(BB 396) A couple of weeks ago I bent both int. and exh. push rods on #8 and it broke the pushrod guide on the int side and droped the valve and bent that too.Wasnt really sure what failed until today.I had the head fixed and put a new roller cam in and ran it for a week or so maybe 100 miles.I decided to change out the cam and the intake and carb so I was taking it apart today and sure enough #1 int. pushrod guide was broke and also #7 int was broke laying on top of the head.No other damage but it easly could have.I grabed #1 rocker arm and was able to move it off of the valve with alittle twist.So I figure that when #8 went a couple of weeks ago it started with a broken pushrod guide then the rocker moved off the valve and pushed the spring down which in turn let the valve retainer loose and droped the valve.Oh well at least I cought it before anything really bad happened.Well I orderd a set of comp cams hardend pushrod guides and a new set of rocker studs as there is some scoring on the ones that the guides broke on.BTW the pushrod guides that broke are the Manley steel 7/16th. NOT GOOD IMO

The geometry must be a mile out of wack. I have blown engines completely in two and never broke a guide plate.

Im changing the cam to a hyd flat tappet and back to a stock 1.7 rocker ratio.I have a retro roller in there now with 1.72 roller tips.Maybe it doesnt like the roller cam and lifters.You have to run a shorter set of pushrods for them to work.

maybe they got a little carried with hardening the plates? Put one on a hard surface and hit it with a hammer, break like glass or bend first?

I've been working on BBs for near 30 years with all kinds of valvetrain gear, never saw a broken guideplate. I can't recall even hearing about broken guideplates. I think it's a problem with the plates themselves.

Thats what I was thinking.They didnt look bent at all just snapped off.Im starting to wonder if it was the rocker that hit it but I really dont know how it could.I adjusted the rockers to zero with only a 1/4 turn so I know they were not tight.Still stumped.I will take them and hit them with a hammer sounds like fun.

That's a new one for me also ????? I can't visualize what could possibly make that happen. . . . If you ever do find out what caused this. . . please add later to this post. . . . . I definatley would like to know.

WOW I was taking off the pushrod guides and I found another broken one on the passenger side.It just fell off when I was taking out the rocker stud.Well I still dont know what happened.I have now replaced all the guides and rocker studs.I also have a new set of rull alum roller rockers and a set of one peice chromemolly pushrods.I did the pre cam brake in adjustment and eveything looks great.No clearence issues.I will be starting it up on Saturday.

:thumbsup:

Good luck with it. I have the CC guideplates and CC 3/8 pushrods on my 781's. I have yet to flash it up, but I sure hope to not repeat your situation.

About 30 years ago I had a manley a 7/16 pushrod guide plate problem which was pushing my pushrods sideways. Could have droped a valve. I solved my problem by going to a GM 7/16 pushrod guide plate

Ever check your piston to valve clearance?