Has anyone ever seen a hotrodded GMC V6 or V12? - 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 08-26-2005, 09:44 AM
Member
 
Last photo:
Join Date: Mar 2005
Location: Mesquite, Tx
Posts: 161
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Has anyone ever seen a hotrodded GMC V6 or V12?

Just curious if anyone has ever seen a hot rodded GMC V6/V12. The V12 had up to 672 ci. Basically it was two V6 GMC's cast together end to end.

I always thought this was a neat looking motor. Usually see them in 1960's GMC trucks. The valve covers are shaped more like a small block Ford. The spark plugs enter at the top of the head as if it were through the intake. Distributer is in the back. It looks more like a Ford than a GM product.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 08-26-2005, 11:14 AM
Bumpstick's Avatar
Hammer and a torch
 
Last photo:
Join Date: May 2003
Location: Southeast TX
Age: 54
Posts: 1,258
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Was called and odd fire V6 lots of torque but basicly a Dino motor... (should have been used in tractors)
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 09-19-2005, 02:46 PM
Member
 
Last photo:
Join Date: Mar 2005
Location: Mesquite, Tx
Posts: 161
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by Bumpstick
Was called and odd fire V6 lots of torque but basicly a Dino motor... (should have been used in tractors)
I know I've seen them in oil fields and in old large GMC trucks.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 09-19-2005, 04:21 PM
1ownerT's Avatar
Home School Valedictorian
 
Last wiki edit: Health and safety in the shop or garage Last photo:
Join Date: Dec 2004
Location: Iowa
Age: 53
Posts: 1,645
Wiki Edits: 4

Thanks: 0
Thanked 3 Times in 3 Posts
A few years ago I had a 63 GMC 3/4 ton pickup, it had a 305 V6 with a 4.10 Dana 60. The engine was great for torque, but low rpms, at 65 mph it sounded like the engine wanted out from under the hood. More than once I had it loaded to the gills taking junk to the landfill, it would walk up some pretty steep hills with out straining.
As for a Hot Rod, I don't think so.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 09-19-2005, 10:48 PM
xntrik's Avatar
Save a horse, Ride a Cowboy.
 
Last photo:
Join Date: Jul 2005
Location: Arkansas
Posts: 5,131
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Saw/heard one of those GMC 350 cube V-6 blow up in a school bus one afternoon on the way home from school in 63.... What a noise and smoke show... yyyyyyyeeeehhhhaaaaawwwww. Ya, he was "hotrodding it" for all it would do against the governor...... I bet she was doing 3800 rpm when she let go......
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 09-20-2005, 01:31 AM
Pony's Avatar
Member
 
Last photo:
Join Date: Sep 2003
Location: Lynnwood, Wa.
Age: 67
Posts: 721
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
The 305 V6 was a heavy duty bus/truck motor that found it's way into some pick up trucks due to an engine shortage at the factory. I had a 63 with a 2 speed powerglide in it for a dump run truck. It was dependable but what a pig. It would shift at about 15mph and labor all the way up to 50mph using a ton of gas on the way. In the few years we had it, it met a log truck on a narrow bridge and both sides lost, went froward over an embankment, backward over and inbakment, hit a tree in the front and hit a tree stump in reverse, (lots of snow and black ice without a posi). The only spot not damaged when we got rid of it was the roof and it still ran like a top.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 09-20-2005, 06:11 AM
Member
 
Last photo:
Join Date: Dec 2003
Location: Montvale, NJ
Age: 58
Posts: 222
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
A few years ago I ws getting this restoration magazinw for a year. They just happened to have an article in one issue about the GMC 305 V6. What they claimed was that the engine used different sized pistons depending on what cylinder # it was! I can't verify this and thought it was strange. If this is true, can you imagine trying to get a set of slugs for it.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 09-20-2005, 07:56 AM
Member
 
Last photo:
Join Date: Mar 2005
Location: Mesquite, Tx
Posts: 161
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
How about a roadster big enough for Shaq. They are going to use a 702 ci V12. built from a Peterbuilt cab and nose.

http://www.blastolene.com/Work_in_Progress/

Here's a good shot of one of the motors. Other than for restoring an old truck or just for the bragging rights of claiming a 702 ci V12, sounds like a poor choice for a rod.

GMC 702ci V12
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 03-08-2009, 09:35 AM
Registered User
 
Join Date: Mar 2009
Location: California
Posts: 1
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
V12 hotrod

Run with it!



http://thunderv12.com/
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 03-08-2009, 09:45 AM
Registered User
 
Last wiki edit: Wheelbase database Last photo:
Join Date: Jan 2007
Location: Virginia
Posts: 3,517
Wiki Edits: 1

Thanks: 6
Thanked 145 Times in 132 Posts
Quote:
Originally Posted by FrankR
Just curious if anyone has ever seen a hot rodded GMC V6/V12. The V12 had up to 672 ci. Basically it was two V6 GMC's cast together end to end.
Actually, it was 702 cu in.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 04-20-2009, 10:28 PM
Registered User
 

Last journal entry: pistons
Last photo:
Join Date: Feb 2009
Location: Texas USA
Age: 25
Posts: 25
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
yes actually its mine and im currently building parts for it. Here is my forum page for my intake manifold build take a look
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 01-09-2010, 10:08 AM
gow589's Avatar
the Clever Turn Signal
 
Last photo:
Join Date: Aug 2006
Location: Indiana
Posts: 399
Wiki Edits: 0

Thanks: 0
Thanked 7 Times in 7 Posts
Quote:
Originally Posted by hardway
You can purchase the GMC V12 there at various levels ready to run.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 04-10-2011, 06:28 PM
Registered User
 
Last wiki edit: Building a GMC 702 V-12
Join Date: Jun 2010
Location: Northeast
Posts: 16
Wiki Edits: 44

Thanks: 0
Thanked 0 Times in 0 Posts
702 V-12 Builders?

So who is building a GMC V-12 project? With the price of gas you want to be sure to be 70 MPH at 1200 RPM. I am building one and do have a great deal of knowledge on "hot_rodding" one of these. Right now the biggest limitation from what others say and I can see are the exhaust passages in the heads. Nothing aftermarket for these babies so you need to seek out their magnum versions. Hens' teeth to say the least. As you can see by visiting Bob's Thunder V12 site, you can push over 5000 rpm BUT there are a good number of tricks to pay attention to or it is going to die a horrible death supposedly between 3000 and 4000 RPM. Both killers relate to oil system. Oil pump cavitation and journal clearances.... be sure to address them.

So.... OD that can handle 1000 ftlbs of torque? I and going to start with a capable tranny but right now I have an old Brownie (Lipe I think) that looks like it will grenade compared to the tranny (Fuller RTO 910). Anyone got any recommendations?
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 04-10-2011, 11:06 PM
CJ_1080's Avatar
known to do dumb stuff!!
 
Join Date: Dec 2010
Location: Racine, Wisconsin
Age: 29
Posts: 183
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
What about an Allison? I know of an Allison that survives many pulling seasons behind a duramax making 975 HP and something like 1600 foot lbs. Or so I was told. Either way it is well over 1000 ft lbs!! Something to think about!
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 04-11-2011, 12:03 AM
Registered User
 
Last photo:
Join Date: Aug 2008
Location: Melbourne, Australia
Posts: 113
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
The V12 is very heavy, has low compression, does not like to rev, and is rated at only 250Hp.

As already said, the heads and manifolds are not wonderful, and making it breathe well at much higher revs will be both difficult and expensive.

But.... A couple of turbos on the V6, or four turbos on the V12 would be magic.

The low end torque is already there, but even very low boost pressure would really build some serious power potential, and the engine is easily strong enough to handle some boost just as it is.
Big strong lazy low reving truck and marine engines make killer turbo engines.
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:
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
1957? GMC truck impala59 General Rodding Tech 22 04-07-2012 05:29 PM
V6 to V8 mini van ? bowtieorbust Engine 13 01-16-2004 07:27 PM
1954 GMC V6 3 speed on the floor swap out Flaming54 Engine 3 10-16-2003 05:02 PM
DOHC 3.0L V6 in 1990 Ford Probe? Alabama Man Engine 5 01-26-2003 11:01 AM


All times are GMT -6. The time now is 10:35 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.