S12OC UK Forum - CA20ET LPG project help

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CA20ET LPG project help

Hi fellas my first post after a long wait to get on these forums which are 8v
rich and always a mystery since there have been some issues with member
approval in the past stopping me from reading the important info here.

I would like to build a punchy LPG turbo CA and have the following
in mind so far for the build (most parts purchased):

CA20e block with undecided pistons.
CD20e crankshaft suits ca18det oil pump (to be lightened and re-balanced)
Prepped Z22 149.5mm c-c rods to suit 53mm BE of CD crank
(lightened, shaved each side, shot peened and balanced 562gsm each)
ORC single plate fly/clutch setup suits CD20 8 bolt flange type
Garrett T28BB disco
Chasing 200hp atw with excellent of response no lag if possible.
8v head modded
Camshaft (piper?) undecided

Im chasing torque with big midrange & 7000rpm redline so 8v is likely.
Thinking of using heatproof jet coated stock exhaust manifold with T28BB and
equal length short runners with custom plenum and mid mounted TB.

I was thinking of welding up the inlet ports and exhaust valve and run
motorbike sparkplugs that allow me to have more meat on inlet ports
to be able to raise the angle and increase the size without worrying
about sealing issues on bolt up flange area. Also the LPG doesnt really
need 2 plugs per chamber as it burns really well with 1, so welding
up exhaust plug (all Australian 8v heads are 8 plug heads here) and
reshaping the chamber to increase swirl from inlet across where the
exhaust plug side would be which interferes with the swirl usually and
causes turbulence that sends mixture more onto the cylinder walls.

Also thinking of heatproof coating the chambers after porting and
reshaping to help keep temps a little lower using LPG.

Intercooler size is not decided but would like to keep inlet temps decent.

Also what ARP bolts should I run? as the ca20 block bolts are thinner
not as deep into the block and not an off the shelve item (searched).

Also thinking I might not need a crank girdle or main ladder brace
as used to stiffen the ca18det block? or best use one? if so it will have
to be custom made to suit the 88mm stroke and counterweights.

Im not interested in the 16v head they are 10kg heavier than the 8v
and I like the space Im saving in the engine bay of my datsun b10
will look more nostalgic too with chrome rocker a-la-s13eater

hiya,

re block crank brace, i havent had any made for a few years. The easiest option is using the DET cast crank brace. It nearly fits, just two front corners need trimming off as it catches the 8v sump and stops it fitting down to the block neatly. 10 mins with a grinder will do the trick.
The machined ones i had made were lighter and took up less space in the sump than the DET version.

re cam, id also look at the Autosprint cam. when i built the 8v engine for my racer, i had Geoff create a cam profile. I gave him my old Piper cam and he worked from there. His creation doesnt need a vernier cam pulley (which i also had made at the time), but had a trick assymetric profile, giving a curved side and almost flat side to the cam lobe, a trick from his old ford tuning days. Certainly worked REALLY well, and is now pretty much the standard fit for all the guys that sprint and hillclimb or circuit race using the 8v engine.

he wont tell you the lift and duration, but i didnt care as it brought the numbers on the dyno and massively improved the breathing over 5k, so i never bothered measuring it.
they used to cost about £100 as a regrind although the scimitar club have done a few group buys of 10 cams and got down to be 80quid each plus return postage which is a bargain.

im not familiar with the rods you mention, but the 8v rods are the weak point once you run more boost, revs and forged pistons. they are like tooth picks! ive bent a few. id look at aftermarket or DET rods (bigger gudgeon little end pin so you will need different pistons).

I used one of the Canadian spec CA20E inlet manifolds, gave a few bhp over stock manifold but a fair hike in torque at same boost. Its a better design than the stock one and the more develeoped your engine becomes the more the benefits.

The stock exh manifold will improve torque to a point as its runners are short and bores small, but ultimately be restrictive when you are looking at 250+hp imho. I made a tubular manifold and that ran 282hp/266lbft at 18psi boost on a low lag T28 custom Turbo Technics turbo. To be honest, i should have changed the wastegate sprimg and had remapped because i think 22psi would have seen 320hp and another hike in torque.

one think i would say is the head design is crap, really poor. Cleaning up the ports and radiusing them to try and reduce the 90 deg bend from port to valve is important, but its always going to be a problem. S13 Eater had an 8v head done which was pretty extreme, but again its the overall design tahts bad--you cant polish a turd as they say!

with regards to head studs, S13 Eater looked at getting ARP to make some iirc, but personally i used brand new std Nissan ones. Some people use them over and over again, but i fitted new ones each time head was off--your call.

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