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P400 head different than others... pics

Twisted Steel Performance

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I have found some differences between a head used on the P400 verses a standard 6.x head...

I'm still finding other things that make this a "different" head.

The casting # are the same but so far that is all, but I haven't cut one up YET, that is coming soon, I'm just too busy with hay cutting right this time, when I'm caught up I will cut it like I did last time and see what changes were made with the castings...

I found the valves are not the same, they are a little larger in the stem base and the height in the seat contact area is also bigger.

I have a new set of 6.5 heads here that I plan to check & record the valve install height " spring height" and also more important the valve depth from the head surface. This is where the major difference could cause piston contact if not checked.

Notice the P valve on the left has what looks like a back cut.. it isn't a straight back cut it's a radius cut, looks to me like someone figured this would help introduce some swirl into the cly. Also notice the larger taller seat area on the left P valve.

Again... P valve left ... stock valve on the right...

I'll have better pics & measurements this week.

Only trouble I see is if at some time in the future valves were needed they would more than likely need to be custom cut due to the lack of ability to purchase them, but custom valve work isn't out of the question at all...

014.JPG
013.JPG
 

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It isn't any good anymore I got a little aggressive porting the first set so I now have a set to monkey with while I'm waiting on the next set to arrive....
 

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I like the R&D info... But you're nuts cutting up good heads! Haha
Well the factory isn't going to tell anyone anything... most will bolt things on and assume and even make claims that things are the same and nothing changed... am I right ???

If I want/need to know I do what I need to do to find out without assuming, after all, we know what assume stands for don't we.... I can't afford to have a subtle change I don't know about mess the entire project up.. they didn't change the name of the motor just to change it, and the block girdle wasn't just the only change, in fact the only thing I have found that's the same is that the accessories will bolt up, that's about it....
 

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Your efforts are appreciated!
AK, I'm just passing info along for the hell of it, this motor project has been going on for 1 1/2 yrs now, I'm anal about this one as it's my last .... and this is a military motor, I want it to be all it can be as I'm also a Vet....
 

Will L.

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AK, I'm just passing info along for the hell of it, this motor project has been going on for 1 1/2 yrs now, I'm anal about this one as it's my last .... and this is a military motor, I want it to be all it can be as I'm also a Vet....
By the use of the line I'm guessing Army?

I really wish I knew you folks back when i had acess to GM and all the testing we did. I bet the duramax would have been put off for a decade- all the changes possible to this platform.
 

Will L.

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Air Force Will.... Nuc Weapon's tec......
:eek::eek:Remind me not to tick you off...

My Dad was USAF lifer, and 2 civy terms. Over 40 years, only final retired before agent orange and rad poisoning put him in a bed perm. A serious lifer.

Thank you btw. Freedom is pretty cool.
 

THEFERMANATOR

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By the use of the line I'm guessing Army?

I really wish I knew you folks back when i had acess to GM and all the testing we did. I bet the duramax would have been put off for a decade- all the changes possible to this platform.
Um, no. Even with all the changes, theres still only so much you can do on a mass production scale with an IDI engine. And lets face facts, even a highly modded 6.5l doesnt standmuch of a chance against even a stock 01 1st gen DURAMAX. Nothing against the 6.5 as I know it has come a long ways, but GM NEEDED the DURAMAX if they wanted to stay in the pickup diesel game. FORD was at 250 hp mid year 99 with the 7.3l, DODGE had the CUMMINS at 235 hp starting in 99 with a manual trans, and for GM to stay in the game after being last for so long, they had to completely change the game. And that they did in 01 coming in at not just a bump over the other 2, but decimating them with 300 hp to the closest competitor at 250 hp. Coupled to 5 speed ALLISON with grade braking, it saved GM in the light duty pickup diesel market.
 

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I agree with ferm BUT I hate electronics... yea it will never be a dmax but a dmax will not be manual pump I doubt.... but someone will do it sooner or later just not me...
 
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