I've got many BBC engines to choose from when I start to build my 71 RS (gotta finish the 72 first) but I have this Gen V engine that is in the best condition of them all. I dont know squat about the gen V though besides that it has the one piece rear main seal, and something about the water ports being different from the mark IV and Gen VI. I have the heads for the gen V in great condition and they are large ovals. The block and crank are also in good cond.

What do you guys think about the Gen V engines. Good and bad. Pro's and con's. Do's and dont's...

I ask alot of questions here and rarely do I contribute much to this forum, but as I learn more and gain your trust, I will.

Thanks for any input.

John

Your block is decent and has 4 bolt mains. The rods are decent enough. If it's out of a pickup then the heads should be the small port models. (I'm not aware of any large oval stock mark V heads) The crank if it's cast iron is pretty light weight and I wouldn't use if you plan to build more than maybe 400 HP. You need the Mark V front cover and oil pan, and compatible heads.

So the crank (it is cast) is the weak link? The heads, although I dont have the casting # handy, are in fact large ovals. And yes, it is a 4 bolt block. I also have the front timing cover, balancer and oil pan. I'll be running 9.5:1 compression and trying to make 450+ HP. I've already got the build components i.e. cam (240/246 @ .050, 575/578 lift), RPM intake, 850 DP,3/8 pushrods...
What I dont want is oil leaks and I have no experience with one piece rear seals. I also have a good 4 bolt mark IV block, crank and 781 heads with new springs to match the cam. The pistons, rods, cam, intake...should work on both. I'm just undecided about which block I want to use and am looking for opinions.
Thanks rustbucket for the info. If I use the Gen V, I'll get a steel crank. I LOVE buying stuff for my cars!

Hmmm, if you have a mark IV 4 bolt then just build it, cast crank stock rods and all, 450 HP is nothing for that. The 781's are already set up for adjustable valvetrain, you'll need to buy the 3/8 guideplates, stock studs are fine. The Mark V heads run 16 rotators which can be a PITA when it comes time to get springs, you'll need 2 sets of rotator eliminators. Do not use stock GM retainers, they have been known to split from time to time.

Yea, your probably right. I forgot about the non adjustable v/train and did not know that all 16 springs had rotators. I just remembered that the heads that I had built already for the mark IV are 049s not 781s and have 8 eliminators. I used the Comp Cams retainers on the heads so hopefully their strength wont be an issue.

I guess I'll sell the Gen V engine...

Thanks again.
John

Nothing wrong with the 049's other than the chance they don't have the factory flame hardened exhaust seats. At least they will have the taller installed heights unlike the later 781 castings. You'll be fine with the Comp retainers.

Glad I could help,

Doug