3/S Head Swap

[Eight-Sixer]

Okay, I was sitting in my garage saturday, looking at the engine of my shadow, and I got to thinking, the 3 liter engine in the Shadow is basicaly identical to the 3 liter in 3/S cars minus the heads. I did a little bit of a visual compairason and noticed that the only visual difference between the 3000GT/Stealth 3.0 is that it's rotated 180* opposite the Shadows'.(see below pic) that being said, would it be possible to swap the heads from a 3/S to a Shadow?

Let me know what you know.

[Ondonti]

the block is casted differently so the timing belt tensioner etc is all different.

Not to mention the dohc heads dont have a distributor.

[m90daytona]

yeah you might be able to do a motor swap and run megasquirt or some other standalone but you cant just swap heads. or you could just do some head work to a sohc and add a turbo

[87turbodance]

I've always had my eye on the SOHC head that come on the 2.5 in the stratus / sebring cars. I'm going to do some test fits in the spring

[Ondonti]

Quote:

Originally Posted by 87turbodance I've always had my eye on the SOHC head that come on the 2.5 in the stratus / sebring cars. I'm going to do some test fits in the spring

Fitting is not the issue.

[87turbodance]

Quote:

Originally Posted by Ondonti Fitting is not the issue.

I should rephrase that to fitting of the timing belt / water pump / intake . Exhaust will have to be custom manifolds. I'm buying the whole top end of a 2.5 24V to see for myself what does and doesn't fit

[Ondonti]

yay thats a better summary.

[Eight-Sixer]

well then i guess i lost that bet.

[irocelectric93]

I wouldnt bother swapping the heads anyway...it wouldnt be worth it in my own opinion since we have already seen that dohc engines dont make much more power than the sohc anyway. Brent made me a believer...dohc engines are overrated.

[Ondonti]

Now once you get into the huge turbo (bigger then mine) huge airflow levels......

Then a dohc motor with the correct mods and headwork cams will perform amazingly. interestingly though, it has been recently shown though that even the forged crank cant make much more then 1000-1100crank hp........At this power level it starts bending and bottoming out on the two center mains (btw the mains in the engine are not very big) if you get any detonation. If you make a little bit more power and avoid detonation, the oil film on the 4 small mains is not enough to hold the crank away from the bearings and you chew up the mains. Only way to fix this is larger diameter mains using a custom crank (that also wont bend if you detonate).
I just found it interesting that it has been recently decided where the 6g72 cant make more power on stock parts (reliably).
My guess is that someone with insane enough ideas could max out the forged crank with only sohc heads. might take a little bit of nitrous cheating but hey, :P whatever it takes (thats of course with upgraded rods to handle all the torque).


I do think it would take a lot of work to make the sohc mechanically stable in the higher rpms. I think Frank thought you would need some custom rocker arms etc to handle 7500+ rpms. The dohc can rev 8600+ on the stock hardware......but they dont make power up there without lots of work and huge turbos.


Another problem with the 6g72 is that the head bolts are spaced away from the combustion chamber. This leads high hp motors to lift the center of the head and pressurize the coolant system.
Oh, and there is never a need for upgrading headbolts to ARP......9.7@150 on stock headbolts ftw. The ARP suck anyways cause they dont make their high end bolts for the 6g72.

[93sundance]

damn Brent....U know more about this motor than I realized. Looks like u been doing your homework. I havent.....

[Shadow24V]

the SOHC 24v heads might work on the 12v block. i dont know, im trying to get a spare set and if i have time ill test fit them on my old 12v block. i just went with a 24v motor swap and am gonna go from there

[c2xejk]

Quote:

Originally Posted by irocelectric93 I wouldnt bother swapping the heads anyway...it wouldnt be worth it in my own opinion since we have already seen that dohc engines dont make much more power than the sohc anyway. Brent made me a believer...dohc engines are overrated.

Dyne proof? I know I am still looking for somebody with a stock 3L to put it on the dyne. Nobody has been willing to step up to the plate.

Also, as you examine Brent's "proof", remember that there are many factors that go into acceleration. Hp is just one of them. Weight and gearing are two more...

[87turbodance]

I'd love to dyno my totally stock Spirit ES but I'm way up in Canada (2 hours from Detroit)

[m90daytona]

Quote:

Originally Posted by c2xejk Dyne proof? I know I am still looking for somebody with a stock 3L to put it on the dyne. Nobody has been willing to step up to the plate. Also, as you examine Brent's "proof", remember that there are many factors that go into acceleration. Hp is just one of them. Weight and gearing are two more...

i dont think anyone here has a stock 3.0...and if they do, they dont live near you.