Cam and valvetrain longevity....??? low duration high lift...

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09-27-2016 | 01:57 PM

#561

Panther

Frank's Marine Service

Joined: Sep 2002

Posts: 11,959

Likes: 142

From: Elkton, MD

Quote:

Originally Posted by MILD THUNDER

Before we get too excited, anyone see my post earlier, about the throttle cable issue on the same dyno? That would certainly have an effect on tims dyno number if in fact, thats what was happening, but not in the boat. Throttle controls when using a servo, can fuk up. I like when some shops mount a camera above the throttle plates during a dyno pull, where you can see creep back.

A more common cause for both the low measured air flow and vacuum would be that the carburetor was not mechanically at WOT during the pull. Sometimes it is hard to get good carburetor travel with the available leverage and linkage. Older dyno's with the water piston used to creep all the time and loose the WOT during a test session, even the newer ones with servo or cable linkages can creep or loose the WOT capability.

I would think it would cause issues in the boat because if it was dyno'd and tuned at part throttle the tune in the boat (WOT) would be off.

didn't he say he was getting really low AFR numbers or something?? If the throttle was open all the way in the boat he's drawing more CFM and the carb is drawing more fuel (rich).

09-27-2016 | 02:01 PM

#562

Baja Rooster

Registered

Joined: Oct 2013

Posts: 2,888

Likes: 148

From: SF Bay Area

Quote:

Originally Posted by SB

What ?

Just joking that when the carb was looking like a restriction because of the high vacuum at wot the solution would be a bigger cam as they have less vacuum. It was loosely even sensible and just a lame joke.

09-27-2016 | 02:25 PM

#563

Panther

Frank's Marine Service

Joined: Sep 2002

Posts: 11,959

Likes: 142

From: Elkton, MD

Quote:

Originally Posted by Full Force

330's

How far is the propshaft below the bottom of the boat?

They had different X's based on engine packages and props that the boat was build with.

Just a thought.

09-27-2016 | 03:43 PM

#564

getrdunn

Registered

Joined: Feb 2009

Posts: 8,356

Likes: 1,515

From: NW Michigan

Quote:

Originally Posted by Panther

Think that got resolved in regards to engines in the boat anyway. Port side was off and running lower AFR's and rpm at wot. He had since installed wideband on both engines and got jetting squared away and same rpm's at wot. Why Tim didn't look down to confirm throttle plates were 100% open while at 6k on dyno is beyond me. Lol. Joke joke. Think we covered that also. SB woulda done it.