914World.com [Powered by Invision Power Board]

Posted by: ScottD914 Jan 31 2010, 10:11 AM

With all the good advice on rebuilding my 1.8L, the best was: Research, research. After selecting a crank from Demello, I turned my attention to camshafts and on the Elgin website there is an obscure reference to Rocker Ratios, but they differ from Intake to Exhaust! Who knew? I verified this with measurements and found that they are different, and what a difference it could make if they were mixed up!

My rockers measure out at a 1 : 1.32 Exhaust and a 1 : 1.39 Intake.

Thanks to all for the advise and especially the suggestion for researching everything (could've been Jake).

ScottD

Posted by: ME733 Jan 31 2010, 11:35 AM

QUOTE(ScottD914 @ Jan 31 2010, 11:11 AM)

With all the good advice on rebuilding my 1.8L, the best was: Research, research. After selecting a crank from Demello, I turned my attention to camshafts and on the Elgin website there is an obscure reference to Rocker Ratios, but they differ from Intake to Exhaust! Who knew? I verified this with measurements and found that they are different, and what a difference it could make if they were mixed up!

My rockers measure out at a 1 : 1.32 Exhaust and a 1 : 1.39 Intake.

Thanks to all for the advise and especially the suggestion for researching everything (could've been Jake).

ScottD

.................I am intrested in how you determined the ratios. The method by which intake and exhaust was measured.......MM.

Posted by: Jake Raby Jan 31 2010, 11:59 AM

Its a well known fact that the intake and exhaust rockers have different ratios..

You CANNOT mix up intake and exhaust rocker arms, this is due to the offset of the rocker in relationship to the pushrod cup and the valve adjuster.

Posted by: ME733 Jan 31 2010, 12:15 PM

QUOTE(Jake Raby @ Jan 31 2010, 12:59 PM)

Its a well known fact that the intake and exhaust rockers have different ratios..

You CANNOT mix up intake and exhaust rocker arms, this is due to the offset of the rocker in relationship to the pushrod cup and the valve adjuster.

.................Yes...(from above)... But I,m still curious how he went about the process,and measurements that were taken/made.MM.

Posted by: ScottD914 Jan 31 2010, 03:23 PM

To determine ratio, I simply measured with my vernier calipers from center of the pivot point to the center of each side. ie valve side and push rod side. Then it's just dividing one into the other. Interesting that this critical item is not mentioned in the few rebuild books I have purchased. Those rocker assembles fall apart easily and a "newbie" like me might never know the difference until startup and the engine runs a little funny.

Posted by: Jake Raby Jan 31 2010, 04:49 PM

It is impossible to install an intake rocker on the exhaust valve and vice versa.. They are not even close to aligning.

Posted by: ScottD914 Jan 31 2010, 05:41 PM

Good to know, thanks Jake.

ScottD

Printable Version of Topic

Click here to view this topic in its original format