Cam degree calculation questions
08-23-2021 | 07:47 AM
#41
Thread Starter
Registered
Joined: Jan 2017
Posts: 315
Likes: 88
From: SE Virginia/NH
Here’s my 2 reasons for telling you to put it in 109-111 icl.
#1: you have been using a degree wheel kit and are using a multi keyway timing set. So why wouldn’t you install it for better midrange power even if not a set world on fire difference? But there will be a difference.
#2: see #1
What movie was this ? “The resistance runs strong.”
I agree. This whole thing has been painful.
Lololololol Oh well.
#1: you have been using a degree wheel kit and are using a multi keyway timing set. So why wouldn’t you install it for better midrange power even if not a set world on fire difference? But there will be a difference.
#2: see #1
What movie was this ? “The resistance runs strong.”
I agree. This whole thing has been painful.
Lololololol Oh well.
If I could, I'd be buying a few of you cases of beer! Tom probably doesn't want to see my face anymore, and I can't blame him lol, but I want to buy him a few rounds.
Last edited by HawkX66; 08-23-2021 at 07:52 AM.
08-23-2021 | 09:22 PM
#42
Platinum Member
Joined: Sep 2001
Posts: 5,769
Likes: 150
From: tn
There are folks who toss a motor together and think they are doing a great job just because they used a torque wrench on the balancer bolt.
You aren't one of those guys and I applaud your eagerness to learn how to do it right.
And 6 degrees on a cam will make a measurable difference in your engines vacuum at idle, your cranking compression psi, your torque peaks rpm, and a host of other metrics.
Is it worth messing with?
If the motor was already installed in the boat, totally buttoned up, all accessories on it. Exhaust manifolds, plumbing, and all of it crammed up against a bulkhead that you can barely fit your arm into? Most folks would say NO.
But with a motor on the stand with no heads?
It's a no brainer..
You aren't one of those guys and I applaud your eagerness to learn how to do it right.
And 6 degrees on a cam will make a measurable difference in your engines vacuum at idle, your cranking compression psi, your torque peaks rpm, and a host of other metrics.
Is it worth messing with?
If the motor was already installed in the boat, totally buttoned up, all accessories on it. Exhaust manifolds, plumbing, and all of it crammed up against a bulkhead that you can barely fit your arm into? Most folks would say NO.
But with a motor on the stand with no heads?
It's a no brainer..
08-24-2021 | 10:48 AM
#44
Thread Starter
Registered
Joined: Jan 2017
Posts: 315
Likes: 88
From: SE Virginia/NH
There are folks who toss a motor together and think they are doing a great job just because they used a torque wrench on the balancer bolt.
You aren't one of those guys and I applaud your eagerness to learn how to do it right.
And 6 degrees on a cam will make a measurable difference in your engines vacuum at idle, your cranking compression psi, your torque peaks rpm, and a host of other metrics.
Is it worth messing with?
If the motor was already installed in the boat, totally buttoned up, all accessories on it. Exhaust manifolds, plumbing, and all of it crammed up against a bulkhead that you can barely fit your arm into? Most folks would say NO.
But with a motor on the stand with no heads?
It's a no brainer..
You aren't one of those guys and I applaud your eagerness to learn how to do it right.
And 6 degrees on a cam will make a measurable difference in your engines vacuum at idle, your cranking compression psi, your torque peaks rpm, and a host of other metrics.
Is it worth messing with?
If the motor was already installed in the boat, totally buttoned up, all accessories on it. Exhaust manifolds, plumbing, and all of it crammed up against a bulkhead that you can barely fit your arm into? Most folks would say NO.
But with a motor on the stand with no heads?
It's a no brainer..
Tom, Not sure what you said before you deleted your message, but I hope you don't think I'm busting your balls. You've been a big help and I appreciate it. Just a difference of opinions.
09-05-2021 | 01:06 PM
#45
Thread Starter
Registered
Joined: Jan 2017
Posts: 315
Likes: 88
From: SE Virginia/NH
Finally was able to get back to the motor. I pulled it back apart and corrected the cam install. ICL is now 108.75° Close enough for me.
I'll post all my measurements, but before I do I want to mention the factory timing set. Before I pulled the timing cover off I put the motor at TDC. The Summit set was still at 2° advanced like I had installed it. This is actually ~0°. I didn't move anything and installed the factory set off another L29 Mercruiser I have. It installed dot to dot which to me means it's 6° retarded at that point. I'm going to have to assume that anyone installing factory cams and timing sets dot to dot are installing them 6° retarded. I've asked that same question before and never got an answer. Am I right?
Either way, I reinstalled my Summit timing set to A8 and then I degreed the cam to almost perfect factory specs.
Thanks again to those that stuck around. I appreciate the help.
Max Lift. .284"x1.7=.4828"
IVO 5° (btdc)
EVO 56° (bbdc)
IVC 41° (abdc)
EVC 10° (btdc)
Int duration=IVO+180°+IVC
5°+180°+41°=226°
Exh duration=EVO+180°+EVC
56°+180°-10°=226°
LCL
Int (61° + 156.5°)/2=217.5°/2=108.75°
Exh (169°+74°)/2=243°/2=121.5°
LSA
(108.75°+121.5°)/2=230.25/2=115.125
Overlap=IVO+EVC
-5°+10°=5°
I'll post all my measurements, but before I do I want to mention the factory timing set. Before I pulled the timing cover off I put the motor at TDC. The Summit set was still at 2° advanced like I had installed it. This is actually ~0°. I didn't move anything and installed the factory set off another L29 Mercruiser I have. It installed dot to dot which to me means it's 6° retarded at that point. I'm going to have to assume that anyone installing factory cams and timing sets dot to dot are installing them 6° retarded. I've asked that same question before and never got an answer. Am I right?
Either way, I reinstalled my Summit timing set to A8 and then I degreed the cam to almost perfect factory specs.
Thanks again to those that stuck around. I appreciate the help.
Max Lift. .284"x1.7=.4828"
IVO 5° (btdc)
EVO 56° (bbdc)
IVC 41° (abdc)
EVC 10° (btdc)
Int duration=IVO+180°+IVC
5°+180°+41°=226°
Exh duration=EVO+180°+EVC
56°+180°-10°=226°
LCL
Int (61° + 156.5°)/2=217.5°/2=108.75°
Exh (169°+74°)/2=243°/2=121.5°
LSA
(108.75°+121.5°)/2=230.25/2=115.125
Overlap=IVO+EVC
-5°+10°=5°
Last edited by HawkX66; 09-05-2021 at 01:11 PM.
09-06-2021 | 06:19 AM
#47
Thread Starter
Registered
Joined: Jan 2017
Posts: 315
Likes: 88
From: SE Virginia/NH
Motor is buttoned up and ready to go back in. Of course that means it's raining...
