347 vs. 351w

[aarvig]

Looking at building a Cobra MK4. I am planning on using this car on the street only. I want some snap along with a sweet exhaust note to rattle my eardrums. What motor would you recommend and why? Who would you recommend I buy it from?
Thanks!

[tkrupinski]

I have no experience with the 347 but my first engine was a 351 with World Windsor Jr heads and it had very good power on the street. From what I have read on here both engines perform very well. As for where to buy one, there is a vendors section on this forum and I am sure one of them can help you out. Good luck with your build.

[edwardb]

Welcome to the forum. Nothing like making one of your first posts something simple :) There are no right or wrong answer to your questions. But lots of opinions, including mine. You will need to decide what is best for you, your build, your budget, etc.

Regarding engine builders first, there are several who are forum vendors here. Many forum members will recommend them and they generally know our cars quite well. Gordon Levy, Forte's, Engine Factory to name a few. That would be a place to start. There are other well known national builders. For me, there are some advantages to a local builder if you personally know the reputation they have, or can contact other specialty car owners in your area.

As far as 347 or 351, personally, I really like the 347. It's relatively light and compact, fits into the Roadster great, and properly built and setup has a nearly perfect HP and torque range for these cars. They can get into the 425-450-475 HP range pretty easily, but do require some not too cheap parts to do so. Many would argue an aftermarket block is better for a stroker than the Ford block. I did choose to go with a DART block on my latest build. A 351, on the other hand, can get similar or more HP maybe with less expensive parts. So it's a popular option. They also fit well, but due to the higher deck, there can be some limitations with induction and air cleaners. It can get tight. My engine builder is not a big fan of the 351 block because of the larger main bearings, and depending on the application bearing speed can be an issue. But this can be addressed with aftermarket solutions if necessary. In general though, probably really not an issue at reasonable HP and RPM ranges.

[CraigS]

The 351 is a taller block to start with. All the extra cubes come from a longer stroke. The good thing there is that you don't need any expensive stuff to get the cubes. Almost all the internal parts are stronger right from Ford. To get the 302 to 347 you end up w/ short pistons that tend to do more rocking in the bore. My 400 hp 351 from the engine factory back in 04 is stock crank, stock rods, somewhat higher compression hypereutectic pistons and Edelbrock performer rpm heads and intake w/ a fairly mild cam. So basically the low end of 351 is 400hp. The taller block requires different headers and intake so, if you start w/ a 351, you have way more you can upgrade to w/o replacing intake and headers. 393s and 408s can be done easily w/ the stock block. If you start w/ a 347 you are kind of topped out, if you start w/ a 351, it is just the beginning.

[MPTech]

The 347 (302 block) is a better fit in the roadster and less trouble.
The 351 has a taller deck, so hood clearance can be an issue and limit intake / air cleaner options. Unless something has changed, the 351 headers were also more problematic than the 302 header (Hooker did make the 351 headers and the header bolts were a major PITA).

[carlewms]

After a long search, and the criteria that I was building a car for the street, I selected a 347 Stroker. As others have said it fits better with more working room than the 351 or the FE BBF, and as I prepare it for the first install, I can say that it is very easy to work on.

I ended up coming up with a set of performance requirements and then shopped the vendors on the suet but also some from other sites. In the end I chose Levy Racing to build the engine for me.

In my brief experience so far one advantage of the vendors on this site is their overall knowledge of the cars and their routine participation on the forums. They are a great resource as well as a vendor.

Carl

[aarvig]

Thanks for the imput. I'll do some research on the 347. Has anyone ever put just a 302 in one of these?

[edwardb]

Thanks for the input. I'll do some research on the 347. Has anyone ever put just a 302 in one of these?

Absolutely. Probably one of the most common sizes used. Everything from a straight-up EFI donor from a Mustang to highly modified. My Mk3 has a 306 -- a 302 that's been bored .030 over during a complete overhaul. It has a lot of aftermarket parts, so a pretty strong one. It powers the car very well. The Ford Racing crate 306 (FMS-M-6007-X302) is an option many have used. All new, with a warranty, reasonable power, and a decent price. Couple guys in our local club have them, and they perform very well.

[frankeeski]

Thanks for the imput. I'll do some research on the 347. Has anyone ever put just a 302 in one of these?

I have a bone stock 5.0 EFI engine out of a 94 Mustang in mine right now. The engine has close to 236,000 miles on it and you'd be very surprised how well it moves the car. Many in the SoCal group here are surprised that the motor is so "well seasoned" and moves the car so well. I have a brand new 347 on the engine stand waiting to drop in the engine bay but I hate to take the car off the road since our driving season is pretty much year round out here on the west coast. It's going to happen here pretty soon, just after the first of the year.
Here is a link to the build threadhttp://thefactoryfiveforum.com/showthread.php?5856-New-Bullet!&highlight=bullet
Here is a picture of the new 347
http://i200.photobucket.com/albums/aa78/frankeeski/20130410_183126_zps50cb8bb6.jpg

[kevin12973]

I have a Ford Racing 392-430 HP crate engine. My next build will be a 302 base engine. The 351 base engine is tight and the headers are real tight against the foot boxes. Many other reasons but just my opinion. Good luck with your build and have fun!!

[seagull81]

The one thing have not seen brought up is the 351 is a heavier engine then the 302 based engines. When I had a 302 with 2.78 it was OK and got really good fuel mileage. But when I changed to 3.78 rear gears it was like putting in a completely different engine. In my opinion road gears are not for this type of car.

[riptide motorsport]

6 of one....half a dozen of another.

[tirod]

Is the 351 heavier, yes. It's the factory stroker motor built to take the workload when used in trucks. Same concept as the 427 SO, in that regard. There is about 70 pounds more cast iron in the short block and higher deck compared to the 5.0 (but not the older 302s which kept the extra iron.)

Move to an after market block like the Dart and they kept the iron, too. Add that the kit has 49/51 weight distribution and that 70 pounds loss doesn't really help in two areas. It limits the upper hp potential of the 5.0. Engine builders find the limit is about 450 hp in the stock block, push it and the block separates across the light cam bore webbing under the head bolts. Plenty of ugly pics on line from the power adder crowd, much less the pile of broken crank parts. So, a stock 5.0 block build needs to respect that the 70 pound lighter block isn't all that. Second, the front of the kit doesn't need to be even lighter, it's already rear biased. That has resulted in builders moving the battery back up front. It's precisely the reason you do move the battery - to get better balance on the car. It just looks race car in the kit.

The inch of "lost" underhood space goes to the originals not using high rise manifolds. They simply couldn't as the technology was focused on Webers, not drag race induction. Stacking an air gap manifold with four barrel and 4" air cleaner is already an issue with the 5.0, which is exactly why hood scoops were invented - to cover the big hole in the hood and grab some air. Ironically, they seem to work better backwards facing the high pressure area at the base of the windshield.

Reversing the motor mounts and moving the engine forward helps things fit with either block. It gets more weight off the rear, makes room for the heads against the foot wells, etc. It's an alternative to having the motor shoved up so tightly in the foot box.

There are a lot of finesse points in laying out the drivetrain building the kit. As is, it will produce a running car. Tweaked with all the modifications, it can do better. It just depends on what is a priority and how indepth a builder wants to go - power steering, power brakes, automatic trans, A/C, supercharging, six speed trans, track suspension, cage, working windows, the list is pretty long. Some of it isn't simple or easy. 5.0 or 351? Weigh all the pros and cons, which is what we all do.

[2bking]

You are asking about a 5.0. How about the Coyote? Light weight, all aluminum, EFI and gets 412 HP, 390 Ft-Lbs out of the box. The cost is comparable or cheaper than an engine builder because its a production line engine. Down side is its a tight fit and not original looking but its getting to be a popular choice.