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Location:
Eastern Sydney
Registered:
May 2002
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Re: 4AC simple Mods? please l'm new to this!! LOL!
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Sat, 15 June 2002 12:46
 
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yes,the 4AC is nothing to get excited about,we all know this.
you'll be lucky to break 45kw atw from a tweaked 4AC in a sprinter.
power isn't everything however.
a few simple mods as asked for:
*open aircleaner. the std housing is utter garbage. something designed for a stromberg on an old holden will virtually bolt straight on,and will make a world of difference to the thing's breathing. you'll actually be able to use the top 1500rpm of the rev range. a round 8 or 9" chrome disc style unit is ideal.
get some cold air to it if you can,but don't worry if that's not possible. it won't make much of a difference on this engine.
*full exhaust. I run a 2 1/2" system,with a mercedes SLK cat (you have to love freebies!)two resonators,and a straight through muffler. leave the cat out if you don't mind breathing in benzene. the two resonators are needed to keep the note somewhere near a legal level. the 4A barks quite loudly.
*grab an AE82's electronic dizzy and coil. nice improvements to driveability with one of these. better throttle response,cold starting,and economy. no real power increase,but you have a much nicer running engine with the electronic spark setup.
*remove the *ahem* performance controls. this includes the EGR,extra diaphragm beside the secondary butterfly control,and various water temp switched vacuum bleeds. all you need is the ported vacuum line to the dizzy,the line from the manifold to the brake booster,and the diaphragm for the secondaries. remove everything else.
on electrics,remove the bleeder solenoid from the O/S strut tower,but leave the choke's power and earth wires connected.
*exhaust manifold:while taking off the "performance controls",
flip the manifold heating flapper in the exhaust manifold to the fully open position(it's normally closed until the higher end of the rev range-aiming nearly all of the gas from 1 and 2 at the base of the inlet manifold). hold it in this position by reversing the spring that opens it to the opposite side of it's stop.
this will improve the flow of the manifold slightly,especially at lower RPM.
that's the virtually free stuff. do all of this,and it should rev cleanly to about 5k,and die off from then onward to the 6k redline.
if you want to spend a few hundred on it,get a reground camshaft (~$100),rejet the std carb,and do a portmatch job on the manifolds.
my inlet manifold got cleaned up quite a bit,as the std runners are tiny and shockingly made.
I've also started to port a spare head,but may not bother finishing it. I'm finding it hard to justify paying for a valve reface,reseat and head surface skim job,and in spending the time it will take me to finish the ports and chambers to a level I'd accept.
my 20V is a more sensible item to spend my money and time on.
hope this helps some,
Justin...
[Updated on: Sat, 15 June 2002 12:57]
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