In my opinion the 302 head is for a mpg 318 or 360. They have 4 or 5cc more chamber volume then the 273 closed chamber heads and the extra cc ends up adding crevice volume and less quench area on a 273 with it's small bore. It is hard enought to get compression or quench with the 273s bore. The 302 would be my second choice but not the first

I would use an Isky Supercam 262 part #390126. It has 262 seat duration which is fairly short for torque. It has .435 lift which is more than the old 340 cam and has [Email]208@.050[/Email] lift. And best of all it is cut with a 108 LSA lobe separation which will keep compression up if you are using low compression pistons. The tight LSA keeps torque high but limits your topend rpm, not really a factor in a street truck. I would also advance that cam 2-4* also good for low rpm torque which you need in a truck with a small cubic inch engine. I know everybody likes the new modern cams like voodoo and xtreme energy comp cam but just try to find a small cam that has a 108 LSA in those modern designs. Its not so easy. IMO that would make a nice cruiser truck engine with probably as much or more power than a 318. This is an old school cam but a 273 is also old school. This cam is available from Summit Racing for about $136
ISKY - Grind No./Type 262-SUPERCAM HYDRAULICLow/Mid-Range performance cam. 9.51 compr. 3.08-3.70 axle ratio. Passenger cars and trucks. Up to 625 CFM Carb.RPM-Range 2000-5500Valve Lift - INT .435 EXT .435Valve Lash Hot - INT

cam, I'd look at the lunati voodoo 60400 or 60401, use comp #901 springs. try get as much compression as you can....

IF you have to go buy new pistons, you'd be better off starting with a 318 magnum, redrill the heads to LA pattern, regrind the roller cam, and put your induction on it. you'd be looking at 300+ horse & torque with better drivability.

I'd start with your 273 block and bore it 0.030. Use the 4" crank, stock length rods and custom flattops. You're now at 335 cubic inches. Or the 3.58" crank right at 300 cubic inches. I'd use Magnum heads with a decent valve job and a Performer RPM. A 600-625 cfm carb would top it off. I'd suggest a single pattern cam with about 210 degrees duration and the biggest lift you can find ground on a 110 degree LSA. With headers you'd be above 300 hp and 350 lb-ft torque easily, it's pull so hard you would be amazed.

It's so much easier to make power with a slightly bigger engine and you won't have to run 4.56s to keep up on the street.

R.

Back in the 70's i remember reading an article about tuning the hipo 273. They said to switch pistons from side to side. I never did it but i'm sure someone here knows what advantage you'd gain. I don't know if it would be the same outcome as a non-hipo 273.

Just for no reason...

Here is the 273 my buddy is Oz has just about finished building for his ute.

(just has a couple little things to do then it's going onto the run stand to get broken in.)

Thanks for the help everyone! Its cool to not see a bunch of people bashing my little motor. Its a 66' virgin block. Id like to keep the solid lifter setup but I can't seem to find a very big cam selection. So far I have an a833 od trans for it,an offy dual fours intake, 4.10 suregrip rear and a 29" tire to run in the rear. I don't know if this helps at all, just throwing it out there.thanks again for the help!

Nothing wrong with a 273, especially if its sentamental, a strokers would be great but doesn't make sence at a dollar standpoint. Looks like you have some good advice so far and should have no problem exceeding your HP goal, a 273 will like to rev so buy a good set of rods and have fun with that 4 speed.

The stroker concept is really easy to justify. You spend more for the crank, maybe a little more for the pistons (273 pistons cost about the same as custom forgings) and save on the valvegear because you don't have to have super-dee-duper springs, etc. The stroker engine doesn't need to see 7000 rpm, the 336 will be drawing the same air at 5800 rpm, the 300 at 6400. There will be a torque increase to the torque peak proportional to the increase in displacement. After the torque peak it'll fall off faster with the same heads but as a decent set of Mag heads are good for about 400 hp I think that's no worries either. I think with the right cam, headers and a little work on the heads you're looking at a 380 hp engine from the 330, and an easy 360 lb-ft of torque.

Notching the block is not difficult, there's a pictorial on the Web by Bigblock Ranger. He did it with pistons in the block, used coffee filters to catch the shavings.

The one problem to which I have no answer is will the rods hit the bores with the piston about halfway down. This comes out of reading, I remember that when Oldsmobile stroked the 425 to 455 they used shorter rods as the stock 425 rods supposedly contacted the lower edge of the bore.

Of course you could build a 360Mag based motor for the same amount and have a better engine, but with the OP's restriction to stock 273 block this is the best way to have a streetable engine with a ton of power, short of nitrous or a supercharger.

R.

The 3.09 first of the OD box and the 4.10 rear may be more like a truck with a granny low.....

Someone brought up flipping the pistons around. This only works if the wristpin is of the offset variety. I do not recall if it reduces friction, thus increasing power or if it changes the effective duration at TDC which would also have an effect on power. Perhaps someone more knowledgeable in this area will pipe up.
Keep it simple. The power you're searching for won't require big dollar pieces and the cost of a custom ground cam to keep the solid lifter setup while also gaining you the cam specs you want is barely any more than a shelf spec cam. You will want as much compression as you can get as a small displacement engine is difficult to make reasonable squeeze and you'll want as much airflow as the heads you choose can supply. Don't go with too much port volume.