The V8 Owners Forum -

i have a early 875.1 cr block and heads ready for rebuild, if i use comopsite gaskets would this lower cr enough for a 471 charger not to blow by and play havoc pressurizing the sump thanks, any other info on the build greatly apprieciated thanks rover v8

Hi

You probably know already that it's the pistons that set the compression on the Rover not the heads.

Composites will drop your compression to around 7.75: which will allow for quite a wadge of boost.

Be carefull though because those earlier pistons are a bit marginal once you get over 6psi.

Allan

I'm not sure that blow-by is related to compression ratio. I thought it was more related to the state of the bores and rings.
Compression ratio will limit max boost before detonation becomes a problem.
Chris.

thanks for info guys , i was just using composites to lower cr ,also milling 1.5 mm off tpo of pistons allows for greater boost but, new rings will be used

Hi

I'd really avoid machining the pistons.

With high boost you want as much meat in the top land as you can get.

Is milling standard pistons a good idea?! Anyway you'll already be at about 7.75:1 which should be plenty low enough for most applications- dont forget there's no point trying for ridiculous power when it is an old block with (maybe) thin ribs and 2 bolt mains...

ok here,s the plan, old block, which i thought had extra webbing, new rings, bottom end shells and mains, 3.9 heads blower cam with longer exhaust duration rhoads lifters keeping hydraulics, composite gaskets, roller timing chain and cogs , hp oil pump spring new gears, 471 blower 390 holley should be good for 250 bhp in my 110 , but any one have any idea how to plumb in the lpg all built by me with arp bolts

Early blocks have less webing than the later 'stiff' blocks.

For 250 you dont need to run that much boost.

Personally I'd find a later stiff block with more meat- just to be sure! Easy to get hold of too!

Never seen a 110 with a big blower out the bonnet- should be interesting!