Here is the skinny. I have a 95 Civic hatch that had a JDM B16A in it. After over 200K miles on the motor the timing belt broke (Yes I kept up changing it…I think it was caused by worn aluminum teeth on my timing gears but that’s another story). Anyway, I swapped the motor with a JDM B18C and pulled the Civic Type R cams out of my B16A and threw them in the GSR head along with a skunk2 Type R intake manifold and Type R throttle body as well as dual exhaust springs. I was really impressed with the acceleration and the torque; it was a completely different car. I set VTEC to kick in at 5000RPM which it liked and it pulled nice and hard all the way to 8K rev limit, and pulled surprisingly hard in fifth gear (something my B16A just didn’t do) I was very impressed with the new combination, most significant I think was the torque, (again something I didn’t get in my B16A).

So the bad news is something about the cams the head did not like, and they seized after about a week (I have a theory on that too, but that’s another another story). So the GSR head and Type R cams are shot and I need to replace them. I decided to go with a 98 Spec B16B head rather than another GSR head and have to spend the money for springs and cams on top of it. I was of the mind that the Type R head would not only come with all the internals I wanted, but should be an additional performance boost as well.

So I get the new Civic Type R head on my GSR block complete with new ARP head studs and new OEM gasket and again with Type R intake manifold and throttle body as well as 98 spec ITR header, 2.5 in exhaust light flywheel, USDM Type R tranny with LSD, the works. The problem is that with this Type R head on the GSR block my car does not have anywhere near the *** that it had with the GSR head on it. The impressive feeling of torque is gone and it really feels more like driving a peppy B16A than anywhere near what it felt like before. How is this possible? I can’t believe the .2 and some change difference in compression ratio between the Type R and GSR head on a B18C block would make that much difference. One explanation I got was that the GSR piston and Type R head just doesn’t work very well together but I don’t know if that satisfactorily explains the power loss or not either.

Do any of ya’ll have any idea what I have going on here? Do I possibly have another problem that I am missing? The car seems to run just fine VTEC engagement is back up at 5600 where it was with the B16A and other than having what I believe is a lack of gumption, everything appears to be fine. What do I need to do to get that impressive feeling of sit you back in your seat acceleration I had before? Are Type R pistons going to cure what ails me, do I need to go back to a GSR head or is something not right?

I know this is a book, but I am hoping someone has had this experience and can give me a clue as to WTF?

TIA

Corey J

 

Try the hybrid forum

 

Have you even compared the combustion chambers between the 2 heads? The GSR one is square and the CTR/ITR head is round. Then you need to compare the GSR piston to the ITR/CTR pistons. The GSR ones are flat and the ITR/CTR ones have a dome on them. You are going to lose more than .2 CR by switching to the ITR/CTR head. A thinner headgasket would help to pick some of it up, but if you really want it to run better I suggest you either look into swapping out the pistons or putting a GSR head back on there and upgrading that valvetrain.

 

Using the following sites as a reference, all of the compression values between a GSR and B16A or ITR head on a JDM B18C block indicate a difference in compression of only .2 and some change.

http://www.c-speedracing.com/h...c.php

http://www.zealautowerks.com/

http://www.lightningmotorsports.com/techpiston.htm

I find it hard to believe there would be such a degradation to performance with such a small difference in compression, but then again I don't know...that's why I am asking. Is it perhaps a "they just were not designed to work together" thing or what. ???

 

Its cause of the compression dump, your back in the 9.xx:1 compression ratio range and vtec motors love compression... hopefully that helps...

 

I don't know where some of you are coming up with your info as to what the compression ratio would be given this particular set up. I can find nothing, anywhere, that would indicate a compression ratio of 9.xx:1 for a JDM B18C block with B16A or Type R head.

I don't suppose you could provide a source for your numbers could you?

Check the web sites I listed above. The compression ratio calculators located there will give you the compression ratio for nearly any head, block, piston combination you can think of.

"Fact"
From Wikipedia, the free encyclopedia....

Generally, a fact is defined as something that is true, something that actually exists, or something having objective reality that can be verified according to an established standard of evaluation.

 

b18c bottom end with b16/itr head c/r will be 10.38:1

b18c bottom end with b18c head c/r will be 10.60:1

so where are yall getting 9.xx:1 c/r from?

 

Like I said from the beginning .2 and some change........