You don't have to. I The previous owner of the engine head gasket matched the the top of the bores to match his head gasket and the non round side of the combustion chamber, so it isn't really notches for valves. It really isn't the best thing to do on a small bore engine like this, takes away a few points of compression. It is something I have heard of people doing in the past to make a smooth transition from the edge of the combustion chamber to the cylinder but I have heard mixed feedback on whether it really makes a difference. Take a look at the attached picture and you should be able to see t.
I reordered my gaskets and will have to run a 4.125 bore, .039 gasket. This will give me a .054 quench and 10.15:1 comp. Taking .010 more off the block will put me at .044 and right about 10.5:1. I don't know if doing that is worth it or not for the effort. Thoughts ?
It's really a hard call. Less quench will get you some detonation protection, even with slightly more compression. But you're still losing out to the big bore gasket. Is it worth the extra cost? Hard to say.
Have you actually measured everything so that you know for sure what the compression ratio is? For instance, those notches and having to use a 4.125" bore gasket gives you a LOT of extra volume. Have you exhausted every possible source for a thinner 4.125" bore head gasket?
The really right way would be to replace the block, getting rid of the notches, and enabling you to run a head gasket for a smaller bore that's also thin enough to get the right quench height.
Yeah the calculations are all as correct as I can be. I do have another block but it is a standard bore and would need to be completely done from scratch. My son and I were actually going to save that one for a future project. If I deck the block .010 more I can get in the best quench range and boost up the comp. to right around 10.5:1 with that gasket still. I may opt to do that.
Based on where my cam RPM range is 2,300-6,300 RPM, .218/.228 duration @ .050, .503/.503 lift. 112 LSA hydraulic roller, do any of you think I will benefit from an X pipe or an H pipe in my 2 1/4 inch exhaust system ? I read some conflicting information as to how it may benefit or hurt my little 265. I would like to hear your suggestions or if you think it isn't worth the effort at all.
Before we get into the X pipe, keep in mind that the advertised rpm range for your cam is probably based on a much bigger engine, likely a 350. But it's still not all that big, but I don't know where they get that 2300 rpm starting point, it's probably a lot higher for a 265.
I've never seen any claims that X pipes are bad for small engines or certain cam choices. Their main benefit is a small torque increase that starts at low rpm and continues through the power band. Plus an X (or H) pipe changes the exhaust note. How can this be bad for you? Unless you don't like the sound.
X pipes started getting attention in the early 90s when the Winston Cup car driven by Sterling Marlin (Kodak #4) ran very well at the restrictor plate races at Daytona and Talladega and had a distinctive sound. This was a relatively low rpm engine by the standards of the day (and today). Not much more power than you'll have, and not much more rpm.
The advertised RPM range for the cam is actually 1,800-5,800. The Lunati rep. said a 300-500 RPM addition to the range for my 265. I am not worried about it changing the exhaust note. I am just trying to get all I can. I will actually be glad if it runs better than it sounds, it will be more impressive to me.
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