Stop in for a cup of coffee

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Mopar Tim said:
Hey guys. I think I know what my issue is with idle. I Think the Rhodes lifters are the culprit. As oil gets hotter, the lifters pump up faster, changing cam timing. Any thoughts?
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The flaw with that idea is that multi-weight oil gets more viscous when it gets hotter. 10W-40 is 10 weight cold and 40 weight hot. Also, lifters pump up with oil pressure and oil pressure drops in the engine when it gets hotter.

Something else is changing. Most likely in the idle A/F mixture or possibly in the distributor timing. I'd suspect the A/F first. Especially since you added the PCV system and that changes air flow through the intake. It may also be changing the fuel load into the cylinders, especially if you are getting fuel wash-down past the rings that is then being inducted back into the intake.
 
Ddaddy said:
The flaw with that idea is that multi-weight oil gets more viscous when it gets hotter. 10W-40 is 10 weight cold and 40 weight hot. Also, lifters pump up with oil pressure and oil pressure drops in the engine when it gets hotter.

Something else is changing. Most likely in the idle A/F mixture or possibly in the distributor timing. I'd suspect the A/F first. Especially since you added the PCV system and that changes air flow through the intake. It may also be changing the fuel load into the cylinders, especially if you are getting fuel wash-down past the rings that is then being inducted back into the intake.
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Is it running rich?
 
look fine to me...

20170714_2.jpg
 
Yeah, I wasn't suggesting it was flooding as much as I was suggesting that the A/F idle mixture is changing with temperature. Things like PCV and vacuum leaks can to it.

It is also possible that the timing is changing as it gets hot. Sometimes the advance springs expand and loosen with temperature so that the advance comes on earlier and raises the idle speed. If your curve is set to come on at 1200 RPM and then when hot, it changes to 1000 rpm...idle speed will go up. You can check the advance curve with a timing light cold and hot and see if it is changing.
 
I've also been considering going true old school too - as in Cragar SS's... which is why I haven't done anything - can't decide..
 
Ddaddy said:
The flaw with that idea is that multi-weight oil gets more viscous when it gets hotter. 10W-40 is 10 weight cold and 40 weight hot. Also, lifters pump up with oil pressure and oil pressure drops in the engine when it gets hotter.

Something else is changing. Most likely in the idle A/F mixture or possibly in the distributor timing. I'd suspect the A/F first. Especially since you added the PCV system and that changes air flow through the intake. It may also be changing the fuel load into the cylinders, especially if you are getting fuel wash-down past the rings that is then being inducted back into the intake.
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Rhodes lifters pump up with rpm, not pressure. :thumbsup: Of course pressure plays its part.Frequently Asked Questions
 
Mopar Tim said:
Rhodes lifters pump up with rpm, not pressure. :thumbsup: Of course pressure plays its part.Frequently Asked Questions
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Yes, full lift is restored at high rpm...but that doesn't explain the idle behavior being related to temperature. Bleed down will happen even faster at low RPM in a hot engine since oil pressure is lower.
 
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