Cam ? (Noise depending on Cam Timing)
Apr 23, 2006, 11:30 PM
#16
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Originally Posted by timzcat
The noise is not the cams. There are a lot of these cams out there and I have put in a few myself, including my old car. The fact that Pd1 put two sets in and had the same noise is a good indication it was not the cams in the first place. Unfortunately he gave up instead of having someone who really knew what they were doing diagnose the problem.
It's real easy to see if you have the cams in right as far as the dowel pins go.
With the engine at top dead center for #1 cylinder the intake cam would have it's lobes pointing to the rear (intake manifold), valves closed. The exhuast cam would have the lobes pointing towards the front (exhaust manifold) with the valves closed. Your marks should then be lined up to the cam cover.
It's real easy to see if you have the cams in right as far as the dowel pins go.
With the engine at top dead center for #1 cylinder the intake cam would have it's lobes pointing to the rear (intake manifold), valves closed. The exhuast cam would have the lobes pointing towards the front (exhaust manifold) with the valves closed. Your marks should then be lined up to the cam cover.
Last edited by Pd1; Apr 23, 2006 at 11:34 PM.
Apr 24, 2006, 05:18 AM
#17
Originally Posted by dsevo
When my cams are set straight up (0,0) I get really loud valve train noise, and when I set them to -2,0 they sound stock. I am absolutely stumped as to what could cause this.
Advancing the intake cam opens the intake valve earlier, which brings the intake valve closer to the piston when the piston is at TDC at the beginning of the intake phase. The -2/0 setting retards the intake cam 4 crankshaft degrees, which would explain why you don't hear the noise at that setting.
I'm not saying this is indeed the case, but this certainly explains it. If Revolver recommends a -2/0 setting, I don't understand why they wouldn't just grind the cams to give the equivalent of that setting when the cams are installed with the factory gears.
Apr 24, 2006, 08:37 AM
#18
Originally Posted by Ted B
It sounds to me like the valves may be making contact with the pistons.
Advancing the intake cam opens the intake valve earlier, which brings the intake valve closer to the piston when the piston is at TDC at the beginning of the intake phase. The -2/0 setting retards the intake cam 4 crankshaft degrees, which would explain why you don't hear the noise at that setting.
I'm not saying this is indeed the case, but this certainly explains it. If Revolver recommends a -2/0 setting, I don't understand why they wouldn't just grind the cams to give the equivalent of that setting when the cams are installed with the factory gears.
Advancing the intake cam opens the intake valve earlier, which brings the intake valve closer to the piston when the piston is at TDC at the beginning of the intake phase. The -2/0 setting retards the intake cam 4 crankshaft degrees, which would explain why you don't hear the noise at that setting.
I'm not saying this is indeed the case, but this certainly explains it. If Revolver recommends a -2/0 setting, I don't understand why they wouldn't just grind the cams to give the equivalent of that setting when the cams are installed with the factory gears.
Apr 24, 2006, 08:41 AM
#19
I just thought of something that makes sense. When I had my head all built, I think they milled a couple thousandths off of the gasket surface, which would make the valves closer to the pistons. I bet the valves open so much with these cams that even a little off of the head will cause them to contact. Sound reasonable?
Apr 24, 2006, 08:47 AM
#20
It's possible, especially since a few thousandths is significant when it comes to piston/valve clearance.
Also, I might mention that milling the head even slightly may possibly cause a change in cam timing as a result of a change in geometry that moves the cams to a slightly different position, depending on the placement of the belt tensioner. I have not examined this with a 4G63, but I've seen it with another DOHC engine.
Also, I might mention that milling the head even slightly may possibly cause a change in cam timing as a result of a change in geometry that moves the cams to a slightly different position, depending on the placement of the belt tensioner. I have not examined this with a 4G63, but I've seen it with another DOHC engine.
Apr 24, 2006, 10:11 AM
#21
Originally Posted by dsevo
I just thought of something that makes sense. When I had my head all built, I think they milled a couple thousandths off of the gasket surface, which would make the valves closer to the pistons. I bet the valves open so much with these cams that even a little off of the head will cause them to contact. Sound reasonable?
Did the mill your head due to it being warped or just to get the gasket off? The gasket should have been able to be scraped off without milling the head.
Apr 24, 2006, 12:04 PM
#22
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Originally Posted by dsevo
I just thought of something that makes sense. When I had my head all built, I think they milled a couple thousandths off of the gasket surface, which would make the valves closer to the pistons. I bet the valves open so much with these cams that even a little off of the head will cause them to contact. Sound reasonable?
Also, the noise could be other things. As was stated in another thread, the PCV valve can "clatter" when the engine vacuum pulses (like our cams at idle using 0/0 settings). There is a lot of overlap in those cams, additional RPM-fuel-timing are needed to run them at 0/0.
Originally Posted by Ted B
If Revolver recommends a -2/0 setting, I don't understand why they wouldn't just grind the cams to give the equivalent of that setting when the cams are installed with the factory gears.
Apr 24, 2006, 01:04 PM
#23
Originally Posted by ogvw
Sounds reasonable - I would definately check the piston to valve clearance. Just for grins I will check in a couple days - we have a motor on the engine stand so I can see exactly when a stock motor will encounter valve and piston contact.
Also, the noise could be other things. As was stated in another thread, the PCV valve can "clatter" when the engine vacuum pulses (like our cams at idle using 0/0 settings). There is a lot of overlap in those cams, additional RPM-fuel-timing are needed to run them at 0/0.
Unfortunately making a camshaft that works well for every car and combo of parts is difficult - this grind is meant to make power, and it has (Buschur has made over 900 wheel HP). We are coming out with a milder drop in cam that will be more suited to cars with less modifications.
Also, the noise could be other things. As was stated in another thread, the PCV valve can "clatter" when the engine vacuum pulses (like our cams at idle using 0/0 settings). There is a lot of overlap in those cams, additional RPM-fuel-timing are needed to run them at 0/0.
Unfortunately making a camshaft that works well for every car and combo of parts is difficult - this grind is meant to make power, and it has (Buschur has made over 900 wheel HP). We are coming out with a milder drop in cam that will be more suited to cars with less modifications.
I know for a fact that it isn't the PCV valve, because I've heard that noise, and it is nothing like the one I encounter at 0,0. I'll do a leak down test tomorrow te make sure my valves are still fine, and then I'll contact the shop that built my head and find out about the mill job.
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