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Old 10-30-2009, 10:01 PM
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Gen 6 BBC and 1.8 rockers

Thinking about putting 1.8 rockers on Ye Olde Gen VI 454 and a lots of questions and concerns...


1) My cam is a Mercury Marine hyd roller cam (.483 lift, .224 duration @ .050, 115 lobe center). According to my calculation going from 1.7 to 1.8 rockers will change the lift to .531 and duration to .246 @ 50. Is this correct?

2) This engine uses stock pistons. With the 1.8 rockers my duration goes over the edge of the .236 duration rule of thumb for a hydraulic roller piston interference. Do you think there will be an issue?

3) The Gen 6 heads can't take more than .500" lift from what I have been told. Is this true?

4) How much power do you think these new rockers would make over the old ones? 10 horse?

Yes, I know I'll have to convert the bolts to studs. Competition Accessories has a kit for this. Maybe I'll even put in stronger springs as I doubt the stock springs have much strength to them.

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Old 10-30-2009, 10:27 PM
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1) My cam is a Mercury Marine hyd roller cam (.483 lift, .224 duration @ .050, 115 lobe center). According to my calculation going from 1.7 to 1.8 rockers will change the lift to .531 and duration to .246 @ 50. Is this correct?

No. Enter .483 into your calculator. Divide by 1.7, then multiply that by 1.8, the new lift will be 0.511". Duration is measured at the cam lobe. Different ratio rockers will not change the duration. It is what it is, as ground into the stick at the factory.

2) This engine uses stock pistons. With the 1.8 rockers my duration goes over the edge of the .236 duration rule of thumb for a hydraulic roller piston interference. Do you think there will be an issue?

Duration does not change, only the lift changes. Piston to valve interference is on a case-by-case basis and must be checked.

3) The Gen 6 heads can't take more than .500" lift from what I have been told. Is this true?

Don't know. Find out the reason for this rumor and check your heads. Could be coil bind, could be retainer to guide interference.

4) How much power do you think these new rockers would make over the old ones? 10 horse?

Maybe.

Yes, I know I'll have to convert the bolts to studs. Competition Accessories has a kit for this. Maybe I'll even put in stronger springs as I doubt the stock springs have much strength to them.

Always use the springs that are recommended by the cam grinder for that particular cam.

Last edited by techinspector1; 11-01-2009 at 01:24 PM.
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