I have a 1991 Prelude SI with the B21A1 2.1 liter motor. I am experiencing 2 problems with it:

First is I seem to need to add a quart of oil every 250 miles or so. The oil also seems to be very black soon after it is changed. And the dipstick also has evidence of burning oil. There is no oil on the ground where I park my car, but there seems to be some leaking from the back of the motor. I just replaced the valve cover gasket, the oil is coming from below that. It is not coming from the oil filter, either. When I accelerate at high RPM (about 4000) there is a puff of black smoke. Other than that, there is nothing coming out of the exhaust pipe that I can see. Head Gasket?

The second problem is that there is a vibration when I accelerate. The car is completely smooth at speed, and during breaking. That harder the acceleration, the more noticeable the shudder. Also, 1st gear does the least shuddering, second gear is mild, third and fourth gears are bad, and fifth seems to be less.

 

The oil burning is 100% normal for that 100% jusnk engine. ( I dont mean to be a dick) That was the absolute worst engine made by honda. You can not find 1 b21 that dose not burn. I am sure you dont have any leaks at all, its all burning. You should try to find a JDM b20a, I got mine for 600$ from a company that no longer exists. Try http://www.honda-prelude.com You may find what you are looking for. As far as the vibrating, I dont have a clue. Motor mount? I dunno. Good luck.

 

As boosted20 said that particular motor is known for burning oil. That engine has a poor rod/sroke ratio, and Honda used a different material inside the cylinder wall for the B21A1. As you can see in my sig, my engine was pretty much shot after 138k. That puff of smoke is only gonna get worse and so is the oil consumption. Good Luck

 

The 1991 is the year Honda first produced the carbon fiber cylendar sleeves, if I am not mistaken. Evidently, it was a @#@&%#&$ idea...

So, would replacing the rings fix the prob (temporarily at least?) or boring the block a little? Or do I need to just deal with it until it goes kaput and then get a new (used) motor?

As for the poor rod-stroke ratio, is that something that can be changed? New crank and rods? Or am I wasting my time?

 

B20A from Japan sounds like a good idea. Couple questions: Did you need to get a new transmission? And did the PK3 ECU work or did you need a new (JDM?) ECU? What else other than the longblock needed to be changed? I would appreciate any advice or tips on the subject.

Thanks.

 

Its a straight foward swap. You can keep your tranny and ecu. The only thing I needed to change was the drivers side motor mount. I also swapped over my old intake manifold, throttel body and exhaust manifold so I could keep my egr valve and not have a check engine light. They all bolt right up with no problems. Its a pretty simple swap.

 

That is a pretty good deal then. Cheap fix. Where did you get the new motor mount for the driver side?

 

you just keep your stock motor mount, dont use the one that comes with the new engine.