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MG MGA - The Old Overheating Question ??

I was at GT30 in Mackinaw. On the way up the car ran hot (200-215) at speed (60mph). Around town in Mackinaw no problem (180-190).... even though the outside temps were very high each day. Same thing on the return trip after the GT ... highway speeds temp ran between 200-215. Last year I didn't have a problem (always 180-190 tops). As for the obvious question ... what did I do since last year !!

Same rad (new 2 years ago)
Fresh 50/50 Mix
Added Waterwetter
Rebuilt distributor (rebuilt by John Twist)
Brand New SU Carbs (new from Moss)
Blanking Sleeve only - no thermostat (same as last year)
Timing and Mixture set by John Twist at the rolling tech session in Mackinaw. He said if it still runs hot cover the gauge with duct tape !!

Other symptoms:

engine pings very badly under load. Even though the timing was set by the "Guru" I have been retarding it a bit to try and deal with the ping. I've tried 87 Octane fuel and 94 Octane .... still runs 210+ and still pings.

Any suggestions ???

Mike - 1960 MGA 1600 Roadster

Michael Hosier

Hi Michael. Have you tried running WITH a 160 degree thermostat? This might lower the coolant temperature. You might also check the vacuum advance unit to make sure it is functioning. (Yes I know it is a new distributor) Also check that there is vacuum actually getting to the vacuum advance unit. The only other thing I can think of is that you may have a build up of carbon in the cylinder head. This can cause pinging and overheating. Im not sure if there is any way of inspecting inside the engine without cylinder head removal. Perhaps someone else has some ideas? Glenn
Glenn

Michael,
Fuel age, octane? Gap the points. New ones can show some early wear before they settle in. How's the valve clearances?
BOL,
Doug
D Sjostrom

I'm with Doug. The distributor seems to be the only thing different between when the temperature ran where it should and now that it is running high. While installing a thermostat may help, since ther is none in there now, that is the same as before the temperature went up (a low temp thermostat will NOT bring the upper temperature down, it thermostat just establishes what the minimum temperature will be). If there is a lock of lubricant on hte rubbing block, the gap for the points will close rather quickly. Also check that the carbs are not leaning out excessively at higher rpm as those are the other variable between tehn and now. Good luck - Dave
David DuBois

The pinking of the engine is a major worry. (pinging) Whatever is causing this is also causing the heat build up. I have to say I would expect this to be caused by the timing being out. This by either the dizzy not working correctly, the points being gapped incorrectly, or simply the timing set wrong!
Bob (robert)

Mike,
Does the pinging occur only when the engine is very hot? It could be a blockage in the cooling system, as overheating by itself can cause pinging. It also could be mixture or timing as they could cause both overheating and pinging. A sticking carb slide, could cause a lean condition under load. You said the carbs are brand new, and I am always suspicious of new parts.

Jeff
Jeff Schultz

I am more inclined to side with Glen, although all the issues raised are relevant. We had a similar discussion in a previous thread: "All out of ideas - overheating" that is now in the archives. My comment in there was that the car should be dynamically timed (4000RPM, vacumm disconnected) to 32ish degrees advance.

Carl Heideman also commented: "I see a lot of customer cars where the static or idle timing is "in spec" but the total is incorrect. This is due to either worn out advance springs or incorrect/swapped out distributors. I regularly see MGAs with only about 20-22 degrees of total timing at 4000RPM (vac disconnected). That 10 degrees of timing is costing 10+ HP and making the engine run warmer."

Steve
Steve Gyles

I wrote my comments without seeing Bob's input - with which I also concur totally.

Steve
Steve Gyles

Steve,

You say :" see a lot of customer cars where the static or idle timing is "in spec" but the total is incorrect"
Yes, definitively yes, I experienced that on my B and discovered the solution in P.Burgess's booklet "Tuning B series engine". I did make check my
dizzy curve by a mecchanics and only these two little springs were out of tolerances, making the advance too short.
Renou

Thanks to all for your suggestions. To answer some of the questions raised:

Yes the fuel is fresh and octane is 94 (also tried 87)

The vaccum advance unit is new installed and tested by Twist when the dist was rebuilt.

I have tried both with and without a 165 deg thermostat.

The point gap was checked and is .30 as I run a High Performance coil - also two years old.

The plugs look correct in terms of mixture - not too black not too white (a dark tan color).

The pinging does increase with the engine heating up.

Performance wise the car runs well.

Mike

Michael Hosier

Mike

The point gap you refer to is I presume for the plugs and not the contact breaker!

Steve
Steve Gyles

Your rad may be only two years old but it would be worth trying another known good one in your car. It would be prudent to completely flush the system, change the rad and then do another high speed run. Whilst your system is OK in the city it seems that it just does not have the capacity for sustained high speed running.
Iain MacKintosh

Sorry Michael, unlike Steve I assume you mean the points gap is 30thou?? If that is the case then that would seriously advance the timing. Whether this advance would be enough to cause the overheating, remains to be seen but if you actually did mean the points were at 30thou then please set them to 15 and give it a try.
Bob (robert)

Bob

We both latched on to the same thing, just worded our posts differently. As you say, if it's the point gap at 30 thou it would explain a lot.

Steve
Steve Gyles

Restricted exhaust will cause overheating at higher speeds, which will cause pinging and poor high speed performance. If pipes are not damaged, clogged muffler from Mousie's winter nest is the most likely cause.
FRM
FR Millmore

Or, another possible exhaust blockage could be a rusted out baffle in the muffler which has broken free and is now blocking the exit.
Bob Muenchausen

Sorry folks I did mean plug gap at 30 and not points. Points are set to 15 per spec. I haven't checked the exhaust for debris although the flow at the tip would seem to be adequate and normal but well worth investigating further. Thanks again !!
Michael Hosier

In the "Bad Old Days", not really the "Good Old Days" (1950s & 1960s), most BMC Dealers (Later British-Leyland) were also servicing Triumph, Volvo, Saab, Morris Minor, and other foreign cars! Unless you did all your own repairs like I did, it was fairly common to find the "wrong" Lucas distributor in your car because some "Mechanic" at the shop discovered that the "available now" in "Parts" (or from the junkyard!) Triumph distributor worked "good enough"! Often he could "get away with it" because Lucas distributors usually had the same exact backplate & weights and only the advance springs were different! Best way to set breaker points is with a "Dwell Angle Meter", 60 Degrees gives you your .015" gap on the nose. 58-62 Degrees will keep you "Within specs".
wattswh1

This thread was discussed on 05/08/2005

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This thread is from the archive. The Live MG MGA BBS is active now.