My 70 Chevelle 307ci, turns over fast when cold, but when the engine gets hot, it starts very slow. uur uur uurr urrr.

Same problem here with my old '70 Torino. What the problem was is that the battery cables were at fault. Replaced them. Started strong and constant after that. Sometimes we can't see whats going on inside of the cables.
http://www.thenebula.com/carpics/pics/checked.gif

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Joe G.
ChicagoChevelle68
Any car past 1972 is just simply transportation, really!

could also be starter brushes or really advanced timing..

The possibilities are a weak battery, a bad cable (either the positive or negative cable) or a bad starter. In my history it has always been a bad starter. Replace it with a completely rebuilt starter and solenoid as it is not that expensive. You can rebuild it yourself with a kit that is very inexpensive and it does include the brushes mentioned earlier.

check your timing it might be a lil bit to high I had the same problem when I had the 307 in my velle I put on a new starter still had the problem then an old timer said the timing might be too high and that solved my problem

Could be heat soak from the header. How much space is there between the header tube and the solenoid? To help diagnose, next time it does it, spray water on the solenoid to cool it off, see if that makes a difference.

Do a search on this topic also. Lots of stuff there.

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Paul Hesco
www.chevelles.net/nfc (http://www.chevelles.net/nfc)