what kinda horsepower can a 400 block hold up to max. race and street. if it was a all out race motor it would run a few trips down the strip every other weekend. if it goes on the street. it will be driven every other weekend. just curious.
it will have forced induction and will have aluminum caps with girdle.

I feel that 850 hp would be the limit... That being said I'd also hard block it to the bottom of the freeze plugs.. Now that just me I'm sure there is others that have ideas also... I think that after 850 its not if it breaks its when..

i was always told that a stock RB block was good for about 600hp max(Safely) and the B block being good for maybe 100 more HP..now with that being said , i would use a main girdle and good main caps to hold the bottom together and then squeeze it for about 800-850hp..i never liked the hard block but as was mentioned above, everyone has their own preference and ideas..alot of guys are making 900+hp with a stock block, but i wouldnt chance all those good parts to a 30+ year old block.

650 is what i was told also about a stock RB block also. i know there is a little more webbing area on the low decks. there is a guy from sulphur louisana with a green dart i seen at the evadale track with a built 500 low deck and he also filled the block to the freeze plugs. dont know exact figures but he was makin some serious power for a street car that was natural aspirated. i asked why the low deck and he said for the strength. later i plan on gettin a after market block but i have to do with what i have for now.

Maybe some of my cap and girdle customers will chime in. I know of several over 900 hp motors that have two seasons on them and quite a few dozen in the 800 hp range and hundreds using my caps alone in the 600-700 range. That being said it all depends on what you start with as far as a block . Get it magged and sonic tested and a fill will only help.
There is no magic # and if one can afford an aftermarket block in the 700hp plus range he should, but if he can't we have the options.


Greg www.bcrproducts.com

dont worry dude your main cap kit is top of the list. just seein what everyone thinks.

I have a '71 400 "B" with the BCR mains and girdle.
This is for a 500" stroker build (4.15" stroke, 6.76" rod.) From what I've been told this is a really good compromise of good cubes, light weight rotating assembly, and good rod ratio. It also fits in the block easely. the bottom of the bores did not even need to be notched, just a small bit of the oil pickup boss needed trimmed to fit the rotation assembly. I think the real area of concern with the stock blocks is the stock oiling system. The lifter bores intersecting the main oil galley, and the #4 main/cam feeding oil to the rocker arms are the big issues if the engine will be turning high RPM. The stock block does not have alot of material to support lifter bushings, not the mention the bushings will reduce the size of the main oil feed galley.
I think if you are making less than 700 HP the stock block is a decent choice, and more than 800 HP I believe your better using the aftermarket block. It seems that between 700 and 800 HP it may depend on how much you want to spend modifying the stock block compared to just getting the new block. Also, the new blocks can be built with the 4.5"+ bore size and have room for larger stroker cranks.

i havent figured the amount of boost just yet. no hurry on this build. but i am building with the parts that i have around my shop. so after market block is out of the question. im tryin to find a safe number for HP to aim for is all. forged steel 440 crank. may use H-beams might use 6 pack. this is a budget build. i still havent decided if im goin with turbo or supercharged.

Something to keep in mind too... by the time you've bought the parts and prepped the block for that level (above 600-700), you have a significant amount of cash in it. Clean, mag, sonic test, fit caps and girdle, align bore/hone, modify the oil passages, lifter bushing, bore, plate hone, and square deck... It's close to $4K for all that for me and that is what I believe you need to do to make reliable HP in this package. And, the block's maxxed out. How much is a new better one compared to that level? With a budget of $9-10K (or more qwith a blower), having a rebuildable engine with room to grow is worth 1 or two thousand more IMO. Nevermind the overall more power produced at the crank because the bores stay straighter and the block doesnt move around.

i ran my RB 440 for 3 yrs/250 passes at 700+HP with no ill effect and now i have a [chenoweth]girdle but with stock caps,ARP studs.i am looking more long term and am getting a KP440 iron block because like stated i will want more HP as most do and will worry less with the investment.
good luck and enjoy your ride.