4.0L SOHC HEAD CC'S???

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Unfalconbelievable

Well-known member
Hey fellas, just wanted some info on the non xr6 4.0l heads. How big were the combustion chambers in those sucka's? Been runnin a turbo on one for a bit and the bottom end has given way, need to know what the chamber cc's are for pistons for the rebuild.
looking at boring 0.6mm and fitting 15cc dished 3.9l 40 thou over pistons but i still think that'll only keep me down to around 9.3:1 which is iffy on 4psi boost :? next option is BA xr6t pistons and rods but they dear

Cheers for any info
 
any rods from pg au and ba are the turbo rods then just a set of dished pistons from 3.9 to ba they are interchangeable
 
Nah piston pin dia is different, and ill use my EF rods and dished 3.9 pistons if the chambers are big enough, only need to be down around 9:1. BA/BF pistons are same size in the bore and pin height but not in pin dia. They required BA/BF rods which with pistons come to around 1200 bucks and thats my budget for the whole build.

Cheers anyway
 
i dont know if you could do it for $1200 unless your getting mates rates machining and assembling your self then still pushng it.
iam looing at a rebuild on the asap and chep for my roady and even using lots of old race parts (good con but lost there edge for racing) i dont think ill get out for under 1g.
 
Yea im a mechanic by trade and my uncle owns the biggest machine shop in tassie :lol: the rebuild as is, is only costing 800 bucks. thats a full 20thou engine kit, crank polish, pistons on rods, bore, hone, tanked and rods checked. I had my head done up 5000km's ago by him to with some chamber and port work so thats ok and i already have all the turbo gear, just gotta bolt it back on once i've run it in. I'll keep u posted on the results, im hoping for the best with the comp ratio, should b ok
 
Well the new donk is in and going :lol: heaps more down low than the old one tho it seems to flatten out at about 4000rpm but i'll wait till it loosens up a bit before getting anoyed. Now im reworking my turbo manifold for and external gate and will fit up once the donk is run in
 
i know im talking to myself but oh well lol. the low down torque gain was due to the cam chain skipping a tooth while i dropped the dizzy in, turning the engine over to align the oil pump drive with no tension on the tensioner as its oil pressure reliant. i did suspect it but it turned over with no probs and i didnt wana pull the cover and check. im tempted to leave it because of the low down gains and see what happens to the top end with the turbo back on. or would it b better to bring it back to zero?
 
Depends what the risk of interference is! If it's not lined up as you intended, then surely it's worth at least trying that way.
 
Yea i always turn engines over a couple times after any work on the timing gear and theres no interferance, the ohc six has a fair amount of clearance and the pistons are dished. thats what im thinking to addo cause its really strong from 12-1300 till 3500 then tapers off and virtually stops at 4100 or so. the redline and limiter for this donk is at 5200 and it used to bounce off it happily but it never had so much low end grunt either. 6 one, half a dozen the other i spose :?
 
Most of my experience is with turbo crossflows so I don't know exactly what th CC's for the head are but I know the piston most guys use is the ACL race series pistons from the earlier EA engine which has the 11 cc dish.

http://www.aclperformance.com.au/6MKRY9390.htm

From there you have to relieve out the chambers to get your compression down to suit. I know guys have achieved down around 8.3 - 8.5:1 compression ratios with these pistons.
 
all done my friend. EA pistons with 15cc dish are what i used i think, maybe 11cc, and i had an EA head ported and removed the swirl bit inbetween the valves and ground out the chambers as much as they dared, tho they arent falcon specialists so i rekon theres a bit more that could be removed. pulled the rocker cover and set her up, cam was a tooth advanced, easy fixed by removing the tensioner and rolling the chain over a tooth. the powers the same it just revs higher lol but its all fun and games i spose. i fabbed up my wastegate flanges today also and will be fitting to J-pipe and exhaust soon. then the real fun begins as the big girl takes it forced.... again. this time pistons are suposed to stay in one piece and boost at 4psi for stage one. then running an extra injector and a solenoid in the MAP sensor line, controlled by a 4psi pressure switch so the ECU never realises its taking more than 4 pounds and tune away with the extra injector. timing being my only issue for this "stage 2" program. oh well trial and error
 
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