Lobe seperation
06-30-2005 | 07:10 PM
#3
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Posts: 699
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From: central NY
Re: Lobe seperation
110* would generally be more prone to reversion than a 112*.
My cam has 110* LSA. On my 3rd season with the engine (ZZ502) and no known reversion so far.
Not a mechanic here, but I would think if my cam had more/longer duration, the possibility of reversion would increase. My cam specs are similar to those of the HP500. Some HP500's seem to have a reversion issue, some don't. The right exhaust can help.
Like GPM said, the 110* LSA cam idles just a little rough. Mine produces a nice lope at idle...very cool.
BTW........Welcome
) Lots of good info on this site. I'm sure more knowledgeable members will chime in.
My cam has 110* LSA. On my 3rd season with the engine (ZZ502) and no known reversion so far.
Not a mechanic here, but I would think if my cam had more/longer duration, the possibility of reversion would increase. My cam specs are similar to those of the HP500. Some HP500's seem to have a reversion issue, some don't. The right exhaust can help.
Like GPM said, the 110* LSA cam idles just a little rough. Mine produces a nice lope at idle...very cool.
BTW........Welcome
) Lots of good info on this site. I'm sure more knowledgeable members will chime in.
06-30-2005 | 10:53 PM
#4
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Joined: Dec 2002
Posts: 6
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From: Texas
Re: Lobe seperation
Thanks for the info gent's.
The reason I asked is I am in the process of rebuilding my 502's and my engine builder was surprised that my Crane roller cams where at 110 deg.When I bought my 31ss Sonic it came with two very strong 502's.The boat ran 80mph (gps) at 5150 rpm,turning labbed 3 blade 25 pitch props. All was well at a little over 200 hours when the starboard engine dropped an exhaust valve seat into the number 7 hole.
The engines already had all the top if the line internals and Crane Gold valve train.The heads are the GM iron Hi perf's with Manley Inconel valves. So we pulled both engines and decided to make them 509's while we were doing the freshen -up.We are also replacing all the exhaust seats with an alloy seat.I am running Gil maifolds with long tails.(wet) My cam's are still in perfect shape so I had not planned on replacing them and the lifters were sent back to Crane under the racer's exchange program.
Since the engines were not Dyno'd the first time I could only guess that they were around 525 hp ? When the build is complete they will be Dyno'd and if the HP is not at least 525 then I will be looking for different cam's.
I will get the current cam specs from the builder and post them for some feedback.
Thanks again and any comments or opinions are welcome.
The reason I asked is I am in the process of rebuilding my 502's and my engine builder was surprised that my Crane roller cams where at 110 deg.When I bought my 31ss Sonic it came with two very strong 502's.The boat ran 80mph (gps) at 5150 rpm,turning labbed 3 blade 25 pitch props. All was well at a little over 200 hours when the starboard engine dropped an exhaust valve seat into the number 7 hole.
The engines already had all the top if the line internals and Crane Gold valve train.The heads are the GM iron Hi perf's with Manley Inconel valves. So we pulled both engines and decided to make them 509's while we were doing the freshen -up.We are also replacing all the exhaust seats with an alloy seat.I am running Gil maifolds with long tails.(wet) My cam's are still in perfect shape so I had not planned on replacing them and the lifters were sent back to Crane under the racer's exchange program.
Since the engines were not Dyno'd the first time I could only guess that they were around 525 hp ? When the build is complete they will be Dyno'd and if the HP is not at least 525 then I will be looking for different cam's.
I will get the current cam specs from the builder and post them for some feedback.
Thanks again and any comments or opinions are welcome.
07-01-2005 | 04:00 PM
#5
I hate the winter!!
Joined: Jul 2001
Posts: 2,707
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From: long island, new york
Re: Lobe seperation
I just built a 540. I had Gil WetOffshore manifolds and pipes. The first run out with this set-up, I had real bad reversion. I ended up with CMI dry headers. Problem is now solved. Below is my cams specs...
intake exhaust
.578 lift .608 lift
238* @.050 .248* @ .050
114* lobe seperation
61* overlap @ .000 lift
15* overlap @ .050 lift
Cam is installed as recommended@ zero advance. I didn't have the idle set too low. It just sucked water back. Luckily I caught it right away and avoided any engine damage.
intake exhaust
.578 lift .608 lift
238* @.050 .248* @ .050
114* lobe seperation
61* overlap @ .000 lift
15* overlap @ .050 lift
Cam is installed as recommended@ zero advance. I didn't have the idle set too low. It just sucked water back. Luckily I caught it right away and avoided any engine damage.
07-01-2005 | 06:38 PM
#6
~~~~
Joined: Oct 2000
Posts: 1,451
Likes: 3
From: Western New York
Re: Lobe seperation
Time for a cam upgrade. This is your ticket for a strong marine powerplant.
I would send OSO's Rmbuilder a private message or email and he can spec a cam that will be spot on for your application.
I would send OSO's Rmbuilder a private message or email and he can spec a cam that will be spot on for your application.
07-02-2005 | 07:10 AM
#8
~~~~
Joined: Oct 2000
Posts: 1,451
Likes: 3
From: Western New York
Re: Lobe seperation
Vinnie,
The response was not directed to you but to Madmax911.
I would like to know how and when you realized that you had a reversion problem.
Did you pull the exhaust to inspect for moisture or did some event direct you to do that?
Russ
The response was not directed to you but to Madmax911.
I would like to know how and when you realized that you had a reversion problem.
Did you pull the exhaust to inspect for moisture or did some event direct you to do that?
Russ
Last edited by RLW; 07-02-2005 at 10:56 AM.
07-26-2005 | 12:41 AM
#9
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From: Texas
Re: Lobe seperation
Update.
First dyno run was not impressive
Quick info......Peak HP 496 at 5100 rpm......Peak TRQ 565 at 4100 rpm.
Sorry forgot to bring home the cam specs on this cam.( 110* LSA )
Changed cams to the Crane 731 ( 112*LSA) and lost both HP and TRQ.
Thinking of bumping the compression from 8.75 to 9.0 ,but we are still going to play with cam timing first.
Also the AF ratio was 11.3 from 3500rpm through 5200rpm. Any opinion on whether this is tooo rich ?
First dyno run was not impressive
Quick info......Peak HP 496 at 5100 rpm......Peak TRQ 565 at 4100 rpm.
Sorry forgot to bring home the cam specs on this cam.( 110* LSA )
Changed cams to the Crane 731 ( 112*LSA) and lost both HP and TRQ.
Thinking of bumping the compression from 8.75 to 9.0 ,but we are still going to play with cam timing first.
Also the AF ratio was 11.3 from 3500rpm through 5200rpm. Any opinion on whether this is tooo rich ?
07-26-2005 | 09:54 AM
#10
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From: Texas
Re: Lobe seperation
Originally Posted by sutphen30
.25 jump in comp is worth squat,,go to 9.5 unless you want to stay with 87 octane.
as for your a/f ,,yes,its rich,hell its rich for a 20lbs of boost,,bring it up to 12.5 and you'll be good to go.12.7-13 will make a little more power but the margin for error is there.i could never hear the knock in my truck at 12.7 but my monitoring equipment saw it,,went to 12.5 and it went away.
as for your a/f ,,yes,its rich,hell its rich for a 20lbs of boost,,bring it up to 12.5 and you'll be good to go.12.7-13 will make a little more power but the margin for error is there.i could never hear the knock in my truck at 12.7 but my monitoring equipment saw it,,went to 12.5 and it went away.
I would think that in the boat (wet exhaust ) it would fatten up even more.
I have seen posted run's with the AFR's as high as 14.4 !!!!!
Are these guy's re-jetting for the real world after the dyno run or are they counting on the exhaust and flame arrestors to richen them up to a safe AFR ?
Would like to leave the compression low enough to run 87 if I can.
What is the highest comp/ratio that can live on 87oc ?
Last edited by madmax911; 07-26-2005 at 10:24 AM.
