61 Distributor Dwell
I've been working on a friends 61 today that had an overheating problem that turned out to be a timing issue. In setting the timing, we checked the dwell and it was at 43 degrees. After trying another dwell meter, it was still at 43. I gapped the points with a feeler guage and checked it again. Still 43. It's a base motor, single point distributor. Any suggestions? Thanks
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Re: 61 Distributor Dwell
Find an allen wrench that fits in the points adjustment screw and adjust the points with the engine running with the dwell meter attached. Simple. Once the dwell is right, set the timing. Job done. -
Re: 61 Distributor Dwell
Thanks, but we did that. I should have been more specific. We can't get the dwell up or down by adjusting the points through the cap.Comment
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Re: 61 Distributor Dwell
replace the points and try again. are all 8 lobes of the distributor's cam worn away completely? problem definitly in the distributor or the points. when you run the allen bolt in and out(with the points on a high side of a lobe, can you see the point coming closer together and widening as you turn the allen bolt? sounds like points to me. good luck,mikeComment
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Re: 61 Distributor Dwell
Thanks Mike, we'll look at the points again. The points will open and close with an allen wrench adjustment, but I didn't look to see if they open while cranking the engine. I'll check the lobes too. My first thought was the breaker plate.Comment
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Re: 61 Distributor Dwell
I suppose this is a stupid question, and I apologize if it seems so, but how are you connecting the Dwell Meter? It seems so strange that you aren't getting any response out of point adjustment, and specially when you've tried two meters and say you can see the point gap move when you attempt an adjustment.
Stu FoxComment
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Re: 61 Distributor Dwell
No problem Stu. There are no stupid questions. As to you question, I'm not sure. Anything's possible. We changed out the points today, and wouldn't you know it, the new points were defective. Couldn't get any spark from them. We returned them for another set and they worked fine. I checked the dwell and set it at 34 degrees. Set the timing again and she runs like a top. No more overheating! Thanks to everyone for your imput.Comment
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Re: 61 Distributor Dwell
Thanks John. I'll set it back to 30. It's amazing how much timing has to do with an engine running hot. His car has been overheating for the last two years, after the engine was rebuilt. He got to the point of not driving it anymore since he was so disgusted. He had even went so far as to replace the radiator with an aftermarket unit that didn't solve the overheating. I'm sure a lot of other guys are having the same problem. His is back on the road now.Comment
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Re: 61 Distributor Dwell
Jerry,
If the vacuum advance or inital timing is not correctly set, the fire in the cylinder is lit too late and is still burning when the exhaust valve opens. All this heat is transfered to the block and exhaust and the engine runs hot. Not to mention the waste of energy because point of maximum combustion is late and not available to push the piston.
Ever notice how the engine speeds up when timing is advanced, thats because the point of maximum combustion is in that sweet spot for idle. This point changes with RPM, fuel mixture, load etc.
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Re: 61 Distributor Dwell
Even if timing is very late for the operating condition, combustion is almost always complete before the exhaust valve is open, but if timing is late the pressure and temperature are greater when the exhaust valve opens due to less expansion.
On a non-emission controlled engine with total idle timing in the correct range of 22-34 degrees (The greater the valve overlap the greater the necessary total idle timing). the exhaust manifolds should measure no more than about 500F with an IR gun.
On a later emission controlled engines set to OE spec with ported vacuum advance, total idle timing is equal to just the initial value, and the manifolds will measure several hundred degrees hotter.
The higher the EGT the more heat is absorbed by the cooling system as the exhaust gas passes through the exhaust ports, and insufficient total idle timing is a primary cause of idle and low speed overheating.
The message is check you initial timing, check your VAC to be sure it is functioning and is correct for the application (not all OE VACs are correct from an engineering standpoint), and convert ported vacuum advance to full time using the "two-inch rule" to select a proper VAC for full time vacuum advance.
DukeComment
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