Engine/Trans selection opinions

[NCShooter]

Hey folks!

I put my order in for a 289 kit recently and have begun pulling together all the engine/trans bits. Here is where I'm stuck a bit...

I essentially get the following bits for free from a family member:

1) A 1971 March 1 351w and C6. A former street n' strip motor, aluminum heads - cam unknown, no intake/carb. Estimated ~400hp when it was parked a decade ago
2) A 1988 Mustang 5.0 with T5. Complete and running (but I'm not using it for donor since the 289 only comes in complete kit form)

So...

Option 1: Yank the 351w out and use a stand alone EFI+intake and mate it up to the T-5 using a machined flywheel (50oz 302 down to 28oz 351). My fear is that T5 may not last very long against an engine that is naturally torq heavy, as they seem a bit opposed in scope. Some folks seem to get theirs to hold together forever, others sneeze and they shatter :| The bonus here is an already decently built motor and all parts available on hand to prep for the drop in a few months.

Option 2: Stash the 351w for a future project and use the 302+T5 combo, adding in the EFI spliced into the existing factory EFI (no additional machine work vs the 351 build) . I believe that 302 is pretty much bone stock, so not exactly a barn stormer... but the whole car is like 2300lbs so I suppose doesn't take much to have fun. Still run the risk of nuking a t5 at mild HP levels, but at least they seem to be plentiful (around here anyway) and less likely to eat it under a mild 302 torque curve.

Option 3: Go hunting for a Tremec 3550 and all the bits to go with it, would have to make that decision before final delivery or buy a new driveshaft. Mate that up to the 351w, keep the 302 on standby for another project.


Scope of use: Just street use for 98% of the time, maybe it will see a HPDE event at Road Atlanta one day. No drag racing, street tires.

[John289]

Your scope of use is the same as my 289 but no track time. I went with a new Boss 302 with T5 and sniper from Mike Forte with the mid shift conversion. Engine dyno was 355 hp. Only roughly 200 miles since finishing in December but all trouble free.

[rthomas98]

I am running a base 302 w/t5 in my mk4 it is still quite lively. My speedhut gauge showed a 0-60 of 4.0 sec flat and that is with me being a hack driver. It is more then enough to get you in trouble. Also you are correct, unless you are doing something to the internals of the t5, the 351 will make mince meat of a stock t5 over time. It doesn't like much more power then 300 hp. Anything higher you are running on borrowed time. The other thing to consider is your rear axle gearing what are you planning on running there?

[NCShooter]

I have a 3.27 rear end ready to go, so that was what I hoped to use. Right now I'm edging back towards the 302 (I started with wanting to build 289) and keeping the big torque motor on standby for another project. I came from the Viper world, I like power but also am super duper aware of how fast something can get away from you ;) I'm good with 300 horse in something that weighs a ton lol

[Bob Cowan]

Your 351W is an unknown quantity. Unknown cam. Unknown compression. And unknown condition. Something that has been sitting for 10 years will require a complete tear down and re-assembly. Probably needs lifters and valve springs. Certainly gaskets. And if there's any corrosion in the cylinders, new rings. Essentially, plan for a complete rebuild.

And that's not a bad thing! I always advocate rebuilding an old engine before putting it in your new project. It will save a lot of work, time, and money later.

Also, you do not need a special flywheel. The stock 351W flywheel is - of course - 50oz, to match the crankshaft and balancer. Just order a stock replacement.

You're probably correct about the transmission, though. A well thought out 351W can be a real torque monster. And even in a light car, that can rip through a stock T5 pretty fast.

I would go with option 3, and use a tremec transmission.

You're building a 289 car. The visual differences between a 302 and a 351 are blatantly obvious. If you want the engine bay to look kinda correct, I would use the 302, and get rid of the stock intake.

[jab351w]

Also, you do not need a special flywheel. The stock 351W flywheel is - of course - 50oz, to match the crankshaft and balancer. Just order a stock replacement.


Stock 351W used 28 oz. imbalance. Did for the entire production run. 302 used both--28 oz. until around 1980 or so, then 50 oz. thereafter. Of course an engine can be balanced to anything (within reason), so if the engine in question has been apart it could be any of the above (or neutral).

[CraigS]

I prefer the 351 since it makes more TQ so you can have a really nice HP# but also a very drivable engine that doesn't need 6000. And later when you decide you want more, it is pretty easy to get a stroker kit to make the stock block into a 408. W/ either engine I'd dump all the OE efi and go Sniper or similar. The OE stuff is just too dang old and the ecus have a habit of going out w/ few replacements available.

[Sdonnel]

Previous car had a bone stock 302 with a T5Z. Rear gear was a 3.31. The engine wound up so slowly, I could look down a couple times at the tach while the pedal was matted, before having to shift. Changed to a 3.73 rear gear and that really woke it up. I later put AFR heads on the motor, which helped even more. I say go with the 302, put in a lumpy cam, and possibly change the rear ratio.

[rich grsc]

Like Bob stated, the 351 will need a complete overhaul, setting for 10 yrs, no intake, questionable. The 5.0 will be a great choice, but get rid of the 3:27 gears and get a set of 3:55's. No idea where you get the idea of the T5 being so fragile, I'm running 400hp through mine, no problems. Now if you plan on drag racing with slicks, then it maybe different.

[drewr]

As you see, you get all kinds of opinions here. You really can't go wrong with either choice. It will come down to how much time/effort/money you want to put into it. The 302/T5 options seems the most plug and play option. Besides, the 302 block looks just like a 289 block. If you like the idea of a vintage look, the 302 will be super cool. Down the line, you can put some aluminum heads and a little hotter cam in it, and you'll have more power than you need in most cases. I really like the 289 kit. Might be my next build!