71' 4 bolt 350 4bbl. - 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> Hotrodding Basics
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 09-13-2012, 11:33 PM
Registered User
 
Join Date: Sep 2012
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
71' 4 bolt 350 4bbl.

Hello, I am wondering how much horsepower my motor is making in the eyes of you all. It's a 1971 Chevy 350 4 bolt main 4 barrel, this stock motor made 270 horses. It's been bored .30 over, we've added ( Me and My dad ) New Summit Racing Heads with the 2.02 intake, a new edelbrock aluminum air gap intake, A 600cfm Edelbrock 4 bbl electric Choke Carb, an edelbrock cam ( Not sure which one ) , flowmaster dual exhaust. It was set at either a 9.2-1 or 9.4 compression ratio when it was rebuilt 4 years ago. Can anyone give me an estimate of what power it might be making? Thank you! Oh also, this is in a 1978 el camino.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 09-13-2012, 11:36 PM
vinniekq2's Avatar
Registered User
 
Join Date: Jun 2012
Location: BC,Canada
Age: 56
Posts: 8,288
Wiki Edits: 0

Thanks: 342
Thanked 809 Times in 775 Posts
250 hp,considering age and small carb
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 09-14-2012, 08:49 AM
RWENUTS's Avatar
Registered User
 
Last photo:
Join Date: Nov 2011
Location: Nanaimo, BC, Canada
Age: 63
Posts: 2,051
Wiki Edits: 0

Thanks: 62
Thanked 220 Times in 208 Posts
Come on Vinnie!!
I think he was hopein' for 400 horses.
You're probably spot on though!!
I'd of said 300 but probably a high estimate.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 09-14-2012, 10:48 AM
my87Z's Avatar
Veteran/Firefighter-EMT-I CRT
 
Join Date: Mar 2009
Location: maryland
Age: 31
Posts: 1,685
Wiki Edits: 0

Thanks: 6
Thanked 11 Times in 11 Posts
okay lets see here, in 1971 the GM chevrolet 350 could be had in 3 different hp options: 245hp/350tq, 270hp/360tq which are both hyd lifter motors with 8.5:1 CR, there was also a 330hp/275tq option that still used solid lifters and had 9:1 CR.

assuming that you have the 270hp/360tq engine, you added and updated version of a set of double hump heads, so you wont have any incrediable gains there. then you added a higher rise, larger runner intake which will free up a little air going into the cylinders, regardless what Vinnie says the 600cfm carb is not choking this engine as a 600cfm carb can turn a mild 350 to 5500RPM without any problems. then you mention flow-masters (i dont care for them but i'm sure they flow a little better than the factory mufflers. you gained about 0.8-1.0:1 on your compression ratio which is likely good for about 5-7% gain. the heads I know flow about 10% better than the factory heads, and the intake is flowing around 20% more than the factory intake. the big question would now be did you put headers on it, if not how is this added amount of air that is getting into the cylinders getting out.

based what i would guess the cam you put in there would be around 210-220 @ .050 and roughly .440-.450" lift.
without headers you are likely making in the 290-315hp range with roughly around 350-370tq, but if you added a set of headers you would likely be in the 310-330hp range with roughly around similar tq numbers.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 09-14-2012, 01:24 PM
Registered User
 
Join Date: Sep 2012
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Alright!

They have a set of headman headers as well.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 09-15-2012, 07:55 AM
55_327's Avatar
Registered User
 
Join Date: Jun 2011
Location: Plano, TX
Posts: 22
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by my87Z View Post
there would be around 210-220 @ .050 and roughly .440-.450" lift.
without headers you are likely making in the 290-315hp range with roughly around 350-370tq, but if you added a set of headers you would likely be in the 310-330hp range with roughly around similar tq numbers.
And here's where it gets fun. I think that 270 hp was a "net" rating, whereas 1970 and earlier used a "gross" rating as well as higher compression. Gross ratings are what we get on a dyno with no alternator, fan, mufflers, air cleaner, etc. And gross ratings are what we hear about in the hot rod world. So maybe that 270 net horsepower would have been 350 gross. Who knows?

So, depending on the cam's torque curve and ignition advance curve, I'd guess his 355 is making 280-300 net with the same air cleaner, fan, exhaust system, etc. as the original car used. Gross rating might be more like 330-350.

And, yes, 600 CFM is not an issue, although an Edelbrock 1405 carb will probably make more power than a 1406. (The difference is more than choke and jetting.)
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 09-18-2012, 10:15 PM
Registered User
 
Join Date: Sep 2012
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Hmm..

Well it has a working cowl induction hood, K&N air filter, headers and etc
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 09-18-2012, 10:28 PM
vinniekq2's Avatar
Registered User
 
Join Date: Jun 2012
Location: BC,Canada
Age: 56
Posts: 8,288
Wiki Edits: 0

Thanks: 342
Thanked 809 Times in 775 Posts
Cowl hoods are good and all street cars need an air filter.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 09-20-2012, 04:02 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,153
Wiki Edits: 0

Thanks: 5
Thanked 380 Times in 374 Posts
Why don't you take your car to the drag strip and do a few passes.
The MPH from your time slips with car+ driver weight will tell you how much HP
you are really making.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 09-20-2012, 05:09 PM
painted jester's Avatar
TAKE A KID TO A CAR SHOW
 

Last journal entry: mopar hump back
Last photo:
Join Date: Jan 2011
Location: Central Michigan
Age: 68
Posts: 1,841
Wiki Edits: 0

Thanks: 103
Thanked 292 Times in 240 Posts
Quote:
Originally Posted by F-BIRD'88 View Post
Why don't you take your car to the drag strip and do a few passes.
The MPH from your time slips with car+ driver weight will tell you how much HP
you are really making.

I agree with f-bird!



Hellcamino 8: you could pay a few bucks and put it on a rear wheel dino or engine dino! and get an exact figure for the conditions the day of the dino run! Your rating out of a book is averaged on the differences on a few engines tested of the exact same build at the factory!!! You can dino 20 engines all built and blueprinted exactly the same and get 20 different h.p. ratings + or - from the rating listed because of small differences in tolerances heat transfer, flow differences, even spark plug and plug wire resistance can reduce or increase hp, efficiency of rings,ETC and factory built engines had wide variations of tolerances and still passed inspection! Cams ground at Gm could have 200 run through a machine before tooling was changed so the first cam would be dead on perfect with a very tight tolerance and the last cam at the outer range of the limit of acceptability! If you happened to get all the close tolerance parts in one engine coming down the line you had what we old guys called a street freak because the hp it produced was exceptional! If you got one at the outer ranges you got a slug! Estimating hp off of aftermarket parts that were added is like spitting at a fly the odds are your way off!!!

If You put your foot in it and it brings a smile to your face be happy, If your disappointed trouble shoot it or redo it!

Jester
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 09-22-2012, 01:30 PM
Registered User
 
Join Date: Sep 2012
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks!

thanks everyone for your input! Means a lot! I might just take it to get dyno'd!
Reply With Quote Quick reply to this message

Recent Hotrodding Basics 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


Similar Threads
Thread Thread Starter Forum Replies Last Post
1976 chevy 350 rochester 4Bbl jetting problem 1976monte Engine 1 03-23-2012 01:23 PM
Is 3" True Dual Exhaust Too Much for Stock 69 4bbl 350? chekemtz Engine 20 05-27-2010 10:07 AM
79 Chevy Scottsdale 350 4BBL 79ScottsdaleGA Introduce Yourself 2 03-25-2009 10:05 PM
Timing On71 Buick-350-4bbl. alrobjr Introduce Yourself 3 03-25-2007 07:22 AM
will 4bbl carb from a 350 fit a 305 chvy engine slim3058 Engine 4 10-19-2004 03:52 PM


All times are GMT -6. The time now is 10:46 PM.


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.