12 valve going in my 99

Got Twins???

Got Twins???

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Feb 12, 2009
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So in hopes of eventually making big power I decided to ditch the 24v from 99 and swap in a 12v. The motor is coming out of 95 donor truck. For the most part this seems pretty straight forward my biggest question is do I need to salvage any of the wiring from the 95??? How difficult is it to make the swap and get everything working such as gauges etc.? Any help advice from the guys that have done this would be much appreciated.
 
I'm in the same shoes as you but with a 02. I'm sure others that have done the swap will chime in as I'm also interested in any advice.

from what i've been told:
gauges:
you'll need to change the thread on the 12v so your coolant, oil, and IAT sensors work.

Not sure about 99 (think they have both crank and camshaft sensors) but you'll need a 99 cam gear on the 12v. Speaking of which, you'll also need a haisley cam sensor relocator.

You should use all the 95 throttle linkage, cable, tps and 12v re kickdown cable (if it's an automatic)

thanks odieub!
 
if i was you, id find a 1998 12 valve engine wiring harness. you can check my gas to diesel swap in the conversions.
 
sleepin-sport said:
I'm in the same shoes as you but with a 02. I'm sure others that have done the swap will chime in as I'm also interested in any advice.

Ok, gauges:
you'll need to change the thread on the 12v so your coolant, oil, and IAT sensors work.

Not sure about 99 (think they have both crank and camshaft sensors) but you'll need a 99 cam gear on the 12v. Speaking of which, you'll also need a haisley cam sensor relocator.

You should use all the 95 throttle linkage, cable, tps and 12v re kickdown cable.
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The 99's only have the crank sensor. 01 & 02 have the added cam sensor so that's a plus. I figured worst case I'd just run aftermarket guages.
 
Got Twins??? said:
The 99's only have the crank sensor. 01 & 02 have the added cam sensor so that's a plus. I figured worst case I'd just run aftermarket guages.
Click to expand...

No the 99's have a cam sensor also, it has something to do with the timing on the vp.
 
smokin24valve said:
No the 99's have a cam sensor also, it has something to do with the timing on the vp.
Click to expand...

You 100% sure on that? Thought 98.5-00 just ran the crank sensor and the 01-02's had both crank and cam. I'm not saying your wrong since i'm still in my learning stages with this diesel thing. Just thought that's what I read somewhere when I was looking to PPump my 24v.
 
Got Twins??? said:
You 100% sure on that? Thought 98.5-00 just ran the crank sensor and the 01-02's had both crank and cam. I'm not saying your wrong since i'm still in my learning stages with this diesel thing. Just thought that's what I read somewhere when I was looking to PPump my 24v.
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I was going to drop a 12v in the 99 I had, but ditched it to put it in a 96 1500.

99's had a crank sensor, located behind the starter(had something to with the tach, alternator, and I think A/C) and a cam sensor(timing of the vp), located below the vp44. The 01-02 had the cam sensor only, it has the same function as the crank and cam sensors, but just in one sensor.
 
smokin24valve said:
I was going to drop a 12v in the 99 I had, but ditched it to put it in a 96 1500.

99's had a crank sensor, located behind the starter(had something to with the tach, alternator, and I think A/C) and a cam sensor(timing of the vp), located below the vp44. The 01-02 had the cam sensor only, it has the same function as the crank and cam sensors, but just in one sensor.
Click to expand...

Ahhh ok good to know thanks!:rockwoot:
 
So why not just p-pump the 24v? That would be better anyway...So where about are you in Northern IL?
 
I realize it will take a while to get there but my goal is 4 digit HP numbers which I think IMO will be easier to achieve with a 12v vs. the PPumped 24v. After this project is done I still plan to do the PPumped 24v and swap it into an old school chevy....that's definitely long term though. I'm in Earville about 12 miles north of Ottawa.
 
I don't understand, why would it be easier to acheive higher hp numbers with a more restrictive head?:confused:

I'm over by Princeton, thats pretty close!
 
The head can be ported.

The P-pump is the main factor. And more reliable.
 
17cumminsboy said:
yeah i got lucky on here and got the wiring with the PCM for $50 bucks.
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That's a heck of a deal, wish I could find something like that. I've searched and only found a guy in TN that was parting out a 98 12v. He isn't mechanically inclined and only locals were coming over and taking the parts they needed.
 
I've just heard about how much better the valve seat's and stem are on 12v and decided to do the whole swap instead of p-pumping the 24v.
 
Limited said:
I don't understand, why would it be easier to acheive higher hp numbers with a more restrictive head?:confused:

I'm over by Princeton, thats pretty close!
Click to expand...

I have often wondered the same but I guess people just port the hell outa it. I still think you could get more flow out of a 24v head even if the valves are smaller, oyu have twice the amount. There is no way you can get a 12v head to move as much air as a 24v.
 
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