Engine/Exhaust ticking mystery??
Apr 26, 2012 | 07:37 PM
#21
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Joined: Aug 2009
Posts: 13,574
Likes: 72
From: Wilkes-Barre, PA, USA
Nope. The cam lobe overlap affects dynamic compression. The pistons affect static compression.
It's hard to explain, but the shorter the overlap, the less air gets into the engine on one revolution hense lower compression and lower vacuum. The longer the overlap the more air that gets into the engine on a single stroke hense higher compression and larger vacuum.
For example if you have a cam that causes a loping idle it's due to the fact it causes a lower vacuum at idle. Alot of these types of cams require some sort of modification in a power brake system because of it.
What I can't remember off hand is if that dynamic compression can be seen in a compression gauge or not or if you have to turn the engine a few more times then normal when dealing with a cam like that to get a more accurate compression reading.
I don't think that 272 cam is one of those cams though. Which one is it? The Engine Builder branded or a Comp Cam?
It's hard to explain, but the shorter the overlap, the less air gets into the engine on one revolution hense lower compression and lower vacuum. The longer the overlap the more air that gets into the engine on a single stroke hense higher compression and larger vacuum.
For example if you have a cam that causes a loping idle it's due to the fact it causes a lower vacuum at idle. Alot of these types of cams require some sort of modification in a power brake system because of it.
What I can't remember off hand is if that dynamic compression can be seen in a compression gauge or not or if you have to turn the engine a few more times then normal when dealing with a cam like that to get a more accurate compression reading.
I don't think that 272 cam is one of those cams though. Which one is it? The Engine Builder branded or a Comp Cam?
Last edited by xxxtreme22r; Apr 26, 2012 at 07:40 PM.
Apr 26, 2012 | 07:43 PM
#22
Thread Starter
Registered User
Joined: Nov 2011
Posts: 199
Likes: 3
From: Northern Arizona
Nope. The cam lobe overlap affects dynamic compression. The pistons affect static compression.
What I can't remember off hand is if that dynamic compression can be seen in a compression gauge or not or if you have to turn the engine a few more times then normal when dealing with a cam like that to get a more accurate compression reading.
I don't think that 272 cam is one of those cams though. Which one is it? The Engine Builder branded or a Comp Cam?
What I can't remember off hand is if that dynamic compression can be seen in a compression gauge or not or if you have to turn the engine a few more times then normal when dealing with a cam like that to get a more accurate compression reading.
I don't think that 272 cam is one of those cams though. Which one is it? The Engine Builder branded or a Comp Cam?
Still like to troubleshoot that "exhaust leak noise".
Last edited by JPL; Apr 26, 2012 at 07:45 PM.
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