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hotting up 308

gday all the old prem has sprung an oil leak so i think its a good excuse for a tear down, whilst the motors out to clean it up i was thinking of getting abit more out of it, im wanting to keep the motor externally stock apart from hei and extractors (ie. stock manifold, quaddy, heads, rocker covers etc) but wanting abit more poke, so far the engine specs are:
flat top hypertec pistons around the 9.5:1 comp ratio
lightly ported heads (orig HG style heads)
crow cam 5761,IN. 38/74, EX.76/36, DUR.292, .50DUR 230, L/C 109, LIFT 0.495"
mallory mechanical advance hei dizzy
pacemaker tri y's into twin 2 1/4 pipes
running through a stage 2 trimatic stock stally and banjo 3.08 diff
Ive got a 9 inch to go into it and will fit a stally at the same time but would like to get the motor sorted so i can choose gears and stalls (i was thinking 3500 stall and 3.5 gears?)I was thinking of getting the heads ported out abit more (any suggestions for shops in central vic?) and maybe some more compression? whats the highest comp i could run on 98 octane? its not a daily and will only be used on weekends. if theres any other little mods that i could do without affecting the original look itd be great to know, thanks

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I am supprised that the banjo

I am supprised that the banjo still works. Before you seek any more power I would ensure it has somewhere to go.

crocky's 308

I've got a similar combo in my HQ:
Forged flat tops, a little over 10:1 comp from memory.
Ported big valve heads (early HQ style)
Comp Cams Magnum hydraulic cam 244@.050 .518lift (it's a little over cammed but it sounds good)
MSD Pro Billet distributor with a 6 series box.
4 into 1 headers into dual 2-1/2" pipes
Shift kitted T400 with a 3000rpm converter
3.36 10 bolt diff.
It's got a single plane manifold and a 650 D/P Holley but I did previously have it set up with a standard manifold that I cut the divider out of the plenum and port matched to the heads and it's probably actually a better manifold to use than the single plane.
It runs fine on 98 but that's because the cam overlap helps to bring the cylinder pressure down.
I haven't run this combo down the quarter yet but this engine with the dual plane manifold and a smaller cam was good for a 13.9 in my old HJ, which only had a twin 2" exhaust and 2.78 gears.

Have you thought about stoking it? If you're going to put new pistons in it anyway, why don't you spend a few more $$$ and put a 355 crank in it at the same time? More power and torque without changing the standard look. Avoid the cheap Pro-Comp cranks and look for abetter quality one like a Scat or a Harrop.


aka hq308belmont

My Shed

9.5:1 comp ratio

First thing I would do is give it a bit of compression.
If it is still running the same set up it was when I last saw it, IMHO 10.5:1 and the ignition sorted would change your mind about what you've got.

Campbells Shed
Postcode 3147.

hot 308

thanks for the replys guys, yeh the banjos dont hold up i have done 7 centres so far an i keep a spare in the boot for the next time! i dont do burnouts or anything tho they just seem to let go. dave i have been thinkin about the 355 option and looks pretty god, im unsure of the block machining required though, the motor is only about 15,000 miles since rebuild and only 20 thou up so im not really wanting to stuff around with it too much more, what would it cost approx just to do the 355 kit and port the heads? campbell yeh its the same ignition as before and ive had it curved to suit the cam but the guy said id get more out of it recurving after the stall/gears go in


My Shed
Email Me


AFAIK it should just need a little clearancing near the oil pan rails for the conrods. You can do it yourself but I don't know if it's advisable because if you go to far you'll hit the water jacket and wreck a perfectly good block. A good machine shop should be able to do it easily. You should be able to pick up a Scat crank for under a grand, the Harrops are a little more. The pistons shouldn't cost you any more than it would for the standard stroke set up. With the conrods you have a few options, you can use your standard rods or you can get some L34 or A9L factory rods or even a set of Scat H-beams or if you get the Scat 355 crank with Chev journals you can use Chev 5.7" rods as long as you get pistons to suit. The beauty of the Chev journal option is there a plenty of good cheap Chev pistons and rods you can use to keep costs down. You'll need to get it all balanced but you should be doing that with your standard stroke set up anyway.


aka hq308belmont

My Shed


Keep what you have, zero deck the block, Felpro head gaskets, L34 type valves with a pocket port, Crow 5616 and 3310 carb.


and ARP rod bolts.

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