Noob m20 rebuild question

[884door]

IMO the limiting factor for most m20s (second to tuning) is the low compression. With custom pistons in the 10:1 range that could actually clear the valves you'd be able to make some serious power.

[RangerGress]

Chip the motor. If you want more hp then that you will probably have to spend >$100/hp and that's madness. Pretty soon it's cheaper to do a turbo or motor swap.

[nando]

Chip the motor. If you want more hp then that you will probably have to spend >$100/hp and that's madness. Pretty soon it's cheaper to do a turbo or motor swap.

that's exagerrating a bit.. maybe $20/hp, 30 on the high side. But a fully built M20 is a completely different animal from a swap or a turbo. apples/oranges

[RangerGress]

that's exagerrating a bit.. maybe $20/hp, 30 on the high side.

It's not an exaggeration. A chip might get you an honest 15hp so now you are at 165-170hp at the wheels. Since SpecE30 uses an unmodified M20 we have lots of dyno sheets that indicate that 150hp/tq is pretty good, and 158 means a cherry build with some time on a dyno testing different AFM's and ECU's.

Even if the chip does as well as the chip-guy likes to believe, >170hp is unlikely. So now the OP has to get beyond 170hp and it's going to be expensive.

Metric Mechanic can build him a hot head with an aggressive cam and springs, but it's likely to cost $2500. Add lighter pistons and rods and stronger rockers and the motor should be able to rev to up to what, 7500rpm? Since hp is tied to revs, that will mean > power. But all that's going to cost.

Forged standard pistons are like $1200. God only knows how much custom pistons would be.

So how would you get >170hp at $30/hp?

[nando]

I'm talking building an over 200 crank HP engine from scratch.. not adding stuff onto the existing engine. say, $6k.

$100/HP would mean a 230bhp M20 would cost $23000. er, yeah. Even if you bought all of the "unobtanium" parts (billet rockers, dbilas ITBs, $1200 pistons), you couldn't possibly spend that much.

MM does good work but their cams are way too conservative if you wanted to make a lot of power. They are designed as engines that can still pass emissions.. so of course they will cost a lot more/HP. But still nowhere near $100.

[RangerGress]

I'm talking building an over 200 crank HP engine from scratch.. not adding stuff onto the existing engine. say, $6k.

$100/HP would mean a 230bhp M20 would cost $23000. er, yeah. Even if you bought all of the "unobtanium" parts (billet rockers, dbilas ITBs, $1200 pistons), you couldn't possibly spend that much.

MM does good work but their cams are way too conservative if you wanted to make a lot of power. They are designed as engines that can still pass emissions.. so of course they will cost a lot more/HP. But still nowhere near $100.

Agreed, but that is not the scenario my first post described. If you start with 170hp, each additional hp is going to be pricey.

[nando]

he said rebuild though - unless he's in a spec series like you, it doesn't make a lot of sense to stick with the stock bottom end if you want more power.

oh yeah, I gained 10whp with a K&N cone filter. that's like $5/hp. Not on a stock engine but still. :p

[RangerGress]

he said rebuild though - unless he's in a spec series like you, it doesn't make a lot of sense to stick with the stock bottom end if you want more power.

oh yeah, I gained 10whp with a K&N cone filter. that's like $5/hp. Not on a stock engine but still. :p

Unusual. We've done a lot of dyno testing of different intake designs. Only one guy was able to equal the OEM intake. Every other scheme did worse.

[nando]

I was pulling 5-7% vacuum at WOT with the stock intake - new filter too. With just an open throttle it was still 1-2% at WOT, but filters are easier to change than throttle bodies. :p\

it also matters if it's shielded. you will lose power for sure if it's open to the hot air from the radiator.