MMS 3500 Stage 2 Pics and Flowsheets

[dbral]

Got a set of stock heads coming to mess around with. The yellow lines in one photo show the direction of the major wear. Only a few valves line up with the rocker arm motion. Def. getting pushed sideways. Other photo shows exh. valve seated pre-lift tip/rocker contact. Does that look okay to you? Granted the seats are obliterated and the valves are sunk into the heads to different depths. The intakes look similar.

Yep, don't see any bronze valve guide liners in these heads either....

[dbral]

X2 post

[SappySE107]

Someone else had MMS heads and cam and when he was measuring for preload on the lifters, found that 1 was I think .020" different. They cut the valve seats various amounts and didn't get custom pushrods per cylinder to accommodate. Dude does not give a single fuck about performance, or these engines.

[SappySE107]

https://www.youtube.com/watch?v=uIVG7tHuj8g

This is what the stock rocker/valve looks like. It won't see the lift I get it to, but you can see it starts one one side of the valve tip and sweeps across the other side. This is what you want. Too difficult to see what yours used to be, but a sharpie on the tip and sweep the rocker to see that its always in the middle part, and not off the edge.

[dbral]

Thanks Ben, that video and info is what i was looking for. Too much damage for me to determine much on these heads. There is this though, the PCV system on this engine was routed in an odd manner. The PCV valve in the front cover had the normal factory vacuum line running to it but the rear cover crankcase fresh air line was also ran to manifold vacuum. The crankcase was under considerable vacuum at idle and probably during light throttle cruise, decel, etc....enough vac. to collapse a rubber hose leading to that rear valve cover and the engine would make a 2-3 second long squeak noise every time it was shut off as the crankcase bled off the vacuum, lol. Could exc. crankcase vacuum have caused lack of proper lube to the valve stems/guides? The engine was ran with that PCV config. for around 20k miles i'm guessing.

Yeah man, mms assembled this engine at their facility using their parts and their methods. The car has led a pampered/well maintained life. Thinking that this valve damage has been going on for quite some time from the looks of it. These are the only set of mms cnc stage 2 heads that i know of with some miles on them and these are clearly garbage. The old stage 2's were hand ported from what i understand.

[Frank Reiner]

The PCV valve in the front cover had the normal factory vacuum line running to it but the rear cover crankcase fresh air line was also ran to manifold vacuum. The crankcase was under considerable vacuum at idle and probably during light throttle cruise, decel, etc....
Could exc. crankcase vacuum have caused lack of proper lube to the valve stems/guides? The engine was ran with that PCV config. for around 20k miles i'm guessing.

Did that fresh air hose have any restriction or valve in it? It seems to me that that large an air "leak" into the intake manifold would cause the mixture to lean out past the ability of the ECU to correct for it. Under most power on conditions there is sufficient blow-by that crankcase pressure would be positive, and excess air entering the intake manifold would lean the mixture.

If, in fact, the crankcase pressure was below atmospheric for considerable periods of operating time, then yes, oil flow into the valve guides could be quite restricted.

[dbral]

Yep, the fresh air hose was essentially capped off being routed that way and the car had terrible low rpm/idle manners with that pcv routing. The crankcase fresh air hose was hooked directly to a manifold vacuum source instead of being routed between the tb and maf like the factory set up. The crankcase was turned into a big vacuum reservoir, until you cracked the throttle then I'm guessing a good portion of already metered air was getting drawn into the crankcase instead of the combustion chambers and wreaking havoc with the fuel trims and the low rpm driveability. Then you would close the throttle start the viscous cycle again, lol. Stalling/surging... pretty awful to drive around town and in traffic but that is how the mms shop had it hooked up for whatever reason. Have always had an intermittent p1133 but i'm thinking that may be due to the cylinder head issue.

Have read about drag racers hooking up a vacuum pump to the crankcase but have no idea or personal experience with the long term effects of that. Might help explain the destruction maybe

[SappySE107]

I doubt you could create enough vacuum from the engine alone to screw up the oiling to the top end. The pushrods deliver it right to the rocker. You should definitely make it like factory, and add a catch can on the vacuum side. If I had to guess, it would be incorrect lifter preload. How long are the pushrods?

[dbral]

Not sure to what vacuum the crankcase was getting pulled down to (Guessing it was close to actual manifold vac. after idling for a few seconds.) but it was definitely sucking, like the low rpm driveablity did before the re-route. I don't recommend the mms PCV mod. The rockers and pushrods do not appear oil starved. Yeah, maybe the preload was an issue. The engine always had a good bit of valve train noise. Some days worse than others. The pushrods are 6.1 and 5.775 across the board. What is a good preload # to shoot for? How much variance it it okay to go + or - that number?

[SappySE107]

You want .075" preload. More will lose top end power. Not sure how much less you can run or what that does. Over .100 will hang a valve open. I wouldn't try less than .050" other than on an engine dyno to see what happens with power.

[dbral]

Thanks Ben!