Predator 212 Hemi Won't Idle After Valve Lash Adjustment

SquidBonez

Member
Messages
208
Reaction score
1
Location
New Jersey, USA
I recently installed a stage 2 kit in my Predator 212 Hemi. While I was testing it out, the valve lash adjustment screw on the exhaust rocker backed out and allowed the pushrod to fall out from beneath the rocker. No big deal, this happened once before and all I did was reset the lash and I was fine. Now, after setting the lash multiple times, I can not get the engine to idle. It will only start with starting fluid, idle for about 5 seconds, and then die. The pushrods aren't bent, and when I cycle the engine everything works as it should valvetrain wise. I picked up a new carb to see if that would fix it (last time I couldn't get my engine running I just swapped the carb and it fixed it...plus it's only $12). But if/when that doesn't work, what should I try? (EDIT: It didn't work.)

LIST OF MODS:
PVL Flywheel, 4 Degree Offset Timing Key, ARC Billet Rod, 22lb Valve Springs, 0.01” Head Gasket - $5 MOD2 Camshaft, Header Pipe, Muffler, 0.38 Carb Jet, Chromoly Pushrods 5.54”, Autolite 3910X Spark Plug
 
Last edited:

madprofessor

Erased.
Messages
165
Reaction score
10
Location
Jacksonville, Florida
Sounds like Predator cap curse. As a hemi, both the intake and exhaust valves each have a lash cap sitting on top of the valve stems. Just a little pea-size cup sitting mouth down on the valve keepers, so that the rocker arm is pushing down on the cap and not on the valve stem. (Except non-hemi, I think they only have a lash cap on one of the valves.)
The cap curse is you unknowingly letting a cap (or both) get pushed off, maybe with your feeler gauge, leaving a huge amount of flapping around by the rocker arm, letting the pushrod fall out from under the rocker. The caps usually fall down the pushrod openings into the case, where they seriously need to be removed before running it again.
Trying to adjust the lash without the caps won't work, the excessive tilting of the rockers will prevent the valves from operating in correct lift and duration of the cam.
Pull off the rockers enough to see if both valves have a cap sitting on their stems, or if you've adjusted the lash with the rockers pressing directly on the stems. If missing, look for them in the head space there. If gone, you've got to split the case and get them out of there.
Please don't split the case without a new sump sidecover gasket in hand. People who live by gasket sealer have troubles with shaft spacing after putting it back together. If you're ordering a new (for hemi only) gasket set, might as well get a hi-performance set with a thin racing head gasket for the same money. Mine was $14, came with a .012" stainless steel head gasket. Noticeably increases the performance due to the increased compression.
 

SquidBonez

Member
Messages
208
Reaction score
1
Location
New Jersey, USA
Sounds like Predator cap curse. As a hemi, both the intake and exhaust valves each have a lash cap sitting on top of the valve stems. Just a little pea-size cup sitting mouth down on the valve keepers, so that the rocker arm is pushing down on the cap and not on the valve stem. (Except non-hemi, I think they only have a lash cap on one of the valves.)
The cap curse is you unknowingly letting a cap (or both) get pushed off, maybe with your feeler gauge, leaving a huge amount of flapping around by the rocker arm, letting the pushrod fall out from under the rocker. The caps usually fall down the pushrod openings into the case, where they seriously need to be removed before running it again.
Trying to adjust the lash without the caps won't work, the excessive tilting of the rockers will prevent the valves from operating in correct lift and duration of the cam.
Pull off the rockers enough to see if both valves have a cap sitting on their stems, or if you've adjusted the lash with the rockers pressing directly on the stems. If missing, look for them in the head space there. If gone, you've got to split the case and get them out of there.
Please don't split the case without a new sump sidecover gasket in hand. People who live by gasket sealer have troubles with shaft spacing after putting it back together. If you're ordering a new (for hemi only) gasket set, might as well get a hi-performance set with a thin racing head gasket for the same money. Mine was $14, came with a .012" stainless steel head gasket. Noticeably increases the performance due to the increased compression.
Both caps are still there. I made sure to check because the first time this happened one of the caps fell in (but I managed to get it out). I also have a metal head gasket installed when I opened up the engine for stage 2 mods.
 

SquidBonez

Member
Messages
208
Reaction score
1
Location
New Jersey, USA
Update: swapped the carb and I'm still having the same problem. It only runs when I rev it, and at that point it's trying to take off. If it helps, here's all the mods I have done. I did a compression test and the highest PSI I reached was 50 PSI. Keep in mind this is with a thin head gasket. I feel like that's low. Maybe when it threw the pushrod the piston smacked the valve? That's probably what I'm going to check next. Still want to hear some suggestions if you have them, though.

LIST OF MODS:
PVL Flywheel, 4 Degree Offset Timing Key, ARC Billet Rod, 22lb Valve Springs, 0.01” Head Gasket - $5 MOD2 Camshaft, Header Pipe, Muffler, 0.38 Carb Jet, Chromoly Pushrods 5.54”, Autolite 3910X Spark Plug
 
Last edited:

madprofessor

Erased.
Messages
165
Reaction score
10
Location
Jacksonville, Florida
Compression: Need to know if your ARC billet rod is stock 3.308" or the longer 3.328" that increases compression. Guessing you did a typo on the head gasket, meaning to say 0.10" thickness. My own hi-perf gasket is 0.12" thickness. Need to know the exact of yours. Currently checking on what stock compression should be, don't know yet.
Carb jetting: My performance guy says that the .036 jets he supplies me with should be the max for my 15+ hp. Predator using any carb, and even that should run quite rich. It's mainly for more low end power. That rich mixture means the spark plug will soot up black very quickly, but not foul. You can basically wipe off that kind of thing. Remember that soot contains carbon, which can divert a spark.
On that same subject, all that fuel is premised on having maximum air flow from a hi-flow air filter, a venturi-face (not flat) filter adapter, and free-flowing exhaust. Have you tried running that engine with the muffler removed? All mufflers have at least some degree of restriction.
Checking also on what stock length is for pushrods, to see if yours are standard. My guy says the only thing better than stock valve retainers is if you go to stainless steel valves, then he sells a valves/retainers/spring kit for $60. Nice to have your chrome/moly pushrods, but wondering just how much help they are.
 

SquidBonez

Member
Messages
208
Reaction score
1
Location
New Jersey, USA
Compression: Need to know if your ARC billet rod is stock 3.308" or the longer 3.328" that increases compression. Guessing you did a typo on the head gasket, meaning to say 0.10" thickness. My own hi-perf gasket is 0.12" thickness. Need to know the exact of yours. Currently checking on what stock compression should be, don't know yet.
Carb jetting: My performance guy says that the .036 jets he supplies me with should be the max for my 15+ hp. Predator using any carb, and even that should run quite rich. It's mainly for more low end power. That rich mixture means the spark plug will soot up black very quickly, but not foul. You can basically wipe off that kind of thing. Remember that soot contains carbon, which can divert a spark.
On that same subject, all that fuel is premised on having maximum air flow from a hi-flow air filter, a venturi-face (not flat) filter adapter, and free-flowing exhaust. Have you tried running that engine with the muffler removed? All mufflers have at least some degree of restriction.
Checking also on what stock length is for pushrods, to see if yours are standard. My guy says the only thing better than stock valve retainers is if you go to stainless steel valves, then he sells a valves/retainers/spring kit for $60. Nice to have your chrome/moly pushrods, but wondering just how much help they are.
Rod and pushrods are both stock length. And the head gasket is the thin metal one that OMB/GPS sells (see here, listed as 0.01": https://www.gopowersports.com/010-h..._lLwbT81pjIIteo36JTvtW9tYoeyCUYYaAtcdEALw_wcB). The jet came from the stage 1 kit. I am running a muffler and high flow air filter, but nothing changes when I remove the muffler. Gonna pull the head and check the valves. Do you reccomend swapping back to the stock jet? What size is the stock jet?
 
Top