Holden V8 combo
Posted: Tue Jun 14, 2016 2:55 pm
G'day guys,
Am just about to purchase a new rotating assembly for my V8 bike build and thought I'd run the plan past the wise heads on here to see if I have screwed anything up. My experience building engines is all with 70's Honda single cam fours so a pushrod V8 is new to me.
The block is an early 80's casting in pretty good nick. It will be getting a BIG overbore to 3.736" to suit chevy 305 pistons (already checked this one and the cylinder walls can take it no problem - can actually go a hair bigger) and .050 off the decks to assist with the lower piston comp height.
Crank is a new replacement 308 with stock stroke of 3.063" chosen as it is the same design as the 253, just with heavier counterweights to make balancing the bigger rods and pistons easier. Rods are 5.7" H-beam and for the pistons I'm thinking of going for KB Hypereutectic jobbies as they have floating pins. They are a little spendy but easy to change if I mess one of them up and I'm told they withstand a higher heat range than the cast ones. I will be using an untested mechanical injection setup so tuning irregularities are guaranteed in the early stages at least.
The cam is a moderate one with .496 lift int and exh and 110 degree separation and as for the heads they are pre pollution style with standard valves and mild porting mostly focussed on smoothing out the short curves (always worked a treat on the hondas). My thinking here is all about gas velocity rather than peak flow keeping in mind this is going in a motorcycle with a direct drive so one gear fits all.
I plan on having .100 milled off the heads and the pistons should hang about .005 out of the block which should put static comp well into methanol territory.
Not sure about the valves kissing the pistons at this stage so reliefs may be required and the rocker arm angles will need sorting out once its all screwed together as well cos they'll be all over the shop.
All told I'm hoping to have an engine that will rev quite hard thanks to the short stroke with a total capacity of 269ci, and still hang onto enough mid range to push a motorcycle and terrified rider through a single gear.
So before I start unfolding more notes whaddya reckon? Worth a bash or am I kiddin meself?
Am just about to purchase a new rotating assembly for my V8 bike build and thought I'd run the plan past the wise heads on here to see if I have screwed anything up. My experience building engines is all with 70's Honda single cam fours so a pushrod V8 is new to me.
The block is an early 80's casting in pretty good nick. It will be getting a BIG overbore to 3.736" to suit chevy 305 pistons (already checked this one and the cylinder walls can take it no problem - can actually go a hair bigger) and .050 off the decks to assist with the lower piston comp height.
Crank is a new replacement 308 with stock stroke of 3.063" chosen as it is the same design as the 253, just with heavier counterweights to make balancing the bigger rods and pistons easier. Rods are 5.7" H-beam and for the pistons I'm thinking of going for KB Hypereutectic jobbies as they have floating pins. They are a little spendy but easy to change if I mess one of them up and I'm told they withstand a higher heat range than the cast ones. I will be using an untested mechanical injection setup so tuning irregularities are guaranteed in the early stages at least.
The cam is a moderate one with .496 lift int and exh and 110 degree separation and as for the heads they are pre pollution style with standard valves and mild porting mostly focussed on smoothing out the short curves (always worked a treat on the hondas). My thinking here is all about gas velocity rather than peak flow keeping in mind this is going in a motorcycle with a direct drive so one gear fits all.
I plan on having .100 milled off the heads and the pistons should hang about .005 out of the block which should put static comp well into methanol territory.
Not sure about the valves kissing the pistons at this stage so reliefs may be required and the rocker arm angles will need sorting out once its all screwed together as well cos they'll be all over the shop.
All told I'm hoping to have an engine that will rev quite hard thanks to the short stroke with a total capacity of 269ci, and still hang onto enough mid range to push a motorcycle and terrified rider through a single gear.
So before I start unfolding more notes whaddya reckon? Worth a bash or am I kiddin meself?