Head difference?

Thanks, Paul for the quick response. I thought as much, and yes, I do understand the difference.



I ask, because I am currently in the process of getting literature and information together for my machinist for my 7X "conversion". I pretty much have that base covered, and now am starting to gather necessary parts for the task. In going over the literature, I apparently had forgotten that 7X's used 232 heads (for the highest compression, obviously). If I remember right, off the top of my head, the 262 should up the compression around 8:1 or 8.25:1. The 232 should be up around 9:1. I have no intention of letting it get out of hand, or doing more than I should for a street-driven car. I just need to make sure I keep my plans and the engine itself purpose-built.



I have on hand a good iron 262 head, which I planned on using, but was second-guessing myself and wondering if I should try and secure a 232.



No such grandiose plans as racing a Hudson, just want some more "pop" than a stock engine, and honestly, probably a little bit of an ego trip is involved to have a 7X. That said, some amount of practicality will have to fill in the blanks. I've been told by reliable sources that using the 262 is an old "racer" trick, but, my opinion is that this was probably before the advent of the 7X.

Rick-



I guess I can't answer your last question, because of my lack of actual experience. I can tell you to pay close attention to Park's response, I'll re-list it, below:



"I do recall Smokey Yunick's saying at Nashville that there's a definite diminishing return when it comes to head milling, as you get to a point where reduction in height of the "transfer passage" from valves to cylinder begins to offset the gain from higher compression. I expect one may especially find this situation with a 232 head and a pre-'54 non-relieved transfer passage in the block."



Two glaring weak aspects of the L-Head engine, at least when we're talking about generating more power, is 1) Park's point; you can only make the combustion chamber so small (to generate more compression), due to the valves being adjacent to the cylinder, as opposed to an OHV engine, where they are directly above the cylinder. I still would like to know of that point that Park refers to, where the "diminishing return" comes into play. Hudson engineers were no dummies, and probably the point where the 7X engines were milled out, approaches the maximum chamber area. and 2) You throw a valve, say, and the fix isn't as simple as changing heads . . . you've actually lost the entire block.



Additionally, I'm going to add this in regards as to whether to use the 232 or 262 head. If you mill a 2" 262 head down .030 to 1.70, your probably approaching compression ratings of a 232 head, anyway. Unless you're racing, and trying to get every micro-horsepower out of an engine, I think for a street engine, we're probably splitting hairs, and it's more or less irrelevant.



I'm going to do as Walt suggested, and as a few others who have e-mailed me and mill my 262 iron head down (which has not been previously milled) the .030. I'll do the extra milling on the block, larger valves, hotter cam (but a street-tamed version), roller timing chain and add headers. I have no doubt this will give me all the extra "pop" that I'm looking for.