rod/stroke ratio and boost

[pokeytemplar]

I am in the design phase of a stroker build. I am trying to decide on if I should go with a 4" or a 4.04" stroke. The difference in R/S ratio is 1.56 vs 1.55. I would like to run around 14-16 psi of boost. I have toyed with the idea of going all the way to a 4.12" stroke that would drop the ration to 1.52. My hope is an engine capable of spinning to 6000rpm but will be limited to 5500. ANY help/comments would be greatly appreciated.

[kick_the_reverb]

I don't think you need more stroke with boost. Limit yourself to 4" and you'll save yourself a lot of hassle.
Also - how are you going to hook with a stroker on boost? Not saying it can't be done, just plan ahead.
Ran

[pokeytemplar]

The truck is AWD. Currently with a 360 and 10psi boost I cannot get the tires to even think of slipping. Going for a Magnum v-10 build with a 4.04 x 4.04 bore /stroke and a little more boost. Should have around 800-900 hp at the crank? That would give me a r/s ratio of 1.55. The 408's out there have a r/s ratio of 1.53. So that would allow me to go to a 4.04 x 4.085 stroke. Bumping displacement from 518ci to 524ci (8.5L to 8.6L). I haven't heard of any problems with the 408's out there. I have always heard there is no replacement for displacement!

[kick_the_reverb]

I don't understand...are you asking about a V-10 or a V-8? I don't know anything about V-10s. If you're asking about V8s, then I can tell you, based on some research I've done, including opinions from respected builders, that strokes larger than 4" in a small block Mopar are possible, but a lot of times cause other problems like rod bolts hitting the oil pick-up tube, pan rail, need for special design of piston skirts to clear rods, etc. Being that you are building a forced induction engine, you can save yourself these hassles, and stick with the 4" stroke. 2 other points - you're thinking of a forced induction stroker - that means a possibility that you'll exceed the power handling of the stock block. Do you have a race block? If not, better factor that into the build. The other point to think about is piston design - the larger the stroke, the shorter the piston gets, leaving less room for distance of the ring lands from the piston top (which you want a little bigger in a boosted engine). Not to mention pistons rocking in the bore more. Yes, you can play around with rod sizes, but don't forget the extra stress that a short rod/long stroke combo puts on the cylinder walls.
See - all that is why I think it's better to stick with the slightly smaller stroke and spend the money elsewhere instead of expensive solutions to problems you could have avoided in the first place.
Good luck,
Ran

[pokeytemplar]

Well this is a v-10 build and NO-ONE has any experience with them. It is basically a 360 (same rods and piston comp height) but with a factory 3.88" stroke. This gives me a factory deck height of around 9.66" up from the 360's 9.58". So I have plenty of room for piston ring lands. Even with a 4.16" stroke and a 6.25" rod I still have enough room for a piston comp height of 1.32". I am trying to find out if I should be worried about hundreds in R/S ratio. I am mostly leaning toward a 4.04x4.04 because that is almost the same r/s ratio that I had before going to a 6.25" rod length. I have been told that these blocks can handle 2000HP as long as you get a mainstud girdle and billet main caps.

[kick_the_reverb]

As I said, I don't know anything about V-10s. What you say about my concerens makes sense. I wouldn't worry about the ratio.
Good luck.
Ran

[CollinsAutomotive]

Rod Ratio on a turbo application is not super critical. Generally however a widley held opinion is that anything between 1.55 and 1.48 is better then higher rod ratios.

I disagree with both camps and highly suggest looking at the combination of rod ratio and chamber design as a pair.

[pokeytemplar]

Thanks for the reply. Looks like I am going to stay with the 4.04 stroke but go with an even longer rod to bring the ratio to over a 1.57. Also going with a specially designed piston that matches my heads combustion chamber.