Hi
I built up a mild 400 sbc about 2 years ago and finally installed it in my 1954 Pontiac custom. It has had a hone alignment on the crankshaft, stock pistons 0.040" over, edlebrock intake and performer cam (350 size cam not the 400 one), etc.. The crankshaft had #1 bearing originally toasted and the crank main journals were reduced to the 350 small size and oversize bearings used (the same ones used to destroke a 400 to make it 377 cid).
When I started it up, there was a loud heavy slapping noise from the bottom end. Not piston slap sound which is a tinny sound. This was loud and heavy. The engine ran quite smooth regardless.
I've pulled the engine and removed the oil pan and quickly took a look inside. Everything is where its supposed to be thankfully as I expected to see broken parts. I did finnd what seems to be interference between the front counterweight and the top of the engine block as there are score marks on the outside edge of the counterweight.
- Is there a size difference between the 350 sbc and 400 sbc edlebrock cam? Is the 400 sbc a smaller radius for clearance?
- Why would I have clearance problems now when the crank came out of the block originally. Can there be a machining problem when the crank/block was done?
- Can excessive crankshaft end play cause clearance problems? I'm wondering if the crank was incorrectly ground down to the smaller journal size.
I won't get a chance to take a good look until Thursday afternoon so any ideas that you have, I'll be glad to hear them and investigate.
Thanks in advance