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1.70 to 1.80 rockers

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I have a BBC with 1.70 rockers? Jesel Sportsman. How much reliability am I going to sacrifice going to 1.80 ratio. I am running a hyd roller with I/E 242/249 @ .635//647

The reason for change is I increased displacement from 496 to 557 and believe it needs more cam to compensate for the increase in displacement. Due to wet boat exhaust I can't really replace cam with more duration as it would likely increase overlap and engine screwing exhaust reversion, currently at only 13 deg.
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Race it, Don't rice it!
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Depends entirely on the current spring, the clearances and the weight of the valve train.
Assuming all good parts and the heads have the room, AND the heads can support the flow, I'd do it.
 

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Race it, Don't rice it!
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Another thought on Bogies ideas.
I'd discuss this with a cam designer but I would think some magic could happen with this by possibly by using inverted lobes to reduce the overlap and picking up the curve mid point on up.
 

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Race it, Don't rice it!
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That doesn't really tell me much.
You're currently at .647, and talking about upping that .038.
The vague info you have, speaks of .700-.900 and is irrelevant. I'd rather see hard numbers.
If you have the .038 worth of room, it's probably fine. Check it anyway......
Might wanna check with the spring company about it and ask some questions about expected spring surge.
 

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Race it, Don't rice it!
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Yes that is what the rocker change would do. Im only considering it as the rockers are new and Jesel has been good about exchanging parts n\c in the past so why not. I will attempt to attach my spreadsheet with the initial and mild cleanup numbers, I think it shows promise.
Only 4 CFM more on the intake between .650 and .700 so another .038 prolly not going to help much there. The 1.8 help even more on the exhaust side though. Im not sure how that translates to a boat. Usually when my exhaust gets wet, it's a way bigger deal if you know what I mean. Gurgle...gurgle...
Personally, Jesel is good stuff and if free or close to it, I'd do it, but if you have to buy them, a cam change might be a better investment depending on what your trying to accomplish.
 
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