MGB Tuneup Part 1: How to Tune Your British Sports Car

One of the biggest misconceptions about old cars is that a tune-up on a Triumph TR6 or an Austin-Healey involves changing the plugs and turning a screwdriver on the carburetors. That's simply not enough, and it's a large part of the reason why they have a reputation for being unreliable. We take an MGB through a more comprehensive procedure.
In this video, we look at the basics. Checking the plugs is important, but while they're out it's a good time to run a compression check. This could help identify problems before they become serious so you have time to prepare. We also adjust the rocker clearances, which may not have been done in decades. Controlling the valves on a new car is very precise, but took a little fiddling if you have a pushrod engine with solid lifters.
We'll continue through until we (finally) get to adjusting the carbs... but follow along. You can tweak those SUs as much as you like, but whether you have an XKE or a Spitfire, your car can run terribly if the distributor isn't working properly!

[@ianwilliams1448]

Remember to wedge the throttle pedal to the floor. You'll get a big increase in compression

[@midwestmotoring]

Depends on the carburetors. In an SU or Zenith-Stormberg, the air piston is still going to be mostly or fully down--so even with the throttle open it won't make a significant difference in compression readings. With a Weber, that's a different story since they don't have an air piston and therefore don't operate the same way. Also, remember that the gauge probably isn't super accurate anyway--especially since the dynamic compression while the engine is running is likely to be quite different than the static pressure from just turning it over. What we're looking for is a comparison between the different cylinders; not the absolute compression reading.

[@jeffharrison5265]

Great video. Yea, don't want to squeeze the electrons. LMAO. 🤣

[@midwestmotoring]

You know that someone's going to hear me say that and take it seriously, right?

[@midwestmotoring]

You do need a sense of humor to work on these things though....

[@jeffharrison5265]

@@midwestmotoring that's for sure. I'm battling a front windscreen install and IRS mount replacement currently. Hopefully have the front and rear windscreens back in and Jag roadworthy this weekend.

[@jeffhildreth9244]

No need for the zip ties on 4. What was your choice of plug gap ? Not enough revolutions on the compression check. Take your compression check after adjusting valves. The professional way to check valve gaps is re-torque the head first. What is your figure for valve clearance ? There is another technique that requires engine rotation only twice. Carb adjust? Timing? Points adjust presuming not electronic.

[@midwestmotoring]

I know, but my OCD would never let me get away with that. :)

[@stevepss]

Hey, another rookie question - Should I block off the fuel lines before I compression test? I have an older pertronix ignition, so my initial plan was pull the negative wire off the coil and then I started to overthink things and wonder if I'm load the carbs up with all the cranking over. Thanks again!

[@midwestmotoring]

No, the floats in the carbs will stop the fuel flow. No need to block them off. As for pulling the wire, that'll work and is a good idea.

[@stevepss]

Great vid! Rookie question, do you need to worry about the valve cover gasket if you're taking it off?

[@midwestmotoring]

It's usually best to replace it, but in a pinch not absolutely necessary since it's not under that much pressure. If the gasket doesn't break, I can't say I've never just reused it.

[@stevepss]

@@midwestmotoring Thank you!