B21a1 Repair

[DunKrS]

I was recently given a 91 Prelude Si for free, as always, free isn't always awesome. In my case, I think it's pretty cool though.
I have some questions, I've never worked on anything this new, and I'm just starting to dip my toe into the whole thing. I've done engine swaps, put lift kits on, rebuilt several v-8's, etc. etc. So I have the building blocks I think, it's just applying the same ideas, but to a whole new way of thinking.

The car has 199XXX miles, and I guess the water pump went out, so the owner replaced it, and when he went to start it, he could tell the timing was off, I know the valves are tweaked, as to how many and how badly, I'm unsure. The head is torn apart, but still attached to the block. I have access to a b16 out of a early 90's crx. I was told that, if I needed, I could put that head on my engine, and run it like that until I'm done rebuilding the original head, or finding a better one. Would fixing the stock head be as simple as replacing the valves, or are the valve seats shot too? The motor never ran with the timing incorrectly set, only turned over with the starter. Any and all help will be greatly appreciated. As I said, this is my first venture into new-ish car territory, and I'm also on a tight budget, I just want to get the car on the road. From there, more improvements will be made.


Also, the previous owner hit a curb at a high rate of speed, and as in most cases, the alignment was badly thrown. He replaced the lower control arm I believe and it helped, but did not completely solve the problem, I think I'll be pulling the whole motor so it'll be easier to work on (everything is already disconnected to begin with) can I change out the framework and have the car drive straight once again?
Once again, I will appreciate any help I can get, and I'm glad I've run across such a helpful forum, I've learned a lot just reading up on some related posts.

[spiffyguido]

Hi DunKrs,

Congrats on your Prelude purchase. I started out on V8s too. You'll have no trouble with the transition.

I think your first task is to survey the damage on your head to see exactly where things are at. If a value or two is bent up, just replace them straight out. It's unlikely that it was damaged too badly since it was just starting at the time. The valves are dead easy to switch. Just pull the cam off and depress the cam spring to get the valve keepers out. The valve will fall right out. New ones from Honda aren't too expensive.

Unfortunately, the head you have from a B16 is useless to you. You will either have a B20A5 engine or a B21A1, and neither of these are from the same family of engine as the B16, even though they share the letter designation. That said, if you do need a new head, it should be pretty easy to find one at a local wrecker. As I said though, chances are the one you have is fine; it may just need a valve or two. Take it off, survey the damage, let us know.

As with any car, the alignment can be out because of many things. I'd get under the car and check that the front and rear stabilizer bars, as well as the tie rod are all straight and true. If the components are all good, it may just need some adjusting. Get under there and look for damage. Post up some pictures if you need a hand with this. As I'm sure you know, any bend in the bars is unacceptable.

Write back with more questions. Glad you found us.

[DunKrS]

Okay, so I talked to my shop class teacher, and a local mechanic, I think my next course of action it to check the positioning of the valves and see if all the springs are at full stretch, and if all the valves are seated correctly, because the cams were already removed when I got the car. That should tell me if any valves are bent and seating improperly, correct? Next, the exhaust manifold was hacked to smitherines, so it's gonna cost me $80 for a used one from a scrap yard, or about $150 for a new header. I was wondering if any other manifold will work, or should I go with a header? or just go ahead and have my scrap guy order the manifold? Next on the list of a million questions to ask, is, what motors will mount up in this engine bay? I think I found a 1.6 vtec that runs, but idk if it'd be worth it to do such a swap, even if it's possible to do so without major modifications, I'm on a super tight budget.
Thanks again for all the help!
-DunKrS

[spiffyguido]

Hi DunKrS,

Sorry for taking so long to get back to you.

Yes, that's a good way to check for bent valves. You'll notice if anything is out of whack.

For your exhaust manifold, you could get a header, or a manifold off a B21A1, other manifolds won't work. Because a B21A1 is an OBD1 engine, the oxygen sensor setup is different than the B20A5, so find one from a B21A1 if you can.

The only engines that will bolt right into your car as it is right now are a B21A1 and a B20A5. The B16s, B18s etc come from a different family of engines and aren't the same shape as the engine in your prelude. You do have the option of getting a engine called a B20A (notice, no number) that has to be ordered from Japan. They came in Japanese preludes and produce more power (160hp) than the B20A5s and B21A1s that we have here.

Some people have put H22A engines in their preludes. This requires a lot of work because new engines mounts, axles, ecu, tranny etc are needed.

[DunKrS]

I checked the spring/valve positioning, looks like they're all closed! I pushed a couple open and air came out, so I'm guessing I've got compression as well! I'm starting to get excited about this whole thing, I've been asking around about a manifold or headers. Then I ended up getting in contact with the only kid in my town who has a non stock 91 prelude Si, He has a manifold! $45 and I'll be able to start putting things back together! I'm still worried about getting it all back together correctly, I need help setting the cam timing, does anyone have a resource for this? Maybe a video tutorial? The Black Si looks like she'll be cruising the streets yet! =)
-DunKrS

[spiffyguido]

The Manuals available from our Manual Page (see top of screen) can help you with the timing. It's not a complex process. The Cam gears are keyed and have alignment marks on them to make sure you get everything put together correctly. Once that's taken care of, it's just a matter of using a timing light to get the timing bang on.

Let me know exactly how far you've gotten and I'll help some more.

[frank444]

Head gasket time
have a qualified machinist check the head & put it back together and drive it....
buy all the aftermarket stuff later ...
your car is due for the head gasket.....
Im in the process of doing a head gasket at 172,000 ....
save yourslef from having to eak it all apart again real soon..
Headgasket
Timing belt
water pump
flow test radiator
happy trails