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MG MGA - muffler in relation to overheating

Now that my mechanic said he fixed my overheating problem. He now tells me after having the car for 3 weeks that there is a hole in the muffler. Hmmmm I know. My question would that have an effect on the overheating. He stated that he checked the timing and mixture. I went driving today in about 85 degrees. Was fine until I hit the freeway doing 60mph at 40,000 rpm. The temp. started to rise to about 210. Not sure what else to do. Spent a bunch trying to get the problem fixed. I am replacing the muffler next weekend.
Would the hole in the muffler affect the temp, during normal freeway driving?

Or better yet, how does not having back pressure from a sealed exhaust affect the temp/ timing and fuel mixture in the carbs..?
MS

Perhaps the problem is that because the muffler is rotting away, its inner baffles have rotted away to a point where they are loose and blocking the free flow of gases out of itself,hole or not? Just a thought.
Bob Muenchausen

You need new gears and a transmission to lower your RPM's from 40,000 to 4,000. The engine puts out more heat at higher RPM. If your engine does 40,000 I want to buy it NOW. LOL
JEFF BECKER

Jeff,
Opps too many zeros....so in lieu of the error of reading the dial. I still have the problem. Not sure what else to do. Just want the temp to read under 190 when driving around town. I could deal with the temp going up as I get on the freeway. Let's see if a new muffler does the job.

MS
MS

I doubt that the muffler is your problem. I recently replaced my entire exhaust system in the course of an engine replacement, and I discovered that the old exhaust system, including the muffler, was peppered with holes along the upper surface. Nevertheless, my old engine ran steady at 170 degrees with that hole-filled exhaust.

Regards,
M.D.
'57 Coupe
M. D.

The last thing I will find out is what were the specs. he timed the engine on. I told him I have an 1800 engine in there, so I would assme he set the timing to that engine and not a 1600 engine. The gauge has been calibrated so its reading the correct temp.

Thanks,
Merl
MS

MS,

Timing for 1800 engine (assume you have early 18G, 18GA or 18GB) is 20btdc @ 850 to 1000 rpm. Otherwise, look for the obvious first--is the thermostat opening? What condition is the radiator? Tried back flushing it? Has the engine been rebuilt and if so, were the galley plugs removed and rifle brushed? Are the grill slats opened or are they as received right out of the box? What's the oil pressure at 3500 rpm? Many things contribute to overheating yet have not heard the "bad muffler" theory yet
Paul Hanley

Not knowing the exact dissy installed means you can not time it in the lazy mans way. The only way to time this engine is to use the proffessional way and the only way I ever use. Remove the vacuum line, rev the engine to 4.5k rpm and set the timing at about 30 degrees BTDC. If this does not cure the overheating then assuming the mixture is correct the next job I would do is to have the radiator re cored, this technique I have found cures 99 percent of the overheating problems I have found on other peoples cars.
Bob (robert)

My ten pennyworth on these overheating issues is always along lines described by Bob. Timed as he decribed and with as close as possible radiator to the original design, my temperature rarely climbs above 170 regardless of outside air temperature.

As an aside, I find it quite nerve racking leaning into the engine compartment to do the timing at 4,500rpm. It always feels as if the engine is about to blow apart so I've taken to wearing ear defenders - what the brain can't hear etc!

Steve
Steve Gyles

Gents,

Thanks for the comments...all a guy wants to do is take the lady out for a nice drive in the evenings after work up to the Napa Valley...
The engine is number is the 18GK series (70-71mgb). The oil pressure is at around 80 when 3500rpm. I am asking the mechanic what was his reference to setting the timing. The radiator and thermostat are newly installed. The car has replacement grill that I will reposition that slats tonight when I get home. To my knowledge the engine hasn't been rebuilt, and have been told it doesn't need to be. I will flush out the engine block, although I told the mechanic to do so when he replaced the radiator.

The car had sat for about three years in a garage. It was my fathers, who I remember never had these problems. His thing was just to recharge the battery since he drove it every couple of months when he was home. He never had a heating problem.

Thanks for the assistance...

Cheers,
Merl
Merl

ANYTHING that changes the flow through the tailpipe WILL affect the CARB'S AIR/FUEL RATIO! Hole in tailpipe or muffler OR fitting a "STRAIGHT-THRU MUFFLER" OR "TUNED EXHAUST HEADERS" will ALL require a "TWEAK" on the S.U.s! You can prove this by purchasing a "COLORTUNE" Transparent Tuning Spark Plug from MOSS MOTORS and WATCH YOUR CYLINDER COLOR CHANGE FROM "PERFECT LIGHT BLUE" to "TOO RICH ORANGE" as the AIR/FUEL RATIO CHANGES! Incidebntly, with TWO "COLORTUNES" in #1 & #4 cylinders you can get a PERFECT A/F BALANCE on your Twin S.U.s! (Because of the "SIAMESED INTAKE/EXHAUST PORTS", #2 & #3 cylinders don't burn as well as #1 & #4, which you can ALSO see with TWO "COLORTUNES"!) The "COLORTUNE," last I knew was good up to 5,000 RPM, but is supposed to be used "FOR TUNING ONLY"!
OLD BILL-67

This thread was discussed between 28/08/2005 and 31/08/2005

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