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Old 02-17-2009, 08:15 PM
defilade's Avatar
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283 vortec heads

does this sound kosher, i wrote to a well known publication i wont say the name only the initials chevy hi performance. it was about putting vortec heads on a 283 they said to take it to the machine shop and have them trace the combustion chambers on top of the bores and cut out reliefs so as to prevent valve shrouding sounds cool huh could i take it a step further and bore it out 0.060 as well with the reliefs i saw on another thread that post 63 blocks were not as beefy and can only be taken out to 0.060 safely.

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Old 02-17-2009, 08:30 PM
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Bore it, I don't know about that tracing gig you were told about. Deck it to whatever height that will get you in the desired compression ratio range you are after. Remember, power pack heads were 58cc- you are going to 64cc. Big reduction in CR. Or find some dome pistons.
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Old 02-17-2009, 08:39 PM
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Is the money spent modding that mini mouse really worth it?

In the end that engine still won't keep up with very mild tree fitty's,i know some 305's would probably make short work of a vortec headed 283, and isn't the point of modding an engine to go faster than most other cars?

I think you're better off with some ported powerpak heads or w/e came on the engine originally. Then get yourself a nice cam maybe some headers.

I'm not saying it wouldn't be cool, i just don't think that it would be worth the money spent in the end.

What would be cool is a super(ooh shiny) or turbo charger(downright evil ), definitely worth the money spent, and then go walk some dime-a-dozen 350/383's up and down the block!
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Old 02-17-2009, 09:19 PM
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The lil 283s will suprise you when built right, Now if your block is safe to bore it to 4.00, 302

Shane
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Old 02-17-2009, 09:27 PM
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Quote:
Originally Posted by Chevrolet4x4s
The lil 283s will suprise you when built right, Now if your block is safe to bore it to 4.00, 302

Shane
I'm not arguing I just don't know, but isn't a 302 a 327 block with a 283 crank?
I'm trying to find this out myself. Also sorry not trying to steal your thread.
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Old 02-17-2009, 09:45 PM
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Yeah the 302 is just a 4" bore engine with a 283 crank 3" stroke i believe.
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Old 02-17-2009, 10:30 PM
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Back in the late 50s early 60s a lot of 283s got punched out to 4.00" by dragracers & hotrodders
Shane
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Old 02-18-2009, 12:51 AM
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I've run quite a few L31 heads on a 283/292 on the Dynosim and am amazed at the power that can be produced. Assuming that is would be possible to cut the L31 decks for 60 cc's (about 0.028") without making a cracking problem, you could make 9.19:1 static compression ratio with flat-top 5cc pistons and a 0.040" squish. I remember reading years ago when these heads came out that it was not recommended to use a domed piston with them to raise static c.r. I wouldn't do it anyway because in my opinion, the dome gets in the way of flame propogation across the chamber.

Of course, with this little motor, you have to rev the snot out of it to make the same power that you could with a 350 at lower r's, so you have to use a solid lifter cam, either a flat tappet or roller. I put together a Dynosim pull here to show what can be done with the motor.

283 bored 0.060" with flat-top, KB165 6cc pistons. Cut block decks to 9.015" for 0.010" piston deck height. Victor Reinz 5746 head gaskets, 4.100" bore, 0.025" compressed thickness for squish of 0.035". L31 heads with stock 1.94"/1.50" valves, screw-in studs, guide plates and spring pockets machined to 1.430" for Comp conventional #986 valve springs or 1.412" for 26986 beehives. Cut head decks 0.028"-0.030" for 60cc chambers, 9.15:1 static compression ratio. (598 cylinder, 60 head, 5.4 gasket, 2 deck, 6 piston).

1 3/4" long-tube, equal-length headers, RPM Vortec intake, 750 carb.

Compcams part number 12-224-4 solid lifter flat tappet cam, grind number 294S, 294/294, 248/248, 0.525"/0.525", 106/114/110, timing figures @ 0.050" tappet lift 18/50/58/10.

RPM HP TQ
3000 162 283
3500 216 323
4000 274 359
4500 330 385
5000 381 401
5500 412 394
6000 435 381
6500 445 360
7000 450 337
7500 447 313
8000 423 278

Motor makes 106.6% volumetric efficiency @5500 rpm's. Wouldn't this be a riot in a light car with a 4-speed/5-speed and some 4.56 gears??? 5000-8000 would feel so good, you'd probably lose your license pretty quickly.
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Old 02-18-2009, 04:11 AM
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Tech, your a smart guy, so i know you cant believe the numbers that your desktop dyno puts out, 394 tq at 5500. Not a chance, not even on a perfect day. More like 294 tq.
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Old 02-18-2009, 06:10 AM
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Quote:
Originally Posted by stroker_SS
Tech, your a smart guy, so i know you cant believe the numbers that your desktop dyno puts out, 394 tq at 5500. Not a chance, not even on a perfect day. More like 294 tq.
This is what keeps us all intrigued
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Old 02-18-2009, 06:30 AM
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Quote:
Originally Posted by stroker_SS
Tech, your a smart guy, so i know you cant believe the numbers that your desktop dyno puts out, 394 tq at 5500. Not a chance, not even on a perfect day. More like 294 tq.
I have no idea how close any dyno programs are, however the 106.6% effeciency would seem to be the variable. I don't think any engine operates at 100% no less 106. I know..I could be wrong, but it would seem that if an engine operated at even 100% effeciency that we wouldn't be so concerned about the cost or production of gasoline, IMHO.

Last edited by woodz428; 02-18-2009 at 04:59 PM.
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Old 02-18-2009, 07:45 AM
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Quote:
Originally Posted by woodz428
I have know idea how close any dyno programs are, however the 106.6% effeciency would seem to be the variable. I don't think any engine operates at 100% no less 106. I know..I could be wrong, but it would seem that if an engine operated at even 100% effeciency that we wouldn't be so concerned about the cost or production of gasoline, IMHO.

Its not saying its getting 100% of the energy from the gas, its saying its filling the cylinders 106% on every other revolution, which is entirely possible. And yes many engines run over 100%, though most of them are race engines. Boost also puts you over that but that's a different ball of wax.

Also 401 ftlb is entirely possible, however it is at 5000 RPM! You can forget about anything that resembles an idle. Yes it is easier to turn a rotating assembly with a shorter stroke and smaller pistons, but you also have to have the vlavetrain to match that, along with the trans and gearing. Not to mention an oiling system- which everyone forgets about. Hitting 7,000 RPM at the end of a track is one thing, holding it on extended stretches on the interstate is something completely different. If you spin any SBC to those levels for extended periods it is going to need frequent tear downs and rebuilds, even if you use top of the line racing components. If you have the money to dump in a set of Vortecs then you can probably afford a cheap 350 or 400 short block to go with it, which will put you miles ahead on the street in both power and reliability.
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Old 02-18-2009, 12:34 PM
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I know, I know. Every time I run a 283 simulation like this, I'm called a liar and a charlatan. But this Dynosim has shown to be from dead-on to within 2% of real on several occasions. If it weren't so close, I'd have thrown it out in the street months ago. As it is, it's a lot of fun dialing in a combination like this. You'll notice I didn't include any numbers below 3000 rpm's. That's because they're horrid. But anyway, as I said, I'm amazed at the numbers laid down with a 292/L31 combination.
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Old 02-18-2009, 03:29 PM
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Quote:
Originally Posted by defilade
does this sound kosher, i wrote to a well known publication i wont say the name only the initials chevy hi performance. it was about putting vortec heads on a 283 they said to take it to the machine shop and have them trace the combustion chambers on top of the bores and cut out reliefs so as to prevent valve shrouding sounds cool huh could i take it a step further and bore it out 0.060 as well with the reliefs i saw on another thread that post 63 blocks were not as beefy and can only be taken out to 0.060 safely.
It's generally safe to take any 283 block to .125 over. The 63 is no exception to this, these engines predate thin wall casting which started in 1974 reaching full implementation by 1976.

Vortec heads work just fine on the 283, relieving the bore for valve flow is totally unnecessary. The whole point of the Vortec is to do away with the minor, reverse swirl off the backside of the valve and emphasis the flow on the spark plug side. Relieving the cylinder wall only encourages these contra eddies and swirls that are unwanted. What an accomplished porter learns is how to use shrouding to manage the flow from or into the valve. Stay away from guys that just scream about grinding everything out. Finding performance is about subtleties not just make big holes out of small ones.

Bogie
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Old 02-18-2009, 04:14 PM
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Quote:
Originally Posted by woodz428
I have know idea how close any dyno programs are, however the 106.6% effeciency would seem to be the variable. I don't think any engine operates at 100% no less 106. I know..I could be wrong, but it would seem that if an engine operated at even 100% effeciency that we wouldn't be so concerned about the cost or production of gasoline, IMHO.
The VE is not about the efficiency of the fuel, it's about packing the cylinder above that which would be present with an at-rest ambient atmospheric pressure. Naturally aspirated motors have been known to exhibit VE's of 115-120% with properly tuned passages and the proper intake closing point. Figures above that will require forced induction such as a turbo or supercharger.

My best guess would put the average grocery getter motor at 75-85%.
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