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302 v 351
I know this is a broad question, but we're getting ready to purchase an FFR kit and are trying to decide between the 302 and 351. What are the big disadvantages of the 351 and of being overpowered? And do many 302 owners retrospectively wish they'd gone bigger?
I'd love to hear from both 302 and 351 owners if they would have gone the other route, and if so, why. Thanks! |
Briefly, they are basically the same block. There are just as many performance parts available for each. Weight is basically the same also. However, you get alot more hp to wt ratio with the 351. Unless you stroke the 351 out to 400+ there should be no overpowering issues. If you build a nice mild 351W you will have plenty of power and will have a dependable engine.
Roscoe |
Don't often see the words "351W" and "overpowered" in the same sentence...:JEKYLHYDE
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I agree with Roscoe - for a street car I'd go with the bigger engine for the same horsepower. It isn't working as hard and will (all else being equal) last longer. But that's just me.
351 cost is about the same - 1 company does a 325HP 302 for the same price as a 410HP351. Both those HP's will get you in a whole world of trouble if you bust them loose at the wrong time .... I think (others will confirm) that there may be an advantage with the 302 in autocross - slightly lighter engine which helps when you are go-left-right-stop-go-right-left-right-left-stop-go-right etc There is an issue with the heat a BB puts out (roasting your feet in the footwells) - but a 351 isn't really a big block - so that shouldn't be much of an issue - but I'd insulate the footwells regardless of the HP you use. regards |
From my perspective...
I have a FFR with a 302 in it... It is about 300 HP and runs great. However, if I were to do it again, I would go with a 351 based motor. For the reasons that Roscoe and Doug state. Mike |
Thanks for the input. This is our first kit / first cobra, and right now we plan to use it mostly as a street car. My biggest concern is that the 302 doesn't seem have as much room to grow if we want to trick out the engine later.
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delin,
Being in Joisey you might want to talk to Chris at Engine Factory. You can get a turnkey or a short block and build it up yourself. http://www.fordcobraengines.com/Cobrakitpack.html Roscoe |
How much "room to grow" do you think you'll need? A 302 block is good to 450-500 safe hp, and even more with a bottom-end girdle. And that's not even an A4 or R302 block -- I'm referring to a street 2-bolt mains block.
To get there, you can make a good streetable 400hp N/A, but you'll lose low-end smoothness if you open it up more (still N/A). Supercharging or turbocharging (probably not too easy in a Cobra) will give you everything you need streetably. That's where the 351W shines -- you can do more hp with a smooth idle. But yes, it'll add some weight. I still feel that overall, 302 mods are far more readily available than 351, but that's not from any scientific data. If you'll stay carbureted, then perhaps the 351 is the way to go. I started life with a 302 thinking it'll be all I need in such a light car, but 8 years later I have 500+ hp on the same 302. A rebuild last year told me that I did not need a rebuild, but I took the opportunity to beef it up somewhat with a girdle, etc. Cheers, -Neil. |
If you want torque go with a 392ci stroker but if you just want a fast car a stock 225 hp 5.0 in a Cobra will outrun almost any production car out there.
Most people say anything over 350 HP is hard to harness in a short wheelbase and lightweight Cobra. For What it is worth most people seem disapointed when I tell them it is a 302 but when they go for a ride they swear I am lying. :) I have had to open the hood and show them the little bitty motor to prove it is a 302. A 405hp Corvette Z06 has about 3300# to haul around or about 8.15# per HP. In a 2400# Cobra all you need is 295HP to keep up. |
I've thought about it long and hard over the years.
I'll stay with the 302 myself. Easy to get parts for, reliable as they come, decent gas mileage, enough horse power AND room to grow. Basically bullet proof. Ernie |
We are talking to Engine Factory -- they have a decent turnkey 351W that I'm leaning toward. They also seem to have a pretty good reputation around here.
Ultimately it comes down to: I'd rather not stress a 302 engine if I can just as easily put in a 351. It's just better to err on the side of too much than too little. I don't really know how much room to grow I'll need -- it all depends on how my driving evolves. It'll be a street car most of all, in fairly heavy stop-and-go NJ traffic. I may do some autocross on down the line, and who knows where else it might lead. With a car like this, though, I gotta keep my options open. Thanks for all the posts. |
Not advocating either option, but I'd guess if you really thought that you'd like to make 500+ hp on this same motor some day, then you'd be looking at beefing up the tranny and suspension for this right now ... are you? Also, if it gets that close of a decision, then consider weight and pick the one that will give you the F-R weight ratio you prefer.
Cheers, -Neil. |
My very first hot-rod held a 302, so I'm possibly biased, or nostalgic. However, please consider the following:
The Ford 302 has the smallest external dimensions of any American V8. This makes it MUCH easier to work-on than other engines. Although many parts are interchangeable, the Ford 351 is both wider and taller than the 302...but the same length, and noticably heavier. The above comment about hp-to-weight is well-taken. Without the anti-skid controls the C5 offers, a 302-powered cobra has enough to get you in trouble. The above comment about fuel economy is also valid. I know people who get 4-5 mpg out of their big-blocks, I get 18-20 (even using the horsepower). Ultimately, you need what suits you best. |
I have a 302. Runs fast, any I'm putting new heads and a cam in. Guesstimating, it'll put out 350-370 horsepower with no other internal mods, the side exhuast, and the fact I'm running less than 4 things on the belt (alt., power steering, water pump). It also has underdrive pulleys.
No internal mods, heads and a cam, easy setup. Easy 350hp. Some people around here have BB that put out 500+ hp. With a car as light as a Cobra, I think 400 is pushing it. I was happywith my stock 302, but a guy always wants more. For me, not too uch more. So, the question is, how much hp do you really need? Some 600 hp engine than can spin the tires at 80 mph isn't my style, I think too much power is can be a disadvantage. |
If you don't want over 400 or so HP, I would go with the 302.
A stroker 302 is about the same price and you can go 331 or 347 without a problem. The 302 is about 65 lbs lighter than a 351. A T5 will work well behind a 302, but with a 351 you would want to go with a 3550. Add another 25 lbs for that. A 302 should make a great Cobra. 400 HP and about 100 lbs less. |
A 351 is considered more desirable by many, this may be worth something when you sell the car. They cost the same to build. Only real questions: will it fit (yes), do you think you might want another 50 inches? Will you be happy with a cobra that has a motor that is only 70% the displacement of the original, 82% the displacement, or a stroker that is 427 inches? The latter two choices require the 351 block if you want to do it with a windsor
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Make that "T5Z". There's little point in getting a basic T5 nowadays, as the z-spec version (aka "World Class" I believe) will handle much more torque than a T5 for just a few more $$$, and the ratios are better IMHO.
Cheers, -Neil. |
302 vs. 351
Hey Guys,
At the risk of sounding stupid, let me venture to say this. I was under the impression that the 302 block is the same block as the 351. If that is true then the basic dimensions should be the same. I have read that the 351 has a different deck height, and the bore is larger. I have a 351W with edelbrock performer rpm heads and cam topped off with a performer rpm intake with a Road demon Carb. I'm told that with some fine dyno-tuning I can expect 375+ HP which would be more than enough to make one of these 2400 lb cars a rocket. Tony |
a well built 302 is no slug...
My friend just installed his (FE Specialties) full roller 302 / stroked to 338 with a stroker kit in his Unique. It has dual carbs, 10:1 compression, with ported GT40 heads, aluminum flywheel. I had no idea that a well-built 302 could run and pull so hard... Man. I have a 550hp 428CJ in my ERA. His stroker 302 is 435HP in his Unique. Side by side, with his car weighing in around 150lbs lighter than mine, its a pretty close race... What amazed me is how quick his motor revs and snaps. He hits that pedal and BANG, its gone. His idle is actually smoother than my car too. Just an observation to pass along on a recent comparison...
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Re: 302 vs. 351
Quote:
The 351W block has a longer stroke, higher block deck height, longer push rods and connecting rods, beefier lower end with bigger bearings. That's why it is 65 lbs heavier. |
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