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Fri Mar 28, 2003 8:57 pm

I have a 1600cc engine and after about 5 to 10 minutes the intake starts to develope frost. not long after the engine stop runing this is in 20 degree weather and the choke is working.

Fri Mar 28, 2003 10:52 pm

DO you have the preaheater tubes runnign up from the holes on the exhaust, to under the intake manifold? If you do is the Exhaust aftermarket? If so did you drill out the preaheater holes (they quite oftne I'm told don't get all the way formed from the facotry). If no to any of these then there's your problem. The preheaters take the head from the exhaust and run it along the intake so that the tube is warm enough to keep the gad from freezing! And if you done all of these... well I'm stumped

Sat Mar 29, 2003 9:10 am

Also if you have the OG aircleaner make sure the warm air pickup is hooked up

Sun Mar 30, 2003 9:32 pm

Viggy is right - aftermarket exhaust systems often come with the pre-heater fittings at the flange not drilled-through to the exhaust itself - this allows the muffler to be used on a twin-carb or other set-up which doesn't need the heat riser. They are easy enough to drill out, but you might need to remove the muffler from the car to do it.

So check the heat riser - the smaller pipe under the horizontal inlet manifold. It should be getting finger sizzling hot and make the manifold above it quite warm to touch.

And Bugnaked is right too - a carby pre-warmer is very important in cooler climates - when the engine is cold it pulls carby air up from close to the cylinder heads to get some heat into the carb quickly. There are two operating systems for these -the earlier cars (pre 72) have a pull-wire linkled to the right hand flap unit in the fan shroud (it provides hot or cold air - nothing in between), and the later style has a vacuum line from UNDER the carb, up to a sensor in the air cleaner and then on to the flap operating device on the air cleaner inlet. This type senses the air temp in the air cleaner and supplies hot, cold, or mixed air as appropriate.

Rob
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Repairs and maintenance for the home mechanic
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