1st vs 2nd gen SBC question - 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

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 07-08-2010, 04:01 PM
Registered User
 
Last photo:
Join Date: Mar 2010
Location: New Jersey
Posts: 35
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
1st vs 2nd gen SBC question

This may be a stupid or simple question, but I've been wondering about the differences lately between the 1st and 2nd gen (LT) small block chevys. In reading about the LT engines, it says that the primary difference between the 1st and 2nd gen engines is the reverse flow cooling featured on the LTs.

My question is why cant you just make a water pump that pumps in the opposite direction and mount it to a 1st gen small block? What makes it so that the coolant has to flow in one direction?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 07-08-2010, 05:00 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,753
Wiki Edits: 0

Thanks: 4
Thanked 419 Times in 361 Posts
Quote:
Originally Posted by eocoolj
This may be a stupid or simple question, but I've been wondering about the differences lately between the 1st and 2nd gen (LT) small block chevys. In reading about the LT engines, it says that the primary difference between the 1st and 2nd gen engines is the reverse flow cooling featured on the LTs.

My question is why cant you just make a water pump that pumps in the opposite direction and mount it to a 1st gen small block? What makes it so that the coolant has to flow in one direction?
The reverse flow has to do with where the coolant enters the engine. Conventional design puts the pump output into the block where it circulates up to the heads and returns to the radiator. Reverse flow is where the coolant first enters the head then flows downward to the block and then returns to the radiator. The direction of pump rotation is not an issue with either choice. With centrifugal pumps, like those used on engines, coolant flow is in the same direction regardless of pump rotation. The impeller is configured for efficient pumping in the intended direction of rotation so it does way better when turning properly, but never-the-less either direction will pump. To reverse a conventional pump either the inlet would have to be connected to the engine and the outlets to the radiator, not easy to do; or the pump's output has to be intercepted before it goes into the block and rerouted. The latter system has been done many times on race engines where the hole going into the block is plugged. The horns of the pump are tapped for fittings and the coolant plumbed into the heads. On the Chevy the forward soft plugs are removed and the casting tapped for return fittings which then hose the coolant back to the radiator. The process of blocking off the flow into the front of the block has also been used for conventional flow on race engines where the supply hose puts the coolant into the block at one or more of the soft plug locations along the side of the block. Another is to feed a stream directly into the head between the paired exhaust valves for which sustained high RPM cooling is always a problem for engines with this configuration of valves while sending most of the flow into the block whether in the usual front location or into the side.

The reason for reversing conventional wisdom is that the coldest coolant is put into the heads first. These are the hottest part of the engine with their combustion chambers. Reversing the flow lowers the combustion chamber temps more than is seen with conventional flow which preheats the coolant in the block before it goes to the heads. The temperature reduction of the combustion chamber of the reverse flow process allows the engine to run at higher compression ratios and with leaner mixtures before the detonation limit is hit. This provides higher power outputs with better gas mileage than possible with conventional coolant flow.

Pontiac tried this with their first V8 from 1955 to 1959, it proved to have a lot of in-service problems mostly due to the era where water without any overflow recovery cooling systems were used and people were more familiar with earlier flat head technology that didn't require so much cooling system care. So in 1959 they went back to a conventional flow system.

The second generation of the LT-1 and 4 in the 1990s brought the system back with some changes; certainly better coolant and more sophisticated cooling systems which people became more acquainted with in the 1970s and 80s along with a vapor vent from the upper rear of the head made the major difference compared to the Pontiac experience of 35 years earlier.

Bogie
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 07-09-2010, 07:47 AM
curtis73's Avatar
Hates: Liver. Loves: Diesel
 
Last wiki edit: How to find cheap parts
Last journal entry: 1999-2001: Getting it on the road
Last photo:
Join Date: Dec 2005
Location: Pittsburgh, PA
Age: 40
Posts: 5,128
Wiki Edits: 16

Thanks: 0
Thanked 2 Times in 2 Posts
Bogie hit the nail on the head. I guess there really isn't a reason why nobody does make a conversion kit for SBC1...
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 07-09-2010, 09:59 AM
Silverback's Avatar
Boost Retard
 
Last photo:
Join Date: Mar 2007
Location: DC Metro
Posts: 373
Wiki Edits: 0

Thanks: 1
Thanked 2 Times in 2 Posts
Yep, what he said... but I'll add that it worked well, but the reason it went away was again, because of service problems, and its not as easy as just reversing flow since the coolant passages in the heads were changed: old school SBC's have openings on the intake gasket face and flowed through the intake, where LT1's have their openings moved to the front and rear of the cylinder head and no coolant enters the intake.
Reply With Quote Quick reply to this message

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:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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
TH400 shifts to 2nd when shifter is in 1st GCooper Transmission - Rearend 2 08-31-2008 04:52 PM
Turbo 400 - poor downshift 2nd to 1st tonykof Transmission - Rearend 2 08-01-2007 10:02 AM
1st gen shell/4th gen chassis? benni_hanna General Rodding Tech 6 02-02-2007 05:27 AM
SCCA CAN AM TRANS AM Series 1st Gen Camaros texasrat Hotrodders' Lounge 6 10-01-2004 05:24 PM
Gen I vs Gen II question Mrfixmaster Engine 4 05-05-2004 06:31 AM


All times are GMT -6. The time now is 12:57 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.