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Big cubes in stardard 454 block

I love my Chevy Chevette!
Posts: 1
Joined: 10/07
Posted: 10/18/07 11:12 AM

Was wondering what is the biggest cubes i can go in a conventional 454 block.
Wanting to know stroke, bore, and rod length.


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I mow my lawn and find Chevys
Posts: 1985
Joined: 10/03
Posted: 10/18/07 01:28 PM

I don't know if simply looking for the largest possible displacement is the best route. I think you should tailor your bore to stroke ratio to the amount of effort you will be putting into the build...

The bore size is very predetermined. Maximum over-bore for a common 454 is probably about .070"-.080". Some blocks can go .100" or even .125" over but figure in the cost of checking this block with a ultrasonic thickness gauge if you want to push the core limits. The maximum advisable stroke would probably be 4.375" but 4.50" probably is possible with a lot of clearancing, but if you want to go all the way to a stroke 4.5" stroke I would highly recommend getting an aftermarket block that can accept this large stroker easier and you will have a very substantial increase in bore size as well. This increase in bore size is a more effective way of adding power while adding cubes than simply increasing the stroke. If the budget allows the larger bore opens up a whole other world of cylinder head choices that will have the potential to make a lot more power.

A "low-deck" block could take a 4.5" stroke with a 6.535" connecting rod. This will be a very tight ring pack though and the rod to stroke ratio would only be around 1.5:1. The rod to stroke ratio probably won't make much if any difference but some builders are convinced that they need to have a certain ratio. There could very well be some more significant issues though if you take this too far. For example, using a stock length rod (6.135") in a 4.5" stroke engine would probably be a no-no, i can't really give you a good scientific definition why, but why push the boundaries? The rod angle will be very severe and it's just better to be safe than sorry. Also, using a 6.8" connecting rod in a 427 may also bring about some problems by means of severely "over-dwelling" the piston.

Overall, learning what you're trying to accomplish may help better decide what your displacement should be.  

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I love my Chevy Chevette!
Posts: 4
Joined: 11/07
Posted: 11/03/07 08:31 PM

The Gib-ster brings about somevery valid points! It's nice to see someone that has some knowledge posting replies!!
If I were you, I would stay at 4.250 stroke & 6.385 rods for ease of assembly.This combo makes LOADS of torque with oval port heads on street engines with proper valve seat angles/valve backuts and minor pocket porting.Rect. port heads do not require much if any help-but the ovals will have better response on a street engine.Keep in mind that .100 over(4.350)  and even .125(4.375)are common pistons for this combo!!Oh, and the bigger the bore, the better the heads will unshroud air in the cylinder.I hope you are using open chamber heads, 'cuz there are hardly any pistons available for the ole closed chamber heads with anything other than stock compression distance.Check a shop that sells PBM brand components and use their rotating assembly,the cranks check so much closer on sizing than eagle(taper and size) and the pricing is almost identical.If you by the cheaper brand and then have to have your crank turned orbuy bearings, you have defeated the purpose of spending less.I chalk that up to experience!  

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