guys i know this threadis old but i am interested in tryng this piston swap into my de block. now i was wondering if i ude the vq40 rods to give me a longer stroke would that help me make more power? and also by using hr cams with springs and retainers add can that help me make good power using stock vq parts without the cost of the aftermarket parts... plz give me ur opinions.. thanks

 

Longer rods don't change the stroke.

 

but the rods on the vq 40 are shorter

 

correction they longer

 

The crank determines the length of the stroke, not the rod. In other words, even if you have a rod that's 25 feet long, it's still only going do move up and down a few inches on the crank if the crank is left unchanged.

A longer rod will give you more compression, but 11.5:1-12.5:1 is the limit for pump gas anyways.

 

Great info here! I just got a 2003 35 on a stand, and did a 'leak-down' test using a us general tester and was about 20% LOSS CONCURRENT ALL SIX pistons but the engine not running and it's about 20 degrees in the garage. But while that motor is on the stand, I was contemplating doing some internal mods, like using the 3.0 heads I read that they have a good exhaust flow, or just keeping the 3.5 heads.
I don't have tons of money but I definitely would like to do all that I can while it's on the stand before putting it in. Also, I read that the 03 vq's had bad rings so that alone would warrant putting in better rings at least.
If I were to buy the cometic hg at 0.040" and use the stock pistons, would that yield anything or probably not? What about the 0.030" on stock pistons? Weimer ben are you using the vq35 heads?
I just figured out that .030" is .8mm stock width, so scratch that!
These are like .042" http://www.ebay.com/itm/NISSAN-VQ35-...item256ab365be

 

3.5 heads flow better than 3.0 heads. Tilly put the 3.0L heads and 00vi on and it got a little less peak HP and a lot less tq than the 3.5 heads. Yes, the 3.0L heads will raise compression, but they don't flow as well.

Yes, I'm using 3.5 heads and I use the SSIM during the winter and another IM with a removed butterfly valve during the summer.

Cometic .040" head gaskets, stock pistons, and 3.5L heads will reduce compression a little. There's no reason for that. The stock gaskets are great for stock pistons.

I don't see a reason for the copper gaskets. But if you do use them, I would use Hylomar for the oil and coolant passages and o-ring the combustion chambers. The stock gaskets are multi-layer steel with viton sealing and work very well.

****, my I'm pulling 30psi on my diesel all day long on stock MLS gaskets and beat the $hit out of it.

They're not like the $hitty-@ss old asbestos/graphite gaskets. Head gasket failures are uncommon on modern motors.

The FWD motors didn't have the ring problems that the Rev-up 350z/G35 motors had. I love my HR pistons and rings though. Within the first few miles of rebuild, my 2005 VQ35 smoked less than the stock pistons/rings with 70k miles on it.

 

So vq35hr pistons, right? With the stock vq35de rods I assume? Did you rehone the block before dropping the HRs in?

 

Yes, VQ35HR pistons. I went with the oversize pistons (+1.0mm IIRC) and did a full bore/hone. So I really have a 3.6L now.

 

sounds pretty good. So the 2003 VQ35DEs didn't have ring issues?
Anyway, do you think that the bump in your HP was more due to the HR pistons, or the 1mm more bore? You didn't swap to a hi-rev oil pump did you?
Oh, you think that VQ35HR cams would be advisable with the HR pistons?

 

The FWD VQ35s have oil consumption issues, but not as bad as the RWD "rev-up" motors.

I just looked it up and it looks like it was a .5mm overbore. That's not that much. My displacement is 3535cc. Stock is 3498cc. 37cc/3498cc= a 1% increase in displacement. The overbore might have given me 2-3hp by itself. But increasing the effective compression ratio helps out with power and efficiency substantially. It might only be a 1.5 point increase in compression, but I'm probably also getting 65psi or so more on a compression test. A good vq35 will get 190psi or so in compression. I was getting 160psi, IIRC. It's not horrible, but not good given the stock compression ratio. With HR pistons, you get around 225psi.

I have the stock oil pump and I have a stock rev limit. When I save up enough Criminal Reserve Notes, I'll put some ARP rod bolts in and increase the rev-limit to 7500 or so with the EU.

Better cams helps in multiple ways. If you use big cams, it lowers the effective compression ratio and can help with scavaging which helps with detonation issues, but it also gives you more power in the upper RPMs.

 

The sticky has been cleaned up and locked. You may continue the discussion here.

 

Thanks Nismology.. I was wondreing what happened to all my posts lol.
Thank you too weimar! I'm in the process of taking the ud pulley off but impact socket doesnt work. I have a small compressor. Gonna go with a strap wrench to try it.
I'm just going to go with the HR cams once I pull the engine apart, and hopefully HR pistons like you.
Think stock valve assembly would be enough?
Also I'm gonna get the block honed, this won't take enough material off to make me need to step up to the 95.75mm piston, or keep using the 95.5mm?

 

Definitely keep the 3.5 heads. As far as I know using the HR pistons in a DE motor requires you to mill a little bit off the quench pad area of the piston. It is talked about in this forum I think.

Using the HR pistons would definitely be a better way to raise the compression ratio rather than using the 3.0 heads.

 

Yup,Thanks. I just hope that the stock valves assemblies would hold up, I think that that would because it's gonna be just NA, no boost. This is a low budget build. I just got some hr cams for $90 used, only 10k on them.

 

What do you mean by valve assemblies?

Like the actual valve and seat?
Or the valve springs, retainers?

 

Like the springs being quick enough to pull the valves closed in time so the piston doesn't hit them. Won't the hr cams increase my rpm(with a tuned ecu)?
This is all new to me, the only other 'big' mod I did was a Quaife install back in 07. I feel like a giant target . right now. this minute.
I am sorry for going off the topic, as this thread is about the vq40 rods, but I'm kinda scared to open a thread just for this meager subject.
Anyways thanks for the help I REALLY appreciate it! I'm just gonna try to reuse the stock valve parts, if thats ok to do.

Edit: I forgot there IS a thread for VQ35HR cams; I'll post there about this from now on.