Re: Re: Re: Re: Re: Re: Benefits of higher compres

Posted by Neil on June 27, 2004 at 08:37:31 from (138.88.222.124):

In Reply to: Re: Re: Re: Re: Re: Benefits of higher compression posted by Ron on June 27, 2004 at 02:41:59:

Ron,

First, let me say you really do know your stuff, which makes this discussion so much more worth while than otherwise - there's nothing more frustrating than debating with someone that is too ignorant/dumb to understand what you're saying.

You mention that it's smarter to swap to an engine that has more cubes than to bore and stroke a smaller one where possible:

AMEN, AND THANK YOU!!

I never cease to be amazed at the desire to spend $15,000+ on a 454 small block. You can easily put together a better 454 big block for far less $.

To the extent that it's possible, the idea to swap to a bigger engine is the right one for tractors as well. Of course, my general modus operandi would be to find a bigger engine to swap in and then bore and stroke it.

As for boring and overheating, I'll admit I kinda glossed over that one. It's true that I am not aware for certain that it causes overheating or in what circumstances it will. On the other hand I've heard various rumblings that it will cause overheating.

I suspect most of the reputed problems are, as you mention, with siamesed bores. I'm guessing it's more of a problem with localized overheating of the material between the cylinders and not the engine as a whole. Of course, if the material between the cylinders is too hot, you've got a problem regardless of the temp. of the rest of the engine.

I don't know how big an issue overheating with siamesed blocks is, as I've never really had the opportunity to get good information on that subject (and boy would I like to). Maybe someday I'll find out as I'm currently lusting over GM's Ramjet 502, which uses a siamesed block, for daily driver use. I guess GM provides a warranty with it (though I don't know how long). My guess is that due to temperature gradients, the cylinders run a little more out of round than a "regular" block and cylinder wear is advanced. And I've not heard whether or not you can do a clean-up bore of 0.030 or so on that block.

I'd say that you're almost certainly right that compression ratio increases are usually the cost effective way to get the first 10-15% increase in torque. And I must admit that if I was building a tractor, one of the first things I'd probably do is bump the compression ratio to 8:1 or so - it just makes sense.

I wouldn't consider it a technique to get "big" power or torque gains, though.

Also, I say compression ratio increases are usually going to be more cost effective because it seems that displacement increase can be pretty cheap sometimes too. This seems to be particularly true where guys swap in larger cranks/pistons from the same engine family. The Minnie Mo guys come to mind first. It seems every time I'm on that board there is someone asking about putting X crank in Y block.

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