TeamSwift

For the wedge head, normally aspirated crowd who have bumped up their compression beyond factory stock 9:1, what compression ratio are you running and what's your minimum octane requirement?

Anybody doing 10:1 on 87 octane?

Anybody discover the compression limit where 91 octane still isn't good enough to suppress detonation? What's that number?

The guys back east can get 94 from the pump, but us debt serfs in California can't buy any higher than 91. And I saw $4.75 this past summer for 91 so even though it's only half that now, I don't trust those bastards who manipulate the markets on behalf of the anglo petrol empire to not do it again next summer after the "messiah" takes office.

So will I tell 3Tech to cut me a 10.5:1 head on 87 or 91 or is it NFW, stay 9:1 on 87 and fuggedabout 2 extra horsepower and useful compression braking on
the downhill...

What's the group wisdom here?

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95 Metro hatch "Tequila lime" all stock
F/S 3Tech economy cam
F/S 90 Metro hatch
F/S 89 Swift GTi body only
F/S 92 Tracker 2 dr rwd stock
93 Sidekick 4 dr 1.9 vw TD, WVO conversion, 6" lift over 33's

I don't know how high you can go, but you can definitely reduce or eliminate
pre-detonation by carving "Singh grooves" in the head.
The people who have done it are able to run higher comp. and more advance.

MM

I've only seen pics of one set of 3 banger Singh grooves. Did you take pics of yours? The grooves have clearly been evolving in design over the past several years, what is state of the art for our open chamber wedge. We ain't got much quench pad to work with and our total quench height is somewhere between almost too big and definitely too big, so the devil is in the details on this discussion.

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95 Metro hatch "Tequila lime" all stock
F/S 3Tech economy cam
F/S 90 Metro hatch
F/S 89 Swift GTi body only
F/S 92 Tracker 2 dr rwd stock
93 Sidekick 4 dr 1.9 vw TD, WVO conversion, 6" lift over 33's

I am looking into shaving my deck on the block side .020 and running 9.5 or so on 87. If the numbers support it I may even go as far as .030 but I want to make sure when all is said and done I still have a good .015/.020 clearance to the head and piston with head gasket in place. The reasoning is to shave the block instead to get the piston closer to the head and squish/quench. I know there isnt much area to squish on the intake side but it cant hurt. I can't seam to locate a set of numbers on what is exactly the deck clearance so I may have to tear down my engine to find out. I know in Iron heads 9.0/9.25 is tops, but we have Alluminum heads so that in itself would allow us to go to 10:0 safely on 87.

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Contact 3tech: [email protected]

hotrodfeguy,

shove an 8.5:1 FE runnin 87 in the rear hatch and do wheelies, no need for quench...

Seriously, I cut the head, (not the block) in hopes the quench pad would grow ever so slightly.
Flat top 4v pistons to get rid of any dish.
However, I was surprised to find the stock GT pistons sticking out of the block +.025, then pleased to find my cheap chinese ebay gasket was .065, minus a couple thou for crush, landing my piston to head right at .038. I target as close to .032 as is feasible for max quench. I've run mid twenties before on a Corvair air cooled engine and had some forged pistons (at 7000 rpm) kiss the heads enough to transfer the stamped piston part number to the head. Oops. Bearings survived, but it made me more conservative on my build specs. That mod did get me full timing advance with 87 octane at 9:1, which is a real accomplishment on an air cooled, ask your VW bug friends what they're runnin...

I keep staring at the spark plug side of the chamber thinking it really needs to be welded up and decked flat to give a second quench pad but so far it's enough effort/expense to deter me from trying. I'm going absolutely berserk for a couple horse here, a couple horse there, and with all the mods in my sig, the best I can hope for is 15-20% improvement on an engine that makes no power to begin with. I take consolation in my 40 mpg as I cruise lil evil up the mountain every night with the tach buried in the red zone for half the 3000 ft climb above sea level.

_________________
95 Metro hatch "Tequila lime" all stock
F/S 3Tech economy cam
F/S 90 Metro hatch
F/S 89 Swift GTi body only
F/S 92 Tracker 2 dr rwd stock
93 Sidekick 4 dr 1.9 vw TD, WVO conversion, 6" lift over 33's

Shorter stroke.

_________________
Contact 3tech: [email protected]

what the most you think you could mill off a g10 head while using the 365/222 before your valves resurface your pistons?

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2000 Integra GSR... Vtec is like getting your d!ck sucked by a lightning bolt
1995 Metro most reliable rust bucket in Canada
1993 MK1 turbo swap needs bottom end

You can't make the valves hit the pistons, no matter what you do.

_________________
Contact 3tech: [email protected]

Sounds like a challenge.