cam degreeing?
11-14-2003, 10:00 PM
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cam degreeing?
is this a must for an engine
cause i used to put then at 0 all the time.you know timing chains have -4 0 and +4 .
i am plannimg to order a dgree wheel but i dont know what difference it will make?
should i put it to somewhere else then 0 ?
thnx
cause i used to put then at 0 all the time.you know timing chains have -4 0 and +4 .
i am plannimg to order a dgree wheel but i dont know what difference it will make?
should i put it to somewhere else then 0 ?
thnx
11-14-2003, 10:22 PM
#3
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Yyou don't have to degree your cam to get the engine to run well. It's close enough from the factory along with the other components.
However, if you are building a hi-perf engine where piston-to-valve clearance is tight, you must degree to be sure you are ok. Also, degreeing is important if you are trying to achieve a specific dynamic compression ratio. Otherwise throw it in straight up and have fun
However, if you are building a hi-perf engine where piston-to-valve clearance is tight, you must degree to be sure you are ok. Also, degreeing is important if you are trying to achieve a specific dynamic compression ratio. Otherwise throw it in straight up and have fun
11-14-2003, 10:23 PM
#4
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Been told many times that 4 degrees one way or the other will make very little, if even a noticable difference in a boat. Unless you are building a race boat. just my opinion.
I always install straight up. Double check everything with the degree wheel, valve to piston clearance, cam grind, and accuracy of the alignment pins and keyways.
I always install straight up. Double check everything with the degree wheel, valve to piston clearance, cam grind, and accuracy of the alignment pins and keyways.
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11-22-2003, 08:14 PM
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You shall check that you have the cam in the right position with an degree wheel. Normally todays camshafts are at the specified cam timings at 0 (at least Lunati cams).
Retarding the cams move the hp up in the rpm.
Advancing it moves the hp down in rpm.
If you dyno you try 2-4 degree up and down to see what´s best.
Be careful not to retard and advance so the valves hit the piston. Normally closest a few degrees after TDC during the overlap.
When you change cam you must make sure that the valves do not hit the pistons, that the rocker arms can take the lift, that no retainers not hit the rocker or that the springs not bottoms out as you maybe already know.
Retarding the cams move the hp up in the rpm.
Advancing it moves the hp down in rpm.
If you dyno you try 2-4 degree up and down to see what´s best.
Be careful not to retard and advance so the valves hit the piston. Normally closest a few degrees after TDC during the overlap.
When you change cam you must make sure that the valves do not hit the pistons, that the rocker arms can take the lift, that no retainers not hit the rocker or that the springs not bottoms out as you maybe already know.
11-22-2003, 10:07 PM
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Many cams come ground with 4 degrees of advance already in them. Install them with a "straight up" timing set and you still get 4 degrees of advance.
If you are running twins, it is more important to MEASURE the camshaft centerline and use a degree wheel to make sure both motors are set up the same. Not so much that they are set to a specific number, but that they are set up the same.
I've seen factory GM cams vary 3 degrees one way or another by stack up errors in the gear and cam variances.
If you are running twins, it is more important to MEASURE the camshaft centerline and use a degree wheel to make sure both motors are set up the same. Not so much that they are set to a specific number, but that they are set up the same.
I've seen factory GM cams vary 3 degrees one way or another by stack up errors in the gear and cam variances.
11-23-2003, 03:06 PM
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Any thoughts on retarding cam to lower commpression.I decked my block to achieve propper quench and now my c/r is about 10:1.I figure if I retard the cam by about 4 degrees it will bring it back down to 9.6:1.How high of commpresion can I get away with on 91 octane and alluminum heads.
11-24-2003, 12:08 AM
#9
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you can bleed low rpm cylinder pressure off by retarding, but it won't bleed off high rpm pressure.
Depending on how big a cam you are running, 91 with aluminums and 10:1 should be good. Just start with ignition retarded to 26 and advance 2 degrees at a time, looking for signs of detonation. You should pick up a few rpm each time you up the timing (trim to the exact same angle every time). Call it quits when you either see speckly spots on the plug insulator, or stop picking up rpm when you advance. (then back down 2 degrees.).
Depending on how big a cam you are running, 91 with aluminums and 10:1 should be good. Just start with ignition retarded to 26 and advance 2 degrees at a time, looking for signs of detonation. You should pick up a few rpm each time you up the timing (trim to the exact same angle every time). Call it quits when you either see speckly spots on the plug insulator, or stop picking up rpm when you advance. (then back down 2 degrees.).
