what fastener is used for #516 valve cover

I have come up with a measurement of .245 on the studs (measured between the threads) and in measuring the supply at the store the only thing they had with that measurement was the #7-1.0 metric. I bought 10 but in putting them on the stud they seem to fit but are a little too lose on the threads to suit me. They probably could only be torqued down to around 15 inch pounds before stripping which would not be good. I will pick some 5/16-24 thread to try but I have already use the tool thread counter and the 24 did not fit. thanx for everyones input.