Neil, whatever the cam lift, you should not change the pushrod length. John
Neil Cotty wrote:
> Hi all,
>
> My engine removal (and now Gearbox, thank you all) is progressing fine,
> albeit slowly. Have the propshaft left to remove and a couple of wires then
> it's time to really freak myself out and lift the bloody thing! <G>. On to
> another topic, the point of my Email.
>
> I'm trying to calculate what length pushrods I'll need if I choose a Cam
> with a different lift, to maintain correct Valve geometry. I realise there
> are a lot of variables to this, some of which I've sourced from mgbmga.com
> (Great reference), the more esoteric components - valve spring tension and
> how it affects quoted rocker ratio etc to produce the effective rocker ratio
> etc. I am doing all this because I wish to pick a cam lift, that will
> achieve the valve lift I require, based on CFM through the head - utilising
> higher ratio rocker arms along the way, so I don't have to pick a really
> high lift cam with the associated, increased load and wear on the cam lobes.
>
> To the point, I have data on the height of a std Tappet (lifter), but I
> can't find info on the length of a pushrod. Admittedly my Bentley's is at
> work, I'm looking at the Haynes manual. Does something have this data to
> hand? I guess, I will need the total length of the pushrod and lifter -
> assembled - to calculate what length rods I will need with the theoretical
> cam. This is only theory at the moment, I won't know what cam to pick until
> I get the head flowbenched. I realise this keeping this geometry is crucial
> to long lasting life of the rockers. I also realise, skimming the head,
> block etc affects these calcs, not to mention valve clearance, so I will
> have to physically measure all my bits before I purchase anything.
>
> Might be best to email me privately on these ones, I tend to ramble. OK, I
> tend to ramble a lot. <VBG>
>
> Thanks,
> Neil.
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