For you motor geeks out there I got my medical burette today (Ebay rules) and cc'd the cylinder head combustion chambers. I will retry again tomorrow to validate.

VQ35DE 51.5cc
VQ30DE 43cc
A difference of 8.5cc

Total combustion space on a VQ35 is 62.7cc
Total combustion space on a VQ30 is 55.2cc
A difference of 7.5cc

VQ35 is 62.7cc - 51.5cc = 11.2cc of head gasket and piston space
VQ30 is 55.2cc - 43cc = 12.2 cc of head gasket and piston space
A difference of 1cc

Total combustion space of a VQ35 block with VQ30 heads. 11.2cc + 43cc = 53.2 (~11.9CR)

9.5cc of metal needs to be removed from a VQ30 head combustion chamber to get back to the factory 62.7cc so it makes the CR back to 10.3:1, if only 5cc is removed CR will be 11.1:1, if 7.5cc is removed CR will be 10.6:1, if I can get 11.5cc out I can get back CR to 10:1

So, can ~9.5cc of metal be taken out of the VQ30 heads to make them the same as the VQ35 so the CR will be the same? I have a set of junk VQ30 heads I will start to play with and find out. That is allot of material but its worth a shot.

Now supose some one makes 8.5:1 pistons for the VQ35 in stock form. Use those with stock cc VQ30 heads and you get a CR of 9.4:1, mill the heads and deck and you could be back to 9.6:1

Thanks to Nigel I should have a digi camera soon to take some pictures of all this.

Well, I got my geek on for the night

 

Like when I dream about growing up... it involves your knowledge of motors.


Thanks for the info. And NOBODY does it better than mardi







I should have all this figured out in about 3 months. Let you know what I come up with

 

nigel bought you a digi cam for christmas

 

Hey Mardi - I'm not very knowledgable about building motors so bear with me. I was trying to understand what your doing, but I'm not sure I see why you want to use VQ30 heads - is it their shape that's an advantage? After you take out the 9.5cc of material you're going to end up with the same cr right, so what's the advantage?

 

gotta follow this one

 

Because there's alot less involved if you use the VQ30 heads. Don't have to change as many sensors, keeps his mevi, not to mention a vq35 shortblock is cheaper than a long block.


For the all motor guys, 11.9:1 CR + cams = yummy

 

I think it would be much safer to get dished pistons to reduce CR than to remove material off (esp. aluminum) heads... Plus you get the strengthened pistons to top it off... my 2 cents.

Finding out you removed TOO much material will be costly.

 

You are correct Chunger. However, the VQ30 head combustion chamber bore diameter needs to be shaped to match the VQ35 bore diameter regardless, perhaps ~4cc right their. Another 5.5 isnt going to be too hard to pull off. So on my junk heads I will take it to the limit then bounce a center punch around looking for weak spots, Ive got six tries to get it right


And Neal is correct.

 

I talked to Don in Texas about this a couple of months back and he has done something similar. He was able to get the compression down to 9.17:1 just by removing material from the heads. Granted this was with the VQ30 but that should give you an idea of how far you can go. He sent me some pics, if you want to see them, I can email them to you.

Good luck.

D

 

I verified the CC info again. I was right on with the VQ35, but the VQ30 was 42cc. I did it a few times to be sure.