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MS3 vs. MS4

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Old 07-12-2008, 02:38 PM
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Default MS3 vs. MS4

Simply stated, why does the MS4 require flycutting wheras the MS3 does not?
Old 07-12-2008, 02:49 PM
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If you are running stock head the MS4 does not require flycutting.
Old 07-12-2008, 02:49 PM
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the ms4 has a taller lift and a wider duration, causing the valves to open farther and therefore closer to the pistons
Old 07-12-2008, 02:54 PM
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Ok thanks a bunch all you guys on here are very helpful.
Old 07-13-2008, 11:43 AM
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Both the MS3, and MS4 are large cams, and depending on what heads you are going to go with, neither or both may require flycutting the pistons.

If you are going with either of those large cams I will tell you that running stock heads will choke your LS1 something fierce, and you will not see a fraction of the potential either of these cams will give you. That being said, if you want to stay away from flycutting, you want the most head you can get away with safely without going to the point at which flycutting the pistons is required.

The largest head you can get away with without having to flycut the pistons I have seen for the MS4 is the stage 1.5 LS6 heads from TSP. If you go with the MS3, you can get away with the stage 2.5 5.3 heads like I did with my LS1 in my sig. Both will make about the same power and not require flycutting the pistons. The MS3 will be a little easier to drive though, and it has better clearance from the piston to valve than the MS4 does. This is what made my mind up on my car that I wanted to go that route.

If you don't mind flycutting, the MS4 with a killer set of AFR heads will yeild the most power. There is someone on this board with fully ported AFR 225's and the MS4 along with all the supporting mods running 485 or so RWHP.
Old 07-13-2008, 11:59 AM
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I'd say the clearances are tighter than recommended with the MS4 and stock heads period, unless you flycut. Just guessing.
Old 07-13-2008, 12:31 PM
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Where is TSP at when you need them
Old 07-13-2008, 07:58 PM
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this had been beat to death.... no it doesnt require it... its CLOSE but not needed.... just call TSP or search
Old 07-15-2008, 07:31 PM
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not to steal the thread but i basically have an ms3 on a 111 lsa. it is also advanced +2? will i have to flycut? again not trying to take the thread....
Old 07-15-2008, 07:45 PM
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Originally Posted by Foys_Z
not to steal the thread but i basically have an ms3 on a 111 lsa. it is also advanced +2? will i have to flycut? again not trying to take the thread....
Invest in a light spring and a dial indicator...and find out. Probably the best tools you can have for heads and cam swaps on LS1s.
Old 07-16-2008, 11:12 AM
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Originally Posted by 98mysticZ
this had been beat to death.... no it doesnt require it... its CLOSE but not needed.... just call TSP or search
This.

I have an MS4 w/ stock 243's, no PTV issues. I spin it to 6800 over and over and over, have missed a few gears and so far no problem.



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