Rebuild A 351w Or 302

Steven Pech · Jun 7, 2017

Ok guys. im on the fence between rebuilding my 302 or going to the junk yard and buying/rebuilding a 351w. My goal is to try and hit the 400 hp range. im trying to keep it street/strip. I just need pros and cons. I am a first timer and pretty new to the game. From the research I've been doing I've found that rebuilding either or will cost about the same. I would like your opinions and suggestions. Thanks.

Davedacarpainter · Jun 7, 2017

351 will give you lots more options for the future.

Way easier to hit your power goals as well.

The 351 is a much stronger engine as well.

Go for the 351.

hoopty5.0 · Jun 7, 2017

^ this, but be prepared to spend more money on parts. You'll need several different parts that don't carry over from the 302 - Intake, exhaust, flywheel/flexplate, balancer, and distributor, just to name a few.

General karthief · Jun 7, 2017

^^^ room to grow will offset the increase in cost vs the 5.0, I think you can get 400hp easily and be more streetable than the smaller displacement engine. Just my opinion.

90sickfox · Jun 7, 2017

351....don't be like me....

I have the ability to make more power....but the block won't take it.
A 351 doesn't have to work as hard to make the same power = longevity.

Mustanglimey · Jun 7, 2017

If you have the option to do either 351w is a no brainer

Bossed · Jun 7, 2017

Even if they make similar horsepower, the difference in torque is significant . I had a 302 years ago in a Mustang II. Small chamber 289 heads with larger valves, ported and polished, Crane Camshaft, Edelbrock Torker II intake. I built a 351 Windsor, using the cylinder heads and camshaft from the 302, same style intake manifold (for a 351W). The car felt like it had twice the power that it had before. Torque is awesome.

revhead347 · Jun 7, 2017

302 hands down, no brainer. Been there, done that. You can build a 500hp stroker 302 for the cost of putting a crap rebuilt 351W in your car. You spend the extra for 351 swap header, the distributor, the motor mounts, oil pan, and you just exceeded the cost of a 4 bolt Dart 302 block that can handle 2000hp. And that's not all the parts. Plus the hood probably won't fit, the spark plugs are harder to get to, the AC lines have to be refitted to clear the headers. Then add 100 other complications I haven't added in this list.

Understand how an engine makes power. The bore is the same on a 302 and 351. The bore is the displacement measure that determines the combustion pressure. The flow rate of the head (couple things aside like valve angle and shrowding which are the same for both engines) determines how much power it can make. The stroke only determines the RPM at which max power is made. A few 100 rpms back and forth can be adjusted with cam retard. There is a bunch of exaggerated info on how much more power the 351 block can handle, but that is predicated on drilling the stock block for 4 bolt mains. An actual stock 2 bolt main 351W isn't much stronger than a stock 302.

Kurt

NIKwoaC · Jun 8, 2017

revhead347 said:
302 hands down, no brainer. Been there, done that. You can build a 500hp stroker 302 for the cost of putting a crap rebuilt 351W in your car. You spend the extra for 351 swap header, the distributor, the motor mounts, oil pan, and you just exceeded the cost of a 4 bolt Dart 302 block that can handle 2000hp. And that's not all the parts. Plus the hood probably won't fit, the spark plugs are harder to get to, the AC lines have to be refitted to clear the headers. Then add 100 other complications I haven't added in this list.

Understand how an engine makes power. The bore is the same on a 302 and 351. The bore is the displacement measure that determines the combustion pressure. The flow rate of the head (couple things aside like valve angle and shrowding which are the same for both engines) determines how much power it can make. The stroke only determines the RPM at which max power is made. A few 100 rpms back and forth can be adjusted with cam retard. There is a bunch of exaggerated info on how much more power the 351 block can handle, but that is predicated on drilling the stock block for 4 bolt mains. An actual stock 2 bolt main 351W isn't much stronger than a stock 302.

Kurt

Longer stroke = more piston swept volume, AKA displacement = more air/fuel mass per revolution = more power. MM&FF did a pretty great test on this a few years back, they ran a 306 and a 347 on the dyno, with identical everything for the top end parts, right down to even having the exact same CR. The 347 made significantly more power and torque everywhere in the rev range. Linky: https://goo.gl/uuOY4o

In regards to your statement about block strength, there are lots of examples to the contrary, but maybe one of the best is TonyR85 over on Yellow Bullet. His completely stock shortblock 1990's 351 has been running 8s in the 1/4 @ mid 150s for like 3 years now. Makes like 850ish to the tire. IIRC his first failure was a bent rod. You're just not gonna see a stock 302 do that.

revhead347 · Jun 8, 2017

NIKwoaC said:
Longer stroke = more piston swept volume, AKA displacement = more air/fuel mass per revolution = more power. MM&FF did a pretty great test on this a few years back, they ran a 306 and a 347 on the dyno, with identical everything for the top end parts, right down to even having the exact same CR. The 347 made significantly more power and torque everywhere in the rev range. Linky: https://goo.gl/uuOY4o

In regards to your statement about block strength, there are lots of examples to the contrary, but maybe one of the best is TonyR85 over on Yellow Bullet. His completely stock shortblock 1990's 351 has been running 8s in the 1/4 @ mid 150s for like 3 years now. Makes like 850ish to the tire. IIRC his first failure was a bent rod. You're just not gonna see a stock 302 do that.

You're talking about Tony Reiners. He's in the Sloppy Mechanics junkyard motor division. He pulls a motor out of a van fills it with Chinese hardware and sees how many runs he can get out of it before it blows. That's what those guys do over there. I think it's awesome, but let's be honest, most people value their time a little more than that.

In your article, they used TW 185cc heads, much bigger than a TW 170cc head, which is exactly what I am talking about. In the long long ago, way before this article, MM&FF did the same thing with a stock motor 302 vs a 342 rebuilt both with the stock top end. The 342 made about 6 more hp, which they attributed to the rebuild. You see how neither of these is relevant.

Kurt

Rebuild A 351w Or 302

Steven Pech

New Member

Davedacarpainter

Chicks can make things hard if they’re inspired...

hoopty5.0

mechanicus terribilis

General karthief

wonder how much it would cost to ship you a pair

90sickfox

Wasn't a pretty sight...and I've got big hands

Mustanglimey

Active Member

Bossed

Well-Known Member

revhead347

Apparently my ex-husband made that mistake.

NIKwoaC

中國製造

revhead347

Apparently my ex-husband made that mistake.

Similar threads

Rebuild A 351w Or 302

New Member

Chicks can make things hard if they’re inspired...

mechanicus terribilis

wonder how much it would cost to ship you a pair

Wasn't a pretty sight...and I've got big hands

Active Member

Well-Known Member

Apparently my ex-husband made that mistake.

中國製造

Apparently my ex-husband made that mistake.

Similar threads

Privacy & Transparency

Privacy & Transparency