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Auto Blogs | Car Forums » Chevrolet Forums » Chevrolet Forum » Hard to turn over engine when hot

Hard to turn over engine when hot

Last post 08-17-2007, 10:33 AM by TIMAAY!. 2 replies.
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  •  08-14-2007, 8:00 PM 22457

    Hard to turn over engine when hot

    Reply Quote
    I have 2 Chevy small block V8's that start and run good when cold and/or warm but when it gets to normal temperature and it's turned off, it doesn't want to turn over.  It sounds like it has too much compression.  Once it cools for 10 minutes, it starts right up.  I've checked timing to be right and have changed grades of gas.  Any ideas?  One engine is a '76 350ci, with a 600 CFM Carter, a Comp 270 cam and Corvette alumium heads.  Auto trans.  The other is a '68 327ci manual trans with a 600 CFM Holley, a Comp 268 extreme cam and double hump (non fuelie) heads.
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  •  08-14-2007, 9:14 PM 22463 in reply to 22457

    Re: Hard to turn over engine when hot

    Reply Quote
    A common cause of high compression is carbon build up deposited on the top of a piston.
    carbon deposit may be the result of incomplete  combustion, a too-rich fuel mixture, or exessive oil that's entering the cylinder and being burned with fuel.The resulting deposits are very hard and tend to stick to the top of the cylinder.Because these deposits take up space in the combustion chamber, the overall size of the combustion chamber becomes smaller.
    Remove the cylinder head and scrap the deposits from the tops of the pistons.
    Are we talking about 76 and 68 chevy?
    Mechanic On Wheels LLC

  •  08-17-2007, 10:33 AM 22566 in reply to 22463

    Re: Hard to turn over engine when hot

    Reply Quote
    Thanks for the reply.  It must be something else on the '68 because I have just rebuilt it. There shouldn't be any carbon buildup with only 5 miles on it.  As for the '76, it's possible.  Any other ideas for the '68?
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