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MK II B roadsters ('67 to '74 1/2) / Speedometer Erratic
« Last post by march2021 on February 14, 2021, 12:58:18 PM »
I have a 1967 MGB and the speedometer became erratic this past week, Initially it would fluctuate from 60 to 120 and eventually now swings to the stop at zero. I initially oiled the inside of the cable to no avail and then replaced the speedometer cable and the right angle adapter but again to no avail.

Do you think that I need to have the speedometer serviced? Do you or Rusty Moose Garage service gauges or where I can have it serviced if that is the rectification.

Thanks John for your advice.

Mike White
Port Sydney, Ontario
Electrical Items / Re: Alternator Replacement
« Last post by JohnTwist on February 14, 2021, 01:06:54 PM »
The 1968 MGB uses a 15AC alternator with an external 4TR regulator.  Following that are 15 ACR (internal regulator), 16ACR, and finally an 18 ACR.  They are all interchangeable, EXCEPT for the plug variety.  There are two varieties of the three wire plugs:  narrow-wide-wide and narrow-extra wide-narrow.  Of course, you can change the spade terminal configuration by soldering different sized spades onto the wires.  The outside wire is BROWN/YELLOW, the center wire is the heavy gauge BROWN, and the inside wire is a sensing/feeder also BROWN.

Some owners have adapted a Saturn alternator which can produce 100 amps (you do NOT need 100 amps and even if you did, the wiring cannot handle it).

Hope this helps!

John H Twist
University Motors Online
Electrical Items / Alternator Replacement
« Last post by march2021 on February 14, 2021, 12:57:27 PM »
Can I replace the standard alternator on my '73 B with a new 18ACR without any modifications? Cheers
Dave Hornby
Engine Related Items / Re: Metering Needle
« Last post by JohnTwist on February 14, 2021, 01:07:39 PM »
The B1AF is the needle for a TR6.  Whether it makes the MGB run richer or leaner throughout the rpm/load range I don't know.  I'm sure you'll be happier with a new 45H needle.
That said, the jet wears as the needle wipes against it.  You can purchase a new jet, drive the old one out, and drive the new on in -- but not without damage unless you make a special tool to do the job.  So, resize the old jet.  Get a tiny ball bearing -- 1/8" or less.  Place it on top of the jet, place a punch on top of the ball, and give it a crack with your hammer.  This will crush the top of the jet inwards.  Now, drill out the jet with a #39 bit (0.0995") and the jet will be round. 
The better way to do this is to remove the carb, remove the float bowl, and support the bottom of the jet on the bench or vise as hitting it from above without bottom support can allow it to move incrementally downwards (causing a rich mixture)

Hope this helps!

John H Twist
University Motors Online
Engine Related Items / Metering Needle
« Last post by march2021 on February 14, 2021, 12:55:38 PM »
What effect would having an incorrect metering needle cause in operation and performance?  I recently discovered that I have a B1AF needle instead of a 45H.


Ron Roland
MK II B roadsters ('67 to '74 1/2) / Re: Loss of Power
« Last post by JohnTwist on February 14, 2021, 01:08:36 PM »
here are many problems you could be having, but from here, Id put my money on a faulty fuel supply.  Remove the fuel feed to the carb, put it into a can or bottle, turn on the key, and expect to pump ONE pint per minute.  If the line just dribbles, then there is a problem with the fuel filter, fuel pump, hoses, or the tank.

If the fuel supply is just fine, then I would look at the point gap next.  Ensure the points are opening 0.015.

After that, back to the carbs as the floats in the HIFs can be installed left to right and that results in low fuel in the carb float bowls.

Hope some of this helps!
John Twist
University Motors Online
100 East Beltline Avenue SE
Grand Rapids MI 49506-2410
Cell  616 307 6737
MK II B roadsters ('67 to '74 1/2) / Loss of Power
« Last post by march2021 on February 14, 2021, 12:53:51 PM »
I have a 1974 MGB that has a loss of power at about 2500 rpm.   The car starts fine and runs fine at low rpm but as soon as I get it up to 2500 rpm it chokes out.  If I take my foot just slightly off the gas it is OK.  But if I try to go faster it does it again.  I had this problem last year already so this year I decided to remove the carbs and clean them and set them back up. Also lapped the valves and adjusted. None of which fixed the problem.

I was wondering if it could be the fuel pump or coil. Please let me know what you think.

Heinz Kettler
B roadsters rubber-bumpered ('75 to '80) / Re: Temperature Control Knob
« Last post by amgba on February 14, 2021, 01:09:49 PM »
Disconnect the cable from the heater valve under the hood and the see if the valve moves freely. Also see if the temp knob now turns easily. Often the hot water valve gets stiff if not used.
Gary Graham
B roadsters rubber-bumpered ('75 to '80) / Temperature Control Knob
« Last post by march2021 on February 14, 2021, 12:54:38 PM »
I have a question about my 1975 MGB. The temperature control knob is very hard to turn. Looks like it has a new cable. Hard to turn it completely off. It had engine work done before I bought it.
White Board
Engine Related Items / Re: Fuel Lines Location
« Last post by amgba on February 14, 2021, 01:10:34 PM »
No. They are on the far side of the tank on the passenger side

Dean W. Hickenlooper
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