Technical Chevy 265 and 283 heads

Hi!

I am going to build a 283 for my 1957 Chevy truck, my priority is fuel economy.
I have two sets of heads to choose from 1955 265 60cc and 1963 283 60cc.
Do you guys know if there is a big difference in flow between these two types of heads?

I am going to use a 2bbl Rochester 2GC carb.
The cam will be a stock 265/283 truck cam.
Advertised Duration 263
Duration at .050 Inch Lift 172
Valve Lift 0.333

Best regards
David

 

Small ports in the 265 heads. They might be better for fuel economy in low power situations but very limited in power potential.

 

Casting numbers on the heads will tell us more

 

283 Heads #3796896

265 Heads #3713569

 

I don't think you will find that much difference performance wise for what you want them for. ONE consideration is what valve covers are you running. The 265 heads have the offset valve cover bolts and those particular 283 heads should have the one above the other valve cover bolts.

Back in the 1980's my son and I put a 307 with powerpack heads, a 300 hp 327 intake and a Holley spread bore 4 barrel with a mid 80's Z 28 Cam that came from the Portland Swapmeet for 25 bucks with lifters marked for the lobe they went with. With a SM 465 and 3.7 gears that thing ran like jack the bear for a city block and on the highway pulled 16 mpg on a road trip to Texas. Odd ball combo that worked.

Still on today's crap gas you are going to have to have hard exhaust seats installed.

 

Id honestly look at 305 ho heads.

 

What year intake. the 265 ports are smaller than the 283.
the 283s you have will be the larger intake and exhaust port size

 

If you want power then choose a 350.
If you want economy then choose a diesel

BUT if you want a cool old period correct Chevy Truck with a period correct engine it is a no-brainer.
Choose the 283 with 265 heads but you must use a matching 265 intake.

265's have different intake ports to all other Chevys and a 283 - 400 sbc intake cannot be used [you will also need 265 specific intake gaskets "felpro ms9200b"]
You will also benefit from having period correct staggered bolt rocker covers .

You'll end up with the engine breathing high velocity at lower rpm so it would be very driveable at low rpm.


We did exactly what you are proposing on our 57 Chevy [in my Avatar] This car still retains 3 on the tree ,so we wanted the engine to pull well from down low without constantly rowing the gears and be economical.

Our engine is the correct 3731548 block but we installed 1956 265 Chevy heads and 2 barrel intake.
We got a decent 3 angle valve and seat job done [so it flowed better just off the seats] and we used a Rochester 2GC with an electric choke.
The block was decked so the pistons were 0.005 above deck to raise the compression and we chose a different cam to your choice.
With high compression we wanted the shortest duration but highest lift cam possible [to get diesel like driving manners.]
We used "drop-in" Stock Valve Springs VS677 from Northern Auto parts which allowed up to 0.450" lift without any machining
The Cam was Elgin #CL1787PK 1200-4200 rpm 204/204 dur @ 50 .428 .428 lift [this cam has higher lift than your choice BUT shorter advertised duration at 260°]

Here's the cam specs


Here is the engine on the stand



The other mods were neoprene rear main seal, canister oil filter conversions, paper element air cleaner.
We used some MSD timing tape on the balancer and set the ignition at 36° Total and the Vacuum advance was ported [not manifold]
The engine has amazing low down manners which is needed for an old dinosaur with 3 on the tree non synchro 1st gear. [but it does fall on it's face at high rpm]

Depending on what year your 283 block is? If it was a later model 283 with scalloped lower bores , seriously consider a 327 crank and 307 pistons [ this is cheaper than decking the block]

Also you would get good mileage benefits from a decent 5 - 6 speed transmission.

 

Thanks @Mimilan
Good stuff

 

Are you saying the later 283 blocks are pre-clearanced for a 327 crank?

 

The 1964-67 283 blocks have sufficient room for a small journal 327 crankshaft.

 

Thanks, I was just reading on that, although the Hot Rod Magazine article said 62-67 blocks are pre-relieved, not sure which is correct. The 327 crank makes it a 307. I'll stick with my 283 crank.

 

Starting in '64, the passenger car 283s got cast crankshafts which required more clearance.

 

When the 327 came out in '62, 283s and 327s got the same crankcase core so the '62 and up 283s have room for the counterweights of a 327 crank.

Gary

 

The suggestion behind the 327 Crank [aka 307] is for a lazy economical engine with low RPM manners.
The added benefit of 24 inches of increased swept volume would negate the need to decking the block to raise compression [as we did]
You can pick up a crank for less than the cost of decking the block and intake [and 307 pistons cost the same as 283 pistons needed for a rebuild]

 

I got 10mpg in my bus with a 350

 

Thanks for all the information.

Do you know if there is a difference in flow between the different 283 heads with the 1.72-1.50 valve sizes? Or the only difference is the combustion chamber CC?

 

Bump