Cam suggestions??
02-23-2015, 08:56 AM
#1
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Cam suggestions?? I'm putting together a L76 6.0 with gm flat top pistons and gmpp cnc ls9 cylinder heads(GMPP says 66.5 cc chambers). Probably going with a single plane intake and 750 holley double pumper. The car is a 98 camaro, auto, 4500 converter and 4:10 gears and mainly a strip car. This is my first carb setup so not to familiar with the cam selection. Thanks for any help.
02-23-2015, 11:48 AM
#6
That really limits your cam choices. And for your application, you will be leaving some power on the table. If you are not planning on running nitrous, I would definitely start cozying up to the idea of fly-cutting some valve reliefs.
If you don't want to flyucut, you are going to be looking at a cam that looks something like 228/242 on 111+3. A cam like that will 60' like a **** with your 4500 converter and pull hard to 7000 RPM. It is plenty enough cam to run well into the 10s in your Camaro, but you might be able to make another 10-20 HP with a bigger stick and fly-cutting.
If you don't want to flyucut, you are going to be looking at a cam that looks something like 228/242 on 111+3. A cam like that will 60' like a **** with your 4500 converter and pull hard to 7000 RPM. It is plenty enough cam to run well into the 10s in your Camaro, but you might be able to make another 10-20 HP with a bigger stick and fly-cutting.
02-23-2015, 01:13 PM
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That really limits your cam choices. And for your application, you will be leaving some power on the table. If you are not planning on running nitrous, I would definitely start cozying up to the idea of fly-cutting some valve reliefs.
If you don't want to flyucut, you are going to be looking at a cam that looks something like 228/242 on 111+3. A cam like that will 60' like a **** with your 4500 converter and pull hard to 7000 RPM. It is plenty enough cam to run well into the 10s in your Camaro, but you might be able to make another 10-20 HP with a bigger stick and fly-cutting.
If you don't want to flyucut, you are going to be looking at a cam that looks something like 228/242 on 111+3. A cam like that will 60' like a **** with your 4500 converter and pull hard to 7000 RPM. It is plenty enough cam to run well into the 10s in your Camaro, but you might be able to make another 10-20 HP with a bigger stick and fly-cutting.
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02-23-2015, 02:15 PM
#8
XA228/370-XA242/355-11+3
Also, I just noticed that the GMPP heads you are planning have 66cc chambers. Before you order your cam, make sure you ask GMPP if the heads are milled and what the "Valve drop" measurement is on the heads. This will affect your piston to valve clearance. Let us know what they say.
02-23-2015, 03:35 PM
#9
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They say as cast 66.5 so do you think they are milled? I'll try to get a hold of someone to ask for sure.
19328743 NEW!
LS9 CNC-Ported Head Assembly (not shown)
• Special A356T6 aluminum Roto-cast head casting for
greater strength. The mold is rotated during production to
create a more solid casting that virtually eliminates porosity
• Reinforced webbing and thicker deck (for minimal distortion)
makes it an excellent choice for supercharged and turbocharged
engine combinations
• CNC-ported for approximately 10 percent greater airflow
(intake side) than the regular-production cylinder head
(similar to LS3 CNC-ported head P/N 88958758)
• As-cast 66.5cc combustion chamber volume
• Fully assembled with production LS9 2.165" (55mm) titanium
intake valves and sodium-filled 1.590" (40mm) exhaust
valves; and beehive-type valve springs
• Valve springs rated for .570-inch" max lift
• Can be used on LS engines with at least a 4.000" bore using
standard 11mm head bolts in place of the LS9’s 12mm head bolts
19328743 NEW!
LS9 CNC-Ported Head Assembly (not shown)
• Special A356T6 aluminum Roto-cast head casting for
greater strength. The mold is rotated during production to
create a more solid casting that virtually eliminates porosity
• Reinforced webbing and thicker deck (for minimal distortion)
makes it an excellent choice for supercharged and turbocharged
engine combinations
• CNC-ported for approximately 10 percent greater airflow
(intake side) than the regular-production cylinder head
(similar to LS3 CNC-ported head P/N 88958758)
• As-cast 66.5cc combustion chamber volume
• Fully assembled with production LS9 2.165" (55mm) titanium
intake valves and sodium-filled 1.590" (40mm) exhaust
valves; and beehive-type valve springs
• Valve springs rated for .570-inch" max lift
• Can be used on LS engines with at least a 4.000" bore using
standard 11mm head bolts in place of the LS9’s 12mm head bolts
Last edited by Y2KSS; 02-23-2015 at 03:37 PM. Reason: more info
02-26-2015, 09:16 AM
#10
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I heard back from Texas Speed on their cam choice and its a 229/236 624/615 111 LSA. I still have not heard back about if the gmpp heads are milled or not.
02-26-2015, 01:55 PM
#13
Then you can measure the "Valve drop" yourself. It is pretty easy if you have a dial indicator micrometer.
If you take this measurement accurately, you can better order a camshaft that will have the piston-to-valve clearance that you desire.
Valve Drop
The object of measuring valve drop is to determine how far a valve can open before it touches the piston while that piston is at top dead center in the cylinder. Knowing this figure is the only way one can estimate piston-to-valve clearance without actually measuring an assembled engine. Furthermore, knowing this allows engine builders to determine which camshafts might fit in a given engine without further modification. There are two ways to measure valve drop. Actual valve drop (assembled) and estimated valve drop (not assembled).
Actual (assembled) Valve Drop
The most fool proof way is to measure valve drop in an assembled engine. Just rotate the crank until the the piston is at top dead center and then lower the valve until it touches the piston. Whatever the distance is between the valve in the fully seated position or closed position and lowered until it touches the piston while at TDC , that is your valve drop. Do this for both intake and exhaust valves as they are most often different.
Estimated (unassembled) Valve Drop
You can also estimate valve drop while the cylinder head is not on the engine. For this start by placing the cylinder head on a flat surface. Whatever the distance is between the valve in the fully seated position or closed position and lowered until it touches the surface in which the head rests, that is your cylinder head "valve drop" distance. This measurement of how far the valve "drops" is your cylinder head valve drop. Next measure your piston to deck height relationship. Most LS engines have a positive deck(between .005" to .008" is most often reported by builders). Next measure the thickness of your head gasket. The formula looks something like this: Cylinder head valve drop + head gasket thickness - positive deck height = valve drop. this is very accurate for an engine equipped with flat top pistons. Here is an example:
.155" + .051" - .007" = .199"
Again, do this for both intake and exhaust valves as they are most often different. Also, engines with dome pistons or dished pistons might better be done assembled as it is difficult to account for the different piston surface shapes using this method.
The object of measuring valve drop is to determine how far a valve can open before it touches the piston while that piston is at top dead center in the cylinder. Knowing this figure is the only way one can estimate piston-to-valve clearance without actually measuring an assembled engine. Furthermore, knowing this allows engine builders to determine which camshafts might fit in a given engine without further modification. There are two ways to measure valve drop. Actual valve drop (assembled) and estimated valve drop (not assembled).
Actual (assembled) Valve Drop
The most fool proof way is to measure valve drop in an assembled engine. Just rotate the crank until the the piston is at top dead center and then lower the valve until it touches the piston. Whatever the distance is between the valve in the fully seated position or closed position and lowered until it touches the piston while at TDC , that is your valve drop. Do this for both intake and exhaust valves as they are most often different.
Estimated (unassembled) Valve Drop
You can also estimate valve drop while the cylinder head is not on the engine. For this start by placing the cylinder head on a flat surface. Whatever the distance is between the valve in the fully seated position or closed position and lowered until it touches the surface in which the head rests, that is your cylinder head "valve drop" distance. This measurement of how far the valve "drops" is your cylinder head valve drop. Next measure your piston to deck height relationship. Most LS engines have a positive deck(between .005" to .008" is most often reported by builders). Next measure the thickness of your head gasket. The formula looks something like this: Cylinder head valve drop + head gasket thickness - positive deck height = valve drop. this is very accurate for an engine equipped with flat top pistons. Here is an example:
.155" + .051" - .007" = .199"
Again, do this for both intake and exhaust valves as they are most often different. Also, engines with dome pistons or dished pistons might better be done assembled as it is difficult to account for the different piston surface shapes using this method.
02-27-2015, 09:41 AM
#18
From a valve clearance standpoint, that would depend on what your valve drop measurement is. From a performance standpoint I would put it in at 108 ICL. But with that said, I would prefer the cam that I mentioned because it has a few more degrees of overlap which is especially helpful for midrange power on engines equipped with a single plane.