Comp ratio...decking and shaving for 10,5 C/R

[str8-6]

I'm a total failure when it comes to mathematics ("and spelling"),looking to get a comp,-ratio around 10.5 "-ish" since Lunati states that the camshaft I decided to use after the upcoming rebuild needs a c/r at that level, and as I understand it the Speed Pro Hyper-pistons ends up around 9.4:1 without decking the block,decking the block 0.020 will get it to around 9.7(??).

Is it possible to take some more of the block and then shave the rest of from the head and will the block and head have material enough left to stay in one piece for a 100-shoot of nitrous? Will be using 258 pushrods as they are 0.047" shorter than the ones from a 4.0,block will be bored 0.060 and the camshaft is a Lunati Vodoo 268/276,is this doable or not?


///Hasse "Str8-6" Davidsson

[Cheromaniac]

The CR with those pistons comes in at ~9.5:1. If you shave 0.030" from the block and 0.020" from the head you'll end up at ~10.4:1. The limiting factor will be PTV clearance so measure that to determine how much decking would be safe.

[jsawduste]

Do it right and have pistons made instead of machining a bunch off the block/head.

Call Diamond piston. They can make you any compression you want all while maintaining quench and avoiding removing a mass amount of metal.

You cannot just assume that a shorter pushrod is going to work. You need to measure your set up then source a PR that meets your requirments.

[str8-6]

Thanks for the replies Dino &jsawduste,the engine is still in the car "hoping for one more drive before the 6 months long winter"

PTV will be checked when i start to pick it apart in a couple of weeks "definitivly winter by then",calling Diamond is just not that,having to get up at 2 in the morning and struggle to make them understand what I'm saying in "Swenglish" is a battle in it self,besides that: I said it before:I'm a cheap bastard...half the fun of beating Chebby smallblocks is to do it with cheap stuff in a Inline 6,makes them sleepless at night...

It's all about simple parts on a low budget,doing what a friend did isn't my way of life,he's been working two jobs beside his own bizniz,sold the wheel-loader,girlfriend left and he almost lives in his garage just to buy a 2800 hp Chevy LS engine,and all of that just for some streetracing,there is other things in life that matters more..."I've heard" The LS will end up in a 1972 Opel Kadett "smaller then a Chevy Vega and Ford Pinto,100 inch wheelbase and that amount of power could be fun he says...

I will let my buddy that will do all the machinework check whats safe before he start decking,he's a good machinist mostly working on Top Sportsman cars and Pro Mods,maybe I'll stay on the safer side and sacrifice some compression and replace the small amount of lost hp with some bigger jets in the nitrous system...

Decking 0.020 and 0.010 off the head maybe is enough,and then up 2-3 steps on the nitrous jets.