Hypothetical Hypo 4ac

[Course_Out]

Hello all,

So I've been thinking about how guys used to make power from engines like old 202 Holdens, Chrysler Hemi 6's, ete and was wondering - what are the limits of the old 4ac? I know of a few old 202's that have had copious work done to them pushing out 300hp + and Hemi 6's in the Biante touring car series reputedly run around 400hp.

So I'm figuring, as a non cross flow, SOHC motor, the 4ac should be able to easily match the specific outputs of these pushrod non cross flow engines (i.e. bhp/litre)

With a bit of lateral thinking I reckon a 160hp 4ac could be built, without going completely mental dollar wise. My thoughts would be:

7afe block (balanced, probably decked) - could also machine 4ac block to accept 7a internal with custom pistons (useful in racing classes where original block needs to be used)
4ac head (heavily ported)
Big cam (300 degrees plus)
Sidedraught carbs/itb's (could use motorcycle itb's and aftermarket fuel computer)
Custom extractors
ae82 electronic ignition

I realise I am taking some pretty broad strokes here, and i realise the end result would be grumpy, thirsty and not all that much faster than bigport a 4age - but if you wanted to stay in a class with your ae71 (for example) that required the standard block/head arrangement to be used (such as many tarmac rallies) I think it might be a workable solution.

Anyway, sorry for the epic post, I thought it might be an interesting topic to discuss, especially with some of the more mechanically adept people here - I look forward to hearing what your thoughts are

DISCLAIMER: I actually have a 4age in my car, so i don't want to hear "just buy a 4age" cos I already bloody have! This is just a hypothetical idea I'm putting up for discussion

[Konakid]

WOuld be cool because its different but a 4age with cams and exhaust would make near on the same power with 200x the reliability and driveability as unoriginal and boring it is.

[ae71]

i have a lightly worked 4ac, its definitely on par with a standard bigport and i haven't spent much at all.

32/36 weber, 290degree cam, electronic dizzy (has huge spark!!) and exhaust.

pair of sidedrafts, extractors, some porting and shave the head and put a thin gasket and it would be a fair weapon. would be thinking you would definately be around the 120hp mark. thats all still fairly low budget.

or for more nuts, fully counter weight crank (for a bigport 4ag) higher comp pistons, preped rods, balanced bottom end, bigger valves, valve springs... rev it to 9k can you would be spinning wheels and doing very crazy things.

[slydar]

id personally consider it if i were to happen across a mint ae71. could be a nice set up and it would be nice to know you could pop the bonnet and have a stock looking engine.

i was thinking more along the lines of 7a-c, stock intake manifold and something like a 32/36 webber or 2 barrel holley/pro comp equivalent, maybe with late acl small port pistons but i guess that depends on chamber volume etc.

the good thing is there is only one cam, one cam gear, and only 8 valves, so any mods associated with these parts are halved.

the problem with the twin dual throat side drafts or bike carbs/throttles is the port spacing/group doesnt make things easy/neat.

[Course_Out]

Yeah - my 4ac is buried somewhere so I haven't had a chance to look at port spacing

The reason the idea came up was a guy I work with is building an ae86 for targa, and he is taking out his 4agze and putting in a 4age as the rules only allow you to use the original type engine, or an engine that was fitted to that car at the time, so if I wanted to run the ae71 I would need to replace my 4age with something that came in an xe7x chassis, limiting the choices to 4k, 2tg, 3tc and 4ac

So yeah, just thinking outside the box, as you do when you have too much free time...

[Dylan]

this guy is building up a 4ac

http://4ac-powered.forumotion.com/engine-f2/the-ultimate-4ac-stage-1-t14.htm

[Course_Out]

Well there you go!

I'll be following that for sure! Cheers for the link, will be interesting to see what he comes up with, good or bad

[Konakid]

wouldnt you just be able to use a 4age as its still a 4a????????

[blair]

kona get the fuck out of this thread.

[slydar]

his pistons look ok but by the looks of it you could just use 4age ones.

[Course_Out]

wouldnt you just be able to use a 4age as its still a 4a????????

Nope - not in ae71, has to be original type engine, so if you want a 4a, it has to be a 4ac, as thats what they came with. a 4age is too different, i.e. it has 2 cams instead of one, so its not "original type". Its a pain in the butt, it would be great if they had an improved production class in Targa

Other markets got 3t & 2tg in the same chassis so they are ok too