Hello all,

First post here. Just got a nice 1998 ITR in CW with 173km (108k miles). The engine is a 1997 Jdm B18C.

I bought the car a couple of weeks ago, there were some engine mods (rebuild) such as:

Mahle Pistons acr181209f01
Head and block were machined
Crank was polished
Ring ACL Race
Head Stud ARP
Bearing ACL Race
Cold Air Intake AEM
OBD1 conversion
Tuned on a dyno (180 whp I was told)

I then added a 4-1 header (to replace the cracked 4-2-1 that was there), added a high flow cat (it was gutted) and replaced the exhaust with a Tanabe Medallion Touring.

The setup is really nice, but on my first ride of more that an hour or so I noticed the engine overheated a bit. I pulled over and noticed the coolant reservoir was overflowing. Let the car cool down and brought it back home. Diagnosis: bad head gasket.

I proceeded with changing the head gasket (Felpro new, Cometic 3 layer old one), and took the opportunity to do water pump, tb and all gaskets. It's now working fine. While doing the head gasket job, I took a picture of the pistons, which are in great shape. I'm now looking online and the information I'm finding doesn't match what the seller told me.

All this info leads to that question :

Seller told me the setup gave a 11.5:1 CR, but these pistons (acr181209f01) seem to be for a B18C1 (GSR). On the website they claim it will bump the CR to 10.5:1 on the GSR engine. Now with a quick online research, with this setup I would be getting a lower CR on a itr than a GSR, somewhere around 10.3 . The stock JDM engine being 11:1, did the guy do a massive mistake or I'm getting it wrong?

He claimed 180whp, which seems low considering when he tuned it he had the CAI, gutted cat, 2.5 inch straight middle pipe to the stock muffler.

So engine gurus, help me understand! Thanks for the help.

 

It appears that your compression with this combination would be about 10.15:1 if your block and head were virgin... but you did state that they were machined, so if you could tell us how much on each, I can re-calculate and be more specific. Either way, it will be LESS than an ITR stock... especially a JDM one with 11:1. Also, how thick is the head gasket ???

The seller was incorrect in quoting that compression with the Mahle piston part number that you have referenced. Sorry. The power output is still very respectable though.

 

Here you go. This will allow you to select different combinations and also modify things to get a good idea of where your compression is. Click the link below.
Honda B-Series Compression Calculator by ZealAutowerks

 

Unfortunately I don't know how much they shaved off the head and block. The head gasket thickness is 0.028 (stock is 0.026 I think). I only got the pistons part number when I dismantled the engine, too late!

Engine is pulling strong so I guess that's fine anyways. I'll try to go on a drag strip and get the trap speed I can get out of this car, that shouldn't lie too much about the numbers!

There are ACL race bearings and rings, these pistons, stock valve train and a tune. Safe enough to rev it up to 9k from time to time? In the end the lower compression ratio makes it less touchy about fuel quality and should be reliable in the long run?

Thanks for the help