School me on the BBC

clutchdust

Millionaire Playboy
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OK, last week I picked up a '93 1-ton with a 454 (7.4L) to replace my '99 1-ton that had the 6.5Lt. My problem is that this 454 is pretty much worn out. It has a significant blow by issue where it is pumping oil out of the valve covers around the PCV and filler cap. I got the truck for a smoking (no pun intended) deal so even if I have to overhaul the engine, I don't feel too bad.
Now here's the tricky part. As a '93, is this still a "Mark IV" block? I ran across a deal to pick up a complete but disassembled long block today. The block is supposed to be a late '60s/early 70's block and has the big oval port heads. What I'm thinking of doing is putting that short block together and just putting the '93 heads on it, then at a later point, building the '93 short block and putting the big port heads on it.
I just want to know if there are any significant architecture differences in big blocks from the early design to the '90s designs. I pulled a cover off this afternoon and peeked down a pushrod hole looking for "dogbones" but didn't see anything so I think this is a conventional flat tappet cam/lifter engine.
I'm fairly knowledgeable on the SBC but this is my first foray into big blocks.
 
OK, last week I picked up a '93 1-ton with a 454 (7.4L) to replace my '99 1-ton that had the 6.5Lt. My problem is that this 454 is pretty much worn out. It has a significant blow by issue where it is pumping oil out of the valve covers around the PCV and filler cap. I got the truck for a smoking (no pun intended) deal so even if I have to overhaul the engine, I don't feel too bad.
Now here's the tricky part. As a '93, is this still a "Mark IV" block? I ran across a deal to pick up a complete but disassembled long block today. The block is supposed to be a late '60s/early 70's block and has the big oval port heads. What I'm thinking of doing is putting that short block together and just putting the '93 heads on it, then at a later point, building the '93 short block and putting the big port heads on it.
I just want to know if there are any significant architecture differences in big blocks from the early design to the '90s designs. I pulled a cover off this afternoon and peeked down a pushrod hole looking for "dogbones" but didn't see anything so I think this is a conventional flat tappet cam/lifter engine.
I'm fairly knowledgeable on the SBC but this is my first foray into big blocks.


The later block are not as strong as the older blocks. Decks are thinner bigger water holes make them weaker, The later blocks are a one piece rear main seal which you can use he older crank with an adaptor.

I think on those newer blocks the main webbs are weaker as well.


On the older blocks some times they are so worn out in the lifter bores it hard to put dog bone roller lifters with out having issues. Most go to a .094 if running a solid roller.

No block is any good untill it can pass a mag and sonic test.
 
A 93 would be a gen 5 engine. Still had flat tappet lifters. The gen 6 had rollers and was 96 and later IIRC. The gen 6 lifters cannot be used in the Mark IV or Gen5 engine.
 
Those 93 heads are probably a small oval design (peanut ports). The big ovals are better for hp.
If you want to know if it's a IV or V, just check for fuel pump boss.
 
What's the difference in Gen IV vs Gen V? The 93 is TBI so it's definitely the later block (no mech fuel pump). The block I picked up is certainly earlier, two piece rear main.
This is for my work truck so for simplicity and costs sake, I'm going to build this short block and just swap the '93 heads on it. I figure I will just need fresh rings, bearings, oil pump and a flex plate to make it all work. Please tell me if I'm wrong.
 
Are you planning on interchanging Mark IV and Gen V blocks and heads?
 
That's the plan, at least right now.
Since this is for my work truck I'm going to do a quick and dirty overhaul on the early short block. Then maybe over a weekend, pull the 93 block out, stick those heads on the older block and put it in.
Of course, all this is contingent on the block and heads interchanging. Really need to know now if that's going to be a problem.
 
The answer is maybe. The cooling passages are different. My experience is on boat motors so I'm not sure all heads are the same. I know with the correct head gasket it can be done on Mercs heads/motors. Try seaching for Felpro 17042 gaskets and your head numbers.
 
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