That was my point about the two bolt being splayed. The question still remains about the 509 blocks being of higher nickle content. Anyone heard the same thing?
Fwiw, I understand this guys scenario, but for me I'm on a budget too, but by the time you buy three center caps, pay to install them, all the other machine work you would be close to the $1500 that would get you a Dart SHP block. Plus it's modern metallurgy, no 40 year old stuff.

i would use 6'' rods,,make the engine think it has a bigger cam in it..

So its been a few weeks now.

How is it running?

No pictures?

Uncle Dave

IMO

The only way you are going to see 400+ hp on a SB is with a 355 with a Cam Lift: .474'' Int./ .510'' Exh., Duration @ .050: 208° Int./ 221° Exh which would peak HP in the 5600 to 5800 RPM range max. GM Bowtie Vortecs or Aluminum Fastburn heads would be good choice.
Make sure all internals are forged.

355 .030 over bore with 5200 peak rpm cam will at most make 350hp. Cam here would be a Comp Cam HR XM 270. Vortec Cast and good dual plane intake. 600cfm carb.



I'm no expert but just my own experience. Comments Welcome

Get rid of that pu$$y 600 cfm carb and go to a 750,,your starving your engine....

It is not worth it...By the time you pay for bore deck main caps and line bore you can buy a Dart block..DONT WASTE YOUR TIME AND MONEY!!!!..

i to have assembed a 509 400 block 30 over for drag/street car we would plug the steam holes and deck the plugs smooth ran cometic headgaskets installed splayed mains ran a scat crank with a 5.7 h beam j/e dome pistons big solid roller cam sprayed it 500-800 hp of nitrous for 2 years of the line id change the plugs everynow and then and adjust valves that was it... block held up well other than one cylinder wall cracking on the non thrust side of the cylinder all at a early stage and i didnt know it took it apart for other reason and found it.. ran a stock waterpump with a mr gasket electric drive kit and a stock 3 core radiator i never once had a cooling issue drove it everywhere and ran mid to low 5,s in the 1/8th. id say you wouild be fine in a boat with cooling..

I get my Dart blocks for a great price..He has a place not far from Dart and stocks more than any one..Terry Rosebush 377 River Road Bay City, MI 48706
(989) 893-8299 Its worth giving him a call...I have done the same thing you are talking about and its not worth it..Listen? do you want to always have that blocks integrity in the back of your mind when your out on the water?..It is not much more than putting those china main caps on your block anyways so why risk it?..Not only that those 400 block and I dont care what number is cast on them is notorious for cracking between the steam holes and the head stud I dosent matter if they are filled and decked..To make matters worse your going to go .060 on it??? C'MON..This is a no brainer..

The 600cfm is enough for a 355 SB and does not starve the motor at all. A 750 is just to big for this size SB motor.

Question, What negative effects have you noticed running the 600 on a 355 SB?

I depends on the build. I run a 1050 cfm on a 409 small block.But thats with 245 cfm heads with 725 lift and 13,1 compression..600 cfm will run fine but you wont get the potential horsepower from it.650 dp is what you probably want but I am guessing since I dont know your build.