference.

:cheers:

Bob
 
We just finished 465 miles of interstate driving and average 21.32 mpg. Our next segment will include some two lane twisty roads.
 
I'm impressed with the mileage people get. All freeway is about 20-22. Town and freeway averages between 10-16.
 
As I live in the mountains at about 6500 ft, much of my driving is windy roads with many ups and downs. I usually do not get a chance to use the over-drive up here. I get 18 to 20 mpg in that kind of driving. When on the freeway and doing 70 to 75 with the over-drive on the mpg goes to 20 to 22. I don't do much city driving but the worst mpg I've gotten is 16. Last wekend we met with 18 other Healeys for a wine country tour and we did over 500 miles and got 21 mpg average. Now lets talk wine per mile. The final tally was 32 people and 29 bottles of wine in 6 hours.
TH
 
We are now up to 740 miles with a combination of I-44, OK-66, other 2 lane, US 69 & 412 and about 5 miles of gravel road (I can't pick where my B-I-L lives. Overall MPG is 20.31 with a low of 17.3.
I'm driving a tri-carb with a 3.54 rear end and a Toyota 5-speed. 3000 rpm equals 70 MPH.
TH - sounds like a fun afternoon.
 
Last edited:
Back
Top