a7 broken inlet pushrod

[rocker21]

just wondering if its old age and metal fatigue

[RDfella]

Thought you said the engine had just been rebuilt, practically everything new? Which is why I wondered if you were getting valve spring coil binding or collets / cap hitting the valve guide. Stuck valve or any of the aforementioned are guaranteed pushrod wreckers (or breaking rockers).

[rocker21]

yes total rebuild, new crankcase's, crank, conrods, cam, all bearings, cylinder block, cam followers, pistons, replacement alloy head, new guides, new valves and springs,  there is almost nothing  left of the original engine, apart from the outer timing case, it has an alton fitted instead of dynamo, recon mag, cam is running on needle rollers and so is the timing gears. the pushrods i kept

[rocker21]

refitted the head, the valve was fine but i put a new one in just to be on the safe side, started to clean the rocker box and found one of the tappet adjusting screws , part of the face that operates on the valve had broken off, but not on the valve that had the broken pushrod, it was on the other inlet valve and i cant find the broken bit.
any ideas?

[muskrat]

G'day rocker.
The only place it could be is down the pushrod tunnel. Probably got cleaned out with the pushrod. How big a bit broke off?
I had an after market allen head type brake when tightening the locknut.
Cheers

[rocker21]

seems the valve springs were getting coil bound, reassemble it all and when the valves were on full lift i could not get any movement on them with a lever pushing them down, so taken everything apart again , ordered new springs valve caps, collets etc from drags,  and now reassembling, the only other thing that might be a problem but i wont know till i get it all back together is there may be a difference in the Ariel rocker box and the bsa one, so going to put the bsa one back on and see what that does,
does anyone know if there is a difference between the 2 rocker boxes?

[berger]

rocker21 i did a dry build on my A7ss engine fitted with a 375 cam and to get clearance on the coils the bottom valve spring cups had to be machined down a bit and if i remember right  the top of the valves machined back a bit where the collets fit. i will hunt for the parts and put a photo on later

[rocker21]

how much did you take off valve spring base?

[Greybeard]

Once upon a time I had to modify my valve spring seats to overcome spring binding. As I don't have access to a precision grinder I used my bench grinder to remove the narrow ridge on the underside of the spring seat.

[berger]

rocker21 a couple of pics showing the valve that has been turned out at the top [ the left valve] so the collets sit higher, and how the bottom spring keepers ended up compared to an original to stop spring bind when fully open using a 357 cam

[bikerboy]

Firstly yes the ariel rockerbox fits the A10. On the pushrod situation, any sign of the head gasket blowing? May years ago I had a head gasket go between the cylinder and the pushrod tunnel. I had alloy pushrods in at the time and it was in two bits where it had melted. Not saying its likely but its not impossible either

[chaterlea25]

Hi Rocker
I would check the valve springs versus the originals for wire size and number of turns
I got a set of pattern springs for a B33 and found there were too many turns on one of the outer springs
Shit pattern parts again
The reason the bottom collar has a step is to reduce heat transfer from the head

John

[rocker21]

thanks guys, all useful info.
Ken

[rocker21]

the springs i got from drags were the same as the ones i took out, 

[rocker21]

berger how much did you machine off the valve to get clearance?