Well it's been pretty frustrating looking for a D15B6 motor. So I'm thinking of just putting a HF head (including intake manifold) on a JDM D15B block to make myself a little HF motor. I'm sure it will require more work than just plug and play, I'm not sure if the pistons are all the same for the D15's. Would this work and still yield the same MPG results as the USDM HF motor?

 

I currently have a d15b2 block with a d15b6 head on it in my HF. Its completely rebuilt. At 55mph on a hwy I can get 55mpg. Above 65mph I get around 40-45mpg. Going 75mph on I95 with traffic I haven't gotten worse than 40mpg.

I'm guessing this is the norm, but I wouldn't know. I got the car with a bad motor and rebuilt it this way. I've never driven a stock HF with original motor.

 

The stock HF motor I had, with 150k got me around 45-50mpg.

I was just wondering if the d15b block + b6 head would make it basically a d15b6 motor. Not sure what this would do to the compression.

 

here's an important question regarding this subject... the d15b/b1/b2/etc. have valve reliefs in the pistons for 4 valves... i thought the hf only had 8 valves total, or 2 per cylinder. is modification to the pistons required to avoid piston to valve interference, or no choice about it the hf pistons have to be used?

 

WOW i only get like 26 in my d15 idk what the exact model is but its the 4 speed one in my ef lucky i wish i got that much

 

The b6 head casting is nearly identical to the b2. I have both and have compared them. The b6 has spots for 4 valves but only 2 have been drilled out at the factory. The b6 pistons has 2 valve reliefs and the b2 has 4. Because the head castings themselves are basically identical the valve angles are also identical.

In short, no modification to the b2 short block is needed to bolt on a b6 head. I know because I have one in my car with now 4k miles since new without issues.

 

That's great news. How much MPG are you getting with that setup? b6 transmission?

 

See my first post for MPG. Yes I have an HF trans.

 

haha sorry I didn't realize that was you..