Hi, just thought I would post this because there are a couple of engines being built here. My goals for my engine were to have a bunch more power than I had with my tired 77 400, to maintain excellent low end torque and driving manners, to have an engine that was reliable and easy to tune, and to work with my 4 speed and 256 rear gears. I am not an expert engine builder and I am not pretending to Know what the experts know.
The engine is a standard bore, standard crank 76 455 that I took to a shop and had them measure everything, hone the cylinders, polish the crank, hot tank and install cam bearings and frost plugs and oil gallery plugs. Everything measured up very nicely and the shop supplied me with all of the parts to assemble it. The heads are 6x-8 that had new valves and seats ground when I got them. I read Jim Hands book and ported the heads myself but did not change to 1.77 exhausts. It has an 800 cfm Quadrajet, stock 70 400 intake and long branch exhaust manifolds.
I measured deck height, combustion chambers etc and came up with 8.96 -1 compression, so now what cam? I studied everything I could find and I still blew it. I chose a comp cams 275 deh, 275,277 advertised, 219-228 @.050 and 110 lsa . It performs well, It does everything I wanted it to do and has a nice idle. The problem is that with this cam I have a dynamic compression ratio of 7.3 according to the "project Pontiac static and dynamic compression ratio calculator" that I used and with my iron heads this requires a steady diet of 91 octane fuel. Its only a 400 or so hp engine, a different cam choice with a dynamic ratio of 6.7=6.9 would have given me everything I wanted but running on 87 octane instead. The Crower 60916 has specs that would have done this well I think with a 4 degree later intake closing angle and 112 lsa. However all is not lost, not only am I stupid, I am also lazy and I did not take the time to remove my inner springs for cam break in. I have about 700 miles on this combo now and the jury is still out on weather the cam survived or not. I have had to re adjust the rockers and even with 1 full turn of pre-load I still have a couple noisy lifters after warm-up. Anybody with thoughts on this? also the cam called for 106 installation, and mine is at 105 degrees. Can I retard the cam 4 degrees to 109 and hopefully achieve my goals? Hopefully this helps someone else and if anybody can give me feedback on my issues I would really appreciate it. Neill