Small Block & Big Block Chevy Specific - guess my rwhp!

alright here we go. ive been building a 406 sbc for my 1972 camaro SS. it is a t56 six speed pro touring car weighing in at 2736lbs. the motor combination is as follows. 1976 2 bolt main 400 block bored to 406 cubes, splayed billet main caps, callies 3.75" stroke crank, lunati 5.7 h beam rods and wiseco .150 dome pistons, rings have been gapped .03 for the n2o, the cam is a lunati solid roller 286/294@.050 and .691/.691 on a 113 lsa. the induction consists of dart pro1 platinum 230 cc heads ported to flow 346 cfm@.630 lift going through 2.08 intake and 1.6 exh valves. the intake is a super vic 4500 with a king demon rs 1090 cfm carb on top tuned with 82h high flow jets. the valvetrain consists of jesel shaft mount rockers at 1.6/1.7 staggered ratios with 3/8 pushrods. the motor yeilds 14.0:1 compression and runs on 123 octane. and for exhaust the spent gasses go thru stahl 2" primary into 3.5 inch collector headers into open atmosphere. the timing is set anywheres between 32-38 degrees. the rear suspension consists of a heidts 9 inch 4 link bolt in rear with 4:56 gears with a detroit locker. only reason im posting this is to see how close someone can gets to guessing a dyno # based off specifications. also going to plumb in a 250 hp n2o fogger so guess both on and off n20 numbers in 38 degree weather

698rwhp

Slow...

565 RWHP on Motor 715 RWHP on 250 shot.

A car like that would FLY...very cool that it's not just a drag car also.

dynojet? I'd guess 540rwhp @ 7400rpm with 35 degrees of timing. and 200 more on the hose.

I am thinking 650 rwhp. Maybe I am a little high but that cam is monsterous no? With a 200 shot I am thinking 840s obviously.

thanks for the guesstimates. as soon as the car gets strapped to a dyno ill post the #s im just hoping that theres not weak link between the flywheel and driveshaft:devil:

I hope the block holds at that power level. Should, but shit happens.

I hope the block holds at that power level. Should, but shit happens.
it will. i always overkill everything. was at a point of doing 18 degree heads and a .730 lift cam with a lot lower of compression with a single 91 mm turbo. at that point it would have made enough power to rip the main webbing out of the bottom end. i just decided to know when enough was enough with this factory block. ill dump my cash into a better motor here as my next new build. im thinking a lil "m" block with sb2 heads & a tornado bolted to it!! but for now this decent powered motor will hold me over for a couple of months.

any prize for the winner? i say it'll make 598 to the wheels.

720 on motor 880 on the spray.

2 bolt main? wont that be a weak link.

He said it is splayed.

i woulda just went with dart block from the start.
i guess 575rwhp

590-620 depending on tune. Maybe closer to like 620-640rwhp range.....????

Idk. That engine on the dyno should make at least 710hp...probably 730.

Where were the heads ported????

Where were the heads ported????u.s.a racing engines. im about to send them a set of lsx heads to see the magic they can do with those.

306 horse at the wheels :D

306 horse at the wheels :D

At 3000 RPM.:chug:

u.s.a racing engines. im about to send them a set of lsx heads to see the magic they can do with those.

usa, i remembr when they worked on my vortecs back in the day.
good place

2 bolt main? wont that be a weak link.

no, 2 bolt 400 blocks are stronger than the 4 bolts.. not to mention a splayed 4 bolt main he has

i was going to go with a similar setup with my 400 block, but i think im going to make it rather mild (450hp) because im afraid of cracking the block

Whats the runner volume on the heads???

The block wil have issues befor the bottom end . I have run these blocks for 20 years and the splayed caps are stronger than the wall to head bolt area. I hope you half filled it . i say 610 on motor 717 on the dope

Whats the runner volume on the heads???
230cc

The block wil have issues befor the bottom end . I have run these blocks for 20 years and the splayed caps are stronger than the wall to head bolt area. I hope you half filled it . i say 610 on motor 717 on the dope
yea a lot of people i talk to all have the same misconception. they all call the 400s pieces of shit. mostly because they never built it right in the first place. and didnt think they needed steam holes in the block and head deck surfaces to run a 12.5:1 comp 406 as a daily driver in summer traffic. then clearance as another factor. most only buy the parts and install but never checking bearing clearances or proper ring gap.

230cc

LMFAO!!!! NO.......What are they NOW???!!! AT LEAST 245cc....To flow 345cfm, They GOT SOME VOLUME.

LMFAO!!!! NO.......What are they NOW???!!! AT LEAST 245cc....To flow 345cfm, They GOT SOME VOLUME.
ill look at the flow sheet that my builder has.motors not too far off from being installed. just had a few small changes that i made .

Def would've gone with at least a 4 bolt main if not an aftermarket block. Seems like you went balls to the walls on the rest of the car...why not the block? Splayed is great but 4 bolt main is better than 2!

Um...613rwhp on motor, 865rwhp on the 250hp shot.

I have a similar setup myself...388ci, little less duration/lift/cfm/compression, but I'm adding a 300hp shot...also running through a th400+dana 60+engine driven fan so I should be robbed of a few more rwhp than you :P.

Def would've gone with at least a 4 bolt main if not an aftermarket block. Seems like you went balls to the walls on the rest of the car...why not the block? Splayed is great but 4 bolt main is better than 2!

Um...613rwhp on motor, 865rwhp on the 250hp shot.

I have a similar setup myself...388ci, little less duration/lift/cfm/compression, but I'm adding a 300hp shot...also running through a th400+dana 60+engine driven fan so I should be robbed of a few more rwhp than you :P.

a splayed two bolt block has the original two bolts plus two extra bolts at an angle, so how in the world is a 4 bolt better than a splayed 2 bolt??? :bang: it only makes sense that two straight and two angled bolts would be far harder to break than 4 straight bolts are to stretch. just a simple matter of fact.

Def would've gone with at least a 4 bolt main if not an aftermarket block. Seems like you went balls to the walls on the rest of the car...why not the block? Splayed is great but 4 bolt main is better than 2!

Um...613rwhp on motor, 865rwhp on the 250hp shot.

I have a similar setup myself...388ci, little less duration/lift/cfm/compression, but I'm adding a 300hp shot...also running through a th400+dana 60+engine driven fan so I should be robbed of a few more rwhp than you :P.

lol what?

you would have to be stupid to use a 4 bolt main 400SBC in a high rpm/horsepower car, UNLESS it is an aftermarket block with splayed 4 bolt main caps..

So what did it put down? You cant start a thread like this and then let it die

a splayed two bolt block has the original two bolts plus two extra bolts at an angle, so how in the world is a 4 bolt better than a splayed 2 bolt??? :bang: it only makes sense that two straight and two angled bolts would be far harder to break than 4 straight bolts are to stretch. just a simple matter of fact.

Obviously splayed is better...but a splayed 4 bolt is better than a splayed 2 bolt, just like a regular 4 bolt is better than a regular 2 bolt. Why would you compare a splayed 2 bolt to a regular 4 bolt?

lol what?

you would have to be stupid to use a 4 bolt main 400SBC in a high rpm/horsepower car, UNLESS it is an aftermarket block with splayed 4 bolt main caps..

Again...for the money he's all ready spent on this motor...why would you assume I WOULDN'T be recommending an aftermarket 4 bolt? I'm sure he knows what he's doing and that the splayed 2 bolt will be fine but if I had the money the first thing I would get is a beastly block that way no matter what I threw at it that's one thing I wouldn't have to worry about.

Still wondering how much power it made...

Obviously splayed is better...but a splayed 4 bolt is better than a splayed 2 bolt, just like a regular 4 bolt is better than a regular 2 bolt. Why would you compare a splayed 2 bolt to a regular 4 bolt?

You dont know what YOU ARE TALKING ABOUT! 4-bolt 400ci's have the inner bolts too close to the outer bolts due the 2.65" mains vs. the 350ci's 2.45" mains....This makes the main webbing very weak...A 2-bolt 400ci IS STRONGER THAN A 4-bolt 400ci in EVERY WAY!

A 2-bolt converted is ALSO STRONGER!..ALSO DUE TO NOT HAVING THE EXTRA HOLES!....

....Dont argue if u dont know....

il go with 704 at 6800 since i have a very similar motor sitting in the corner waiting for me to get off my ass and put it in

il go with 704 at 6800 since i have a very similar motor sitting in the corner waiting for me to get off my ass and put it in

not at the wheels....

LMFAO!!!! NO.......What are they NOW???!!! AT LEAST 245cc....To flow 345cfm, They GOT SOME VOLUME.the heads were cc'd the combustion chambers were at 58cc the intake runners at 248cc. still have more material left to port into by far these heads have absolutely flowed awesome. the motor was dynoed friday night it made 773fwhp & 741 fwtq. that was with a tuned 895 cfm barry grant street demon on 116 octane with 82h jets at 28 degrees of timing spinning the motor to 6500 rpm. im going to change out the bg street demon for a 1095 cfm king demon rs, change plugs up the timing to about 32 degrees and fog a 250 hit of n20 into it and pull it up to about 7500-8k rpm and see what it makes this coming weekend

Affirmative! The 4 bolt block is weaker than its 2 bolt cousin. We learned that one first hand back in the 70's.

wow 773 and 741, bad ass! Cant wait to see the rest of the numbers!

wow 773 and 741, bad ass! Cant wait to see the rest of the numbers!yea im pretty happy with power output vs the money i have in this build. even worst case at 15% drivetrain loss itll be cranking out 659 rwhp on motor. in a 2700 lb car that is a very brutal ride with traction.:devil:

yea im pretty happy with power output vs the money i have in this build. even worst case at 15% drivetrain loss itll be cranking out 659 rwhp on motor. in a 2700 lb car that is a very brutal ride with traction.:devil:

773 hp from a stock gm 400 block?

holy crap

what all did you do to the block to strengthen it up?

the crazy thing is that i priced out a bunch of stuff for my 400 block, and everything was almost the exact same except that i went a little milder with the cam, at 254/258 @.050 and .630" lift

may i ask how much you put into this engine? i was up to $6500 minus the little stuff and getting the block machined

773 hp from a stock gm 400 block?

holy crap

what all did you do to the block to strengthen it up?

the crazy thing is that i priced out a bunch of stuff for my 400 block, and everything was almost the exact same except that i went a little milder with the cam, at 254/258 @.050 and .630" lift

may i ask how much you put into this engine? i was up to $6500 minus the little stuff and getting the block machineddidnt think that much hp was out of the ordinary for these block. not like they are made from porcelain. just good machine work and the right builder to make it live and be reliable. i have right at 7k$ invested in this. the heads were the area i spent the most money on. 2200$ port job and shaft mount rockers 932$. adds up really fast. cannot wait to see how this thing pulls. and scare a few passengers while im at it!:D

How the hell did you get 773hp from only $7,000 invested? Who did you steal from or where did you get your insane deals from?

How the hell did you get 773hp from only $7,000 invested? Who did you steal from or where did you get your insane deals from?
most of the stuff i bought was at vendor pricing and the machine work was done as mostly a return favor. so figuring in port work and the actual price you would pay for everything in reality theres about 12k in this motor. but like i said i only have 7k out of my pocket!

Nice build, great numbers! My friend (daycare provider's hubby) runs a similar setup in his Vega minus the port work and with a Holley on top. Through a 'glide he runs 9.30's all day and is good for high 8's on the bottle. Not sure what he sprays though.

Great job, should make for one nasty ride!

ah 12k sounds more like it. Probably have about 13k in the 388ci I have at home. Hoping for ~675hp at 7,000-7,200 rpms and 925hp on the bottle.

Serious question for you then. I'm using a 4 bolt 350 block punched out .060 over. Would that stock block handle a VERY occassional 300hp shot (I need nitrous pistons/rings anyway) like...maybe 5-10 hits a year at most or should I get a dart block because you say you're spraying 250hp on a stock 2 bolt 400.

ah 12k sounds more like it. Probably have about 13k in the 388ci I have at home. Hoping for ~675hp at 7,000-7,200 rpms and 925hp on the bottle.

Serious question for you then. I'm using a 4 bolt 350 block punched out .060 over. Would that stock block handle a VERY occassional 300hp shot (I need nitrous pistons/rings anyway) like...maybe 5-10 hits a year at most or should I get a dart block because you say you're spraying 250hp on a stock 2 bolt 400.i would say its good for it. ive seen bigger foggers on motors just like that. just make sure that fuel system is up to the task of it. only reason im going to a merlin or dart block later is to get more cubes from my sbc and the added strength of course. but thats later on. i just want to enjoy it as is now. one thing is that the motor may not respond to a shot bigger than 250 hp. my builder dynoed a 357 ci sb that the customer wanted to spray a 400 hp fogger on. after shooting the initial 200 hp to it. they jetted up to 350 hp jets. and it didnt make any difference in hp. actually made less !

Nice build, great numbers! My friend (daycare provider's hubby) runs a similar setup in his Vega minus the port work and with a Holley on top. Through a 'glide he runs 9.30's all day and is good for high 8's on the bottle. Not sure what he sprays though.

Great job, should make for one nasty ride!thanks,
cannot wait to see what see car traps with the m6 in it. i still gotta overcome the traction part when i get there. ill tune on the 4 link till its just right and hope it all holds together

Update??

didnt think that much hp was out of the ordinary for these block. not like they are made from porcelain. just good machine work and the right builder to make it live and be reliable. i have right at 7k$ invested in this. the heads were the area i spent the most money on. 2200$ port job and shaft mount rockers 932$. adds up really fast. cannot wait to see how this thing pulls. and scare a few passengers while im at it!:D

from what i hear the 400 blocks are a bit weak and its easy to crack them after 500hp or so

did you fill the block at all?

A 2-bolt main 400 with the 2-freeze plugs is the strongest factory block.
A 4-bolt main 400 is the next strongest.
A 2-bolt main 400 with the 3-freeze plugs is the weakest.
(unfortunately I spotted my 4-bolt main block, and got it just for the sake of 4-bolt mains, before I learned all this :( )

Splayed caps with arp studs in a 2-freeze plug block that's been filled might handle 750whp but personally, I would have gone aftermarket block if I had you top end. Keep her cool and be gentle with the spray!

from what i hear the 400 blocks are a bit weak and its easy to crack them after 500hp or so

did you fill the block at all?
too much speculation . i would just go into it balls to the wall. i did it and dont regret it. too many people that are full of shit about these motors too quick to make em look bad. i made 773 all motor on mine and itll be making a hell of a lot more on the bottle. ive gone thru every aspect of this build from taking into account block strength and torsional flex. none seem to have been a problem for me. theyve built wilder motors based on the same block i have. and have equipment to measure the stress on every angle of this block while its being run on the dyno. and when you actually invest into splayed caps and good hardware, quality machine work there should never be issues with reliability.

too much speculation . i would just go into it balls to the wall. i did it and dont regret it. too many people that are full of shit about these motors too quick to make em look bad. i made 773 all motor on mine and itll be making a hell of a lot more on the bottle. ive gone thru every aspect of this build from taking into account block strength and torsional flex. none seem to have been a problem for me. theyve built wilder motors based on the same block i have. and have equipment to measure the stress on every angle of this block while its being run on the dyno. and when you actually invest into splayed caps and good hardware, quality machine work there should never be issues with reliability.

i know a guy who does machine work on blocks and he says out of all of the chevy blocks he does, there are more cracked 400 blocks than any other

im assuming it is due to core shift, which seem to be somewhat of a problem with the 400 blocks

Update??finally got to make a nitrous pull on it. my builder didnt have time to plumb up the direct port fogger. so we installed a plate kit on the 150 pills. backed timing down to 27 degrees. ran the motor up to 7k rpm. it made 905fwhp & 865 fwtq. not one hint of trouble:D, actually just one.:bang: not enough crankcase venting. after that pull it built up enough pressure to push up a breather!

you kick ass, just want to let you know, you sir can build a motor,!!!!

Gonna be one sick 2nd gen :devil:

you kick ass, just want to let you know, you sir can build a motor,!!!!thanks! however i didnt build the motor, just gave the builder my personal tolerances, and what i wanted to run and spec'd out the right cam and heads for it and let him go to town on it!

Gonna be one sick 2nd gen :devil:we will see how it delivers once the motor is bolted between the fenders. my 2700 lb car with this setup will have some very nasty street manners but ill still drive the wheels off of it! probably more than my new car! lol :D

niceeeeeeeeeee...cant wait to see this beast in person...

i miss my 2nd gen...:eyes: