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abigassbowtie 03-17-2009 10:31 PM

horsepower guesses?
I am new to this site I am building a sbc 409 (.040 over 400) Im kinda new to the engine building I would love to put it on a dyno but just cant justify spending 400 on somebody else tuning my motor and knowing how much horsepower it makes anyway this is what I got and please bare with me I dont know all my part numbers

holley street avenger (670?)
ported edelbrock performer rpm heads stock valves 64cc chambers
holley strip dominator intake
speed pro forged pistons -4cc dish = 11-1 cr
solid roller comp xr 292
in a 509 400 block
stock polished and shot peened rods (5.7)
stock crank

anyway what do you think for hp and torque I know some of you guys are real good at this and I know everyone thinks that theyr motor makes way more than it does so dont hold back

abigassbowtie 03-18-2009 10:36 AM

what am i missing here to not get any answers sorry if it is something stupid I missed just really would like to know

heyjude076 03-18-2009 11:10 AM


Originally Posted by abigassbowtie
what am i missing here to not get any answers sorry if it is something stupid I missed just really would like to know

Can't help with Hp but give the guys some time. You posted at midnight and 12 hrs later want answers. Hey the west coast guys are probably just on their second cup of coffee and the east guys are on lunch. Have patience and I am sure someone will chime in with some figures.

abigassbowtie 03-18-2009 12:24 PM

thanks guess Ill just have to be more patient

454C10 03-18-2009 02:33 PM

should be a lot. So kind of hard to guess.

carb and heads are little small.

I calculate 11.3:1 cr for your setup, which is a little high. I think you will need to run 93 octane and retard timing a little. 10.75 or even 11:1 would be better.

but I would say 500/530 ftlbs if the engine is assembled and tuned correctly. Heads are most likely holding you back, but will make extra low rpm torque for the street.

abigassbowtie 03-20-2009 10:47 PM

I really wanted it to make good torque cause my pick up weighs about 3700 with me in it I have messed with alot of old bottom ends you know putting cams in changing heads and junk like that but this is my first real build up and I have been told that I should hit the 500 hp mark but wanted second opinions thanks I appreciate your guesses

ericnova72 03-21-2009 12:13 AM

It would be worth it to have the heads cut to 2.055 intake valves if you have the cash, the 400 needs air like it was a small big block. IMO the 670 carb is too small, even for a torque motor, so don't worry too much about torque because the 400 will have it anyway. Way, way more than a 350. Intake is a good choice, cam is also. STUD THE MAINS, ARP bolts in the rods, Stud Girdle on the rocker arm studs. 1-3/4" headers best but 1-5/8" will work nearly as good, get what will clear the angle plugs.

I've built several nearly identical versions of this combo, you could easily see 540+hp if the heads are good. Believe me, once you mash the gas on this, you will never look at a 350 the same way again.

EDIT: Compression ratio is a little stout for pump gas unless you stay on top of the tune and ignition advance curve. If you want to take some away, open up the combustion chambers some to the bore outline around the intake valve, curving over to the spark plug.

cobalt327 03-21-2009 03:14 AM

I don't want to open a can of worms here but some 400 4-bolt blocks have had issues w/main webs breaking when stressed.

I believe the reason that Chevy went to a 2-bolt later on was due to this- they found better reliability from it, rather than the 4-bolt configuration. If you look closely at the 4-bolt web, you can see how the bolt "holes" it.

A better scheme is to use a 2-bolt and splayed caps if you don't go w/an aftermarket or bowtie block, IMHO.

I know others swear by the 4-bolt blocks, and have had great luck w/them, and I have absolutely no prob. w/that.

ericnova72 03-21-2009 04:29 AM

Cobalt is right about the weakness of the 4-bolt 400 and why Chevy went to 2-bolt, and it is why the smart racers don't go looking for a 4-bolt 400. That being said, there aren't 400 blocks on every street corner and so we have to run with what we have. I've run 4-bolt 400's at this power level without a failure but it was not by choice. Getting up over 500hp in a stock block of any brand is always a gamble, that's why Dart is doing good business. :)

cobalt327 03-21-2009 06:56 AM

EDIT- moved to start a fresh thread.

abigassbowtie 03-23-2009 12:09 PM

hey guys I sold my 4 bolt 511 block to help fund this build but the 509 block is a two bolt main im sure excited all i have left to buy is push rods and guide stud girdles and everybody I have talked to around here (my machinist) has told me I need to run some race gas to accomodate for my high compression wich I am ok with I dont plan to drive this truck as a daily driver and thanks so much for your guys input and now you got me thinking to take my heads off to have new 2.05 intakes in do you know if 2.08 would fit performer rpm heads my dad always told me it was better on 400s to run the biggest you could on the intake valve side it sucks not having him around to ask these ?s

abigassbowtie 03-23-2009 12:15 PM

and I have lots of holleys I have a 780 cfm single pump vacuum secondary would that be a better choice for my application

cobalt327 03-23-2009 01:05 PM

Personally, I really like dbl. pumpers/ mechanical secondary carbs. For your deal, at least a 750.

While larger valves can be worth some power, if I were to have wanted 2.08's say, I'd have bought different heads (Dart, etc.) with a larger port and combustion chamber volume than the RPM's.

This starts a never ending cycle- at some point you have to commit to a build, optimize the components, buy them and build.

If you keep changing your mind (I know how this works :pain: ) the costs and complexity keep rising.

Were it me- and I had amassed the parts that you have, and given the weight of the truck- I think I'd go ahead with the build as-is. But a different set of heads sure would be nice... and then I could use different pistons, and gears, and then...

See what I mean? :D

abigassbowtie 03-23-2009 01:25 PM

very true thats how this build got started I had a all stock 511 400 in it and I wanted to change cams and then I thought well I could go with a better cam if I can find some decent 64cc heads so I had it down to a short block then I thought well Ill just pull it out and check the rods and mains make sure they are nice and then they werent so it was a complete rebuild then I found a 509 block a better crank I found my heads for 500 complete rebuilt with all port work already done and had some 5.7 rods laying around already shot peened and polished and I had the forged pistons with them and all of a sudden I didnt use a single part of the original motor thats what I hate about tearing stuff apart it always costs you money

ericnova72 03-23-2009 06:32 PM

The 780 carb is a better choice than the 670, and I have good success with vacuum secondaries, but you need to know how to tune the accellerator pump and the vacuum secondary spring, otherwise a DoublePumper is more fool-proof. If the heads are already on the motor, I'll agree with run them as is, you could always pull them for a valve size upgrade next winter if you find you want to look for more power at that point in time.

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