GM stated the 2.8 series rods to be balanced up to 7000 RPMs. The 3.1 got a different rod so, it could be balanced higher and so the 3.4 DOHC could aswell. But, GM is not making their engines to run at 7000+RPMs stock so, cation should be taken.
Get your rotating assembly balanced and get everything blueprinted. Have the block bored with the boring plates and have the latest honing technology used as most cylinders will not be consistant when using conventional honing methods.
You will pay a lot of money but, your bottom end will be setup to run smoothly at high RPMs. Then you must just setup the rest of the engine and you will have one beast of an engine.
Gm, and other car manufacturers, do not always machine their engines to the highest of tolerances. This is just a flaw of mass-production and high cost of manufacturing. Unfortunately, due to variances between casting to casting, you really cannot safely use un-machine castings for performance usage. Even excess materials left on the casting (flash) and such will cause material fatigue and could cause a failure.
Anyhow, realistically, i think you are crazy if you trust 4 cams spinning at 8000 RPMs, being driven by a giant rubber-band that must be replaced every couple of oil changes. Now that's a little unsafe. Also, there are certain situations you may put your motor into, take shifting for example, where shifting at 8000RPMs might make the rubber band (timing belt) go bye-bye.
Also, about the valve float. We could refer to both conditions as valve float but, nonetheless they are both a non-ideal situation where the valve get's away from the valvetrain.
The fact of the matter is though. Not only does valve float allow the possibility of a piston/valve colliding, or multiple valves colliding, you are also doing extreme wear to the valvetrain and making it undergo abnormal working conditions.
You must remember, first, your lifter is not designed to be used for extreme RPM's more than likely. Which means, at 8000 RPMs, the required amount of lubrication to inhibit wear may not be present. Then, you have serious valve float. What happens? If the valve floats past the cam's lift and also floats back to the seated position, as opposed to riding the cam, the cam may no longer have that lobe out at all. Which means, that .550 lift is how far the valve spring is goign to come back. Slam back. 400LBs open pressure springs may be underated in some crazy situation and cause valve float, right? What happens when that spring with 400LBs of fource is left with nothing to hold it? It slams, REALLY hard, either against the valve seat or, if the cam has come back around in position, which would be extreme, the cam is going to get slammed on the lobe. Cams don't usually like to be slammed by the valves/springs. As durable as a cam seems, if it repeatedly gets slammed by lifters at high pressures you may split your cam.
Actually, a buddy of mine with a Ford 351 just did that a few months back. Really bad valve float and then... We pulled the cam out in pieces.
Also, back to the rods. I know from experience, GM's rods are not always what they seem. Many of them have offset small ends and look at the balancing weights, some of them are really messed up. The 660's seem a little better off than SBC Rods though (Small and large journal, I've compared all)
Oh yeah, anyone interested in a set of small journal SBC rods? they were from a 60's 327 Vette. Can be modded for the 660's.
-Dave
Get your rotating assembly balanced and get everything blueprinted. Have the block bored with the boring plates and have the latest honing technology used as most cylinders will not be consistant when using conventional honing methods.
You will pay a lot of money but, your bottom end will be setup to run smoothly at high RPMs. Then you must just setup the rest of the engine and you will have one beast of an engine.
Gm, and other car manufacturers, do not always machine their engines to the highest of tolerances. This is just a flaw of mass-production and high cost of manufacturing. Unfortunately, due to variances between casting to casting, you really cannot safely use un-machine castings for performance usage. Even excess materials left on the casting (flash) and such will cause material fatigue and could cause a failure.
Anyhow, realistically, i think you are crazy if you trust 4 cams spinning at 8000 RPMs, being driven by a giant rubber-band that must be replaced every couple of oil changes. Now that's a little unsafe. Also, there are certain situations you may put your motor into, take shifting for example, where shifting at 8000RPMs might make the rubber band (timing belt) go bye-bye.
Also, about the valve float. We could refer to both conditions as valve float but, nonetheless they are both a non-ideal situation where the valve get's away from the valvetrain.
The fact of the matter is though. Not only does valve float allow the possibility of a piston/valve colliding, or multiple valves colliding, you are also doing extreme wear to the valvetrain and making it undergo abnormal working conditions.
You must remember, first, your lifter is not designed to be used for extreme RPM's more than likely. Which means, at 8000 RPMs, the required amount of lubrication to inhibit wear may not be present. Then, you have serious valve float. What happens? If the valve floats past the cam's lift and also floats back to the seated position, as opposed to riding the cam, the cam may no longer have that lobe out at all. Which means, that .550 lift is how far the valve spring is goign to come back. Slam back. 400LBs open pressure springs may be underated in some crazy situation and cause valve float, right? What happens when that spring with 400LBs of fource is left with nothing to hold it? It slams, REALLY hard, either against the valve seat or, if the cam has come back around in position, which would be extreme, the cam is going to get slammed on the lobe. Cams don't usually like to be slammed by the valves/springs. As durable as a cam seems, if it repeatedly gets slammed by lifters at high pressures you may split your cam.
Actually, a buddy of mine with a Ford 351 just did that a few months back. Really bad valve float and then... We pulled the cam out in pieces.
Also, back to the rods. I know from experience, GM's rods are not always what they seem. Many of them have offset small ends and look at the balancing weights, some of them are really messed up. The 660's seem a little better off than SBC Rods though (Small and large journal, I've compared all)
Oh yeah, anyone interested in a set of small journal SBC rods? they were from a 60's 327 Vette. Can be modded for the 660's.
-Dave
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