Offshoreonly.com - Rocker Ratios...variances

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Offshoreonly.com (https://www.offshoreonly.com/forums/)

- General Q & A (https://www.offshoreonly.com/forums/general-q-20/)

- - Rocker Ratios...variances (https://www.offshoreonly.com/forums/general-q/331349-rocker-ratios-variances.html)

SB	10-06-2015 06:11 AM

It wasn't too long ago, BBC's with HFT and HR ran into valvetrain instability in the upper 5k rpm region. If it was spring related, people added more spring psi, but then the lifters ran into stability issues. Leaving you kind of stranded at the same rpm point.

Enter the 1.8 rocker 'less durable' remarks. The 1.8's seemed to make this rpm 'fuss' point happen 200-400 rpm earlier.

Anyway, today's day and age gives us lifters with better internal clearances and valving where the lifters can sustain a higher rpm. Better spring quality with lower weight, has also let us get past this point.

So.....if you have the right valvetrain pieces in place, you can up the rocker ratio ..

ICDEDPPL

10-06-2015 08:31 AM

SB you`ve made 416 post a year, can you really be trusted??

SB	10-06-2015 09:06 AM

Quote:

Originally Posted by ICDEDPPL (Post 4362887)

SB you`ve made 416 post a year, can you really be trusted??

Yes, you can trust me for snide , condecending, and off the wall remarks...plus, you can really trust me once in a while a great female bikini photo.

http://getabikini.com/photos/wp-cont...ini-girls2.jpg

MILD THUNDER

10-06-2015 09:18 AM

Quote:

Originally Posted by ICDEDPPL (Post 4362887)

SB you`ve made 416 post a year, can you really be trusted??

Thats 1.13 posts per day.

chancer540

10-06-2015 09:46 AM

Quote:

Originally Posted by SB (Post 4362807)

I'm just having fun, nothing more.

30 Dyno tests every single day straight for 45.6 years = the claimed number.

I like just having fun calling people Jackass's

And sir , you are a JACKASS....

Budman II

10-06-2015 01:17 PM

Quote:

Originally Posted by MILD THUNDER (Post 4362168)

I can attest, that there is a significant difference, in the geometry of a Crane Gold, Scorpion, and older style Comp Steel rocker when studied back to back on icdedppls engines, doing valvetrain geometry checks. The sweep patterns, and roller tip placement varied quite a bit between the 3, when setting the rockers up using the mid-lift method.

Yep, I "discovered" the same when trying to get a decent valve tip pattern using the mid-lift with standard Scorpions. Exhaust pattern was landing too close to the edge for my comfort. Tested with a set of Scorpion Marine Endurance and found that the distance between the tip and trunion was shorter, which brought my pattern into an acceptable range.

Budman II

10-06-2015 01:18 PM

Quote:

Originally Posted by Rookie (Post 4362805)

The first thing anyone should learn in any statistics class is... "You can make the numbers look any way you want"
If you consider 1 pull on the dyno a test (which it should be) and you do 30-40 pulls/day it would get lower. Also, if that is your daily job/passion it is more reasonable. :)

Yep, as Samuel Clemmons once said, there are three kinds of lies - lies, damned lies, and statistics. :)

SB	10-06-2015 02:31 PM

Performance 540cid Marine I/O

How would this work:
Custom Spec'd / Ground by LSM

Intake Duration at .050" = 226°
Exhaust Duration at .050" = 228°
Lobe Lift Intake = .300". With 1.7 Rockers = .510"
Lobe Lift Exhaust = .300" . With 1.7 rockers = .510"
Events at .050"
Intke Opens : -1° BTDC
Intake Closes 47° ABDC
Exhaust Opens 48° BBDC
Exhaust Closes 0° ATDC
ICL = 114° ECL = 114°
LCA 114°
Overlap -1°

Knot 4 Me

10-06-2015 02:56 PM

What ratio works best with a 3/4 race cam? 1.275's or 1.35's? :drink:

SB	10-06-2015 03:12 PM

3/4 Race 1.7's would be 1.275's.
3/4 Race 1.8's would be 1.35's.

They do make 1.6's for the big block, so maybe this is a better bet for a 3/4 race cam......since 1.7's can be considered full race.

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