The Plan
The basis for the engine is a K20A (Eco block) that we picked up from
the wreckers with only 68,000 clicks on the clock. Unlike the Type R
(K20A2) variant, it’s a much lower compression engine (9.0:1 versus
11.0:1) with no forged crank, and only intake-side VTEC and 1mm
smaller intake and exhaust valves. The only thing we will be keeping
from the head is the exhaust-side roller rockers; the rest will go into the
bin. We will be back at the scrapyard shopping for a second set of roller
rockers to use on the intake side in the new head. While you can buy
fancy kits, this is a budget option to keep costs down, but it will cost
you rpm due to its weight in comparison with the aftermarket options.
With our desired rpm range, we will be using stock Type R cams on
both the intake and exhaust, coupled with Drag Cartel adjustable cam
gears.
The head we’re using is a K24 RBB casting. While these are
not hugely popular in engine swaps, for our application, the smaller
ports are what our cylinder-head specialist believes will be perfect to
work alongside the 32mm restrictors. The head will spend time on the
Horsepower Heads CNC machine to be reshaped in a few areas, but
will not be overly ported, and will have 1mm oversized intake valves.
The valves are 5000-series Ferrea stainless items, and we’ll use Kelford
springs, plus manganese bronze guides and special valve seat inserts
to suit the fuel of choice: methanol — in an engine that’s using pump
gas or such, these would not be needed, but methanol is very corrosive.
Our 68,000km block was found to be in great condition, but will
still be getting oversized by 1mm to sneak in as much capacity as we
can. The crank is a second-hand Type R and will hold a set of I-beam
Pro-A rods from Carrillo. These are Carrillo’s economical I-beam, but,
as we’re not boosting the engine or revving it too the moon, they are the
perfect lightweight choice for us.
Our pistons are from Wiseco, its high-compression offering in
K20 of 12.4:1 and 1mm oversized at 87mm to make the most of the
class maximum cubic centimetres of 2050. We will be using ACL race
bearings throughout. The block itself is off being machined to suit, and
we will cover that in the next issue, when we dig into assembly and
prep.
Like all K-series blocks, the block is ‘open deck’, meaning that the
steel cylinder bores are unsupported in the top. In racing application,
where high rpm is often the norm, the bores are known to oval, especially
when oversized. While a full sleeve job is often considered the best
option in this case, block guards, like the billet one from ASP that we’re
using, are a cheap alternative and stiffen and support cylinders.
By next issue, we should have everything back from the machine
shops and ready to assemble, so check back if you’ve ever wanted to
piece together your own race engine.
Checkout that block gurdleWe picked up a second hand Type R crank, which will be
checked over before installlation
The guard will be pressed into place once the block machining has taken place