I'm afraid I don't. All I can tell you is that it uses stock valve springs but they have been shimed up .050. I'm reading the specs as Tom wrote them in 1997 and I don't see anything that might help. You probably know that he passed away some time ago before he finished this motor so it would be very sentimental for me to finish it since I considered him my friend. According to Toby all it needs is for the pistons to be fly cut.