The 283

[Domenic T.]

A while back I read a thread about 283's. I couldn't help thinking that it put Chevrolet on the map. Not to many would reach in their wallet and bet against one. They would wake any car up and I think we forgot just how good they were. Yes some say their were rod problems, but I saw few. Most rod problems were oil starvation to #1 & 2. They would turn 10K, and 1n 1957 would wake any driver up.
I was the grand son of the 265 and father of the 327.
You had to have one to appreciate it, without the 283, I wonder how things would have worked out for Chevrolet in 1957? That small block carried it's weight for years.
Hats off to it, I sure enjoyed being there.

Dom

[Keith B.]

Re: The 283

This reminds me of my dad always telling me stories of his Chevy II he owned that where inline six cars and he would swap in 283 and a four speed and how much fun of a car they where. not sure if he couldn't find or afford a 327 or the 283 was good enough on retread bias tires.

[Michael J.]

Re: The 283

Yes, the first performance engine I craved was a 283 to replace the 6 banger in my cheap, first car, '57 150 Chevy. I had a hard time finding one I could afford, then a junk yard had one they said was better, they said it was a 283 with a 327 crank in it and thus said it was a 301. I got it and never looked back.......

[Duke W.]

Re: The 283

A standard bore 283 with a 327 crank is a 307. That particular bore-stoke combination was actually produced in the seventies.

A 283 bored out to 4.OOO" is a hotrod 301, but Chevrolet called the 4 x 3 Z-28 engine a 302.

Duke

[Michael J.]

Re: The 283

Right Duke, but to a 15 year old, the junk yard marketing worked........

[Al R.]

Re: The 283

And to think, my little 1959 283 FI Fuelie bored .30 over with the Duntov cam dyno'd at 332 HP and 334 Ft/Lbs torque on today's high test non ethanol gasoline!

[William G.]

Re: The 283

Al:
"On today's high test"......................you mean race fuel, right? Unless the compression has been significantly reduced. What is the c. r.?

[Al R.]

Re: The 283

William, no it was with the 92 0r 93 octane (don't remember which) non ethanol gas. IIRC, it made nearly as much on 87 ethanol, but that's been roughly 5 years back. The CR is whatever the factory CR was on the pistons was at the time 10.5-11.0? I have all the material lists used in a file somewhere. I do know they used a good strip/strip rod. It was balanced and blue printed and I watched all the dyno tests at the time. I think the only other thing that may have been changed from stock was doing a multiangle valve job. The engine shop even rebuilt the fuel unit for me at minimal charge! I do run it now on AVGAS or 93 Non Ethanol where available or a combination of the 2 to help with summer driving along with a duct system blowing outside air onto the spider and fuel lines and have heat resistant insulation on all fuel lines and filter from the fuel pump up to the unit. Runs like a scalded dog!!!

[Domenic T.]

Re: The 283

Al,
Nice to know it has all stock parts that it was born with. I do the same with mine when building and the same fuel with exception that I have to mix CA's best 91 with av gas.
Changing pistons and thick gaskets makes it a different engine and the numbers are the only thing that says what it used to be. My 350 HP would not be a 350 HP with lesser modifications. Maybe a 310 HP after a compression reduction.
Yes, it's hard to feed the engine the right fuel, but sure worth it to get the original HP.
On long trips years ago I installed water injection which did well.

Dom

[William G.]

Re: The 283

Okay.........Al and Dom--question. Recently I've had a 1966 327 block built with Icon 11:1 pistons and I'm mixing Kemco real lead that I've purchased from Wild Bill. That stuff gets pretty expensive when mixed at the level the label suggests (three oz. per gallon of 91 no ethanol gas to raise the octane to 100, R+M divided by two). Any suggestions as to how much lead is actually needed? Two ounces, perhaps?

One of my goals with the 11:1 pistons is that back in the long ago past those high comp. sbcs really had a crisp exhaust note to them.........you could identify a high compression small block at idle from 50 feet or more away. Can't say I'm experiencing that exhaust note from this engine with an L79 cam and the Icon pistons.

Bill

[Domenic T.]

Re: The 283

Bill, wish I could help on the lead but I mix 100 LL av gas with the only available high test here in Palm Springs CA, 91 with the crap in it.
So I get my bangs out of the mixture. Tried straight 100 LL and it seems to run better mixing it.
Tried 91 from the pumps and the engine in my Chevelle with auto trans dieseled so bad it cracked a piston. No way to shut it off because it had an automatic. so I finally keep it in gear and turn the A/C on with everything else to do so.
Yes I can de tune it with the timing, but I built it to run. It's a 427/425.
Going to read up on what Duke suggests and see what that does.
Your right, does cost to run them the way the factory built them, but by far av gas is the cheapest. ARCO 91 is 4.199 and av gas is in the 5 doller range.
Funny, but a mod on the car is not accepted, but you can mod the heart of the care. The engine.

Dom

[Duke W.]

Re: The 283

And to think, my little 1959 283 FI Fuelie bored .30 over with the Duntov cam dyno'd at 332 HP and 334 Ft/Lbs torque on today's high test non ethanol gasoline!

Hmmmmm! You didn't say what kind of dyno - lab or chassis - or what kind, if any correction, but I'll assume a lab dyno with STP correction.

For comparison I was system engineer for the first two prototype "327 LT-1" configurations. One (originally a '65 L-79) was tested on a lab dyno - made STP corrected a little over 330 lb-ft at 4500 and about 350 GHP at 6500... 30 over, LT-1 cam, 10.35:1 average CR across the cylinders with about 0.1 max variation. nicely massaged OE heads, and OE exhaust manifolds and front pipes connected to the large dyno exhaust system. The second (OE '65 L-76) was tested on a chassis dyno with SAE correction, and given generally accepted empirical conversion factors, correlation was good.

I also have a lab dyno test report of a "stock rebuild" 327/340, SAE corrected 344 lb-ft (actually met the advertised value!) and 295 HP @ 5500. The owner asked me what happened to the other 45 HP, and I said it just existed in some marketing guys wet dream.

Peak torque is basically a function of displacement and CR. For example, peak advertised 327 Corvette engine torque ranges from 344 to 360 lb-ft, a spread of less than five percent, yet the last FI engine at 375 advertised GHP was 50 percent greater the base 327/250. Gross torque figures of that era were slightly inflated and GHP was at least 10 percent optimistic.

I can pretty accurately guess the displacement of a naturally aspirated engine, especially a "stock" or mildly modified vintage Corvette engine by just looking at the torque data.

Just sayin'...

Duke

[Duke W.]

Re: The 283

Okay.........Al and Dom--question. Recently I've had a 1966 327 block built with Icon 11:1 pistons and I'm mixing Kemco real lead that I've purchased from Wild Bill. That stuff gets pretty expensive when mixed at the level the label suggests (three oz. per gallon of 91 no ethanol gas to raise the octane to 100, R+M divided by two). Any suggestions as to how much lead is actually needed? Two ounces, perhaps?

One of my goals with the 11:1 pistons is that back in the long ago past those high comp. sbcs really had a crisp exhaust note to them.........you could identify a high compression small block at idle from 50 feet or more away. Can't say I'm experiencing that exhaust note from this engine with an L79 cam and the Icon pistons.

Bill

Very few engines left Flint with "11:1" CR due to high decks from broach tool wear just like like most left with ten percent or less of the advertised peak horsepower, and that was with the OE .018" head gasket. (two on 340/360 HP engines from mid'62 to the end of '65).

11:1 pistons doesn't mean much because that's with an assumed deck clearance and head gasket clearance. A high deck and thick head gasket can easily make those 11:1 pistons not much over 10:1. Get the spec on the pistons you have installed. I'm not familiar with Icon. The OE pistons have a net 5.3 cc dome.

Most guys don't really know the true CR of their engine because they or whoever "built" the engine didn't measure deck clearance and compute the actual CR with the installed head gasket.

Measure your head gasket thickness with feeler gages at the corners of the head-block interface and report back. Chances are it's a lot thicker than OE, so the CR is probably low enough to run on pump gas and not necessarily the highest available octane.

Today's 93 PON has about the same detonation resistance as 98 RON gasoline from the sixties, and contrary to popular belief sixties premium was not all 100 RON, but in a range from 97-100 RON and marketers only blended enough octane to minimize detonation complaints. Also if you live at high altitude octane doesn't need to be as high due to lower air density, and during winter octane is usually lower due to colder inlet air temperatures that reduce the tendency to detonate.

It happens all the time that someone buys a vintage Corvette that has 11:1 advertised compression or rebuilt with "11:1 pistons" and think they have to run avgas, racgas, or some kind of snake oil additive. Most of the time it just isn't true because the engine was rebuilt sometime since the seventies with "low compression" and some don't need more than current 87 PON regular.

Duke

[Domenic T.]

Re: The 283

Very few engines left Flint with "11:1" CR due to high decks from broach tool wear just like like most left with ten percent or less of the advertised peak horsepower, and that was with the OE .018" head gasket. (two on 340/360 HP engines from mid'62 to the end of '65).

11:1 pistons doesn't mean much because that's with an assumed deck clearance and head gasket clearance. A high deck and thick head gasket can easily make those 11:1 pistons not much over 10:1. Get the spec on the pistons you have installed. I'm not familiar with Icon. The OE pistons have a net 5.3 cc dome.

Most guys don't really know the true CR of their engine because they or whoever "built" the engine didn't measure deck clearance and compute the actual CR with the installed head gasket.

Measure your head gasket thickness with feeler gages at the corners of the head-block interface and report back. Chances are it's a lot thicker than OE, so the CR is probably low enough to run on pump gas and not necessarily the highest available octane.

Today's 93 PON has about the same detonation resistance as 98 RON gasoline from the sixties, and contrary to popular belief sixties premium was not all 100 RON, but in a range from 97-100 RON and marketers only blended enough octane to minimize detonation complaints. Also if you live at high altitude octane doesn't need to be as high due to lower air density, and during winter octane is usually lower due to colder inlet air temperatures that reduce the tendency to detonate.

It happens all the time that someone buys a vintage Corvette that has 11:1 advertised compression or rebuilt with "11:1 pistons" and think they have to run avgas, racgas, or some kind of snake oil additive. Most of the time it just isn't true because the engine was rebuilt sometime since the seventies with "low compression" and some don't need more than current 87 PON regular.

Duke

Duke,
With all due respect, the last sentence says MOST of the time. What about SOME of the time for us that ping or have to make a 350 HP a 310 or something else by engine modification? Like to see dyno reports using real gas vs what we have. I can feel the extra power I get with a mixture of av gas, and back in the day of SONOCO 260.

Dom

[Duke W.]

Re: The 283

Sure, some engines might have the actual advertised CR, but they are in the minority, but many assume, apriori, that modern pump gas won't do the job. I always suggest running a test. Let the tank get very low and install three gallons of the highest octane pump gas. If it detonates check the spark advance map. Maybe there's too much initial advance or the centrifugal is too aggressive. If some rational adjustment, like lowering total WOT advance to 34 degrees doesn't quell detonation with the OE centrifugal , then you should probably consider a blend of pump gas and racgas or avgas.

If it doesn't detonate on the highest octane pump gas let it get low again and add three gallons of midgrade and redo the test. Eventually you will find the blend that allows the engine to operate detonation-free except maybe for extremely hot weather or high engine temperatures in heavy traffic, and that's what counts.

Duke