Weight of the car in a trim like yours – both the total weight, and the contribution of your weight-reducing efforts to both front and rear axle weights. \u00a0For Street Touring for instance, your front seats and mounts should weigh 25 pounds each – how much weight will be saved there? \u00a0How much in headers, exhaust, lightweight battery? \u00a0Are there any options you can remove? \u00a0 How low can the car be run on fuel? \u00a0You have to look at published weights, or weights from people that have weighed their cars, then offset from those figures to account for the modifications you’d make.<\/p>\n
How much wheel\/tire can the car fit within your rules? \u00a0How much of it can go inboard from stock?<\/p>\n
Dyno pull of the engine with modifications made for your class. \u00a0This may just be a cat-back exhaust, or that plus a CAI, headers, and a tune, or maybe even more extensive mods. \u00a0You also have to take into account the different types of dyno (Mustang, Dynojet, Dynapack, direct engine dyno) and build in some correction factors amongst the dyno types and operators. \u00a0Some massaging to do here, but a dyno is MUCH more valuable to evaluating autocross acceleration, than peak numbers.<\/p>\n
In a future post I’ll maybe go into some detail into the thinking used to take all that information and try to apply it to autocross, to see what cars will be faster than others, where on course. \u00a0But for now, that last bullet – engine dyno – is something I was missing somewhat in the pre-purchase planning stages of the build. \u00a0I figured an 11:1 compression 5 litre V8 should be able to make more power than a 2.8 litre BMW or normally-aspirated RX8 rotary, but how much more, and where in the powerband? \u00a0There’s all kinds of legend out there on the 302’s real power output, but not a lot of good hard data. \u00a0You end up reading through a lot of threads like this:<\/p>\n
http:\/\/www.camaros.net\/forums\/showthread.php?t=13864 <\/a><\/p>\n And not really figuring much out. \u00a0Like stock Z28 quarter mile times, you get numbers all over the place, but most are either wrong or completely unsubstantiated. \u00a0I did find this dyno:<\/p>\n I happen to know the DTS4000 is an engine dyno, so this was done out of the car, likely without accessories and definitely without any drivetrain loss. \u00a0That’s about 345hp – certainly more than the factory’s 290hp rating, substantiating many’s claims of the factory having underrated the engine. \u00a0However we still don’t know the details of the build – whether the motor was fresh or high mileage, if it had headers or stock manifolds, whether it was tuned at all, etc. \u00a0Assuming the reading is correct the air\/fuel ratio seems on the lean side, over 14:1, not quite ideal for power.<\/p>\n So for me, the engine’s power was a really big question mark when it fired up for the first time this past Friday, 11\/26.<\/p>\n J-Rho’s 302 is born, first startup<\/a><\/p>\n The smells coming off this thing were fantastic, it brought me back to the days as a young teen watching the cars go down the 1\/4 mile at the now-defunct Carlsbad Raceway. \u00a0I attribute the smell largely to the fuel used – we didn’t have any of the Sunoco GT100 fuel I plan to run on hand, so we made a mix of 91 octane pump gas and 110 octane leaded fuel. \u00a0No fancy widgets here to foul up from the lead, just my brain to intoxicate with carcinogens, yummy! \u00a0\ud83d\ude42<\/p>\n There’s a lot of myth and legend about this motor out there, perhaps more than about any other small-block Chevy. \u00a0The components used to make the engine changed from 1967 to ’68, and again in ’69. \u00a0They made way more ’69 302’s than the other years, but in some ways, the ’67 engine is easier to reproduce. \u00a0This is because there really isn’t anything special about the 302 motor in ’67, it was all parts-bin stuff – the same 4″ bore, small-journal block used by the 327 and 350; the forged crank from a 283; “fuelie” heads with 2.02\/1.60 valves from the Corvette, along with its “30-30” cam. \u00a0The carb is the same used on the SS396.\u00a0 There really wasn’t anything unique or special in the ’67 Z28 engine, which made piecing together a reproduction, possible. \u00a0It took a few months, but my chosen engine builder (some may recognize the engine dyno room from these videos) has excellent connections in the vintage and A-Sedan racing circles, having built many smallblock Chevys under varying, but always strict, rulesets.<\/p>\n Here’s a video of a full pull, the only one where we went over 7 grand:<\/p>\n 302_dynopull<\/a><\/p>\n![\"\"](\"http:\/\/www.rhoadescamaro.com\/build\/wp-content\/uploads\/2010\/11\/z28dyno-212x300.jpg\" "\\"z28dyno\\"")
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