Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - Powerhouse 305 build
View Single Post
  #26 (permalink)  
Old 04-03-2012, 06:47 PM
oldbogie oldbogie is offline
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,805
Wiki Edits: 0

Thanks: 4
Thanked 443 Times in 380 Posts
Quote:
Originally Posted by Raith87
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!
Not without a blower or nitrous. BMEP has nothing to do with grenading the motor, it's basically a pressure efficiency measure, gas street engines run in the zone of about 8.5 to 10.5 BAR. A bar is about 14.5 psi (not 14.7) at standard temperature which doesn't exist in a running engine. It's thought of as the average cylinder pressure over the length of the stroke. Again in the real world there isn't any such thing. The pressure on the piston is a massive blast of heat and force in about the first 90 to 110 degrees of crank rotation on the power stroke, what remains of the 720 degrees in the cycle is coasting from that blast.

The problem with the 305 is that it has all the disadvantages of a long stroke, small bore engine. It has high piston speeds, high centrifugal loading at the rod to crank attachments combined with the poor breathing of a small bore diameter. At least a 350 does away with the breathing problems. A high flowing head tested on a 4 inch bore will not flow the same on a 3.73 inch bore even with the same valve sizes, not even close so forget the port volume to displacement comparisons to the 383 it's meaningless because the physics of the small bore work against the simple solution. A small displacement engine has to substitute high RPM horsepower for lower end torque. The problems of a 305 as to getting into high RPMs are a lot more difficult than the 4 inch bore 302. So if you want a small motor that goes fast; the venerable 302 with its 4 inch bore and 3 inch stroke is the way to go. Otherwise just build a 350, that at least will end up having the power of your dreams instead of becoming a technical nightmare.

Yes you can build a 500 horsepower 305 but the BMEP equations you're playing with will take you into the arena of serious power output engines like NASCAR Cup motors with BMEP's up in the range of 12 to 15 bar. This moves you out of factory 2 bolt main blocks, cast iron cranks, factory rods or even cheap 4340 rods, and certainly no hypereutectic cast pistons. This is moving into the area of Callies cranks, Dyers rods, and Mahle pistons. This quickly converts a 3000 dollar street performance build into a 30,000 race engine to get at the kind of power with some length of life you're dreaming of. You can get that kind of power out of a 350, or better yet a 383, for a lot less money as they are so much more efficient at turning gasoline into power than a 305. A 350 that delivers 400 horses is an absolute no brainer and 500 is not too much more difficult or expensive, it's almost taking a 350 with Vortec heads and a comp XE272 cam and trading the heads for some RHS's or AFRs or Darts and jazzing the cam to an XE282 with some tweaking to the compression and valve train then standing back and smiling; OK, s**t eating grinning. Most of this is in that extra quarter inch of bore, it's a world of difference. Ford has the same experience with the 289 and 302 Windsor (4 inch bore short stroke). A lesson about bore diameter to stroke ratios that Chrysler with the LA block didn't learn till the 340. There's something magic that just happens at 4 inches of bore and beyond with an inline valve wedge engine. The backside advantage is an engine that just makes lots of power and doesn't cost an arm and leg from your first born to get it.

"...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."

I have to wonder how these guys get the power numbers they toss around in these magazine articles. Kind of like back in the age of dinosaurs I was at the San Diego County Fair where this ambulance company had a booth with a Caddy 390 powered ambulance that they claimed delivered 500 horsepower. They did it with an OEM 4 barrel Rochester carb, stock Caddy cam, factory exhaust manifolds and dual exhaust into a Hyda-Matic 4 speed transmission (iron box automatic not today’s stuff). I was campaigning a 390 Ford FE at the time and with all the rocket science of the day it couldn't get to 500 horses. So I have my lingering suspicions about magazine articles and ambulance companies that pick out numbers from thin air. Add to that it appears the spell checker isn't working, Mr. Moderator are you behind the curtain. I saw no errors when first running the spell checking. I'm a professional engineer so I know it's not possible for me to compose this much without spelling errors so I dumped this into Word and got more of what I expected, as I know I ain't gonna win no spelling bee.

Bogie

Last edited by oldbogie; 04-03-2012 at 06:59 PM.
Reply With Quote