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Old 07-19-2006, 02:29 PM   #1
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Default Autocross/time attack build up

I just bought a former National Pro Solo tour winning autocross car without an engine. I have a 94 1.8 engine in my garage that I am starting to rebuild to go in the car. I am trying to figure out how far I can take this, within a reasonable dollar amount. The car is fully stripped with everything cut away so it is incredibly light (scale weight was 1850 with a supercharged 1.8 last build up). I am thinking about building the engine with 85mm pistons (would love to do to the 84.5 11:1 compression) and then running a 57 trim .63 ar t3/t4 turbo, 3 inch exhaust, water/meth injection and all the other little tricks. If I can get over 350 and push over 400 hp I would be happy. I probably will do some head work as well and bare minimum port and possibly go to 1mm oversized valves. Will run atleast 100 octane or higher fuel. I see that they stroke cranks on motorcycle engines all the time and short of buying a $3k crank for this car I wonder how feasable sending the existing crank out to have 2-4 mm extra stroke added to it is. Right now I have about $300 invested in the car, and would love to brag that I have less than $2k invested and can run top time of the day.

Any tips would be loved, I know I have alot of the right pieces its just getting everything together to get the most out of a few bucks.
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Old 07-19-2006, 02:34 PM   #2
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'99-00 head.
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Old 07-19-2006, 03:42 PM   #3
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I cant see the back of the head on my 99 to see if I bought a 99 head if you can run a cas on it? Then run the 99 cam as well because lift and duration are a bit more as well? Any need to go to oversized valves or just port and polish and all set?
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Old 07-19-2006, 04:10 PM   #4
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the solid lifters and the flow characteristics are more appealing over a built older version. i don't know about the CAS. an prm window switch for the vics (or lock it open) and some mild porting would be ideal.
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Old 07-19-2006, 04:12 PM   #5
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the cas swaps right on to the 99-00 head
http://users.pandora.be/miata/englis..._head_swap.htm
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Old 07-21-2006, 02:47 AM   #6
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I'm not expert, but why would you want high compression if you are going to run a big turbo? You will greatly limit you HP potential by running 11:1 ...
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Old 07-21-2006, 03:12 AM   #7
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Yeah I would go 9.1 depending how u want to run boost, im a big fan of saftey factors. We really dont know how things will react sooo lets add 40% to everything for safe measure, and that way if were wrong well have to be really wrong to mess things up.
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Old 07-21-2006, 09:06 AM   #8
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well if its an autocross car, 11:1 and a 8-9psi T28 on some good fuel would give you some serious response
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Old 07-21-2006, 10:26 AM   #9
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Agreed... High RPMs... + hard on it for autox/track... you should actually make sure you have the safety zones there.... bad gas, slosh in the tank... heat soak.... I would say keep the stock 9:1 ratio... and just run "good" boost. It will work better for you in the long run.....

Dave,
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Old 07-21-2006, 11:31 AM   #10
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Ok I can see being in the 9's for compression for a variety of reasons listed and making the car a little easier to start and run. I was debating on pushing the envelope a bit to get more out of the car. Sure I can build it safe, but the car is only going to be a track car, it is so stripped it could never be driven on the road (there isnt even a windshiedl, dash, lights or a passenger seat. I bought the engine for less than $200 bucks so if I have to get another block because I toast this one its not that big of a deal and I learn a lesson I suppose. But if I toast the block because I get good performance gains, I can push 400hp and have a winning car then I willing to go there. Im also thinking that running the water meth injection, a monster intercooler, oil cooler and 3 inch exhaust with no converter will help with cooling considerably.
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Old 07-21-2006, 01:16 PM   #11
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Its not the block its the material that go into the blocks. thats expensive!
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Old 07-21-2006, 02:39 PM   #12
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I think a 1.8 block, 99 head and a good diy turbo set up CAN make 300hp without doing anything expensive to the engine. I think you could do this within your $2k budget, but it will require some smart shopping (really good deals on used parts and hours on eBay) and lots of fabricating on your part. - rob
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