Twin cam block prep?

[nickp]

Hi Guy,

I'm after a bit of advice on a block I'm preparing to put in my Montecarlo. I aquired the block which already has new bores / pistons at 84.6mm, but it has been stood around for some time apparently. The bores have been kept well oiled, so are all fine. But when I knocked out the core plugs there seems to be excessive corrosion in there, easpecially around the cylinders. What would be the best process or product to reduce this? The block's going in to the machine shop shortly for decking (to bring up the CR), so should I just get them to 'dip' it for me?

Thanks in advance,
Nick

[Guy Croft]

No, don't do that.

Just get in there yourself with hot water, bits of stiff wire etc, wire brushes to agitate the crud and corrosion as best you can and leave it at that. I have to do that all the time. I don't know of a reconditioners dip that will really clean off corrosion (mostly they are for carbon and oil removal) without damaging the precious aluminium/tin auxiliary driveshaft bearings or turning the whole thing into soup.

Light solution of phosphoric acid is quite good but you don't want it in the fresh bores or on the block deck after machining. It's such unpleasant stuff to work with and dispose of after I never bother with it.

G

[nickp]

Thanks Guy,

I hadn't considered the precious aux shaft bearings, they're like rocking horse whatsit aren't they? Or perhaps rarer!! I'll have a good scrape around in there then blast it out with hot soapy water then.
Another quick question, while I'm on if you don't mind? I've gasflowed a Volumex head, it was my first attempt but seemed to go OK. I had new 'bullet-nose' guides fitted and had it skimmed right down to the inlet seats (about 1mm removed I think). I need to get 0.9mm decked off the block, running the pistons 0.5mm into the head gasket area to get the CR up to 10:1. I was just wondering with material removed from both the head and block, at what point do you run out of adjustment on the cam belt? If I do run out of adjustment, is it possible to use the shorter 146 tooth belt off a 1600?

Thanks in advance,
Nick

[nickp]

Hi again Guy,

I've just recalculated my CR and even with the block decked it's only coming out at 9.5:1. I'm hoping to use some 300deg 40-80 10.3mm cams from the US. I'm just a bit worried that the CR won't be high enough to let these cams really work. I may have the option of some new domed (not sure how high) 85mm pistons, but that would mean starting over again and more expense. How much power/torque to you think I would lose due to my relatively low CR? BTW - the car has a pair of 42 DCNFs on an Alquati manifold and a 4-2-1 Ansa manifold that will be mated to a decent single outlet performance silencer.

Thanks again,
Nick