Hot Rods 283 sweet spot

Jim the 1103 is the cam I have. It is the mildest cam summit offers.We will see what happens after crab and timing changes by end of week.Jim do you think the comp 262_270 that Montanal in post 54 suggest would be a better choice ? I don't think these small motors like that much lift in a basically stock engine.
Gregg

 

I would not bother changing the cam...the extra power you get is probably worth the small sacrifice in mileage. The cam you have is not as bad as some guys seem to think it is.

 

Not to worry I have no intention of changing cam's. I will likely live with what I have after the trans swap.
Gregg

 

I know it's apples and oranges,but years ago I had a 283 in a Chevy LUV pickup with a Saginaw 3 speed w/overdrive that got in the low 20's for mileage on the highway. 4.10 rear gears and short 60 series 14" tires. I don't remember the rpms it was turning. Got better mileage than the 4 banger I pulled out if I drove it nice.

Gary

 

I'm interested in what the Edelbrock carb and timing change did for it. No rush,I'll check back.

 

For what it's worth before changing timing I only had 28 decrees all in.
Gregg

 

Man..... I think you just found a big part of the puzzle here.

 

Gregg,
I would use a 250*-260* XE in a 283. That's advertised duration NOT @ .050" lift. Then I would gear it accordingly. Small motors like small duration for mileage. Larger motors are a little more forgiving in over caming.

XE cams have a faster ramp than other cams of equal duration. I still think 1.6 rockers would benifit the 250*-260* XE. Generally more lift per degree of duration makes more low end torque and 1.6 rockers is an easy way to get it.

Also, I like 110* Lobe Separation Angle instead of 112* or higher. More LSA takes some of the rumpety-rump away by taking away overlap.

I had a 1103 Summit cam and it was lazy compared to the 262*-270* XE. I also tried a Comp "blower/turbo" cam with 115* LSA. It was identical to a stock emissions controled 305 Chevy. What a dog that was. I could feel it in the seat of my pants!

I took it out and threw it away after only 300 miles!

If I was in your position, I'd run what you have and tweek it a little and live with it. You might try advancing the cam about 4*, but the next time, I'd make some major changes. IMO

Get a copy of "Desktop Dyno" from Comp and play with all the perimeters and see what you need. It's fun and we may all learn something.

 

Hey Greg, Long time No talk! i've been reading your thread.You know i have one of those trucks and it may weigh a little more than you think. But anyway, just wondering if you had put light springs on your dist advance. I would think you would want the timing to come in pretty early on the size truck? Not sure that would help a whole lot but couldn't hurt.

 

My 283 combo specs out as follows :

.030" up, cast slugs, 305HO heads,
9.4:1 CR,
cheap Summit 1102 cam, roller chain
Eddy Performer, Holley 465, 1" 4 hole phenolic spacer,
Mallory DP dist with trailing point removed firing hidden MSD box,
2" rams horns and dual SS 2" exhaust,
shift kitted T350 with stock vertor,
57 Chevy rear with 3.5 gears, 28" OD Firestones.

Its in a 46 Chevy coupe.

Car runs killer, its great on fuel (6.6ltrs per 100kms on a recent interstate run) is punchy down low and when you stab the throttle and will chirp the Firestones from 1-2 and sometimes from 2-3 as well.

When looking at cam selection I was careful to choose a cam that that suited the trans, gearing and weight of the car/small CI and to keep the airspeed in the intake as high as possible with the small dual plane, carb venturi and four hole spacer. Slightly hotter plugs and the MSD burn it properly and plugs stay clean.

Very happy with the street performance AND the mileage.

 

Gregg, its easy to sit at this desk and spend your money. I seldom watch threads as closely, but 283s are my favorite engines. Second to that a 327. I did a similar task in an OT 3200# chevy by replacing a tired 350 t-350 with a 1965 model 283 and rebuilt PG. The engine was BONE stock and the rear was a 3:08. Yes mileage was important to me, as gas was 2.50 or so a gallon during an oil embargo. Here is how this went. With the 350 burning oil and all, 22 mile one way 2 lane to work. I averaged 14. This was with a q-jet, points and all that was in a 1970 chevy. Put the 283 in and averaged 12. Run the air and 10-11 was your best. All my buddies said, open the exhaust, get a breather, change the cam, ditch the PG. OK after headers, open breather, a crane aftrmkt cam [don't remember the grind, been too long] and installing a torque robbing t-400 I" boosted" my mileage to 12. I ONLY squeezed another mile out of it by going to a 2bbl. Moral of this story is this. You are not the only person that has had this set of problems. I know now that my avatar weighs 2400 LBs and the 283 will power it just fine. You have not mentioned the weight of your truck, but quite simply, weight robs fuel mileage above all. You are going about this the right way. One thing at a time. I finally threw in the towel and put a sign in the window of that car and never looked back. I have just chalked it down as a learning experience. Chevy discontinued that motor for a larger displacement for a reason, but it sure is a fun little engine.

 

Cheepsk8 I hear where your coming from. This truck is just an s-10 with a different body and engine. A stock s-10 weighs about 3100 lbs. I don't see this truck as being much if any heavier than that. Like I said before I'm not looking for Prius kinda mileage. I think I had some tuning issue's that hopefully between the smaller carb and getting timing right solves part of the puzzle. For what it's worth this engine run's so damn nice it's unreal. I honestly think the gearing is a major factor in the equation. I will install the 700 r-4 in a couple week's but first I want to see what the carb and timing changes get's me .If after the trans swap I'm still not getting the mileage I want then I will just live with it because the truck is an absolute pleasure to drive. But I'd like to have my cake and eat it too. You are right about these 283s I have one in my roadster with an Duntov 097 solid lift cam and it run's so much better than the 350 I used to have in it.
Gregg

 

I do, Gregg. My 27 turned 3,000 at 60 when I had the 4.30 gears in it. Then I went to 3.70's and it is now at about 2400 at 60. The engine is much happier and gas mileage seems a lot better. I bet if you went to something in the 3.23 range or even less, it would help a lot. Just think what overdrive does and how it affects gas mileage, or if you drove around in second gear instead of 3rd gear. Reducing rpms does help a lot.

Don

 

Thanks Don that's why I'm installing a 700 r-4. Hopefully that will get me where I need to be.
Gregg

 

Gregg, I just had to run some errands, and I checked the tach in my daily driver Caddy just out of curiousity. At 60 mph I was taching 1750 rpms, and my car gets 27 mpg at that speed. I realize it is a computer controlled, fuel injected V8, not a carbureted sbc, but I think the reduction in rpms really accounts for a lot too.


Don

 

just for amusement....my wife has a later model full size Chevy truck with the little V6, 262 cubic inches. It has 3.42 gears, tall tires, 4L60E (computer controlled 700R4, basically) and weighs about 4500 lbs empty. it gets 20 mpg most of the time. But we live in the country, we don't get into much stop and go traffic.

 

I think 60 at 3000 rpm is high-but the 'math' is the 'math' so to speak. Your combination of gear and tire size is what it is. If you swap out to a700r4 with a .70 overdrive you would be turning70% of what you are now with the converter locked-so 2100 rpm at 60 mph which would likely do wonders for your fuel economy and your engine life, engine bay heat rejection, noise level, etc. If you swap to a 200r4 which is close in size to a TH350 the OD ratio is about .67 or 67% of what you are turning now-just over 2000 rpm at 60 mph (assuming your speedo is correct now)

 

Angel you are right the math is the math. So I have to change the
Number's. So the700 r-4 will be going in shortly
Gregg

 

If it helps you: I had a big ol 66 impala with a factory original 220 hp 283/3 speed stick with a 3.36 ratio 12 bolt. Car came with a 4 barrel [Q-jet in '66] and dual exhaust. I never checked mileage in town but on the road it got a solid 19 mpg....with no overdrive. Back tires were about 27 inches tall. The car had no power robbing options except power steering . I'd have to estimate the RPMs at about 2700-2800 at 60 with the 3.36s. Had lots of punch for a little engine. The sweet spot was at a little higher RPMs than a little 195 HP, 2 barrel engine because of the bigger cam [not much bigger]...loved that car

 

I think my Mom's bought new '65 Chevelle Custom 300 4-dr with a 195hp/283, 3-speed stick had a 3.36 10-bolt under it along with, (I think?), 7.00/14 tires got right at 20 to 22 mpg on the Hwy driving easy at 60 to 65 mph.

So please look at weight, rear end gear, and rear tire dia.

pdq67

 

I hope that with the timing change you made you noticed a big improvement with performance and mileage.
What did you set the total timing at 34 -36 Degrees?
I am really worried that if you change to the O/D Tranny that the short stroke 283" will not be able to pull the O/D Gear and will actually get worse mileage than if you left it in Drive.
The Truck @ 60 MPH is pushing a ton of air out of its way and you cannot compare it to a car in this respect.
Just my thoughts, I would like to hear if anyone else thinks the O/D is questionable with the gear, Engine stroke, & Truck Body configuration.
Good luck with it!

 

Well fedman at worse if OD doeesnt work I can just put it in drive instead of OD . Oh yea I did set the timing at 34 degrees all in

 

Hair over 2500 rpm..

 

Heck gas is below $2 a gallon. If your that worried about gas consumption. get a motorcycle.

 

There's one in every crowd ! First I'm not looking for an economy car I just want to maximize what I have. This truck is going to be my daily driver and it would be nice if it was somewhat economical. Besides can you assure me that gas wont go back up to 4.00$ plus again. If the extent of your participation in this thread is to be a smart ass then go somewhere else. Old I find it ironic that your bustin my ball's when I find a thread you started called' gas hog' where you are guess what ' yep complaining about gas mileage. So if you have something constructive to add then fine other wise go play somewhere else.
Gregg

 

12 to 14 MPG was all the 283,s got back in the day when they where new. and they commonly got better fuel economy than the 235 six. To do a certain job it takes a certain amount of energy(fuel) there isn't a magic carb or anything that will change that fact. the easiest thing you could do to increase fuel economy would be to drive slower. You could install a fuel injected later engine like a 4.2 V6.

 

Yes-or put your converter on a manual switch-it'll still go into 4th gear but the converter wont lock until you tell it to.
Your 4 speed auto will work like a 5 speed.

 

Wolf first off I would be happier than a pig in slop with 14mpg.like I have said allready Im not looking for this truck to be a damn prious.Second Im well aware that it takes a certain amount of energy to do a job. I have been in the car business for over 40 years.Having said that thhis is only my ssecond 283. My other283 is in a 2000lb roadster. It does get 18/19 mpg. But its like comparing apples and oranges due to the size and weight difference

 

Is that around town or on the highway,my convertible got 15 to 16 on the trips down your way going 70 to 80 and I have a bigger motor. That 283 is getting the same mileage as my 66 F100 with a 460 so something wrong.

 

Thanks Angel thats how I usually hook up O.D. trannys. Thats what I do for a living .Note I hook them up like tha in hot rods