this isnt a blog evil nick im here for answers to questions from builders.

ok so part of the results are in on my broken camshaft incident from last weekend.
the exhaust cam was broken in 3 parts. i will provide pictures in the next day or 2. i have yet to pull the valves to see how straight they are.

so anyways besides the obvious broken exhaust cam i now have some "galling" on the very outside edge of 4 out of the 8 exhaust retainers. looking at the underside of the rocker arms i see no wear at all. anyone have a clue what could have caused this?

piston #3 got tagged by both exhaust valves. piston #4 got tagged barely at the valve relief by only 1 valve.

all 3 places that broke on the camshaft were between the VTEC lobe and the right hand primary lobe. any speculation on why this happened?

valve to valve clearances were measured and all piston to valve clearances were checked too.

for some reason or another i have a broken valve guide on the intake side. not sure why this happened. didnt look like anything fell into the cylinder cause the entire piece is still there. i didnt know it was broken until i tipped the head on its side and it fell out.

lastly i noticed a slight mark on all 4 pistons in the center. looking at the direction of the spark plug its apparent the spark plug strap is hitting the tops of my pistons. i havent measured the gaps on the spark plugs at this time so i dont know how hard or if they hit for sure. could possibly be thousandths of inches of clearance but no contact.

ill update as the results come in and id appreciate any builders insight on any or all the issues i presented above.

thanks

dustin

 

Jun3 cam curse finally kicked in? Sorry to hear it Dustin

 

after 6 years i cant complain todd.

 

that sux man, i'll have to stop by and check out the carnage

 

bump

 

man u've had nothin but problems bump for u

 

I'm curious to know how this might of happened too.
anyone? DonF,Tbone,VtecKiDD,......Clean rice, other builder?

 

is there galling in the cam journals of the head, anywhere on the cam, on the rocker faces, on the lobe's noses? anything out of the ordinary wear wise? hot spots? shavings in the filter or pickup screen?

core flaws and coil bind are the only two i can think of. well actually.. a piston that hits a head would be an instant of a coilbind-like scenario. ill bet youve got some valves with a nice bow to the stem. might wanna be careful about running those rockers in another engine

 

i worked 12 hrs today mike. i havent looked that hard. i took a peek at the rocker and they look fine. one of them has a little chunk out of it but thats where the cam broke. tomorrow ill tackle on tearing down whats left of it and taking pics of the results. im still waitin on DonF to reply. Don? are you there?

 

Look toward valve spring coil bind and or valve float as a source of the problem. If you are using reground cams, that could add to the problem. You should question the head builder and his choice of parts also. Were the cams installed upright, advanced or retarded?

 

I was reading one of your threads in your signature when I came across this statement...
Alot of people talk about install height on JUN cams. Install height, whats that??? Didnt even check it, just threw them in
You just can't take anything for granted

 

Installed height does directly affect spring pressure. In an extreme case, you could have more pressure on one half of the cam than the other.

 

This is going to make me look like a complete fool, but again, what is installed height?

Where do you measure? And whats the purpose?

The only thing I can think of is the height of the cam journals in relation to the rockers?

I think I'm incorrect, but I woud like to know more about this.

- Derek

 

its basically how tall or uncompressed the spring is allowed to sit when it is "installed" upon a closed valve. different length valve stems, grinding on the seat, refacing valves, seat replacement, different retainers or spring seats and machining of the spring seating area around the guide head will alter installed height. if the spring needs to offer a certain poundage when closed then being installed "too short" will put you above that pressure and "too long" will leave you below it.

 

Ahhh, I see.

Now I know.

Thanks.
- Derek

 

you busted me earl. that was back in 01 or 02 before i started to learn. since then ive made mistakes and learned valuable lessons in return. my mishap from the beginning of the year prompted me to buy mike belbens P2V kit. nice piece i might add.
i suppose i outta get off my *** and get some pics taken.