OK, got the 327 running last night, (new build). Tonight I was going to set the timing and ****on up everything. As we were just finishing up the timing the engine began backfiring through the carb. Pulled the valve covers and found two thing of concern. First there were a couple of drops of water in the oil on the right head. The oil looked fine, no foam or anything. Just a couple of drop of water. I ***ume because it has been really humid and raining here that there may have been some condensation in the valave cover. (I hope) Second, the cause of the backfire was one of the roller rockers seems to have backed off. The screw in stud did not come out. It looks like the nut just backed off the rocker. Is that normal for a newly built engine? I have no experience with the roller rockers so hopefully someone can enlighten me. Also, is it ok to just retighten the rocker? If so how are they set?
OK, First thing is the water....The head bolts and the rocker studs go thru into the water jackets. A small (very ) amount of water on initial fire-up is pretty common. Do not loose any sleep over it just yet. It will most likley cure itself.. The rocker backing off is also fairly common.. The lock nut for roller rockers has an allen set screw in the center of the nut. BEFORE we go into how to set the valve we need to know if your cam is solid or hyd...... Can you check with the builder and let us know ?? Dave
They are solid valves. Shouldn't the rocker adjustment have some kind of locking device to keep it from backing off?
I had this happen once...but although the rocker was loose the adjusting nut was tight...turned out I had a lobe on the cam wiping itself out. When you fired that motor...did you follow cam break-in procedure?
Do you have the typical nuts used on rockers, or do you have polly locks? I personally use polly's on ALL roller rockers, be it full or just the tip style and never have any issue's with them backing off.
You can see that the rocker has backed off. I did the best icould to follow the breakin. It only ran about 15 minutes total.
as far as i know its the standard Comp Cam Roller Rockers. and it looks like nuts with the hex head studs inside.
Had a cam go bad during break-in a few years ago. After all is checked hook up a vacuum gauge and see if the needle is steady (good sign) or if it fluctuates rapidly (bad). Sounds like an exhaust valve is not opening and it is exiting through the intake/carb.
You did use an allen wrench to lock the set screw in the center of the adjusting nut ?? Didn't you ?? >>>>.
That was my next question . I've never had a polly lock back off , just a mechanical failure that made the rocker loose..like a bad cam
I didn't build it. I have a call into the builder now. I don't think the cam went bad in just 15 minutes. I primed the pump, used good ZDDP oil, and all i have done is crank the engine and long enough to see if it was timed. Maybe 5 minutes last night and then tonight was just going to confirm the timing and run the break in, 30 minutes at 2000 to 2500 rpm. it ran about 5 to 8 minutes and thats when the back fire started. Shut it down and founf the rocker backed off. you can easily tell its backed off by the way it looks compared to the rest of the rockers.
There ia a ALLEN set screw in most of the adjusting nuts for roller rockers. I have NEVER had one back off ... If I had the screw good and tight Check and see if the screw is loose in the offending rocker. .
Slowly tighten the rocker till it just closes all the slack. Remove the spark plugs then turn (BY HAND with battery DISCONNECTED) the engine and see if the valve moves the same amount as the one on the next cylinder. If it does, you're lucky and just need to set the clearance. If its LESS movement, the builder needs to be there before anything else is done.
Exactly. Contact the builder and explain what's happened. If he dosn't think there is a real problem, find out what the clearance should be. If it look's like it just backed off like you said, he may not have tightened that one lock. Reset the lash, make sure the jam nut is tight, restart the motor and see see if it happens again.
the picture of the rocker you have shows the hex nut inside just like mine. The hex nut is maybe 1/4 to 1/2 inch down inside the the nut where the others are almost flush.
Hmmmmmm...contact your engine builder, if you're not acquainted with hi-perf engines. If you DO have solid "lifters", not valves, I would have him teach you how to adjust them properly, when he looks at and corrects your problem, IF it is a loosened up Poly Lock. You'll have to perform this procedure quite often, if you put miles on the car. And YES you can ruin in a cam in less than 15 minutes!
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