Is valve shrouding a concern in a 318 w/ 2.02 & 1.6 valves

yellow rose said
Like I said, not trying to talk you out of anything. I don't care what you do.

You are correct in the 360 main bearing size. It's too big for what you want. BUT, I never like to give up bore size. Don't kid yourself, bore size makes HP.
If you are ok going out and being a back marker and having fun, so be it. But, when you come to a forum and ask advice about something so simple as valve shrouding but not giving exact details, you are going to get answers all over the map. You are not just asking about valve shrouding. You are asking about compression ratio, cam timing and all that.

THERE IS NO WAY I WOULD CALL COMP AND GET A CAM FROM THEM ON THIS DEAL. I know all the comp fan boys will hate my guts and flame me up for it but I don't care. You need to call somewhere that you get to talk to the guy who grinds the cam, or who is not some snot nosed kid just starting out. If you have an inside connection at comp then go for it. Otherwise, you need to call Jim at Racer Brown, or one of the guys at Cam Motion, or Mike Jones at Jones cams. The guys at Bullet are good too. Call them all and see what they say. Deal with the one who YOU get on with best.

BTW, you can put billet caps on a 318 (or a 340 or a 360) and it is just a waste of time. The cap is NOT the issue. The blocks are weak. Girdles do not help either.

Best of luck to you.

Keep us posted.

I'd love to see you succeed.

Okay, you seem to think it's much more simple than it actually is. A 4.00 bore does not automatically equal a podium finish, a 3.91" bore does not automatically equal a last place finish. The block I have is bored .030 over already, I'm planning on boring it another .010. That means 328.5 c.i. and a 3.95" bore, that means that the bore will be 1.25% smaller than that of a 360. The displacement will be about 8% smaller. However, the 3.31" stroke and 6.123, 6.125, or 6.00" rod has a better rod/stroke ratio than 360s 3.58" stroke. In fact, the 318s factory rod/stroke ratio is 1.85 approximately, with 6.00" rods it is 1.81; almost perfect. The 360's rod/stroke ratio is 1.71 approximately. If you were to run 6.00" rods on a 3.58" crank, the ratio would be 1.675, not good. The 318 crank weighs less due to less material for the shorter stroke and smaller journal sizes, the pistons will weigh less, the rings will weigh less, to get an optimum rod/stroke ratio; the rods will weigh less because they will be shorter than the 360s equivalent (to get a rod/stroke ratio on a 360 of 1.81 you would need to run rods that are 6.5" long). There's a lot more to making power than displacement; at least when you're dealing with high performance racing engines. The 360 will have more torque. It's just a sacrifice I'm going to have to make, and it doesn't mean that I'm going to be in the back of the field. Like I said, if you have an R3 block you want to give me or a 360 block, or even a 340 block, maybe I can change my plans. The valve spacing on most small block heads is 1.87". 1.87"+ 1.025" (half the diameter of the intake valve on a B1BA) + .8 (half the diameter of the exhaust valve on a B1BA) + .375" (to avoid valve shrouding a clearance of 3/16" between the valve and the cylinder wall is recommended) would equal a bore of 4.07" which is a 340 bore .030 over (assuming the valves are centered in the bore).