Hey all, I am looking for some info on how I should build out my 302 that is going into my 1980 ford, I attempting to build it out for low end tourqe. I have several items picked out, the edelbrock 2122, edelbrock 1406 and either a factory intake, or edelbrock 2121. I am curious about what modifications should be made to the bottom end, heads, and valve train. There is a local machine shop who will be able to help me out. Any help would be greatly appreciated!

 

What is your definition of "low end toqure"? Your user name has "diesel" in it so I'm preparing a disclaimer about how the 5.0 will forever be a '90lb weakling at anything below 3000rpm no matter what parts catalog you throw at it.

 

The problem with the 5.0 engine when it comes to a torque build is that it is only 302 cubic inches. Without forced induction torque comes from displacement and it just doesn't have a whole lot. With that said, keeping the port cross sections small, cam duration short, running long tube headers into collectors that are the right length and diameters and a carburetor with a good fuel curve will be surprisingly more effective than a stock engine. I think it could make around 315lbs pretty easily.

Earlier this year I finished up a 5.0 build for a customer that was interesting. It had a set of the smallest AFR heads, stock HO 5.0 cam with 1.7 rockers, headers and a set of Weber IDA carburetors. It made 382lbs/ft at the peak and at the start of the tests it was making over 340lbs at only 2700rpm.

 

last 302 i built was turned into a 347 inch, made 425 Horsepower / 415 FT. LBS. Torque

 

That's the way to do it, more displacement for the win.

 

A 302 will never bee a torque monster. Yeah, you can add a bit more with the milder parts you've mentioned, but 302s like RPMs to build power. 302s have a 4.00" bore and a 3.00" stroke. Think about that for a moment. Only 3" stroke as your 'lever arm' for torque. The 300-inch (4.9L) straight six has the same bore but a 3.98" stroke. Think stubby ratchet handle vs breaker bar. Much longer lever arm yielding gobs of low-end torque, which is why the 4.9L was used in trucks for so long. Much more power where it is needed at lower RPMs than a 302 V-8.
Then you start to get into the 'there's no replacement for displacement' argument into stroking your 302 to a 347. OR--- A 351W will fit where your current 302 resides. Or, stroke the 351W to a 393W or 408W. Again, torque is your truck's friend!

 

If two engines have the same displacement per cylinder one with a small bore long stroke and one with a large bore short stroke it makes no difference in the amount of torque output, it will be identical with the same amount of pressure in the cylinder.

 

But they (5.0 and 4.9) don't! The 4.9 has 50 cubic inches per cylinder, and the 5.0 has 37.7.

Then we'll get to the Ford 427 vs 428 of the 1960s. Both were similar-block FE V-8s. The large-bore/short-stroke 427 was built as a high-rpm screamer, whereas the the 428 was a smaller-bore/longer-stroke lower-rpm torque motor. The long stroke 428 has its peak torque at a lower RPM than the short-stroke 427.

 

The 300I6 displaces 50 cubes per cylinder.. same as a 400 V8, while a 302 V8 only displaces 37.5 cu.in per lung, that is where the torque comes from. The I6 would be a monster if it had a cylinder head that flowed like a big block V8 head.

A great case study in the differences(or lack there of) bore and stroke makes in any given displacement is between the 4.6 and 5.0 V8s, there isn't enough difference IMO to choose one over the other they are both weaklings at low rpms in a heavy vehicle like a truck, in both cases the answer to better performance is more axle gearing.

 

What you gain in leverage from the longer stroke you lose in piston area and the force you have to work with in exactly the same amount. The only reason there would be any difference in performance between the 427 and the 428 would be from other factors than the bore/stroke ratio. When I get home I'll run the numbers and show you. The best example I always use for this is a 400 Ford 4X4 vs a 400 Chevy 4.125 X 3.75. Those bores have to be adjusted very slightly to make each engine have a cylinder that is exactly 50 cubic inches but what happens is if you pick an amount of pressure, say 200psi X the area of the piston X the stroke the number produced is identical.

Interesting too. If you keep the rod/stroke ratio the same with each combo the piston sweeps the cylinder at an identical rate. The rate that the volume changes per degree is exactly the same.

 

Here are the numbers: To make this work right with a 50 cubic inch cylinder roughly 4x4 and 4.125x3.75 the bore sizes need to be adjusted a little bit. The 4 inch stroke engine has a 3.9904 bore and the 3.75 stroke has a 4.1213.

Now just using a cylinder pressure of an arbitrary amount, 200 PSI what we get for numbers are:

4 inch bore(3.9904) ends up with 12.522 square inches of area on the top of the piston that X 200 = 2504.4 lbs of force. This force is multiplied by the stroke of 4 inch with a throw of 2 inches to get that = 5008.8 lbs.
4.125 bore (4.1213) ends up with 13.333 square inches of area and that X 200 psi = 2,666.6 of force. This force is higher but it is multiplied by a lesser amount because the stroke is only 3.75 with a 1.875 throw distance which gives 4999.8 lbs. This is within .2% and that just comes from me cutting off the decimal places to make my calculations easier.

 

The first truck that I ever drove was a 1976 F250 with a 300-6. I thought the engine was a slug and would never have called it torquey. From the factory, the 302 put out more torque at 1000 rpm (and at peak) than the 300-6 did, so I don't really understand why people think that the six is some kind of a torque monster. It definitely doesn't compete with the 351W trucks that I have driven and not even in the same arena as the 440 in my Challenger. Dave is correct that two engines, with the same cubic inches will produce the same torque, given the same cylinder pressure. You may move the torque around a bit by changing the bore to stroke a bit, but you really just need to increase the size of both of them to get a real torque monster. My suggestion to the OP would have to be to stroke the 302 to a 347. Beyond that, it's a question of how much of your money we can spend.

 

and they were when we made the head, i worked with a now late friend whose name was jerry meade, from paramus nj ,who ran a altered opal gt,in i /gas

with a motor like this one, 3 boss 302 heads sectioned, furnace brazed the chambers into a head ,man could that motor sing

 

funny one dave
we did a 331 for a cobra, that motor made the same power levels as the 347, up side of the 331, was the power came on at a slightly lower rpm making it a tad more streetable with MSD EFI and ignition a mild roller conversion cam set up as to title the car in jersey without having to add cats we used a 68 block . which we didn't want to stress to much

 

What all of this is really all about is mean intake port velocity which is simply the average air speed through the port. This is important because at the intended RPM level with the amount of displacement per cylinder a certain mean port cross section is needed to produce the right velocity. This can be calculated using programs like Pipe Max and others quite accurately. Then the port can be tested on the flow bench to measure using a pitot tube and by checking the CFM to know if it is right or wrong. Too fast, wastes too much energy due to pumping losses, too slow and the cylinder is not filled as effectively as it could be.

As an example back in 1980 and 1981 my dad worked on a circle track racing team that ran Ford engines in USAC and in NDRA dirt late models. The engines that they used came from Jack Roush, the USAC legal 355 inch engines made about 525 horsepower at around 7800rpm. The dirt car used a stroker combo of around 400 cubic inches. The basic engines were the same otherwise but the larger engine made almost 100 more horsepower at I think about 7400. In 1981 USAC changed the rules and allowed smaller lighter cars but those could only be 305 cubic inches. They had Glen Bopp build a really nice Mustang and Roush built a Boss 302 based engine. He struggled to get it to make 500 horsepower and in the race car they turned that engine over 10,000 rpm to make it competitive. It was all about the the port velocity and those heads were so big that the bigger the better clearly applied.