Unleaded but not sure

[Bridgetthemidget]

Hi Guys,
The previous owner of my 79 Midget 1500 has ran the car on unleaded fuel for the last 3 years as did the owner before.
But looking at the documentation a recon engine was fitted in 95 and it say unleaded fuel NO.
Is there away of telling if the engine is supposed to run unleaded?.
Should I put a lead additive in with the unleaded anyway?.
The engine is pinking(SP)(timing chain rattle) in 3rd and 4th gear under load and sometimes missing and gets jerky, could this be due to wrong fuel?.
Cheers.
Ian.

 

[Kurtis]

Ian,

Based on most if what I've read regarding the subject, running unleaded in a car with a head designed for leaded fuel under *normal* driving conditions is not likely to cause any problems. Over time, there may be slightly more valve seat recession, but not enough of a problem to warrant adding lead substitutes.

I would continue to run unleaded gas with no additives and save any money you would spend toward a head rebuild. I'd bet that by the time any increase in the valve seat recession becomes an issue, you'd have more than enough money to rebuild the head with hardened valve seats.

Are you sure the pinging you describe isn't just pre-ignition? You might try retarding the timing a little to see if that clears it up, though a little pinging in high gear under load is typical even when the car is timed correctly.

Good luck!

 

[Bridgetthemidget]

Thanks for the advise.
It's making that timing chain sound as described and under hard execleration, it's loud enough for me to back out of the throttle.
It also runs on for a second of two when I switch the engine off. I had many MK2 Escorts and Fiestas that did the same, a good set of HT leads and getting rid of the points made a big difference.
Cheers.
Ian.

 

[Kurtis]

The run-on problem could be a timing related issue as well. Even premium gas today doesn't have as high of an octane rating as gas available when these cars were new. Did '79 Midgets have any kind of antirun-on device? If so, you might check that. I know my TR4 is sometimes prone to run-on. I've just gotten in the habit of leaving it in gear as I kill it while releasing the clutch pedal.

 

[StevenA]

There is a run-on sensor on my 76 and on my 78-79 Bs so the 79 Midget might be fitted with it. Check near the firewall on the passenger side. One of my Bs has a bad run-on sensor and it caused the battery to go down... it seems that when bad they can cause a short.