Took the heads off and found a blown headgasket (between 1 and 3)and broken pushrod (intake of no.5)both on the same side..Engine had been running for 40K miles..No mark on the piston for no.5 ,no.3 piston is clean from all the coolant and no.1 is semi clean with still some carbon.WHile removing the intake I notcie that all of the bolts were loose specially the passenger side..I always see a pool of coolant between the intake and the head..I thought it was just a leaky t-stat housing(doh)..Only reasons I can think of is that Coolant went inside the combustion chambers blew a gasket .About the pushrods breaking I have no idea..

Daz

 

broke or bent? i've never saw one break, other than the ends wearing from lack of oil. i've saw a lot of bent ones.

 

bent and broke...and they are hardened(obviously)

Daz

 

may be a metalurgical thing with the hardened ones that they don't bend as much and break, just a WAG. you have guide plates? you using SA rockers and guide plates? the holes in the head larger enough for the push rod to move?

 

Im using guideplates with non-SA rockers..All came with the pushrods 350K miles ago..So it could be just failure(right?)THe pushrods are well in the middle of holes..This is the casting that Im using

462624.....75-86...350/400......76cc chamber, 1.72/1.5, 1.94/1.5 or 2.02/1.6 valves according to Mortec

Its got a 1.94/1.5 valves and a 3 angle

Before I change the gaskets Im going to get the heads rebuilt at least is it worth it?Change the springs,pushrods,lifters(the paired lifter of the broken pushrod is deep inside the valley-another possiblity)and the cam if its hurt..

This is the engine combo maybe you can make a suggestion..

Qjet-
Performer 2101
4 bolt and hypereutectics 9.5:1 compression with the said head
cam specs are in the 212-220(I think) with ..447/,447

Its a clone of the ZZ1 285/300 hp motor ..supposedly

go ede
Daz

 

I've bent some myself before, but never broken one. It may have gotten jammed after it bent and something smacked it in two. If the valves arent bent and the rocker and stud are ok, the rocker was probably loose and came off the valve tip. Thats what happened to me, both times.

 

I have never heard of them breaking, but an instance I would think they would be a detonation of the cylinder in the other end of the firing order, throwing the lifter up with enough force. High revs bend em, but are gentle enough not to break. Maybe it was already bent, and got shoved into the head. May also have something to do with your tappets: hydraulic vs. solid, and if flat, not changing em properly.

 

usually its the exhaust side that snaps but have seen a couple with busted intake pushrods-its prolly the stem to guide clearance was set too tight and the valve starts seizing in the guide when it gets hot, and somethings gotta give -so- also if yer gonna run them dang p.c. seals at least pull the spring off of the ones that are installed on the exhaust side. all metal needs a c-hair of lube on it if its rubbing up against another piece of metal. hey did you say 350k-as in miles? 350,000 and the motor just experienced a mechanical failure? bah it was rebuild time 125k ago you are way ahead of the game. whatever you did to have it last-repeat it on the rebuild hey daz your face (um yeah face) looks familiar hahaha

 

I forgot to mention that the valve tip has a bunch of nicks on it which makes the loose rocker a possibility.I dont if the valves are bent(yet)..WHat do you think the push rod hit to bend and break like that if it the rockers did come off the pushrod?

Daz

 

The motor was rebuilt 40K miles ago and stupid me for believing the shop that my springs and lifter are "still good" and the pushrods "never break"..Im going to get the heads rebuilt

Daz

 

valve float, overrevving, or dropping your BFH down into the lifter valley with the intake off

 

I've seen some bent pushrods from misalingment
the only broken ones i've seen were a result of a mis installed cam, that hung the vavles open for the pistons to hit them