Hi,

I have a 1997 502EFI engine. the block was damaged. I thought it has a GEN6 block. Now I ordered a Dart GigM block. IT was sold as GEN6 too, but it has hole for the mechanical fuel pump, all other things look same. What is different of the Gen5 to Gen 6 blocks? only the fuel pump?
The camshaft suppliers also make a difference in Gen5 and Gen6.
Any help? Please...

Daniel

Lifter bore hight, timing chain cover and head gaskets are different on the GM gen5 to gen6 .

The GM gen6 lifter bores are mech for a spider bar and dog bone roller lifter set up the gen5 is not

I thought the Dart blocks were all baced off the Mark IV. I do not think the Gen V or VI heads will work on a Mark IV block. Like was said the timing chain, chain cover, cam, lifters are all different.

Gen V engines never came with roller cams. Thats why they where only made a few years, then replaced with the Gen VI.
The Newer blocks GEN VI have the fuel pump boss. The cam on the new engines do not have the lobe for the fuel pump. I purchased 2 brand new last year and only one had a fuel pump mounting, if I was smart I was have asked to make sure both had mech fuel pump. I did replace both cams and they cam with fuel pump lobes. Did not do much good with the one that I cold not use it on.

I think you have to get the Gen VI service block or Gen VI Bowtie block to get the mechcanical fuel pump boss. The standard Gen VI did not have the fuel pump boss. That is why just going on the presence or abscence of a fuel pump boss is not a 100% accurate way to determine if its a Gen VI.

I have the fuel pump boss, but also the roller camshaft. It seems that Dart produce the GEN6 blocks with the older style fuel pump boss to make them useable also for mechanical fuel pump engines. Where are the differences in the haed gasket?

Back to the original question..

The easiest way to tell the difference is the timing chain cover.
Gen 5 has stamped steel timing cover Gen 6 has cast timing cover as stock from Merc . Gen 5 has ten bolts Gen 6 has 6 bolts.

Thanks,

I have a cast alloy cover, it fits also the new engine, so it should be a Gen6 block

Dart Big M comes in both mk lV and gen 6 style. Both are set up for mechanical fuel pumps and they both use a 2 piece rear main seal. As stated earlier the lifter bores are raised for the gen 6 lifters. Komo you might want to check out the rear main seal as the GM gen 6's have a 1 piece seal. You may not be able to use your crank in that block. Might be time for a stroker.