12 valve question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

AntiGov · 03-09-2013, 01:10 PM

so my plan has been to keep the 454 in my crew but squeeze some more pwr out maybe top end , headers, etc. keeping the the tbi.......however a friend of a friend has a 12 valve been sitting for a while, was to go in a crew cab project but has since sold the crew. he said make offer..year,miles,and condition unknown at this time...whats this worth ? does year matter ? and what about rebuild costs ? thanks guys.....i know nothing bout these ..

Tx Firefighter · 03-09-2013, 01:47 PM

There's a lot to know about them.

Whether it has a rotary or inline pump is a large determining factor in its value. Also beware of killer dowel pin damage. That's not a deal breaker necessarily but it's quite a trip to take to repair it if the front housing is broken because of it.
Posted via Mobile Device

wyattglock · 03-09-2013, 11:31 PM

I have been actively pricing these for about 2 months now. I have seen prices for engines and transmissions anywhere from $725-$12k. It all depends on condition. For just the engine, it seems that if it runs $1000-$3500 seems a good ballpark to work in. I don't know a whole lot about the engines yet, but after doing some research it looks like you can get a re-ring kit for as low as $350. You can also get a kit to change everything but the crank for around $950. The inline pump is definitely the better way to go, but I have seen several that have been converted. The transmission is another sticking point. Yes the TH400 can hold the power, but from everything I have read or been told by guys running these, the 400 has a hard time living in a daily driver due to the low fluid pressure under 1000 rpm.
The good thing about this swap, if you have a 2wd you don't have to change any crossmembers. The conversion mounts should bolt to the factory big block mounts and locate the 12v right where it needs to be.
Good luck if you go with this.

andrewmp6 · 03-10-2013, 01:48 AM

A 12 valve is the small block chevy of the diesel world the aftermarket is endless on them.The swap depends your budget and can you make parts or have to buy everything.Trans is the other big question using a dodge one is easier but you have to make the trans crossmember work and cut a driveshaft.Other option is some pricey adapters to use a gm trans and a pricey controller if you want a 4l80e.Take a look around http://www.autoworldmt.com/Page_11.html and http://www.tndieselpower.com/site/products-page/

mattcrp1 · 03-10-2013, 03:34 PM

I started a 79 crew cummins swap a few years ago and 4btswaps.com was full of info. If I had to do it again I would definatly go with something other than the dodge transmission. There was an individual who was selling swap mounts and allthough they were expensive they fit perfectly. Good luck

03-09-2013, 01:10 PM	#1
AntiGov Registered User Join Date: Oct 2011 Location: central Oregon Posts: 1,225	12 valve question so my plan has been to keep the 454 in my crew but squeeze some more pwr out maybe top end , headers, etc. keeping the the tbi.......however a friend of a friend has a 12 valve been sitting for a while, was to go in a crew cab project but has since sold the crew. he said make offer..year,miles,and condition unknown at this time...whats this worth ? does year matter ? and what about rebuild costs ? thanks guys.....i know nothing bout these .. __________________ 88 3+3 454 400 205 410 drw to srw still in pieces 90 3+3 350 400 205 410 srw 84 1/2 ton lb 6.2 4x4 parts truck

03-09-2013, 01:47 PM	#2
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: 12 valve question There's a lot to know about them. Whether it has a rotary or inline pump is a large determining factor in its value. Also beware of killer dowel pin damage. That's not a deal breaker necessarily but it's quite a trip to take to repair it if the front housing is broken because of it. Posted via Mobile Device

03-09-2013, 11:31 PM	#3
wyattglock Registered User Join Date: Jul 2010 Location: Lafayette, IN Posts: 622	Re: 12 valve question I have been actively pricing these for about 2 months now. I have seen prices for engines and transmissions anywhere from $725-$12k. It all depends on condition. For just the engine, it seems that if it runs $1000-$3500 seems a good ballpark to work in. I don't know a whole lot about the engines yet, but after doing some research it looks like you can get a re-ring kit for as low as $350. You can also get a kit to change everything but the crank for around $950. The inline pump is definitely the better way to go, but I have seen several that have been converted. The transmission is another sticking point. Yes the TH400 can hold the power, but from everything I have read or been told by guys running these, the 400 has a hard time living in a daily driver due to the low fluid pressure under 1000 rpm. The good thing about this swap, if you have a 2wd you don't have to change any crossmembers. The conversion mounts should bolt to the factory big block mounts and locate the 12v right where it needs to be. Good luck if you go with this.

03-10-2013, 01:48 AM	#4
andrewmp6 Registered User Join Date: Jan 2009 Location: Louisville,Ky Posts: 5,811	Re: 12 valve question A 12 valve is the small block chevy of the diesel world the aftermarket is endless on them.The swap depends your budget and can you make parts or have to buy everything.Trans is the other big question using a dodge one is easier but you have to make the trans crossmember work and cut a driveshaft.Other option is some pricey adapters to use a gm trans and a pricey controller if you want a 4l80e.Take a look around http://www.autoworldmt.com/Page_11.html and http://www.tndieselpower.com/site/products-page/

03-10-2013, 03:34 PM	#5
mattcrp1 Registered User Join Date: May 2010 Location: Mountain House, CA Posts: 555	Re: 12 valve question I started a 79 crew cummins swap a few years ago and 4btswaps.com was full of info. If I had to do it again I would definatly go with something other than the dodge transmission. There was an individual who was selling swap mounts and allthough they were expensive they fit perfectly. Good luck



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