Is it better to give up 0.15 compression ratio or 0.16" valve lift?
10-25-2009, 07:40 PM
#1
Is it better to give up 0.15 compression ratio or 0.16" valve lift? Need to sacrifice one of the two in order to create proper valve to piston clearance. Plan to keep the 0.15 CR & reduce the valve lift by 0.16". Any reason not to?
10.97:1 SCR w/0.580" lift
10.82:1 SCR w/0.596" lift
10.97:1 SCR w/0.580" lift
10.82:1 SCR w/0.596" lift
10-25-2009, 07:44 PM
#2
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I'm not the expert, but it's typically the duration that causes the interference, and not the lift. So I'm curious how you determined that reducing the lift slightly will result in the desired clearance?
10-25-2009, 07:51 PM
#4
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10.82:1 SCR w/0.596" lift even if putting the smaller lift one ... I`m a higher lift guy ... to me I`d like to be able to put a 665 lift cam and not worry about it if I`m putting aftermaket pistons in my engine
even if I`m just putting 580-630 lift one.
even if I`m just putting 580-630 lift one.
10-25-2009, 10:49 PM
#7
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I dont think your checking your pv correctly with that small of a cam you should not have zero. Do you have the engine rolled over so that number one is on over lap?
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10-26-2009, 09:42 AM
#9
^^^
I agree that something is not right. Installed cam Dot to Dot w/ #1 piston @ TDC. Can feel the intake valve contact the piston while rotating by using the crank bolt, with heads just sitting on the block, not bolted down. Once they contact, I stop.
As noted, heads are off. So, I can check piston position easily. What do you guys recommend to ensure proper cam position?
I agree that something is not right. Installed cam Dot to Dot w/ #1 piston @ TDC. Can feel the intake valve contact the piston while rotating by using the crank bolt, with heads just sitting on the block, not bolted down. Once they contact, I stop.
As noted, heads are off. So, I can check piston position easily. What do you guys recommend to ensure proper cam position?
10-26-2009, 02:51 PM
#13
The gaskets are in place. I am aware of the pistons coming out of the hole; 0.010". The intake vales, are contacting the pistons. Coated the edges of the valves so that it would leave a small grease mark on the top of the piston where they are making contact. (I know that the gaskets are not compressed).
What has been uncovered here is that I made a mistake w/ the cam timing alignment. Am in the process of confirming & correcting the mistake.
Thank-you for the reply, though. The out of the hole statement is good information for the archives.
10-27-2009, 05:48 PM
#16
Follow up:
Measured PTV clearance after adjusting the cam set up & it is just .040" w/an 0.45" head gasket being used. So, it's gonna need a shallow flycut to reach the standard 0.080"+. So, that little 224/224, .596/.596 cam can cause a clearance issues. Measured 64 cc combustion chamber on the heads means that generally speaking 0.010"-0.012" has been removed from the heads. Am also using 1.8 rockers of which adds to the issue.
Measured PTV clearance after adjusting the cam set up & it is just .040" w/an 0.45" head gasket being used. So, it's gonna need a shallow flycut to reach the standard 0.080"+. So, that little 224/224, .596/.596 cam can cause a clearance issues. Measured 64 cc combustion chamber on the heads means that generally speaking 0.010"-0.012" has been removed from the heads. Am also using 1.8 rockers of which adds to the issue.
10-28-2009, 04:37 AM
#18
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Follow up:
Measured PTV clearance after adjusting the cam set up & it is just .040" w/an 0.45" head gasket being used. So, it's gonna need a shallow flycut to reach the standard 0.080"+. So, that little 224/224, .596/.596 cam can cause a clearance issues. Measured 64 cc combustion chamber on the heads means that generally speaking 0.010"-0.012" has been removed from the heads. Am also using 1.8 rockers of which adds to the issue.
Measured PTV clearance after adjusting the cam set up & it is just .040" w/an 0.45" head gasket being used. So, it's gonna need a shallow flycut to reach the standard 0.080"+. So, that little 224/224, .596/.596 cam can cause a clearance issues. Measured 64 cc combustion chamber on the heads means that generally speaking 0.010"-0.012" has been removed from the heads. Am also using 1.8 rockers of which adds to the issue.
2- You should not be using 1.8 rockers with that much lift on cam, bad for valvetrain control at higher rpms.
3- What size valve are you running? Ferrea?
10-28-2009, 07:39 AM
#19
The cam is an LSX regrind. 224/224, .563"/.563", 114 LSA. The .596" is through 1.8 rockers. So, the lobe lift on the cam itself is .331"/.331". The valves are 2.020" (standard AFR). Have not done anything to change the ICL, but am not sure if it remains 114 or if the stock grinds are on 112. Am in the process of purchasing a Cloyes adjustable cam gear, as well (+,- 6*). Also have AFR 8019 springs.
Exhaust valve clearance was .073".
10-28-2009, 08:28 AM
#20
Just looked a bit closer & saw that the intake pushrod is approx. 0.092" higher than the exhaust valve pushrod just before the piston moves down from TDC. Also noted that the dot to dot alignment has moved approx. 3/8 ths of a tooth @ this position. This is the closest point between the top of the piston & the edge of the valve. Don't know if this seems about right or if the ICL on the cam is more offset than it should be.
Also, wanted to clarify your comment (Predator-Z) in regards to the lift. Were you stating that achieving 0.596" by way of 1.8 rockers is too unstable @ high rpms?
Also, wanted to clarify your comment (Predator-Z) in regards to the lift. Were you stating that achieving 0.596" by way of 1.8 rockers is too unstable @ high rpms?