Dart Aluminum Block or Ford Racing Aluminum Block

[rezell3d]

Ok guys,

I want to start designing my 427. I want an aluminum bock, but I don't know if I should go with the Dart racing block or the Ford racing aluminum block. Any thoughts?

Thanks,

Rod

[edwardb]

I'll throw this out there, admitting it's perhaps dated information and also one person's opinion. Also since my experience was with the 302 block, can't confirm this applies to the 351 block. So absolutely FWIW. I had Fordstrokers, a highly regarded engine builder, put together the 347 for my #7750 build. We talked stock versus aftermarket blocks. Jim at Fordstrokers said he strongly preferred Dart. As I recall he wouldn't do a Ford Boss block, but don't quote me on that. The main reason he cited was that Dart has longer piston sleeves. He believed that for a SBF stroker (which I assume you're asking about, e.g. 351W bored and stroked to 427) the pistons came too far out the bottom of the piston sleeves. I ended up with a Dart SHP iron block. Couldn't justify the double cost of the aluminum block, even with the roughly 100 lbs of weight savings.

[Jim1855]

Rod,

My current 427 is built on the Raceparts Distributing, Inc. (RDI) aluminum "Z" block (2004 version). This is the predecessor to Ford's offering. Preston Miller, the owner of RDI was instrumental in the development back early 2000's, Ford did the casting. RDI went out of business and Ford took over the block. The original RDI has longer cylinder sleeves, 4 bolt mains on all 5 journals and a lot of metal in the sides between the cylinders and main webs. It is a very stout block it also significantly heavier than the Dart. As Preston said, "it wasn't built for light weight, it was built to be strong".

I also own a Ford 351Z block purchased a few years ago as a spare. Paul's comments on it carry some weight. The cylinder sleeves are shorter and #1 & 5 journals are 2-bolt. There are other changes that are not as important.
https://performanceparts.ford.com/part/M-6010-Z351

A friend has two Roush aluminum 427s built on the Dart blocks. One is in his Brock Coupe the other just rebuilt and on a stand. I suppose I could open it up for inspection but then I'd have to reseal it, not high on the list of things to do. FWIW, he also owns Peter Brock's RDI AL 427 that came out of his red Coupe when Brock switched to an LS7, this motor has been rebuilt to about 640 NA HP, will be at +/- 800 with NOS. One obvious thing on his Dart blocks is the sculpting around the cylinders on the block sidewall. The RDI/Fords have a lot more meat in this area. I believe that the Darts are 2-bolt 1 & 5 designs, this is probably not a concern on a normal street motor i.e. <700hp.

Another friend built a Dart Aluminum to high 600 HP and spins to 7,000 ++. as a track only motor.

So there's my $0.02. In the big scheme it probably doesn't make a lot of difference. But the short skirts in the Ford Z block should be looked into, I wondered about it too. I suppose you could punch them out and put in longer ones.

Jim