305cid/372hp who said it couldnt be done - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Closed Thread
 
LinkBack Thread Tools
  #1 (permalink)  
Old 11-11-2008, 09:05 AM
Member
 
Join Date: Dec 2007
Location: Garage
Posts: 33
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
305cid/372hp who said it couldnt be done

I was never one of those guys who disliked or talked down on the NEVER so popular 305sbc. When I started my project lots of guys taunted me about my craziness. I believe in making use of what you have, along with $1000 to burn. Yep, thats all. Thats what I love about chevys, cheap horsepower.

I bought a 1974 chevy pickup for about $1800 which had what I thought was a 350cid. I took the guy I bought from word that it was a 350 but later discoverd it was a 305cid with centerbolt heads. I later put headers and a holley on it just cause I had the parts laying around. Horsepower was ok afterwards but nothing to boast about. I have an Uncle who is a truck freak. In his collection he has a 59 chevy pu,66 chevy pu, 81 chevy pu, 85 chevy pu, and an 86 chevy pu. All are restored to originalty with monster motors.

Anyway, I wanted a monster too but was sort of on a budget(that damn economy). My uncle was one the ones who told me I'd be better off getting a 350cid but I was set out to prove him and everyone else wrong. Did a lot of research on 305's and those who attempted the build and came back with fascinating results.

The motor was a bone stock truck 305 with dished flat tappet pistons and poorly breathing heads. I had the truck dynoed just for pete sake and I was surprised of the 212hp, way more than what I expected. So with the idea I had in mind I set out to find a nice set of vortec heads. Vortec-style castings are just the ticket, with the right size valves, at 1.94/1.50, to fit and function in the smallish bores. Besides good flow, price is a key consideration when dealing with a 305.Ebay was where I found them and they were in very good shape. Obviously, cam and valvetrain would be part of the strategy. With the engine's small-displacement and undoubtedly compromised compression ratio, too much cam would be counterproductive. Since this is a flat-tappet engine, I decided to stay with that type of camshaft, as opposed to a retro-fit hydraulic roller, which would have been considerably more costly. Had this been a higher compression roller block, I definitely would have gone with a more aggressive hydraulic roller camshaft. While erring too big would ruin the build, erring too small is also a mistake-one that would curb peak power. After much consideration, a COMP XE268H flat-tappet hydraulic was chosen. This cam allows a smaller engine to make power up into the 6,000-plus rpm range, yet its relatively short duration, at 224/230-degrees, preserves cylinder pressure and maintains acceptable street idle quality. For a general purpose real street cam, this stick is hard to beat.The manifold decision was easy, since the Edelbrock Performer RPM AirGap consistently shows the capability to make good peak power, while having much better torque than a single plane. With the 180cc EQ heads, the AirGap would be a perfect match when considering the port sizes. To top the manifold. I kept the original holley 600cfm that was already there. Out of nearly 900 bucks I was curious of power. Keeping my same firing system and same th350 tranny with B&M shift kit I was out the garage door hauling pure ***. of course after taking her around the block I had to come back and fine tune her but later during the week it was off to the dyno. And what do you know 372hp to the rear wheel. Sounds like bologna but its true. Thats a respectable horsepower range for any street machine huh. I think im track ready but the rear-end needs a posi track which will be coming much later. The truck has stock 3.73 so all I need now is more grip and less slip.


Comments are welcome

    Advertisement
Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 11-11-2008, 09:29 AM
curtis73's Avatar
Hates: Liver. Loves: Diesel
 
Last wiki edit: How to find cheap parts
Last journal entry: Found an LQ9 today
Last photo:
Join Date: Dec 2005
Location: Carlisle, PA
Age: 41
Posts: 5,173
Wiki Edits: 16

Thanks: 7
Thanked 9 Times in 6 Posts
Wait... Here is what I extrapolate from that fluff:

A dished-piston 305 with 305 vortec heads will make about 8.5:1 compression. With 350 Vortec heads it will make about 7:1 compression. So you put a big cam and intake on it and claim 460hp at the crank? I call BS.

Either Dyno slips or a better explanation of where that power is coming from would be great. Maybe a 200 shot of Nitrous? Or a 15 psi turbo?
Quick reply to this message
  #3 (permalink)  
Old 11-11-2008, 09:32 AM
Registered User
 
Last photo:
Join Date: Jul 2006
Location: Baroda, MI
Posts: 210
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
So you are saying 372 at the rear wheels with this:

305, stock bottom end, stock pistons
Hydraulic flat tappet cam
Vortec heads (but later on said they were EQ's?)
RPM airgap intake
600 Holley
Headers
Stock HEI

So using about a 1.21 correction factor we'd estimate this thing at 450hp at the flywheel.

Not knowing stock dish I'll estimate it's 10cc. So 3.736 bore x 3.48 stroke, 9.025 deck height, 64cc heads - that puts you right at an 8.1:1 C/R.


Ok - I did the math - someone else fill in the two words that come to my mind?
Quick reply to this message
  #4 (permalink)  
Old 11-11-2008, 09:33 AM
Registered User
 
Last photo:
Join Date: Jul 2006
Location: Baroda, MI
Posts: 210
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Curtis73 beat me in the speedy reply

And he beat me for the two words that came to my mind too!
Quick reply to this message
  #5 (permalink)  
Old 11-11-2008, 09:36 AM
Member
 
Join Date: Dec 2007
Location: Garage
Posts: 33
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
No where did say 460hp. I did say 372hp and dyno sheets to prove
Quick reply to this message
  #6 (permalink)  
Old 11-11-2008, 09:38 AM
Registered User
 
Last photo:
Join Date: Jul 2006
Location: Baroda, MI
Posts: 210
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
You said 372 at the wheels. Being conservative with 17% loss that puts you at 460 at the flywheel.

Odds are with a worn out T350 and rearend with a bunch of miles on it that 17% is really conservative.
Quick reply to this message
  #7 (permalink)  
Old 11-11-2008, 09:38 AM
curtis73's Avatar
Hates: Liver. Loves: Diesel
 
Last wiki edit: How to find cheap parts
Last journal entry: Found an LQ9 today
Last photo:
Join Date: Dec 2005
Location: Carlisle, PA
Age: 41
Posts: 5,173
Wiki Edits: 16

Thanks: 7
Thanked 9 Times in 6 Posts
Quote:
Originally Posted by King Kong
No where did say 460hp. I did say 372hp and dyno sheets to prove
You said 372 at the rear wheels. That means 450-460 at the crank.

I'll say it again.

BS.
Quick reply to this message
  #8 (permalink)  
Old 11-11-2008, 09:41 AM
Jmark's Avatar
Registered User
 
Last photo:
Join Date: Sep 2003
Location: phoenix
Age: 61
Posts: 4,849
Wiki Edits: 0

Thanks: 0
Thanked 5 Times in 5 Posts
So I guess this would not be the place to bring up my 87HP Briggs lawn mower?
Quick reply to this message
  #9 (permalink)  
Old 11-11-2008, 09:45 AM
Registered User
 
Last photo:
Join Date: Jun 2008
Location: Mt.Vernon,IN
Posts: 484
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
ok guys

Alright guys, Why would this guy get on here and lie about this?? Just to spark a conversation????
I agree with you that it does seem quite unrealistic to achieve these digits, but it's not impossible..... Mabey it is with a 7:1 cr, but I highly doubt thats what he's got. Mabey you should ask questions before you start throughin stones and callin him a liar and its BS.

to king kong, you better tart listing some stuff to back up this claim, like a compression ratio, which heads you actually ended up using, ect, are you saying thier EQ 180cc vortecs?? They aughta have atleast been milled to 52cc chambers to get the CR right, show sopme dyno sheets or more parts specs or this thread is gonna get tore apart.

I got a buddy thats got a 305 HO, not sure the engine specs, but he's got a 101mm turbo on it and a 250 shot and is gettin close to 750
Quick reply to this message
  #10 (permalink)  
Old 11-11-2008, 09:47 AM
Member
 
Join Date: Dec 2007
Location: Garage
Posts: 33
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
RPM Stock TQ Mod TQ Stock HP Mod HP
2,600 285 290 141 144
2,800 283 297 151 158
3,000 287 320 164 182
3,200 291 328 177 200
3,400 290 334 188 216
3,600 284 337 195 231
3,800 279 340 202 246
4,000 271 346 206 264
4,200 264 349 211 279
4,400 256 349 214 292
4,500 252 350 216 300
4,600 250 348 219 305
4,800 241 344 220 314
5,000 233 342 221 326
5,200 221 343 219 339
5,400 - 337 - 347
5,600 - 330 - 352
5,800 - 324 - 358
6,000 - 322 - 368
6,100 - 320 - 372
6,200 - 314 - 370
Quick reply to this message
  #11 (permalink)  
Old 11-11-2008, 09:49 AM
curtis73's Avatar
Hates: Liver. Loves: Diesel
 
Last wiki edit: How to find cheap parts
Last journal entry: Found an LQ9 today
Last photo:
Join Date: Dec 2005
Location: Carlisle, PA
Age: 41
Posts: 5,173
Wiki Edits: 16

Thanks: 7
Thanked 9 Times in 6 Posts
Quote:
Originally Posted by eatonde
Alright guys, Why would this guy get on here and lie about this?? Just to spark a conversation????
Not only is the combination incapable of making 460 hp as he says its built, but its the way he worded it... he's on a crusade to make himself feel better about having a 305 despite all the guys telling him its not a very good performance base.

He also claims 212 from a stock 305 with centerbolt heads. Since he said he upgraded to vortecs, one can only assume it was a TBI. 212 to the rear wheels from a stock TBI 305 is ridiculously way off the mark. They didn't make nearly that much at the crank

He also said, "comments are welcome." So I commented.

Last edited by curtis73; 11-11-2008 at 09:58 AM.
Quick reply to this message
  #12 (permalink)  
Old 11-11-2008, 09:52 AM
Member
 
Join Date: Dec 2007
Location: Garage
Posts: 33
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I milled the heads to a modest 0.030-inch, to reduced the chamber volume to 60cc, so that I wouldn't lose compression ratio compared to the typical production small-chamber heads used on these engines. assembled the heads with a budget 1.94/1.50-inch valve combination, along with convention single performance springs with dampers.The cylinder heads were the cornerstone of the 305 modification plan.
Quick reply to this message
  #13 (permalink)  
Old 11-11-2008, 09:54 AM
Member
 
Join Date: Dec 2007
Location: Garage
Posts: 33
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
QUESTIONS AND COMMENTS ARE WELCOME
Quick reply to this message
  #14 (permalink)  
Old 11-11-2008, 09:57 AM
Member
 
Join Date: Dec 2007
Location: Garage
Posts: 33
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
The EQ Lightning cylinder heads were a key component in making the engine modification package a success. Without a doubt, one of the worst features of the production 305 is the factory "smog" cylinder heads, which are choking even at a measly 305 ci of displacement. With decent heads, a small engine can breathe, and that allows it to take advantage of its rpm potential to make power. Without good heads, it isn't going to happen.EQ heads are replacement vortec castings

NOW WHAT
Quick reply to this message
  #15 (permalink)  
Old 11-11-2008, 10:16 AM
curtis73's Avatar
Hates: Liver. Loves: Diesel
 
Last wiki edit: How to find cheap parts
Last journal entry: Found an LQ9 today
Last photo:
Join Date: Dec 2005
Location: Carlisle, PA
Age: 41
Posts: 5,173
Wiki Edits: 16

Thanks: 7
Thanked 9 Times in 6 Posts
I ran a dyno sim of your combo. I get 308 hp at the crank at 6000 giving you the benefit of the doubt:

305
8:1
vortec 350 heads with a peak flow of 239 cfm
dual plane manifold
headers
plugged in the comp numbers for the XE268
600 cfm carb

RPM---tq---hp
2000 263 100
2500 275 131
3000 284 162
3500 302 201
4000 314 239
4500 318 272
5000 313 298
5500 294 308
6000 268 306

That translates to 255 at the wheels, and that's giving the benefit of the doubt with regard to compression, and actual airflow considering the shrouding of the valves in those bores.

You'll have to do more than come up with numbers. You'll have to explain why your engine magically makes 150 more hp (a full 50% more) than VE theory can explain. I can understand 10 hp, or even 15, but 150? something's fishy. Here is a chart of the dynosim:

Quick reply to this message
Closed Thread

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 10:14 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.