charlie c5

iTrader: (6)

I have a 408 with a crazy cam . When you pull off the oil fill cap, will there be a vaccum? If so what causes the vaccum??? I pull off my cap, and get a huge vaccum.. Thanks guys...

3.4camaro

iTrader: (1)

its probably caused by the exhaust strokes of the engine. just be glad it doesnt blow out, that would mean you have bad piston rings.

rmitchell242

iTrader: (2)

did you cap or change the line that goes into the passenger side valve cover? that will cause vaccum from the oil cap if you did you should change that

GOaT Cheese

If you are not running a vacuum pump to the crankcase, then you have a problem. If you have a vacuum at the oil fill hole (crankcase) then you have an intake that is not sealed properly, or some other goofy problem. You should have a very small amount of pressure, not vacuum, even with the fixed orifice PCV valve, it cannot keep up with crankcase windage at idle (hence the KV line to the throttle body). Now, if you are running a crankcase evacuation system, then no worries.

charlie c5

iTrader: (6)

Well, I don't have a vaccum pump. I do have a huge vaccum at the oil fill neck, even when I take off both the intake and the throttle body vaccum lines. Now that's not good, huh??? Any ideas...

GOaT Cheese

Ya, if all the PCV lines are removed from the throttle body and valve covers, and you still have vacuum at your filler tube, then yes you definately have a big problem. I've seen aftermarket heads pull crankcase vacuum through the rocker arm bolts that aren't sealed. Thinking on it now, it cant be the intake gaskets because the crankcase is sealed from the intake. So it would have to be a cylinder head problem. It can't be a piston or ring problem because you would have excessive pressure, not a vacuum. Strange.

charlie c5

iTrader: (6)

Your telling me. I am pulling what little hair I have out right now as I type.....

JoeyGC5

iTrader: (24)

Can you blow air through the lines from the valve covers to the throttle body and intake? It sounds like there is blockage keeping air from equalizing crankcase pressure.

charlie c5

iTrader: (6)

I pulled off the driver's side valve cover. Yes, well, I found our little problem... #7 cylinder rocker pedistol is broken. I can't believe it. I'll call Texas Speed on Wednesday. I'm sure Jason, and Jon will take care of me.. I'll let you guys know how it goes. The motor, heads rear-end and tranny only have 5 miles on it.

The1N_only

iTrader: (7)

There has been quite a very heads that the rocker arm pedestal broke off and they all happen to be PRC heads.

The1N_only

iTrader: (7)

Are you really going to spray a 500 progressive single shot?

Irocss85

iTrader: (1)

wonder how in the world that happened? any chance a valve hit a piston? is it striped out, or the stand is as you said broken? get some pics just cause Id like to see them. hopefully we can figure out why that happened.

The1N_only

iTrader: (7)

The heads was over ported and the stress and the harmonics from the valve spring caused it to crack and finally break off. The same that happed to a buddy of mine not to long ago

charlie c5

iTrader: (6)

I am planning on spraying a 500 progressive on a direct port. Not impossable at all. I have set this same set-up up many times... Yes, the stand itself broke. I had the thought of maybe over porting, or the push rods may be too long, or the cam too big. But I spent 8 months planning this set-up. I made sure all of the builders and designers knew what was going on. I know how good communication is key. My thought is I hope this doesn't happen to the other head. I'll call Texas Speed Tuesday. I knnow they'll take care of me. They do have great customer service...

charlie c5

iTrader: (6)

Here are a couple of pics for you guys.

GOaT Cheese

Well it is completely obvious to me from the pics that the head was over ported.

mcamarols1

iTrader: (9)

F#CKKKK....im scared now!!!! are those 2.5 heads???? 243 castings???

Dan_the_C5_Man

Charlie, Dan Smallwood here..

Yikes, glad you found the issue.. Was this the side w/ the screwy LTFT's?? Seems like it took a while for it to break, as it ran o.k. for a bit.

I'd be concerned about this combo, you don't want the motor to grenade at high RPM's..

Irocss85

iTrader: (1)

damn, that is scary. glad I didnt raise the roof on my ports, as I'll be using the new super springs and LSK int. lobe too. are they sending you a new head? what happened to the pushrod? was it still sitting on the lifter?

what is the thickness of the port walls where it broke? could you measure this and put that in this thread so others know to avoid goin to that much material removal? Im goin to measure the thickness of my port walls in those areas if I can get to it somehow. all you need is a mic. or dial calipers since its right there opened up.
how high have you reved the engine so far? wonder when it happened. and what about the other side?

charlie c5

iTrader: (6)

I have both valve covers off, and the driver's side is the only broken one. My issue is this happened with only 5 miles on the motor. I was still in the break-in mode. I haven't even thought about the 500 shot yet. I could imagine being at the top of the 1/4 @ 7500 RPMs on a 500 shot. That would suck. Dan Smallwood, yes this the srewy side. I'll be calling Texas Speed this morning. I know they'll take care of me... They want good publicity in GM High Tech and Corvette Fever Maagazines. I'm just worried about the other head.. If this one is thin, what about the other??..