R32 W/r34 Head - Not Boosting

[DanShirts]

Here is the back story:

I had the timing belt tensioner stud break while the engine was running. My engine had a few bent valves as a result.

I had a freshly rebuilt R34 head sitting on the shelf that I was saving for an RB30 build. It found its way into my R32. I used the R34 cams and swapped the R34 cas too.

The problem:

It only makes about 1/2 the boost that it should. It also sounds odd. It sounds like the timing is wrong.

Is there a difference between the R32 and R34 timing marks? Do I need to remap for the R34 head and cams? Or something else?

[r32-25t]

What engine does your r32 have in it?

[GTSBoy]

If you have put an RB25 head on an RB20 block..........wowsers!

[DanShirts]

Sorry! I left out an important detail! Its an R32 GTR stock RB26.

[StevenCJR31]

need more details. . ie are you using 34gtr head? 25det head ? manifold? etc

[DanShirts]

It is a stock R32 RB26 block. The manifolds are R32. I have replace the head, cams, and cas with parts from an R34 RB26. The head was rebuilt by a very experienced head builder. I rewired the cas plug to suit the R34 cas. I used a new oem head gasket. I also put in head studs while the head was off.

It's probably not relevant, but I also has an R34 crank, oil pump, and turbos installed. These upgrades were done a few years ago, and shouldn't have any effect.

I think that covers everything!

[Ben C34]

Your compression ratio would be a fair bit higher now.

http://www.webbersrbguide.com/index.php?option=com_content&view=article&id=90:rb30dettt-compression-ratio-a-piston-selection&catid=50:rb30dettt&Itemid=29

[DanShirts]

Your compression ratio would be a fair bit higher now. http://www.webbersrbguide.com/index.php?option=com_content&view=article&id=90:rb30dettt-compression-ratio-a-piston-selection&catid=50:rb30dettt&Itemid=29

I think my first post was a little confusing. I didnt use an RB30 block. I bent some valves. Rather than replace the valves, I replaced the entire head with one that I was saving for a different build.

Edited July 28, 2013 by DanShirts

[KiwiRS4T]

According to your link the compression ratio would be exactly the same across all GT-Rs.

There is a difference in valve timing (not lift or duration) according to this Tomei chart but I don't know if that would halve the boost:

http://www.tomei-p.co.jp/_2003web-catalogue/e090_camshaft-specs.html

Your compression ratio would be a fair bit higher now. http://www.webbersrbguide.com/index.php?option=com_content&view=article&id=90:rb30dettt-compression-ratio-a-piston-selection&catid=50:rb30dettt&Itemid=29

[Ben C34]

Yeah sorry about that, I thought he put a rb25 neo head on. miss read the post