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post #1 of 11 (permalink) Old 01-16-2005, 05:38 PM Thread Starter
 
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4.2 engine questions?

I have been thinking about building a new engine for my s.c. I have been reading on and off about 4.2 blocks. Can I use a 4.2 block and crank to use as a base for a S.C. engine? I am a big beliver in more cubes is better. I know the crank is cast but could it be cyro treated or something for strength? what about the knock sensor? I figure this has to be cheaper than a custom crank. Is there any advantage to the 4.2 heads? Thanks Tim
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post #2 of 11 (permalink) Old 01-16-2005, 06:49 PM
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I would just put the 4.2 crank in your block if anything, why mess with another block. And if you want to assemble it in a different block, do it on an sc block, you need to use an sc block for your supercoupe.

I personally wouldnt go with a 4.2 crank unless you plan on not making a lot of power. I have seen the 4.2 go to 400rwhp but that was on a centrifugal blower, which puts a LOT less stress on the rotating assembly since it makes power up higher. The low end power of the roots m90 puts a lot of stress on the internals. So if you arent doing a lot to your car then it may be okay, but remember that there's a reason you have a forged crank.

the 4.2/3.8 split-port heads are totally different from your heads so you cant use them without a custom lower intake manifold, but the intake valve is larger at 1.9" and the exhaust port is shaped a lot better for increased velocity.

-Thomas

1988 Notch Mustang: - 438W, direct port n2o, t56
2003 SVT Focus: - SCT X3 tuner
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post #3 of 11 (permalink) Old 01-16-2005, 07:51 PM Thread Starter
 
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Well so much for that idea. Iam already making fair power. The whole idea was to get more cubes for more power. To bad the extra inches and longer stroke should really make torque. The car is not a daily driver, putt around to car spots in town and drag racing. A custom crank at $3000 is way out of my budget.
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post #4 of 11 (permalink) Old 01-16-2005, 07:56 PM
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i think someone had one made for more around 2k. How fast does your car run right now?
-Thomas

1988 Notch Mustang: - 438W, direct port n2o, t56
2003 SVT Focus: - SCT X3 tuner
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post #5 of 11 (permalink) Old 01-22-2005, 08:35 AM Thread Starter
 
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My best so far is 13.547. I really need more converter, right now it stalls at 2200. I am going to get a 10 inch 2700 stall to replace the 12 inch lentech that is in the car when I have the money. I am also getting a set of aluminum underdrive pulleys to reduce the rotating mass. I have been trying to find a manual rack to replace the power but so far no luck. By the end of next summer I hope to be in the 12.75 range. It really depends on money and what I can afford to do. The car is not a daily driver so pretty much the sky is the limit. I also want to do a smaall zex kit. I remember meeting you at Saint Louis. I still Have the t-shirt I bought from you, nice to see you got your car running.
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post #6 of 11 (permalink) Old 01-22-2005, 10:10 AM
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2700 would help you out a lot, but dont fear the verter, go 3000 if think it would help more. If you p[lan on hitting 12's get an autorotor, they are amazing. An Autorotor 1.7L with a 3000 stall could yield powerful gains. I'd keep the 3.8 crank you have in there and see how far it takes you.

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post #7 of 11 (permalink) Old 01-22-2005, 01:06 PM Thread Starter
 
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I think 26-2700 will be enough. I want it to be somewhat streetable. I would love to have an autorotor and I will some day, but I want to free up as much power as possible by getting rid of all the stuff the engine has to turn first. Aluminum pulley set, electric water pump, and last but not least a manual steering rack. Light weight racing seats,fiberglass hood and put the battery in the trunk. Right now I have a stick early model blower. I figure somebody with a magnum powers setup will be selling theres cheap sometime when they go to an auto rotor. Even without the better blower I should hit high 12 sometime this year. Are you really going to run a turbo setup? That to me will be better than any blower setup.
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post #8 of 11 (permalink) Old 01-22-2005, 05:24 PM
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well theoretically a twin screw supercharger, which is what the autorotor is, is more efficient than a turbo setup, but displacement can become a factor in the supercharger. Yeah I plan on running twin t3's or possibly something larger, unsure as of now, but the heads and cam I have are spec'd for a turbo with larger exhaust lift and a 1.6" exhaust valve.
-Thomas

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post #9 of 11 (permalink) Old 01-22-2005, 06:39 PM Thread Starter
 
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Sounds like a good idea to me. I know there is less power loss with an autorotor then a m90 but the idea of a turbo sounds good to me. Superchargers take power to turn which relates to strain ang stress on the engine. Turbos are almost free power. I like the idea of 2 small turbos vs 1 large one. Do you have any idea on how to set one up or is this a learning process? Cant wait to see how it turns out. Oh and I need another T-shirt too.
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post #10 of 11 (permalink) Old 01-22-2005, 07:26 PM
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I've got routing all plotted out and sketchings all over my desk lol. I've made one nice one on photoshop though but I dont know if I want to let out all my secrets before it's been done
-Thomas

1988 Notch Mustang: - 438W, direct port n2o, t56
2003 SVT Focus: - SCT X3 tuner
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post #11 of 11 (permalink) Old 01-22-2005, 08:07 PM Thread Starter
 
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Sounds good let me know when its done.
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