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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Bill, Thanks for posting back on the subject. I understand the concept that retarding or advancing the cam in relationship to the crank degrees changes the valve opening and closing degrees. Are you also saying it's really the profile of the cam and not the rocker ratio that governs the opening and closing degrees of the valves? Off site, it's also been suggested to me that hydraulic lifters come into play with changing rocker ratio. Any comment? |
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Waterdog
Grand Poobah Joined: April-27-2006 Location: United States Status: Offline Points: 2020 |
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I talked to Scott at Cam Research a couple of times before installing there ski boat grind cam 2* advanced with a Crane double roller timing set. He really didn't have a opinion about it ether way (you install it 2* retarted to get 2* advanced on a reverse rotation engine)It should have a stronger hole shot w/ a 540 prop.
The engine "should" be running this weekend and the cam broken in or maybe just broke I liked the "ported" carb spacer but only have 1 inch clearance so I got one from Auto Zone ($20-) and ported the 4 hole insert with a cartridge roll & a hi speed. We'll See... |
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81nautique
Grand Poobah Joined: September-03-2005 Location: Big Rock, Il Status: Offline Points: 5778 |
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What did you hear Pete? |
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You can’t change the wind but you can adjust your sails
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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It was a PM that came to me from the PN site defending Bill's statement on rocker ratio affecting the opening and closing timing of the valves. I don't know who it is because the PN site only uses screen names. He obviously must be on CCfan as well because he saw this thread. He stated that hydraulic lifters with higher ratio rockers will cause the valves to open sooner. I'm having trouble with the concept and if anything would think the hydraulic compression of the lifter would cause the valve to open slightly later? BTW, he thinks we "pick" on Bill!! I do not feel this is the case and just the way some wording is interpreted. As always, I'm listening and always curious. EDIT: I forgot that "bobchris" was 79's screen name on PN!!! |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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I just got a email from "bobchris" (aka79) of PN along with a explaination. He also suggested posting his explaination:
"Yes on paper the starting point is the same and is based off of the cam lobe profile, but the resulting effect of when the fuel/air mixture actually moves and enters the combustion chamber happens faster with a 1.7:1 ration thus sooner than a 1.6:1 rocker, what you can’t see in the graph is the fine detail of where the slope of the curves are because of the scale shown." "The end effect being the fuel mixture enters the camber sooner with a 1.7:1 because it has traveled faster than a 1.6:1 rocker, then it travels greater distance generating more lift because of the increased lever arm and stays open longer because of the quicker closing of the valve due to the lever arm." "So if you want to look a Point O then yes they are both the same only problem you have to look at the points after point 0 and the 1.7:1 will always be ahead of the 1.6:1 regardless of the distance traveled thus resulting in a larger sooner entering charge of fuel into the cylinder." BTW, he still hasn't gotten any better with his spelling!! |
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Waterdog
Grand Poobah Joined: April-27-2006 Location: United States Status: Offline Points: 2020 |
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I can see the 1.7 following the cam profile "quicker" than 1.6, what I can't get my head wraped around is the degrees of the cam base circle hasen't changed, as long as the lifter is on the base circle of the cam the valve is closed.
Kinda sounds like I may want to retard the timing with a longer rocker arm ??? |
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SS 201
Senior Member Joined: October-20-2003 Location: United States Status: Offline Points: 232 |
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To answer your question yes it effects when the valves open and close. ex. advance open the valves sooner, retard they open later in relation to dead center.
As I said all Fords with a stock Ford timing chain gear are 8 degrees retard. To wake up that engine purchase a non ford timing timing, the retard was built into the crank gear. Hydraulic lifters do play into opening, the biggest thing the is to do a perfect preload that lets the lifter work properly. If not you can lose power. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Ok, I think I've got this!!
Getting back to square one on the ratio and putting cam advance/retard aside which is a different subject, here's how I see it. Rocker ratio does not change the opening/closing degrees of the valve but does cause them to open quicker and farther. Next on the lifters: Hydraulic lifters will cause the valves to open quicker slightly because they preload the valve which removes the valve clearance needed on solid lifters. ???? correct???? |
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SS 201
Senior Member Joined: October-20-2003 Location: United States Status: Offline Points: 232 |
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You got it. Every bit helps, the biggest thing I see is preload most don't even what it means and does.
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3357 |
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But, consider the following... I think it all depends what one defines as 'open'.. Obviously, zero-lift is not yet 'open'. If one where to call .1" or .2" , or .16435236" 'open', then it appears to me the 1.7 rocker met the arbitrary criteria, sooner. |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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Waterdog
Grand Poobah Joined: April-27-2006 Location: United States Status: Offline Points: 2020 |
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I ported this 1 in.spacer in less than an hour.
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Watarski
Groupie Joined: January-10-2009 Location: United States Status: Offline Points: 78 |
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I didn't want to rehash this post from 2 months ago...but there isn't much info on the topic-
I'm about half way through my 351W rebuild and I will be using an Edelbrock Performer intake - concern obviously is clearance. I can't seem to find shorter arrestors anywhere...any problems with running shorter carb spacers? |
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1985 Ski Nautique 2001
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kapla
Grand Poobah Joined: March-27-2008 Location: BA, Argentina Status: Offline Points: 6148 |
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Craig
what year is your boat? I recently did the engine rebuilt/upgrade on my 1992, and put the performer intake, stock spacer and stock flame arrestor, and it fit under the box fine. Maybe if you choose the performer rpm that its a tad taller you will need to cut the arrestor but someone else can verify. Don´t forget to buy the adapter plate edl-2732 or summit sum-g1420 to put between the intake and the stock spacer as if not you will suck air as the carb spacer is bigger than the intake base...that will also make the setup a 1/4 inch or so taller.... |
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<a href="">1992 ski nautique
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Watarski
Groupie Joined: January-10-2009 Location: United States Status: Offline Points: 78 |
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Thanks for the reminder - I had planned on picking up an adapter plate when I place my last round of parts order.
My boat is an '85, and I believe the box is shorter than yours. I'd rather not cut my arrestor - hoping to find one shorter, or hear if a shorter carb spacer won't cause problems. |
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1985 Ski Nautique 2001
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21168 |
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A shorter carb spacer is fine. There are also shorter arrestors available: Marine Engine Parts (scroll down to part number 3745649).
I would be surprised if the Performer didnt fit under the 2001 box though, even with the stock arrestor and 1" spacer. Have you actually measured it? |
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kapla
Grand Poobah Joined: March-27-2008 Location: BA, Argentina Status: Offline Points: 6148 |
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A tip I was given here to measure the clearance is putting a ball of clay bar or like over the arrestor and close the cover, then see how much it was compressed, the thickness it ends up is the clearance you have...is it clear my explanation?
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<a href="">1992 ski nautique
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Watarski
Groupie Joined: January-10-2009 Location: United States Status: Offline Points: 78 |
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TRBenj - I was basically going off the original posts on this thread. I've learned a lot, mostly last minute, from this site...I was trying to be proactive. I'm getting closer to having my boat in the water and I didn't want something like this to bite me in the end. Thank you for pointing me in the direction of additional arrestors.
Yes, kapla, your explanation makes perfect sense. I will try that. Thanks for the help- |
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1985 Ski Nautique 2001
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