SquidBonez
Active member
Yeah even if this had nothing to do with the play I was feeling it's still great I caught it so early. Not trying to be out of close to $1000 this soon lol
Predator 420 Hard To Pull, Sputtering
- Thread starter SquidBonez
- Start date
Bansil
Painter of gnomes....
The bearings are definitely scrap, but they don't look worn to cause slop, what clearance are they at? You can squish the plastic gage and not turn engine over, also never oil back of bearings or rod and cap surfaces at install, that could make it look like you have .002 or .003 less clearance and when engine warms up and oil leaves, you have too much clearance and you can spin a bearing.
Just info to teach you about building engines.
Just info to teach you about building engines.
Last edited:
madprofessor
"Loose Cannon Creations"
Just went back looking for what you replied concerning break-in oil. I got it that you used Royal Purple's 10W30, but that's just oil, albeit very good stuff. Did you at least put in a break-in additive with it? Only believe in purpose-designed break-in oil myself (Royal Purple), but in lieu of that the need is still imperative for some kind of zinc-rich something during the initial period of clawing off metal until things seat.
BTW: Bansil, that's a good tip that I never remember to tell people about not oiling the back side of a rod bearing or the inside surface of rod itself and its cap where a rod bearing is used.
SquidBonez
Active member
Got the new bearings in aaaaand it feels exactly the same as before. A bit of play at TDC/BDC. At least the bearings are nice and new. I made sure to not oil the back of the bearings as to not cause them to spin. I'm just gonna say screw it and run it. If it blows I can swap a lot of the parts stuff over to a new engine (pushrods, valve springs, carb, pipe, flywheel, etc).
madprofessor
"Loose Cannon Creations"
Remember to plastigauge it this time?
SquidBonez
Active member
I did. Originally thought the bearings would solve the slop because it read fine. Don't know what's causing it or if it's even an issue so I'm just gonna send it.
Bansil
Painter of gnomes....
Is it possible the slop you feel is backlash on crank/cam?
And you feel it in the Rod/piston?
And you feel it in the Rod/piston?
madprofessor
"Loose Cannon Creations"
Okay, I'm really convinced now. Either.................
(1): There is no endplay of the rod/piston, but somehow the way you're trying to feel for it, pushing, pulling, shaking, whatever, is making it feel like there's a small motion somewhere, possibly the natural side2side of the rod on the wristpin. Or....................
(2): My favorite guess, not enough oil got splashed up to the underside of the piston in the beginning, and the piston journals for the wrist pin and/or the rod journal for it are slopped out, and the endplay is the piston jumping up and down on the wristpin and/or the rod.
NOTE: When installing the wristpin, it's best to turn the snap-ring gap 180 degrees to the journal edge's divot.
(1): There is no endplay of the rod/piston, but somehow the way you're trying to feel for it, pushing, pulling, shaking, whatever, is making it feel like there's a small motion somewhere, possibly the natural side2side of the rod on the wristpin. Or....................
(2): My favorite guess, not enough oil got splashed up to the underside of the piston in the beginning, and the piston journals for the wrist pin and/or the rod journal for it are slopped out, and the endplay is the piston jumping up and down on the wristpin and/or the rod.
NOTE: When installing the wristpin, it's best to turn the snap-ring gap 180 degrees to the journal edge's divot.
SquidBonez
Active member
I did make sure the snap rings on the wristpin were facing away from the divot when I installed it, so that shouldn't be an issue. I might just be paranoid. I know for a fact the bearings were shot but again I think that was the fault of no oil + metal shavings. Only way to find out is to rip it. Worse comes to worse I blow this engine and swap the parts to a new one. Once the engine is running again I'll take a better video and see if you guys notice anything.
SquidBonez
Active member
Ok so the engine is back together and is easier to pull over. Still trying to tune it to get it running reliably but I set the lash to 0.003 and it's been a decent improvement. It still occasionally rips the pullcord out of my hand but it's nowhere near as bad as before. Are these engines naturally harder to pull start than the 212 simply because of the added displacement?
madprofessor
"Loose Cannon Creations"
My understanding of basic physics says that even with very similar compression ratios, the more cc's you try to compress, the more work (harder pull) is required to do so. Did you ever read my post about "how much pullrope?".
Don't know about other people, but when I had lots of repeated snatchbacks of the pullrope with differently modded 212's, the revelation of taking a step back away from the engines so I could get a longer pull (4' instead of 3') let me never have a single snatchback ever since.
Don't know about other people, but when I had lots of repeated snatchbacks of the pullrope with differently modded 212's, the revelation of taking a step back away from the engines so I could get a longer pull (4' instead of 3') let me never have a single snatchback ever since.
SquidBonez
Active member
Well I finally figured out the issue. The reason it wasn't running right was because the cam would sit way farther back in the journal than it should, causing it to become misaligned due to the helical gear on the crank. Now why was it sitting so far back in the journal you ask? I think this might have something to do with it...
I have a lot of 420cc spares if anyone is interested...
I have a lot of 420cc spares if anyone is interested...
madprofessor
"Loose Cannon Creations"
Recess is cracked all the way through, and the face is scarred up. What am I not seeing? Are you saying the journal on the end of the camshaft was slid all the way into the recess but should not have been? How could that happen?
Bansil
Painter of gnomes....
X2...CRACK IS BAD...MMMKAY... 
...but that would allow cam to move laterally?
...but that would allow cam to move laterally?
SquidBonez
Active member
I believe so. Because of the helical gears on the crank, if the cam is allowed to move laterally too far it causes the engine to fall out of timing. I believe the cam journal has expanded slightly due to the crack. And even if this wasn't the issue, it will certainly become one in the future. I'd rather just get a new engine and start over. All the expensive parts can be swapped over. And next time I will be breaking the engine in BEFORE modifying it.X2...CRACK IS BAD...MMMKAY...
Hellion
Disc brakes are for cowards
Man, this is a sad sad thread. Sorry to hear such misfortune.
Were you running it with enough oil?
Were you running it with enough oil?
SquidBonez
Active member
Yep, made sure to. This build isn't over, just a minor setback. This is going on a custom frame which still is a long way off from finishing. Check out my other thread in Build Logs if you want to see what this engine was going on.Man, this is a sad sad thread. Sorry to hear such misfortune.
Were you running it with enough oil?
Full Suspension Big Block Mini-Buggy Build
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