280z4me2 Posted June 27, 2009 Share Posted June 27, 2009 What would be the point? Ive known of several people who do a 347 stroker rather the finding an old 351w. Quote Link to comment Share on other sites More sharing options...
nick77 Posted June 28, 2009 Share Posted June 28, 2009 lighter botom end rotating assembly i think a 351w is about 30 pounds heavyer Quote Link to comment Share on other sites More sharing options...
Michael Yount Posted June 29, 2009 Share Posted June 29, 2009 Bigger weight difference than that when both are equipped with heads/intake/exhaust manifolds out of the same material. The 351 (9.5" deck height) weighs 75-100 lbs. more than the 302-based 347 (8.2" deck height). With very similar bore/stroke - if they're built to a similar level of tune, output will be similar - but you'll be carrying around more weight with the 351, and it's harder to fit under stock hoods. Also, the rotating assembly weighs more and the 3" mains in the 351 are prone to oiling issues if you really want to turn high rpm - both those issues give the edge to the 347. Those serious about rpm fit them with smaller main journals. Of course, the 351 can be stroked up into the 430 cubic inch range - and then the game is over in terms of comparisons. Lastly - the 351 blocks are stronger than the stock late model thin-walled casting 5.0L motors. The 5.0's are great for a mild street/strip build, but if you're going to add boost, juice or rpm (lots of time above say 6200-6500 rpm) you'd best start with an aftermarket Dart block because the stockers are notorious for splitting right through the lifter valley when really pushed. With the big bore Dart block and custom rods pistons you can build up into the 370 cubic inch range on an 8.2" deck -- it'll look just like the old 260 from 1964 --- but act like a 400 cubic inch small block. Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted June 29, 2009 Share Posted June 29, 2009 Lastly - the 351 blocks are stronger than the stock late model thin-walled casting 5.0L motors. The 5.0's are great for a mild street/strip build, but if you're going to add boost, juice or rpm (lots of time above say 6200-6500 rpm) you'd best start with an aftermarket Dart block because the stockers are notorious for splitting right through the lifter valley when really pushed. With the big bore Dart block and custom rods pistons you can build up into the 370 cubic inch range on an 8.2" deck -- it'll look just like the old 260 from 1964 --- but act like a 400 cubic inch small block. Please don't tell me these kinds of things Quote Link to comment Share on other sites More sharing options...
Michael Yount Posted June 30, 2009 Share Posted June 30, 2009 Dart block (aluminum if you'd really like to have fun) - 4.185" bore (.060" over on the 4.125" block) X 3.400" bore = 374 cubic inches. The big bore unshrouds the intake valve and with quality components a 6500-7000 rpm screamer is relatively easy to put together. 450-500 crank HP without too much drama. Just goes to show - there is no substitute for cubic DOLLARS. Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted June 30, 2009 Share Posted June 30, 2009 I was looking over at darton, they have....4.4 something sleeves that would get 380.something ci on the stock stroke. I just need to find out if they'll fit a dart alumi block.... big cam....ITBs..... This isn't even for a Z swap, but I'll probably pm you in a few months when I really get started on it for some more info Quote Link to comment Share on other sites More sharing options...
Michael Yount Posted July 1, 2009 Share Posted July 1, 2009 ?? As I recall, the bore center spacing on the Windsor blocks (221" - 351" W) is only 4.38" -- so there'd be no way to get a 4.4" bore out of them....?? Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted July 1, 2009 Share Posted July 1, 2009 ?? As I recall, the bore center spacing on the Windsor blocks (221" - 351" W) is only 4.38" -- so there'd be no way to get a 4.4" bore out of them....?? Dunno, I've never been a V8 guy till this project started bouncing around, and won't be for awhile till I have the money to pour into it :/ Quote Link to comment Share on other sites More sharing options...
Michael Yount Posted July 2, 2009 Share Posted July 2, 2009 The biggest bore you can get for the 8.2" Windsor small block from Dart is 4.125" -- with ultrasonic checking to be sure the wall thickness is there, you should be able to take it .060" over to 4.185". I'm pretty sure that's max. Bore spacing on the 351 (9.5") is the same; you have to go up to a 10.2" big block to get larger than that. Quote Link to comment Share on other sites More sharing options...
Gollum Posted July 2, 2009 Share Posted July 2, 2009 wow, surprised nobody's mentioned one of the key differences, rod length!!! The 351 has a nice rod/stroke ratio that will allow you to SCREAM up the RPM band if the engine is built for it. The 302 at 347 has a nasty rod/stroke ratio that isn't ideal for high RPM at all, causing more cylinder/ring wear than you'd want in a street car. There's lots of talk out there about how with stroking engines becoming so popular these days that sometimes bigger isn't always better. Just because you CAN get a stock 351W block to 440 cubic inches doesn't mean it's a good idea. With stroke alone the recommended CI for the 351 block is around 380-390. Same goes for the 302, 347 is pushing it, but it's much safer and wiser for extreme builds to run the 3.25" stroke which gives you 331ci. I've also seen very little info confirming the weight difference between the 351 and 302 blocks. Judging by how little the bock weight itself really contributes to the total weight of an engine I have a feeling the difference is less than many people think. I can only speculate unfortunately, but I think the difference is less than 75 pounds, maybe less than 50 pounds, and that difference is negligible in the grand scheme of things. There's been talk about aftermarket blocks here, but we also have talked about the fact that those dart blocks are EXPENSIVE, and for that added HP potential you pay the penalty in weight. There's a reason they're so much stronger. Design has a part of that role, but beef does too. Unless you're going to be doing some competitive racing (which means you probably won't have a ford V8 in a Z...) then for the cost you're better of just building the bigger engine. The 351W can take a lot more power than the 302 block, and is capable of more CI. For the cost of some of those fancy aftermarket blocks, it even makes building a 460 seem economical. Those blocks will hold gobs of power, you just need to figure out how to build it on a budget. There's crankshafts out there with bearing diameters to allow use of chevy big block rods and pistons, which brings some costs down. Quote Link to comment Share on other sites More sharing options...
Michael Yount Posted July 3, 2009 Share Posted July 3, 2009 The R/S ratio with a competently built 347 isn't any worse than a 427/454 Chevy big block. If you've been to the track lately around well built strokers based on the 8.2" short deck block - you'd see that the r/s ratio and rod length on the baby strokers doesn't limit rev-ability at all. All the noise about rod angles and cylinder wear is simply a non-issue in a properly built motor with quality machining and parts. As for the aftermarket block weighing more - it does. Nevertheless, the difference between the 8.2" block and the 9.5" block is significant. You needn't speculate -- check out shipping weights from various crate engine manufacturers and you'll get an idea of the difference. It's more than 50 lbs. with the rotating assembly - and you have to account for the rotating assembly. And the 3" mains that the 351 comes with result in a crank that weighs more (rotational weight increase is a parasitic loss) and cause oil shear issues at high rpm. The really hi-po 351's are set up to run smaller mains to solve that issue. Keep in mind - the original poster's question was 347 vs. 351. If that's the question, and similar parts are used - the 347 is going to outperform the 351. If we're talking about getting the most output one can regardless of weight/size of the block/etc. -- sure, other options will prevail. Quote Link to comment Share on other sites More sharing options...
Gollum Posted July 4, 2009 Share Posted July 4, 2009 I understand that a 347 stroker can still rev, but what rev limits are we talking? With that same effort put into building a quality 347 you could build a 302 bottom end and valvtrain to rev well beyond 7k, making gobs of power for the displacement. The reality though is that cubic inches are always cheaper to build than revs. Quote Link to comment Share on other sites More sharing options...
Michael Yount Posted July 5, 2009 Share Posted July 5, 2009 Whatever valve train parts that let the 302 rev will also let the 347 rev. My brother's shop preps the racing 347 in a Shelby 350 replica that's a vintage racer. It sees 7500-8300 rpm on a regular basis without incident. The key for either one is a Dart or other aftermarket block as the stock 5.0L blocks are thin walled castings that will be splitting right down the lifter valley under that kind of stress. And most folks that are gonna spin a 351-based motor up there or higher will be using smaller rods and cutting down the crank rod journals to a Cleveland-size 2.75" or smaller so that oil shear at high rpm with the 3" bearings isn't a problem. Of course -- you don't need lots of revs to make lots of power with these. A well built stroker (Dart based) with 340-360 cubes and 10-15 psi of boost is more than capable of turning out 600-800 HP all below 6500 rpm. Quote Link to comment Share on other sites More sharing options...
Adam Posted May 20, 2011 Share Posted May 20, 2011 I just so happen to being going from a 347 to a 351W. Well I have the parts to do the 408 however, I think I might put it in there as a 351w and see the difference (it wont cost but a few dollars for some gaskets). I still need to mock up the turbo kit for it anyway so I could kill two birds with one stone. Just a little information.... I pulled everything off of the 347 and used it on the 351 so it will be all comparable to just show the difference. AFR 64cc heads with 215cc intake runners and 205 valves Custom Competition Cams "roller cam" Scorpion 1.7 roller rockers Stealth Intake Demon 750 cfm double pumper All of this except the intake I had on the 347 (Eldebrock RPM Performer)...... I think I will put the engine back together and give it a shot in the car I will be able to do a good comparison of one to the other. This should answer the difference without any questions. Quote Link to comment Share on other sites More sharing options...
Gollum Posted May 20, 2011 Share Posted May 20, 2011 The 351 (9.5" deck height) weighs 75-100 lbs. more than the 302-based 347 (8.2" deck height). Reading through this older thread reminded me of some information I was unaware of at the time of this thread. The difference between the 351W and 302 is closer to 50 pounds, not 75, if both engines have aluminum heads and intake. As you can see from this post from a well trusted member his difference was around 60 pounds, but the 351W block had a larger oil pan along with a main girdle that the 302 block didn't. Though he is talking about a 289, so I presume it's an older small block thus is probably slightly heavier than the later fox-era 5.0 blocks. It's still surprising where the weights end up though. I finally got the 289 out of the Z and compared its weight with the 383 (351W stroker) that will replace it. These weights include everything a running motor needs (except for the T-5 transmission itself). This includes entire induction system (carbed), plugs wires, water pump, pulleys, damper, flywheel, pressure plate and disc, starter, and headers. For information, the heads are aluminum on both engines, the intake is a Victor Jr on both engines, the headers are medium length 1 3/4" headers on both engines, the flywheel is aluminum in both engines. What is different is the 383 has a heavier oil pan (9 quart baffled road pan verse the OEM 289 oil pan), and the 383 has the heavy (5/8" thick) Canton main girdle which the 289 did not have. Both of these added about 14 lbs over the comparable equipment on the 289. Engine weight: 289 (or 302) = 454 lbs complete. 351W (383) = 513 lbs complete. My expectation was that the Windsor motor would add about 75 lbs to the car, but it looks like it will in reality will only add 60 lbs. 94 additional CID for a 60 lb penalty. I'll get a photo and some transmission weight and have Paul insert them into this post after the edit option drops off. Quote Link to comment Share on other sites More sharing options...
Adam Posted May 23, 2011 Share Posted May 23, 2011 (edited) Gollum, You are correct indeed there is very little difference among the weight of the Windsor blocks, there is only about 50lbs difference. This can be reduced even further when you remove the heavy cast intake and heads. the blocks themselves are not the dramatically heavy. With the installation of aluminum heads and aluminum intake on a 351w 441lbs complete weight. This is actual weight of my 351w with a shaved crank and rotating assembly. I just thought I would weight it while it was out of the car still. Hope this information helps more people. Adam Oh I forgot it is bored 30 over. Edited May 23, 2011 by Adam Quote Link to comment Share on other sites More sharing options...
Adam Posted June 1, 2011 Share Posted June 1, 2011 Got it all done and by the seat of the pants dyno it picked up a ton of torque and maybe a few horses. There seems to be very little weight difference between the two engines. The nose of the car did not get any heavier, the only thing that was needed was to reshape the headers and make a new exhaust. Adam Quote Link to comment Share on other sites More sharing options...
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