Hot Rods 283 sweet spot

Thanks this is the kind of info I'm looking for

 

3000 rpm is par for the course on an old truck with low gears and short tires. Why not get a vacuum gauge and go for a cruise, vary the rpms until you find the highest sustained Vacuum reading/rpm and find a tire/gear ratio calculator online. Figure out what gear ratios are common for the series S-10 frame you have(I don't know much about S-10 rear end interchangeability) and plug in the different tire sizes until you find the one that puts you at the desired RPM. Your 600 Edelbrock carb is too big for the combo. a 450 holley or 500 Edelbrock is a better choice for your combo.

 

Rpms and mph are very important for me, I'm running a 322 Buick and don't have a whole lot of rpms to work with.

 

Check with GPS if possible, my speedometer was off due to tire size, etc, so my mileage calculations were off.

 

Speedo was calibrated using a GPS. Also I'm gonna swap carb's with my coupe . It has a 350 and a 500 cfm edelbrock. I think the 500 will be a better fit for the 283 and the 600 will probably be better for the 350 I'm also going to go ahead and install the 700r4 I have and see where that get's me

 

I have had several bone stock 283 engines in various cars and I always tried for about 2300 rpm at 60 mph. Dual exhaust was the only change I made. I usually had a 3 or 4 speed manual transmission though. I averaged about 20 mpg. Hope this helps.

 

Thanks Norm

 

The 2200 (2 bbl) 3000 (4bbl) figures came off a list of Chev 283 HP and torque figures put out by Chevrolet in the sixties. The idea that an engine is most efficient at its max torque speed is an old rule of thumb. Your mileage may vary lol.

3000 does seem to be rather high, but don't forget we are asking a small displacement engine to power a large truck.

Based on my experience of Chev trucks, in this case 20MPG or even 18, is a pipe dream. 10 may be as good as it gets, you may get it up to 15 or even 16 if you throw enough money at it but don't expect more than that in the real world.

 

Gregg
The Edelbrock 600's were offered w and w/o electric chokes, the manual choke version has internal calibration for performance applications where the elec. choke version is setup more for fuel economy. The good thing about them is they have a good selection of parts available for fine tuning and the Edelbrock tuning booklet is pretty easy to grasp.

 

Try changing the tyres around the air.....
If you go to a taller tyre it would change things.
Trucks were designed to haul a load. If it has original diff that would explain a few things. Have you worked out diff ratio correctly ?
I would have thought 60 mph at 3000 revs for a '50s truck would be spot on.

 

I think the smaller carb and the 700r4 is going to change for the better mpg and performance. remember a 283 dates back to 1957 in a standard trans gearing was in the 350 range and 2speed powerglide was usually around 308 so with the s-10 gearing you have and 700r trans you are going to see about 2000-2500 rpm cruising so 15-16mpg should be attainable imo tom

 

The 283's I have run all like the 2400-2500 range
my suggestion was going to be try an overdrive but I see you came with that on your own. Might look for a 200r4. They will easily handle the 283 torque and you wont have to shorten the driveshaft and keeping the 3.73 gears will help the 283 get the heavy truck moving

 

You are going to sink a lot of money just to save a few bucks on gas. Sure you can put a 3:08 gear in it with your t-350 and drop your rs to 2500 or so , maybe even as low as 2300 with a 2:73. The trouble is, as mentioned before, a 283 is not a powerhouse engine on the lower torque end. They are what they are. A smaller engine with good HIGHER rpm response. I am afraid you may dog it down too much with a gear change. You may improve mileage with a cam change. Is your cam an off-idle cam or a mid-range? You said basically stock. A 600 unless its jetted lean may be dumping a lot of unused gas in the engine for a stock setup. Also, as mentioned before, put a taller set of tires on the rear and inflate them well, play with your carb as has been said, and you may stretch it out to 12-14. I have never really done much better than that. Have one under my work bench that's going in the 34 this summer. If it gets 12, I would be tickled. Good luck to you.

 

To find the RPM range for your motor you need to know what cam you have. Then look it up in the manufactures catalog. It should give you an idea as to the RPM range/power band of the motor. And of course there is the option of putting the car on a dyno to see exactly what you have. A 283 is not a high torque engine, so that might add to the equation.

 

I started off with a 283 (new rebuilt), 350 trans (unknown cond., but it seem to work alright). I would pull 2000 RPMs at 60 MPH, with getting around 18 MPG. Now this is in a 57 Chevy car. I let the car sit for two years, and my brother drove it a year. When I came back, after a good tune up, where everything was working the same before I left, I started off with 2300 RPMs at 60 MPH, with around 16 to 17 MPG. Added another 2500 miles, and I was going higher on the RPMs to maintain 60 MPH and getting 12 to 15 MPG. The decrease I felt was due to the trans slipping. I was pretty concern about gas mileage due to the fact that I was traveling along way to work and school.

 

Thank's for the response guy's . Today I checked my timing again . It was set at 10.0 and all in at 28.0 . I reset it at 16.0 with all in at 34.0. I am going to install the 700 r-4 this is a no cost swap for me as I am a ****** tech and already have the tran's and will swap right in with same driveshaft. Only mod will be to crossmember. Also going to install a 500 edelbrock that I have on a car with a 350 engine. I think the 350 will benefit from the 600 and the 283 will benefit from the 500. So while this might be a little work there is virtually no cost involved . Cheepsk8 I am aware that a 3.08 might bog it down that is why I am changing the tran's first. I am not rich and don't have extra money to throw around.However I can try these changes at no cost
Thank's I will keep yall posted
Gregg

 

The average nearly stock 283 should cruise fine from about 2200-3000. Your carb is probably sized close it would be more crisp with a 500 CFM but that depends entirely what mild cam means to you.

I am not a big fan of a stock GM HEI but you use what you got.

Most 283s got or get between 12 and 16 MPG, I have tuned them to as much as 18 but 12-16 is good on one and you will never get exceptional mileage with the HEI (if it is GM) and the Edelbrock. The eddy can be tuned as can the HEI but you need to remember that GM was trying to hit federal emissions standards with that distributer and the Edelbrock is an out of the box carb for the average street rodder and needs considerable tuning to make it reach its potential.

You can spin 3K without ever opening the secondaries, it depends on how your carb is setup. The eddy is depending on vacuum to open the secondaries, the 283 may not be pulling enough @ 3K to pull the ****erflies open. Maybe it is.

Something to think about is that the 283 is a short stroke motor and you cannot think of it in terms of a more modern long stroke motor. it reaches its potential in revs, not in low end grunt.

 

****** This is cam spec's Lift288/298 and duration is0.444/0.446 lobe separation 112 .
Gregg

 

I think you got lift and duration backward but its no biggy. With your heads and about 9:1 compression ( which is probably about where you are0 you should want to be running between 2500-3000 @ cruise. I would think closer to 2500. I'll bet the company claims off idle to about 5K but there tests are going to be on a more common motor and not a 283. you don't want to lug it, not good for mileage or the motor.

Those are actually pretty good cam shaft numbers for your little motor. I use a Lunati for most of my later cruiser 283 builds that have numbers really close to those. if you chose that cam you done good.

 

They actually do claim 1500 to 5000 . I thought it would be a decent cam. I was not building a race engine just a nice daily driver. I was kinda figuring around 2500 for cruise speed. I turn 2200 on my 350 chevy in my coupe and figured the 283 would like a few hundred more rpm. Thank's
Gregg
ps I did choose that cam .

 

You probably hit "Ctrl+Shift+I" instead of just "Shift+I" when you started this sentence. "Ctrl+I" changes the font style to italics. "Ctrl+I" again changes it back. Yeah, that's right... I've got fat fingers too.

 

How about installing a vacuum gauge in the cab of truck connected to a source of full manifold vacuum? Drive it for a few days and watch what the vacuum is doing under different conditions. Watch what happens when you barely move the throttle, when you're pulling a grade and when you're coasting downhill. Then post back here what kind of vacuum it's pulling at idle in neutral, at idle in gear, at a steady 35 to 45 mph, at a steady 55 to 65 mph.

 

P'n'B, If I can partial hijack here (but 283 related), this thread is schooling me on the characteristics of the 283 short stroke engine.
In my 32, it has a stock 57 283 mated to a 40 trans. I was told by several that the 283 would be easier on the 40 trans (on first gear starts) than a built flatty because of the torque difference at low rpm.
Is that what you're kinda talking about here.

 

Hi Gregg,
There is where your gas mileage went! If you want mileage you need to stay under the 250*-260* range. Also you want lots of lift for torque (.490"-.500" range). It won't have that rumpity-rump your after, but the mileage and drivability will be there. Ask me how I know...

I use a Comp 262*-270* Extreme Energy with 1.6 rockers to achieve this in my blown 385 cu. in. Chevy and it gets 19-20 mpg @ 2200 rpm / 70 mph in the '32 with a 750 Edelbrock.

It was getting 22 mpg with a 250*-260* XE, before I went hunting for some rumpity-rump! Four cams later I settled for the 262 XE.

I know this ain't a 283, but I think I could get at least 25 mpg with a 283.
TR

 

More or less. The flatty is a low RPM motor as compared to most valve in head motors. part of that has to do with breathing characteristics and displacement as well as weight of internal parts. But part of that has to do with bore to stroke ratio.
Snag some numbers and compare bore to stroke ratios of the flathead and the short stroke SBC. I think that you will find that with the bore to stroke ratios it will appear to be a long stroke motor. Not actual numbers but ratios. The short stroke GM valve in head motors have a tendency to be bore heavy. if that makes any sense to you.

 

Yeah, looked it up. The 283 is making more torque than the flatty at any given point.
gauging from a chart, looks like about 145 ft lbs for the flatty at 1000r's vs 205 ft lbs for the 283 at 1000r's.
So much for the easier on the 40 Ford trans idea...... It's about how much foot you use.

 

Direct from FORD, This suggests a stock 239 CID 1953 Ford flathead is about 180 ft-lbs at 1000 rpm.

Chevy claimed the 265 was over 200 net ft-lbs.

 

Back in the 60's a 3:08 gear was pretty standard for a 283 and a P/G ******.

 

That's what I understand. If I was leaving the 350 trans in it I would consider going to a3.08 . I installed a 500 edelbrock today and set my timing to achieve 34 degrees all in. I will drive it a week or so before installing the 700 r-4 . Montana thank's for your input. I do have to disagree with you. I'm pretty damn sure that's too much cam for a mild 283 . I did not pick this cam for a rumpity rump idle.In fact this cam has a very smooth idle. Maybe someone smarter than me about cam's"pork&******" can chime in on this one.
Gregg

 

maybe this cam? numbers are close.

http://www.summitracing.com/parts/sum-k1103/overview/

214/224 at .050. Yeah, that's a tad big for a mileage cam, rpm range 1600-5200, but it should work ok at 2500 rpm.

It is a truck...

Wonder how the recent ignition timing change affects mileage?