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Im about to put a delightful stage 3 YT head on my 202. Just lapped the valves in last night :-)
It's a 161 head, so apparently i'll need 186 or similar pushrods. Is this just length, or durability? These are adjustable rockers where they're located by the narrow pushrod slots in the head. 186 are slightly shorter than 202, but this head was shaved by YT, and to make sure it was square, lightly shaved when i had the valve seats put in. Low comp pistons in my motor so compression will be fine.
So, will the shorter 202 rods work? Or do i need hardened ones for the rubbing on the head? Or, will i need to measure and get the right length to ensure best valvetrain geometry?
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i think 202 rods are 1/8 inch shorter but 161 heads have adjustable rockers where 202 didnt so i think its more a factor if you use 186 rods in a 202.
as long as you have enough adjustment to set your lifter load i cant see how it will be a problem. not sure on the hardness i figured it was all the same material used to make all holden 6 pushrods?
If you have an old rocker cover cut the top of its easier to adjust them because you will need to when its running to get it spot on and its less messy with the rocker cover on. i have never adjusted them on a holden 6 while running but have adjusted them on a small block and bigblock chev i use to own while running and you could do it by ear.
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quote:
Originally posted by HQforme
Or, will i need to measure and get the right length to ensure best valvetrain geometry?
Cheers.
Yes.
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a shorter or longer pushrod wont effect valve lift, that is done by the rocker ratio. the only thing that will change is the angle your rocker sits at while valve is closed. if your worried about it get new ones but i dont see how it will be a problem with adjustable rockers.
If you Zero deck your 308 block and also take a bit of your heads you could lose over 1.5mm. you dont get custom made pushrods you either shim the rockers or use adjustable rockers.
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Havent you learnt anything from that guy that gives sermons at church?...Captain whats his name. |
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I was back to front, i meant 202 are shorter than 186, so youre right there Bundy. Thats why i wondered if theyd be fine with the shaved head taking that difference up.
I know the rods dont affect lift, im talking contact from rocker to valve and keeping rocker angles correct so it sits in the right spot on the valve stem and doesnt side-load them or wear off centre too much. Suppose with adjustable rockers ill be able to adjust to suit as long as its not a major difference that im compensating for.
Would still like clarification on the wear/hardness factor.
I like the rocker cover idea. My current head runs shaft mounted rollers so i set lash by feel/preload. With a motor running im looking forward to doing it by ear actually.
Cheers. |
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i read somewhere that there are actually 4 different pushrod lengths...
You need to get the angle of the rocker gear level at the "rock" position.
so correct length is very important - you can raise your rocker gear by placing washers underneath them.
Get an old tappet cover and cut the top out of it so you can adjust rockers while running.
when adjusting by ear, load valve until the engine misses, then back it off 1/3rd of a turn.
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