John/Ted,

Since determining accurate clearance specs. (within a few 10,000ths) seems to depend on the quality of the measuring tool & experience of the mechanic, can you suggest any specific/extra break-in/run precautions that might possibly help to counteract stainless/bronze guide clearance that COULD be just a bit under the safe margin?


6 VOLTS/POS. GRD. NW INDIANA

Thanks for the clarity John,

Now I am wondering if it wouldn't be wise to break in an engine with the weaker push rods, just in case there is binding this weakest link would be an easy change, rather than broken lifters, rockers etc.

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?

If guides that bind initially would eventually loosen up during break-in, and the more flexible worn pushrods do not create a mismatch/wear problem for certain with rocker/lifter mating surfaces, and the changed geometry resulting from likely head/deck milling would allow enough adjustment without a damaging type of rocker interference, and the the old pushrods don't create another kind of problem during run-in (if they bend or jump out), then sounds like a GREAT idea!

6 VOLTS/POS. GRD. NW INDIANA

Tight is tight.  Running the engine on the cool side with tight guides might delay a problem but once the valves get hot enough and especially once any throttled load is put on them, the possibility of an exhaust valve sticking in a guide that has minimal clearance is still going to be quite high. Use of the early skinny pushrods might save a lifter at the expense of a doubled up pushrod though but if there’s that much doubt about the guide clearance, it really should be addressed before the engine is fired up.  There’s very few places where being on the tight side clearance wise anywhere in an engine is not the potential for a problem versus being on the loose side.

Lorena, Texas (South of Waco)

And babying the motor until some guide wear is realized likely not feasible I assume, since hard acceleration is needed to break in the rings properly?

6 VOLTS/POS. GRD. NW INDIANA

Jerry C took the heads to R&R Performance in Spring Lake Park MN.



This is a very reputable race shop that builds a lot of Fords



He had the heads disassembled and the guides checked for clearance.. Brian, the machinist, determined that the clearance was at the minimum he would recommend, however there was no galling or scuffing that would indicate the valve got tight in the guide during testing. Jerry is having additional clearance added per John's recommendation. The guides have thin wall bronze liners. I think Jerry has finally completed the grieving process and is ready to pull the motor apart, replace the injured parts and try again.. He wanted to make sure nobody thought he was pointing fingers at any supplier.. Stuff happens, parts break, sometimes without obvious explanation. The vendor should not be responsible for random failures



Hopefully in the next few months we will have repairs made and be able to resume testing..

Royce.  Was it an intake or exhaust lifter that broke?  Just curious but if it was an exhaust lifter, it just adds fire to a tight exhaust guide being the root of the problem.  Same question goes for the broken rocker arm but it being bushed makes the cause of breakage in that case questionable even if it was an exhaust rocker.  I recognize that the rocker assemblies had been recently R&R’ed by Rocker Specialists but do you know the age of the rocker arm that gave up?

Lorena, Texas (South of Waco)

Ted, I checked with Jerry and it was an intake valve that had the lifter failure and the rocker arm failure

Just pulled our 312 down today and surprisingly half the lifter fell our the wrong directions.

A definate fatigue break with the FOMCO stamped on the reverse side.

That is a picture.  Doubt if it is possible but sure hope worse damage didnt result.  Quite the first post!  Welcome!

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.