Split Block ???? - Page 2

Lynn · 10-20-04, 05:26 AM

Built2rev,

I beg to differ on one point, I would put the Ford R302 and A4 blocks, in that order, well ahead of the Ford sportsman block and only slightly behind the Dart sportsman in terms of strength. The have the exact same main cap layout of the Dart sportsman. The R302 has slightly thicker webs than the A4, but both are thicker than a Ford sportsman. The Mexican block, BTW, is dimensionally the same as the other Ford 2 bolt blocks of that era, but enjoys a higher Nickle content so that the metal is somewhat stronger.

Lynn

killroy · 10-20-04, 02:50 PM

Let's look at the A4. They are no longer made, so you have to find a used block, of find one that has been sitting. Then, it's not as strong as a Dart. If you find one cheap, it's a good part, but I would not bother looking too hard when you can get the Dart brand new.

The R302 is a good piece. It might be stronger than a Dart, but with the price you pay and the required machine work to make it ready to run, the Dart seems more economical. The Dart also allows a bigger bore.

For me, the choice is clear. The Dart seems like a better block unless a great deal falls in your lap.

Lastly, the Mexican blocks used the last of the beefy hipo main caps. I think that their tooling was also worn out, so there was a bit more metal. The extra metal was probably only a tiny part of the extra strength, the main caps are the biggest contributor. As for the high nickel content, I have heard that before, but I have also heard that was not true, just a rumor started when Ford started making the high nickel 5.0 and 3.8 blocks.

flatchat(Chris) · 10-20-04, 07:35 PM

It appears that we need to use every quality HiPo after market product in building a reliable go hard motor that just looks like a ford
To use OEM ---bit like flogging a dead horse!
imho [img]/ubbthreads/images/graemlins/cool.gif[/img]

Mark Worthington · 10-20-04, 07:35 PM

Your basic, runof-the-mill 5.0 block is prone to cracking at the main webs as shown in the above pictures when:

a) it is over-revved, and
b) when it puts out more than 500 hp.

The 2-bolt production blocks are great if the revs are kept low and if you don't try to squeeze too much power out of them. Still, there are a number of bad apples out there due to core shift in the casting process. I think the Dart aluminum block would be perfect for a GT40.

Oh yeah, regarding nickel content, the Ford Racing catalog states that the Mexican blocks had the same nickel content as the US production blocks. Just a rumor. As Built2rev said, though, they are a little beefier.

killroy · 10-20-04, 09:37 PM

[ QUOTE ]
It appears that we need to use every quality HiPo after market product in building a reliable go hard motor that just looks like a ford
To use OEM ---bit like flogging a dead horse!
imho [img]/ubbthreads/images/graemlins/cool.gif[/img]

[/ QUOTE ]

It all depends on what you are after.

I play hard with my toys. I have to build them to take it.

When I'm spending extra money for super strong forged parts, the $900 price difference between a Ford sportsman and a Dart sportsman does not seem like much, and with a set of custom pistons, I can get a hand full more cubes.

Mainly, I want to build something that I can't break easily. If some extra power comes with it, I'll take it.

Other people might say "300hp scares me". A high performance rebuild using mostly stock parts would be perfect for them.

When you start to talk about strokers and big cams, you are getting dangerously close to the breaking point of the stock block. The Mexican is a bit stronger, and the Ford sportsman is a bit stronger than that.

The Darts, A4's and R302's are much stronger than a Ford sportsman. If you have to take the leap, you might as well go in head first.

On the other hand, I have the luxury of building my engine out of the car and keeping my 5.0 as a spare. For Mustang owners that don't have the money for that, they will keep adding parts untill the block splits.

The biggest problem with the stock block is that if it splits at the wrong time, it can eat your whole rotating assembly. So the stronger blocks are insurance for the rest of your parts.

For me, it's really pay now or pay later. I know I'll be the guy with the split block if I chance it. So, why not pay up now and get more power in the bargain?

Bill Musarra · 10-20-04, 10:23 PM

Would a main cap girdle help stave-off some of the inherant weakness in the webs of the 2 bolt mains(351W base) for say 500-550HP???
Bill

flatchat(Chris) · 10-20-04, 10:38 PM

Well said Daniel.
Perhaps we should catagorize them--say:-

* OEM (stock)

* Improved perfomance OEM (road legal- cruiser)

* Road and Race (weekend worriers)

* All out Race (circuit purpose built)

* Drag ( 12sec,11,10,9,----5??)

Love to hear from the experienced engine builders,maybe some combination examples--guess they'd be rated in hp and longevity [img]/ubbthreads/images/graemlins/cool.gif[/img]

killroy · 10-20-04, 11:13 PM

I think that there are only a few combinations that make sense:

Stock/performance rebuild. It should make good power and last if the rev's are held below 6,500 and the oil system is done right.

Cheap stroker. Use a Mexican block or early 302 with good main caps and probably a girdle with a cheapo cast crank stroker kit for more power without breaking the bank.

Over the top street motor. Use a race block, forged rotating assembly and good machine work. Accusumps and pre-oilers highly recomended, especially if it will ever see a track. This is a motor that can take 8,000+ rpm if the oil is there. With good heads and intake, it can make great power.

Full race. Same as over the top, but add a bigger cam, dry sump oiling and regular parts replacement of valve springs, retainers, rocker arms, pushrods, etc. Plan for frequent rebuilds. This is a 600+ hp engine if done correctly.

To quote Smokey Yunnick: "There's cheap racing, there's expensive racing, and there's damned little in between"

Of course those are all for 302 based engines, the 351 block is much stronger, so there are a lot more combinations that make sense.

Also, supercharging can make more power with a stock block than a NA motor. A turbo-supercharger or positive displacement blower can create lots of low rpm torque, so you can avoid the high rpm's that are usually associated with split blocks. To put it simply, less rpm = less stress on the main journals. The cylinder pressure and torque don't seem to hurt things as much as swinging all of that weight around. So supercharged engines can make 500+ hp on a stock block if it's built right and the RPM's are held below 6,000 or so.

Craig White · 10-21-04, 09:05 AM

Well the engine in question is back together again as a 347 stroker. Used another old Ford block. Didn't check if it was crack tested. I know they are using a main cap girdle.

After advice they have written the previous block of as defective.

Well we will see how it goes this time? My fingers are crossed as I wouldn't wish these problems on anyone.

Lynn · 10-21-04, 10:27 AM

Some people just like to live dangerously.

The girdle is certainly better than nothing, but in some cases, I think it is a bandaid when stitches are needed. Then again, sometimes, all you need is a quick lick and off you go. Diffr'nt strokes for diffr'nt folks; that's what makes the world go round!

Lynn