If I stick with dished blower Pistons, I'll have to get a piston with a raised compression height or do I need to get a longer rod to increase the the comp to 8.25-8.5?

Which model of powerbond damper do you recommend?

https://www.summitracing.com/parts/pbb-pb1018ss

A blower piston doesnt have to be dished. You dont increase compression by installing a longer rod. Rod length is determined by stroke and block height. You can use a 6.385 rod if you wanted to , in your build, but that would require a piston with a shorter compression height. Slightly better rod angle, but nothing thats gonna really matter. The stock 6.135 rod works fine. Now, if you ever thought down the road, you might install a 4.25 crank, the 6.385 rods would be able to be reused.

but anyhow, stock stroke, stock rod length, this piston would fit , and is a forced induction piston.

http://www.jepistons.com/Products/257980.aspx

Thanks MT, I have a powerbond PB1018SS on the way and the blocks in the truck to get dropped at the machine shop.

I've read a couple threads about bearing clearances, should I follow the Mercruiser book or is there suggested bearing clearances for the rods, mains, and cam?

Also I called JE and according to them the SRP 139477 and the JE 257980 are physically the same, both flat tops with a -3CC relief for the intake valve BUT the 257980 has different forge bosses and is made from 2618 alloy instead of 4032 alloy which I was told is much more brittle and won't hold up to detonation as well so they recommended the 257980 over the 139477, I wonder if the $400 price difference had anything to do with it.

I wouldnt get wound up in shooting for tight bearing clearances or anything. .0025-.0027 rods, .003 -.0035 mains, works.

Same goes for the pistons and rings. A set of plasma moly speed pro file fit rings will work fine, or the JE plasma moly file fits. I have around 140 hours on my short 468 short blocks mike tkach put together for me with speed pro plasma molys. Over 800hp, was running 9lbs boost . 6200rpm. Cylinder walls look like the day they were honed , and zero oil consumption between oil changes.

if buying new rods, i would opt for the arp2000 bolt upgrade.

i would have the line bore checked and honed if need be.

the bbc bottom end is stout. If the machine work, assembly, and oiling is good, they last. The valvetrain and tune is where main focus needs to be. Proper setup is key.

Im blown away by the work ive seen lately on cylinder heads. Ive seen several sets of cylinder heads from boat engines that have had half ass work done on them by professional shops. The main one that I noticed, is these heads all came in with no spring locators , or cups. Some had nothing at all under the springs, some had thin non hardened valve spring shims directly below the spring! The best valve spring in the world isnt very good when they are wobbling around, nor is metal shavings being sent thru the engine a good thing .

The other is mismatched hardware. Springs come in all different od and id. You need the hardware to match the springs. Having a locator with a .670 or .680 O.D, and a spring with a .740 ID , is no good. Valvespring setup is just as if not more important than the material they are made of.

I'm in the same boat as you...no pun intended lol...rebuilding my 525 currently...the machine shop I chose told me 700 hp should be an easy target with my setup....bored .030 dart heads ported eagle rods JE pistons roller cam and rockers with the 256 blower at 6-7 lbs intercooled....I'm not sure that i'll get 700 easily but we shall see...

BTW if you're looking for a blower upgrade...I posted my 256 for sale in the swap shop as I'm leaning more towards the 6-71 I have sitting at my house....just a thought

Good luck!!

Stewart

I think the 6-71 is the way to go, the 256 is just a small step above the 177. If I do a blower upgrade I think that's the route I'm going unless you're letting your 256 go for a good price.

What cam & rollers are you putting in?

I feel its a decent price for what it is...if I didn't already have the 6-71 I would use it without question but I got a good deal on it so just trying to get my money back out of it....not sure on cam specs as they are ground off...I bought the heads and cam lightly used from a guy which came off of a Keith Eickert built motor and from what I'm told he uses comp blanks and makes his own cams out of them...the lifters are comp and the rockers are crane golds...I also have a used set off crane golds I could sell cheap if you're interested...surprisingly my 525 already had them on it when I pulled it apart...I'm open to offers on that blower btw....the chiller and blower/intake are like a 9 out of 10 as far as condition...they are literally close to new

Stewart

oh I do have a few specs on the cam that I found...just off of the guys word I bought it from he said its 245 int 255 ext and 635 lift...not sure on duration or anything so the machine shop is going to check specs for sure before it leaves their shop to make sure it will work well for me

Stewart

thats alot of duration for a 454 based supercharged engine assuming its a hydraulic.

the 6-71 would be a much better choice if you want to make over 700hp.

Weiand Blowers On A Built 454 - Camaro Performers Magazine