I'm new here and I'm glad I found you! I am building a long rod 489 with KB flat top Hypereutectics and while You have probably discussed this before, I did a search and last post was 2001. From what I found, casting #10141279 should work on a MkIV but since the 2001 post i'm sure you have learn't a lot! Thanks in advance!!:thumbsup:

OK, I found some threads under L29.

Ok, I have seen enough evidence that L29's work on a MkIV, To prove i'm nuts I'll tell you what im doing. This is going to be a direct drive airboat motor, sorry:sad: not a Chevelle! Max RPM will be 3200 RPM so torque is the key.
I'm starting with a 454 MkIV block, 4.25" stroke crank, +.030 KB Hypereutectics at +3cc. 6.385" rods, I ordered the L29 heads 99cc. dual plane intake, 600cfm Holley double pumper, small diameter long tube headers, HEI, MSD, Hamburger's 8 qt. pan. I'll talk to cam company about cam, I was told to do a 108 degree lobe seperation to have a peakey torque band between idle and 3200 RPM.Thats about it for now!:hurray:

I'm just looking for any tips as far as head bolt up, drilling steam holes? grinding coolant passages? enogugh meat to machine for MkIV rocker studs or do I have to buy the conversion ones? I will be able to answer some of these questions when I get the heads but your input is appreciated:thumbsup:

Also anything you can suggest regarding the build, porting etc! I know I'm not asking much but maby I can help you guys some day. Thanks!:hurray:

PM sent.

Thanks again Schurkey, your the best!:thumbsup: :hurray:

Why not just use a mark6 block for build up???????? no need to drill or grind.....they make an adapter for one piece rear main to 2 piece rear crankshaft...........

Im no cam whiz,thats the long thing in the middle of the block with bumps on it right? why not tighten the lsa even more? 106 maybe.