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90 Civic LX / 90 CRX HF
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Discussion Starter · #1 ·
Hello again

Some context first. Recently I picked up a CRX HF. Now I would normally be all about the extra gas mileage considering how costly it is to drive but the engine is fucking dying. Clearly the previous owners where more worried about trying to make a 50hp car look like a race car than proper engine maintenance. No matter since I have a D15b2 sitting around that has just been collecting dust (and rainwater) ready to be slapped in after being machined. I figured since the cylinder sleeves are rough that I'd get them bored out and slap some oversized pistons in there and call it a day. Unfortunately, it seems that the selection for D15b2 pistons that are slightly oversized is fairly slim.

I found some by a company called "Partsology" that come with the piston rings and what not in a .5 oversize. I was wondering if anyone had experience with / have a better alternative to them.

Thanks again (y)
 

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90 Civic LX / 90 CRX HF
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Discussion Starter · #3 ·
Almost as good as oe, almost.
They offer a coated skirt option as well, havent noticed a difference between them though, aside from price.
Sweet

Now I'm a little more confident that it wont immediately blow up after slapping it together, thanks a thousand :D
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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If memory serves correctly (its been a few years since my last full d15 build) these silvolite pistons are a few grams lighter than the oe, it throws the balance off a tad and can cause the crank pulley bolt to come loose, so use a new one and hit it with a good impact wrench on install to avoid losing your bolt, pulley and key. Or spend 2-300 extra and have the bottom end balanced, pick up a small but noticeable power gain, some mpg and extra longevity.
 

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90 Civic LX / 90 CRX HF
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Discussion Starter · #5 ·
I will probably have it balanced later on when I actually build this engine. Wanted to throw this one together cheap so I can get my hands into an engine and drive it around for a bit.

I'll break out ye ol' scale and see how different each piston is to one another and see if there's a cause for concern
 
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If rebuilding, rockauto.com sells a kit. Just run it as a 1993 civic dx or something, same engine basically.


However, verify it is really dying. Bad valve lash and out of spec timing will make the engine feel like it is dragging its nuts across glass and giving up power.

Bad valve lash can cause a compression test to fail.
 

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90 Civic LX / 90 CRX HF
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Discussion Starter · #7 ·
I think the HF engine always drags its nuts regardless lol

But I figured that if I was going to do all that work to that engine that I should probably put in a little more work and have a slightly more competent engine instead
 

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93 Civic HB SI, 95 Civic HB CX
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I think the HF engine always drags its nuts regardless lol
Its that trans lol.

According to @Soul Engineering, If you could get the HF to redline in 5th, the world would probably look like this:

Liquid Water Fluid Icicle Electric blue


Luckily for us, the engine cant do that, otherwise you'd exceed C by a multiple, and destroy life on earth as we know it.
 

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I think the HF engine always drags its nuts regardless lol

But I figured that if I was going to do all that work to that engine that I should probably put in a little more work and have a slightly more competent engine instead
When the HF engines are running and everything is adjusted properly, they can outdo the d15b2 engines in the low rpm, and suffer a little up top. They were made for low end torque, and given they started with 60-70 crank horse, they needed some extra help. The HF's intake runners were very narrow, and ever so slightly longer than the d16a6 runners. Not by much. But the thinner runners made more air velocity at lower rpm's, combined with the increased air velocity due to one intake valve.


From a stop sign, it would jump on a d16a6, and basically as soon as the d16a6 SI shifted, it was gone lol.

The bottom half of the engine matches d15b2/d15b7 engines. Well, if you got the engine with the original 2 valve relief pistons, rather than the 4valve relief pistons.
 

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