Looking for everyones .02 cents....
 

Current power: 7.4l mpi motors (oval port heads, 310hp and MEFI 3's)

NOW?!?!

I am planning on building motors and robbing as many accessories and brackets from the old motors as possible. Upgrading what I have to as I go. I also have HP525 EFI intakes laying around, which I would love to use. Looking to burn 89 to 91 octane.

Option #1: Take current blocks to be tested and make them into 489's or 496's, good set of heads, cam and use the 525 intakes.

Option #2: Get 502 long blocks, change the cam and use the 525 intakes.

Option #3: Find myself 502 blocks, turn them into 509's and use the intakes. And have the capability of turning into 540's later.

Option #4: This is what my plan was until now(after reading about so many builds), build 540's with some (525 intake massaging).

End goal...

89-91 octane
use the HP525 intakes(which I understand are the limiting factor)
looking for 550-675 HP and rpm range of 5400-6000

thanks guys

502/540 all steel parts, whipple and be done

2 cents. how much are you wiling to spend? 2k or 20k?

What he said.

Or sell your current long blocks, buy GM short blocks, have ADK1 here build you a set of heads, Holley HP Fi, and start shopping for new outdrives.

Well I want to do it right. I have to build 2 so I would at least be budget minded, but not cut corners. I have the 525 intakes so I would like to use those.

the only i have with using the 502 pistons&rods is when you decide you want more power so you crank up the boost the piston that is not designed for boost will eventuially fail,also for what you can buy a decent set of rods today with arp2000 bolts why chance a rod failure with the stock gm rods.

Good 4.250 rotating assemblies are fairly reasonable and the route I went some years back. Used dart 310's with dart single plane intakes and holley 850's and made 620 hp @6k. Member here on oso purchased and dynoed. Personally I'd sell the efi intakes. Also could consider ADK61 promaxx heads. He will set them up and ship to you ready to bolt on. Just an option to think about. You have endless options but this would likely be the most cost effective and achieve your goals. Btw the cam used was a custom comp grind.

Good rotating assemblies are very reasonably priced and good heads will always help and don't have to cost 5k like others have stated. I ended up with a 548 with 088 heads, 850 carb and a mild roller cam that ended up at 621 hp and 670 ft lbs. at 5400 rpm. Like others have said I would drop those intakes and go with something more adaptable to cubic in growth if that is what you are going to do. Build a good base motor with a quality bottom end and decent heads then you can always upgrade as you want with a cam, head porting, etc.

Those intakes would make cool end tables

525EFI intakes aren't worth much without the harness, computer, fuel pump, sensors etc. They could end up costing you a lot to limit your build.