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Old 04-01-2012, 06:16 PM
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Powerhouse 305 build

Ok, before i get started, let me ensure everyone who reads this, I fully understand that i could do more with a Gen 1 SBC, an LTX or an LSX. I also know that i will probably receive several negative comments about the 305, and how it is best suited to be a boat anchor, coffee table, etc... I am, however, determined to prove that the 305 is not the junk motor that most people think it is. I have done some research, and stumbled across an article from the January 2007 issue of Popular Hotrodding on a 305 build they did (here is the link for anyone who wants to read it, http://www.popularho...ks/viewall.html ). I have based my build plans on the same basic setup they were using, with some adjustments. In the article, their final result was a 372 horsepower 305, and that was using off-the-shelf aftermarket parts.

The motor, after it is finished and dyno tested, will be going into my 1984 Recaro Edition Trans Am, backed by a Tremec T56 manual transmission.


-What I'm proposing: A 500-525 horsepower fully built Carb'ed 305. (insert snickering, laughing, and 305 bashing comments here)

-My Plan: It consists of the following parts (subject to change assuming i can find parts better suited to the end goal)

-Block: completely stock 305 iron block from my 92 Camaro.


-Rotating Assembly: New 3.48" stroke crankshaft, new 5.700" connecting rods, new flat-top pistons, all standard size, no overbore, and no upstroke.


-Heads: 185cc intake runner Vortec Heads. Heads will be milled down by approximately .030" to reduce combustion chamber size to 58cc and in conjunction to the pistons, i should be running 10.2:1 compression (roughly). They will be running 1.95" intake valves and 1.5" exhaust valves, Comp Cams Elite Race dual springs.
A word on the heads, the Vortec heads from GM have an intake flow of roughly 233 cfm, this is, proportionately speaking, the equivalent of running a set of 290+ cfm intake flow heads on a 383 small block. running the 1.95/1.5 inch valves will keep shrouding to a minimum, but still allow enough flow into the cylinders for decent power.


-Camshaft: I am going to be running a custom grind cam. 276/282 total duration, 232/238 duration at .050" lift, .492"/.492" valve lift (with 1.6:1 rocker arms the valve lift would jump to .525"/.525") I will be running Hydraulic roller lifters, and 1.5:1 full roller rocker arms.


-Intake Manifold: I will probably run either a Victor Jr. or Super Victor single plane Intake Manifold for the top end power, I have looked into both dual and single plane, and the single plane seems a better fit for the build. I am still torn on this, as I have been looking at both the Victor's and the RPM Air Gap units...


-Carburetor: Holley 770CFM Ultra Street Avenger Carb (with black anodized metering blocks of course... since its going in a black car)... Electric choke, vacuum secondaries.

now, i have a few questions of my own...I have been running scenarios through desktop dyno 2003, and I have a question about BMEP numbers... what is the BMEP range for pump gas... i have a friend who was telling me that if the BMEP was too high, the motor would grenade itself.

If anyone has any questions, comments, or any input at all, please feel free to comment!

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Old 04-01-2012, 07:27 PM
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hey i think what u ur thinking is a decent set up but need some minor changes depending on if this is for a street car or for a race car first thing get a 650 cfm carb with a bigger throttle plate the 770cfm is just to much for it also if you plan on turning high rpms use the single plane and change the rocker studs to screw in instead of the stock press in kind also are you planning on doing this all motor or are you adding nitrous or super charger or turbo to it personally if its a street car i would go to a dual plane weiland intake port match it to the heads also to reach your goal you should think about some aluminum heads or port and polishing the vortec heads if you can get it done cheap enough get larger valves screw in rocker studs and add the bottle it is going to be hard and really expensive to get 550 out of a 305 with stock bore and stroke i have a couple ideas of how to get the power you want just asked if you want to know hope this helps some
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Old 04-01-2012, 07:36 PM
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I'm trying to hit the 500 horse mark on all motor, but if I cant get that to work, I will turn to a supercharger. I refuse to bottle feed anything... never did like NOS, my little brother just cracked his intake manifold because his motor backfired when he hit the nos yesterday...

I have a friend in NC who has built 2 remote Supercharger setups, one using an Eaton M90 and the other using an Eaton m122. If i have to got supercharged, I will probably build a setup very similar to his, though i would prefer not to since i really dont want to mount an Intercooler on the 84 Recaro T/A...

I am open to suggestions as to what i would need to get it to 500+ horse, I have already gotten a couple emails back from Comp Cams on a custom grind cam.
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Old 04-01-2012, 08:06 PM
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one way would be get you a 334 stroker kit from summit with ur vortec heads port and polish job that kit wit just the vortecs and a mild cam will put you around 400 ftlbs of torque so get a good cam port match everything and you will get some power out of it also remember if you decide to run a super charger you need to lower you compression try using so dish pistons instead in my opinion those heads a good cam with that stroker kit would be a fun street engine that would impress but would be a lot my fun with a supercharger set up ontop of it it would be a real torque monster that would be beating up alot of 350s out there
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Old 04-01-2012, 08:50 PM
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Dude you are not even close, the set up you have described would get you about 360hp out of a 305. Vortecs flow around 230 @ .500" with a 4.000 350 bore but with a smaller bore it creates less flow due to reduction in the size of the "vaccum". Those same vortex heads on a 305 with a 3.736" bore would only flow about 215 cfm @ .500". And this by no means converts to a 383 with 290 cfm heads, it doesn't work like that. A general rule of thumb to follow when looking at how much power a set of heads can produce on a perfect motor is to take its peak flow and multiply it by 2. Since on a 305 vortexes would put out about 215 cfm then about the maximum that you could expect to get from that motor is around 430hp and that would be on a perfect build.

Pretty much to get a 305 to hit 500 hp you will need to go forced induction or be able to spin it upwards of 8000 rpm and be running 13:1 compression and the combination you have there would only spin up to around 6000-6200 rpm.

I'm sorry bud but you are WAY off
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Old 04-01-2012, 08:52 PM
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the stroker kit is a possibility, but I really wanted to keep is as close to stock bore and stroke as possible... i will probably have to bore the block to make sure the cylinder walls are good (ie no gouges, not too far out of round, etc).

Assuming a .030" overbore, I'd be running it as a 309.9, which wouldnt really upset me too much. I am aiming for roughly 10.2:1 compression with the vortec heads, the 62-64cc combustion chamber in conjunction with a .039" gasket, 0cc flat top pistons and having the block zero-decked would get me close.

If I decide that i have to go supercharged, I will most likely drop compression to 8.5:1 or maybe a touch less.
I would be using an Eaton M90 from a 3800 series 2 or 3 supercharged v6, and running it through an intercooler. With the stock 3.8" supercharger pulley and the stock harmonic balancer, it would give me an approximate belt ratio of 2.1:1, so it would be running at about 14-16 PSI. (on the 3800 the 3.8" pulley runs a 1.58:1 ratio and is set at the factory for about 8 PSI.). I should be able to make well over 575 horse and 500 torque at 6000 rpm with the right cam.
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Old 04-01-2012, 08:53 PM
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And oh by the way, the 305 is a gen 1 SBC
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Old 04-01-2012, 08:56 PM
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Quote:
Originally Posted by my87Z
Dude you are not even close, the set up you have described would get you about 360hp out of a 305. Vortecs flow around 230 @ .500" with a 4.000 350 bore but with a smaller bore it creates less flow due to reduction in the size of the "vaccum". Those same vortex heads on a 305 with a 3.736" bore would only flow about 215 cfm @ .500". And this by no means converts to a 383 with 290 cfm heads, it doesn't work like that. A general rule of thumb to follow when looking at how much power a set of heads can produce on a perfect motor is to take its peak flow and multiply it by 2. Since on a 305 vortexes would put out about 215 cfm then about the maximum that you could expect to get from that motor is around 430hp and that would be on a perfect build.

Pretty much to get a 305 to hit 500 hp you will need to go forced induction or be able to spin it upwards of 8000 rpm and be running 13:1 compression and the combination you have there would only spin up to around 6000-6200 rpm.

I'm sorry bud but you are WAY off
what i had said about the heads flowing the same on a 305 as a set of 290cfm heads would flow on a 383 was pulled directly from the Popular Hotrodding article i linked to, I am going off their information... and I plugged their build into my dyno program, and it was almost dead on, and started making my changes from there.
EDIT: didnt realize the link was jacked up... http://www.popularhotrodding.com/eng...s/viewall.html

Last edited by Raith87; 04-01-2012 at 09:05 PM.
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Old 04-01-2012, 09:03 PM
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WOW!

I have never seen a 0cc flat top piston, they all pretty much have valve reliefs in them ranging from 4cc to 7cc

575hp and 500tq @ 6000 rpm with a 305!!!

I'm sorry but based on the things you have mentioned, you are no where near where you need to be knowledge wise to take on a project like this, cause everything you have mentioned is something a "magazine reader" would say.

Lower your expectations to say 350hp, and you may be successful with a lot of help from people on here.
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Old 04-01-2012, 09:15 PM
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A dyno sim program is exactly what it is, a computer making guesstimates. My dyno sim program has my motor making over 670hp, on a true engine dyno it pulled 100 less hp. And the comment on the heads between a 383 and a 305 makes no sense, maybe I would have to read the article to better understand what they are trying to say but the way you put it makes no sense.

Put it like this, my old set up on my 385 had 292 cfm @ .550", a 240 @ .050 cam and 10.4:1 compression, it was professionally dyno tested and tuned and it came out with 512hp @ 5900 rpm. You are expecting similar numbers from far less flowing heads, 80 less cubes, one of the smallest cylinder bore SBC motors ever, and to do it all at the same rpm
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Old 04-01-2012, 09:17 PM
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You are going to fall way short of your goals with those heads and that camshaft trying to feed a small amount of cubes. An engine is an air pump, nothing more. In goes the air with a corresponding amount of fuel, and it goes boom. To get 305 cubic inches up near the 500-525hp mark those heads will need to flow around 300cfm, and the cam will need to be generous. Something around a 250/260 @.050" minimum. The only problem is that there are no cylinder heads capable of flowing that kind of air with a small bore 3.8" which is what you have. Even if you got a heavily ported set of heads to flow near that number, you'd need a camshaft that would peak well over 7000rpm. To run that kind of rpm, you'll need a solid roller cam, strong lifters, big pushrods, shaft rockers, good springs, etc, etc. That stuff adds up real quick. You'd have yourself a nice $10,000 305, that makes as much power as a $6000 383 but about 100ft/lbs less torque.

I'm not knocking your 305 idea, but 500hp isn't going to happen unless you go forced induction or n2o. You can still build it stout and make 400hp.
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Old 04-01-2012, 09:18 PM
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Quote:
Originally Posted by my87Z
WOW!

I have never seen a 0cc flat top piston, they all pretty much have valve reliefs in them ranging from 4cc to 7cc

575hp and 500tq @ 6000 rpm with a 305!!!

I'm sorry but based on the things you have mentioned, you are no where near where you need to be knowledge wise to take on a project like this, cause everything you have mentioned is something a "magazine reader" would say.

Lower your expectations to say 350hp, and you may be successful with a lot of help from people on here.
http://www.cnc-motorsports.com/pisto...-736-bore.html
that there is a 305 sbc 0cc flat top piston from keith black.

I have been basing all my numbers off my desktop dyno 2003 program, (i have questioned the accuracy before, but for chevy small blocks it seems to be very close to an actual dyno, as i have used friends build specs on actual dyno'd motors) all numbers that i have quoted have been at the crank.
The 575hp and 500tq @ 6000 rpm was based off a supercharged setup running 14PSI into an intercooler at 50% efficiency, that again, dyno 2003 spit out.
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Old 04-01-2012, 09:40 PM
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It sure enough is, and you want to know why people don't see those type pistons very often, it's because at a moderate lift and high rpm were you run into valve float you are going to smack the pistons and bend the valves. Even a forced induction 305 will need to run up past 7000 rpm to hit 575, and a NA 305 would have to spin upwards of 8000 to hit 500hp.

I'm not knocking your idea of building a stout 305, I have one in my spare Iroc that I built last year that I would say produces around 340hp. My current motor set up I have over 8,000 into it, it's the same 385 but with machined heads producing 319cfm at .650" (flow tested in front of me), I have a A cam that is 255 @ .050 .640" 11.2:1 compression i shift at 6600-6700 rpm and it makes 570hp/530tq.

In a smaller cube motor you have to turn more rpm to make higher hp (rpm=hp)

I'm sorry but you are just not close, what you have described is only a 350ish hp motor
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Old 04-02-2012, 07:05 AM
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Consider forced induction. I just finished putting the long block together for a twin turbo 305 this weekend. I'm going for 400-450hp at 12 -15 psi. It may come apart but hey its a 305. No one wants them and I only have maybe $300 into it. Listen to what everyone else is saying. Theres a reason why very few build these for performance. Your not gonna prove anyone wrong and come up with some amazing secret. Any thing you can do on a 305 can be done on a 350 and make more power.
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Old 04-02-2012, 08:59 AM
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Quote:
Originally Posted by Florence95
I refuse to bottle feed anything... never did like NOS, my little brother just cracked his intake manifold because his motor backfired when he hit the nos yesterday...
Your lucky that 100 shot of NOS didn't blow the welds on the intake!! LOL oh fast and furious
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