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Old 03-10-2010, 03:10 PM
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My Engine Idea, any suggestions would be welcome

I want some input on building a 383 sbc stroker...
I want it to run smooth, have between 350 and 410 horses and torques.
I want to set it up with mpi, I am thinking about a Holly Defender MPI kit, and I want it to sound good when opened up and taring around but I would really like to be calm when I am driving past the cop shop...
Any suggestions

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Old 03-12-2010, 06:52 PM
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reply stroker

What are you starting with for a block?
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Old 03-13-2010, 12:42 AM
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Quote:
Originally Posted by Veinot
I would really like to be calm when I am driving past the cop shop...
Slip it into neutral.....

Actually, I have an example of such a motor.
It makes only 363 hp, but is a torque monster (and therefore, a great street motor). It uses production 882 heads and 9.7:1 static compression ratio...
RPM HP TQ
2000 161 423
2500 201 423
3000 250 438
3500 301 452
4000 337 442
4500 361 421
5000 363 381
5500 312 298
http://www.compcams.com/Cam_Specs/Ca...x?csid=85&sb=0

Last edited by techinspector1; 03-13-2010 at 12:55 AM.
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Old 03-13-2010, 08:06 PM
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Quote:
Originally Posted by Fast 4 Door
What are you starting with for a block?
I figured I would start at a 383 short block purchased with the appropriot pistons, crank, rods, and clearanced. From there I figured I would get an idea from people with more know how than me what kind of heads, intake, values and sizes I might want.
Right now I am keeping my eye open for a block on the local buy sell and trade sites.

After talking to my cousin though, he thinhks it might be better for me if I stick to the basics, i.e. 350, 302, 283, 305 ect, due to my lack of experiance.
I wanted to do a 383 just because it is roughly 6.2L and the new AC Cobra is running a 6.2L LS Chevy Engine...

But anyway I'm just trying to figure out really what kind of components would I want to put together that would make a good street/roadster engine that runs and idles smooth, but still perks up when the throttle opens.
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Old 03-13-2010, 08:28 PM
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i would still stick to the 383, they aren't hard to build once the block is clearanced, it's just like building any other motor

since you dont want real high hp/tq numbers i think your best bet would be vortec heads, you dont need anything bigger than the stock 1.94 valves, i would just have the guides cut down, and rebuild them with Z28 springs so you can run a cam with over .465" lift
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Old 03-16-2010, 05:43 PM
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Ok, tis is where my stupidity shines through...
I understand clearanced, and I know what Vortec heads are, when in comes to the in's and out's about values, guids, and Cam lift, its out of my current knowledge. I understand that the .465" lift is how far the cam opens the valve, but what difference would Z28 springs make? Don't they just close the valve?
And arn't vortec heads mainly for trucks and pulling? or does it matter?
btw...
If I use vortec heads off an engine with EFI can I keep the EFI for the 383 or would I need to reprogram an ECM for the 383 application?
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Old 03-16-2010, 06:40 PM
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Quote:
Originally Posted by Veinot
Ok, tis is where my stupidity shines through...
I understand clearanced, and I know what Vortec heads are, when in comes to the in's and out's about values, guids, and Cam lift, its out of my current knowledge. I understand that the .465" lift is how far the cam opens the valve, but what difference would Z28 springs make? Don't they just close the valve?
And arn't vortec heads mainly for trucks and pulling? or does it matter?
btw...
If I use vortec heads off an engine with EFI can I keep the EFI for the 383 or would I need to reprogram an ECM for the 383 application?

Z28 springs could either be a replacement spring for a mid 90's Z28 camaro as they are more of a performance vlave spring, but really when i mention it, it is more in reference to a set of cheap aftermarket springs that can handle around .550", like these

http://www.competitionproducts.com/H...uctinfo/98212/

now you will need to know what cam you will be using before you get your springs, cause seat pressure and open pressure needs to be matched to what is recomended for the cam, as well as the lift capabilities of the springs.

vortec heads are certainly not just for trucks or for pulling, they where primarily used GM trucks in the late 90's, but that doesn't mean they are truck heads. vortec heads are the best performing heads that GM ever put on a production vehicle. just putting vortecs on an old 76cc smogger motor will easily raise the power out put by 30-40hp. these heads (w/ new springs, but other wise stock) with a mild cam on a 350 can produce 400+hp all day long.

you will only get vortec heads off of a 96'-00' 5.7L vortec (EFI) engine (stock) but personaly i would not use the EFI, you would have to reflash the ECM and this is PRICEY. IMHO you would just be better of getting a vortec compatable intake and a carburetor
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Old 03-16-2010, 06:45 PM
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When GM cast the Vortec L31 heads, they cast the valve guide boss as a very large outside diameter boss. The idea of this is that the I.D. (inside) of the valve spring is kept in its proper location by the guide. Since the guide is so fat, you can't run a good valve spring that includes a damper or another type of dual valve spring on the head without cutting down the diameter of the boss. The fix would be to cut the valve guide diameter down to 0.630" with a cutter that locates from the I.D. of the valve guide. Then cut the top of the guide to 0.530" for positive seals. Then you could run most any spring you want to. This is an operation you can do at home with a low-rpm 1/2" drill motor. It just takes a little time and patience. Total of the tools to do this is about a hundred bucks, available from Summit. I can give you the part numbers if you're interested in cuttin' on some heads.

The other problem with these heads from a performance standpoint is that the bottom of the spring retainer will crash into the valve guide seal at valve lifts over about 0.450". If you eyeball the whole mess, you can see where you could get more lift from them without coil bind, but there must be some safety factor involved in the spring. When assembled and with the valve pushed down to where the cam will lift it, you should be able to insert a 0.010" feeler gauge into each of the 5 spaces between the coils. This will add up to 0.050" of clearance in the springs before they go into coil bind and the motor will operate fine.

Some fellows will do what is called a "ghetto grind" on the bottom of the retainers to gain additional clearance between the bottom of the retainer and the top of the valve guide seal. If we assume that we can run a valve lift of 0.450" and be ok with the stock components, then you can readily see that if we cut 0.050" off the bottom of the retainers, then we can use a cam that will lift the valve 0.500" and we will still have enough clearance between the bottom of the retainer and the top of the seal to prevent a crash. Now, that still doesn't address the weak-suck stock springs, but that's another story.

I hope this helps you understand what's goin' on with Vortec L31 heads. If it's still not clear, ask again.

Last edited by techinspector1; 03-16-2010 at 06:51 PM.
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Old 03-16-2010, 08:18 PM
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Wow... I think its time to pick up a book lol or get a turn key...
If I was to go turn key what kind of crate engines fit my description?

But yeah still not entirely clear but I am the kind of person who has to see it, I was lost on differential until I found a diagram showing me what was going on.
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Old 03-16-2010, 08:32 PM
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Quote:
Originally Posted by Veinot
Wow... I think its time to pick up a book lol or get a turn key...
If I was to go turn key what kind of crate engines fit my description?

But yeah still not entirely clear but I am the kind of person who has to see it, I was lost on differential until I found a diagram showing me what was going on.
Get the book, a good one, maybe 2 or 3. Thats how I felt a year ago and Now , I am the proud owner of a new engine that has been built by me. Oh what a feelin !! Don't be scared, it's not that hard.
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Old 03-16-2010, 08:48 PM
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i agree, we all had to start off somewhere, and dont make it harder than it has to be. there is a decent amount of math involed in putting together an engine correctly but all the math is fairly easy 4th-5th grade stuff, you just need to know what to do the math on and that is where the books and this site come in handy
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Old 03-16-2010, 09:16 PM
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383 LT1. It'll bolt in and easily meet your goals. Go with an ignition retrofit.
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Old 03-17-2010, 10:03 AM
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Math isn't perticularily hard for me, its an important part of my career, spelling however, www.dictionary.com my saviour... Completely useless without a Dictionary

383LT1, I have seen some on Ebay and other places the scary thing to me is, and this is for all engines not just 383's or LT's, is one guy is selling his for 2k another is selling for 5k... why is one some much less than the other?
Thats why I started think self build that way I know whats in it....
If I was to go this route, what sort of things should I look for? Any Tell Tale signs I'm getting ripped off? How do I figure out what I'm getting is too much, either money or too much engine for my application?

Any suggestions on some good books?
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Old 03-17-2010, 10:10 AM
How fast is fast enough?
 
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Any book related to small block chevy engines written by David Vizard or Smokey Yunick is a great place to start. You can get them on Amazon for about $10 for a "like new" copy.

If you go the 383 Lt1 route I would run a Scat crank, get splayed mains, 5.7" rod, hyper pistons, a coil on plug or distributor retrofit, and megaquirt EFI. A hydraulic roller cam is the easiest thing for you to use, something along the lines of 220/224 on a 110LSA would be a healthy cam that will give you plenty of off idle torque. If you can get a decent core engine for about $500 (seems to be fair market price) then you're looking at having about $3,000-$3,500 into this project before you're done. You'll easily hit 400hp and 400ftlb and in the right car could see 25+MPG.

Target compression for 87 octane would be about 10:1, 11:1 for premium (93).

Last edited by ap72; 03-17-2010 at 10:21 AM.
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Old 03-17-2010, 10:17 AM
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Quote:
Originally Posted by ap72
...get slayed mains
Those are easy enough to get, free! lol

Seriously, there are good books like mentioned- Vizzard is as good as most. Avoid the ones that haven't had a revision since they came out- you will want info AT LEAST that includes the roller blocks ('87-up) and Vortec heads ('96-'02 or so), if possible- though less important, they are available (book on heads) separately.
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