Hi guys, im planning on a complete rebuild of a 1.8 8v engine... head and block, towards the end of the year, so want to get the parts together, its for my 8v digi racecar, so i need the work spot on and a fair bit of power. I've got to build it to these regs... anyone got any idea where to get oversized pistons/rings and associated parts? what cc will a 1mm overbore make it? should i go to vw for gudgeon pins/bearing caps etc? valves/springs probs rather expensive from vw,what about oil pump? gsf ones are working ok in my other digi. but thatsd not always redlining. will post pics when it gets underway. most probably will just get the "man in the shed" to do the head if he's got time. cheers guys 1. Modifications Permitted: a) Balancing of the reciprocating parts minimum removal of material; THIS DOES NOT MEAN LIGHTENING. Flywheel and clutch assembly minimum weight 10.0 kgs, including all flywheel and crankshaft securing bolts, clutch release plate and circlip. b) Only 3 pistons / connecting rods may have material removed. Pistons can only have material removed below the gudgeon pin centreline. c) Gudgeon pin centreline to piston crown must remain to standard specification. d) Crankshafts may be reground down to 0.50 mm. Crankshaft journals must remain within VW positional tolerances if a repair and/or regrind is carried out. Stroke must remain unchanged from standard specification (Table 6.5). e) Cylinders may be re-bored up to + 1.0 mm using standard pattern (in shape, profile and material) unmodified pistons only, specified for the corresponding engine code only. f) The cylinder block may have material removed from the upper face up to a maximum of 0.005 inch from standard height. g) The cylinder head may have material removed from the combustion face up to a maximum of 0.025 inch from standard height. h) Replacement valves & valve guides may be fitted but must be standard or standard pattern (in shape, profile and material). 2. Modifications Prohibited: Any other than those permitted in 5.7.1. For clarity: a) Cylinder head - MUST remain to standard specifications. No material may be added to or removed from the cylinder head; inlet and exhaust ports may not be modified in any way and must remain as cast and as per standard specification. b) Aside from 5.7:1.f, above, the head casting material cannot be ground, smoothed, welded or in any way altered, whether to achieve optimisation of gas flow or otherwise. Any attempt to alter the shape of the ports, valve throats or the valve seats (i.e. multi angle seats) is prohibited. c) Standard pistons may not be replaced by forged pistons or machined-from-billet pistons. Piston crowns must not be machined from standard in shape or profile. d) Valve sizes must not be altered from standard specification. e) Uprated lifters and lightweight spring caps are prohibited. g) Fitment of an oil pump from a different production model is prohibited. i) Fitment of a metal head gasket whether sourced from other vehicles within the VW model range, or elsewhere is prohibited. j) The use of higher grade aftermarket fasteners for cylinder head, main bearing caps and flywheel ie ARP or similar is prohibited. l) The swapping of engine components or any ancillary components between 8-valve and 16-valve engines is prohibited. This is inclusive of any components in the engine bay such as, but not exclusively, pistons, radiator (5.7:4), and electronics.
For the machining I'd suggest you talk to David Knight Engineering for the machining - he's just off the A5 near Weedon. Try him for the parts too, and compare prices. I expect the 1mm oversize pistons will be the hardest bit to get. The Man In The Shed has done heads for a lot of the racers - standard rebuilt ones, obviously, rather than ported. Personally, there are lots of bits I wouldn't replace, including: Gudgeon pins, valve springs and caps, and check the valves, but I expect they'll be fine. If any of the valves need replaced, then the man in the shed will have spares, or can get new ones. New valves are likely to be slightly heavier than reground old ones... so why bother? I'd also only replace bearings if they're scored. Otherwise you're just tightening up the engine for no reason... You can check the clearances using plastigage (from Frosts). I'd check the oil pump before deciding whether to replace it too... If I did buy one I'd consider aftermarket, but I'd want to check the brand first. Make sure you DON'T use single piece thrust washers!
