Forum Participant
Posted 04 June 2013 - 06:20 PM
Hi, just installed my yella terra roller rockers an they are giving me greif.
The witness mark was closer to the rocker side of the valve stem so it seems like i need a longer push rod but it looks like the rocker is going to foul on the posi lock, any ideas?
Sorry if the pics are a bit big.
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_tryhard_
Posted 04 June 2013 - 06:25 PM
your roller should be horizontal when at top dead centre then you should have no trouble you can measure the correct distance and buy the correct length, regards marcus
Scrivet Counter
Posted 04 June 2013 - 07:30 PM
Is it my imagination or does one half of the collet (compared to it's other half) on the depressed valve in this pic look like it's not seated properly in the valve cap?
Forum Participant
Posted 04 June 2013 - 07:43 PM
The collets are seated just different heights, haven't got around to changing them yet.
Forum Member
Posted 04 June 2013 - 08:08 PM
On the issue of the rocker fouling the posilock, I had the same issue. If the rockers are Street Terras st2007 I believe there is not enough clearance and you may have to machine the rockers to achieve this.
I couldn`t be bothered so I sold them and bought these http://www.summitrac...parts/csp-s1001 for the same money, much better in my opinion.
Forum Participant
Posted 04 June 2013 - 08:18 PM
Yeah, was hoping i didnt have to buy another set. ill have a look cheers
_STRAIGHTLINEMICK_
Posted 04 June 2013 - 10:48 PM
G 'day mate,if it is not too much trouble can you please send a pic of the contact patch ,put some marking blue or grease on a valve tip ,wind the engine over by hand then remove the rocker and take a pic.Thanks ,Mick
Posted 05 June 2013 - 07:07 AM
Forum Fixture
Posted 06 June 2013 - 07:25 AM
At half lift the rocker should be in the centre of the valve. I have 1.6 Summit rockers with 186 (long?) pushrods on my 202. Don't have a problem with it.
By the way, I priced YT streets and was quoted $715. The Summits cost, from the States, bout $360 at my door. The exchange rate was worse than it is now. I did also have to relieve the back of the rockers to clear the pushrods, as the geometry of the V8 rockers is different to the more vertical design of the 6.
_oldjohnno_
Posted 06 June 2013 - 07:40 AM
At half lift the rocker should be in the centre of the valve.
Nope, at mid lift it should be past the centre. It should be centred at around 1/4 and 3/4 lift. See the pic below that I stole from the innernets, it's about the clearest explanation I've seen. Also note how at mid lift a line drawn through the nose roller pin and the centre of the trunnion is perpendicular to the valve stem - if you want to get the geometry exactly right it means checking the distance from valve stem to rocker stud as well as pushrod length:
Edited by oldjohnno, 06 June 2013 - 07:44 AM.
Fulcrum Fixture
Posted 06 June 2013 - 10:07 AM
^ that maybe so for roller tipped rockers, but solid tip rockers can follow a very different arc to what you have shown.
_oldjohnno_
Posted 06 June 2013 - 05:19 PM
^ that maybe so for roller tipped rockers, but solid tip rockers can follow a very different arc to what you have shown.
Agree entirely, the sketch above doesn't apply to non-rollers. And I should add that for most applications as long as the contact patch turns out to be somewhere near the centre everything will be fine. For very high lifts and heavy springs though, I think it pays to be fussy about geometry.
Forum Participant
Posted 06 June 2013 - 07:56 PM
Cheers for the pic Oldjohnno. Borrowed a small block chev roller rocker and had another look tonight, there's heaps more clearance for the rocker stud.
push rod still looks short but atleast there is room to adjust now.
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_STRAIGHTLINEMICK_
Posted 06 June 2013 - 10:45 PM
Yep you definatley need to get the contact patch nearer to the valve centre and as jonno said it doesnt have to be perfectly on center to work well .
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