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Optimum CR for a 470cc stroker with RHC cams?

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Given I have 98 gas available, who knows what the optimum compression ratio is for a 470cc stroker (94mm piston) with RHC cams? I'm trying to make pretty big power though I can't afford the springs and valves just yet so the head will be stock with the exception of the new cams...

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Oh I know he does :thumbsup: I'm hoping he will drop in soon.

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I would be really worried about a stock valve train with rhc cams. You will have a lot of money in the engine to drop a valve and destroy it.

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I would be really worried about a stock valve train with rhc cams. You will have a lot of money in the engine to drop a valve and destroy it.

+ one on that , i really want +4mm stroker on my bb bike but i haven't the money for the proper cams , springs and valves...

Patience Svery..!

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what are you using the bike for? what fuel will you be running?

Mainly street and a bit of track. I use BP ultimate 98 here in NZ. I didn't realise the RHC cams put that much extra stress on the valves, don't they mainly have greater duration rather than lift?

The bike is fitted with a fat stainless header, 39mm FCR and Procircuit T4 muffler.

Edited by Svery

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there is more to it than just duration. dont forget with the added duration you have much less of a cushion space for error getting the valve out of the way of the piston or each other.

luckily with the carb and pipe you have it wont make power that high effectively so you will be short shifting alot any way.that will help your spring situation.

i would go with 3 base gasket layers total.1 on the top of the spacer 2 on the bottom.

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Yeah, ok - I'm not too worried about valve float as I don't wring it out that much - but I would have thought my exhaust system is fairly free flowing with the big fat header and T4...? If not, what muffler is the preference in this situation?

Is it the carb (39 v 41mm) thats the main breathing issue at higher rpm? Thanks Eddie.

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the pipe and carb.

there only 2 pipes made for a drz that will supprt more than 44-46hp.

thats yosh ti ($900) and the MRD/SSW ($470).

its not just the muffler.

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The cams also have much steeper ramps. You really do need the springs to go with the cam if you want it to live very long.

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weve done what we can to keep the opening and closing velocity in check with 187's but the fact of the matter is they are faster.not much you can do about other than try and keep the valves in control as much as you can with the proper spring (seat pressure,over the nose etc).

stock springs arent horrible. just heavy which in itself makes them work harder.

watch the bmw valve train video thats floating around. makes the jaws drop of people that had no idea whats going on in there.

it wonder we can make them live at all really.

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Oh well, guess its time to save....

Three layers of base gasket (0.25mm each layer) along with the 2.25mm spacer and cometic three layer head gasket yields a CR of 12:1 (according to the software program I wrote). I used digital micrometer to measure up the various thicknesses.

I was thinking more like 13:1 but perhaps the stroker prefers something lower than this....

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