B20A Flywheel, the truth is out there!

**Gregg86DX** · 12-03-2003, 09:28 AM

Hello all!

I have good news and bad news...

The good news: I have located a B20A 5 speed tranny and it is paid for and shipping soon!

The bad news: I need to locate a flywheel and clutch/pplate.

I have read every thread I can find on the topic of B20A Flywheel and there is a lot of good info, but not a conclusive answer. I am asking for information from anyone who has actually worked on one of these and has factual information.

I know the B20A5 flywheel and clutch assembly will work, but may require grinding the tranny case. I'd rather not do this! I really want to source a setup that will not require the grinding.

Does anyone have the part number for the correct JDM B20A flywheel?

Has anyone succesfully used USDM parts without the grinding?

To all you folks with B20A's out there, please step up and describe what setup you are using.

Any help is appreciated!

Gregg

**RobT5580** · 12-03-2003, 12:16 PM

Well i assume your reffering to Mike Lee's situation on grinding down the bell housing. One thing i did notice is he said it was a SOHC prelude flywheel so maybe that is why. I remember i was messing with an A20A3 flywheel and comparing it to the b20a one and i know it didnt fit but looked like the same bolt pattern but the pilot stub didnt fit if i remember correctly. So the B20A5 may actually work w/o grinding the bell housing.

**Gregg86DX** · 12-03-2003, 01:13 PM

Rob,

I assume the 2 B20A setups you have both came with flywheels? What clutch are you planning to use?

Thanks,

Gregg

**RobT5580** · 12-03-2003, 03:10 PM

I actually went on a search for an aftermarket lightened flywheel and ran into yasu's post and it says its a B20A5 flywheel so maybe im wrong. I have one flywheel and spituning screwed me out of the other but at the time i didnt care because my bottom end from mike lee and the tranny from spituning got stuck in customs for about 2 months. So i will have to look into it further for my second B20A but i was thinking of getting a lightened one for my turbo setup if i can find one. As for clutch im planning on using an ACT for the B20A5 but still not sure what level because its gonna be a street car.

**mykwikcoupe** · 12-03-2003, 08:01 PM

I have done the same probably not as much research as rob. I have a act clutch kit model ho19x. I believe its for the b20a5. I am planning on using it with my b20a turbo. I have been assured that it will work as a bolt in but havent actually checked the parts side to side personally. Hope this helps alittle. I am with rob on the flywheel. A lightened aluminum even with a little machine work to fit peerfect will still be good.

**RobT5580** · 12-04-2003, 08:40 AM

I swore i say a company that made one but i cannot find it. I will look further into it when i get some time in a week or so cause im working on finals for next week.

**toastyghost** · 12-04-2003, 11:26 AM

fidanza does
their site is aluminumflywheels.com

**RobT5580** · 12-05-2003, 10:21 AM

Yeah but thats for the 88-89 and it shows a size difference between them so i dont know which one is correct.

**Sean** · 12-05-2003, 01:22 PM

spec make a aluminum flywheel or the b20 in 1988 in the usdm preludes so pick up the phone and give them a ring.

**RobT5580** · 12-05-2003, 03:19 PM

Fidanza makes them as well for the 88-89 but it shows a size difference between the 88-89 and 90-91. Also looking at clutches the part numbers differ and the one i want is only made for the 90-91 so i will have to look into it more.

**Sean** · 12-05-2003, 09:02 PM

id think they might have changed the input shaft splin count or something of that nature.

**RobT5580** · 12-06-2003, 09:15 AM

Iv been doing a lot of research on a prelude forum and it seems to me that we have a 210mm flywheel which is the same as the 88-89 preludes. And fidanza does have that application available. But if it was a 90-91 prelude flywheel 220mm we could use the B16-B18 parts except for friction disc. But it seems that its the 88-89 since carotman did verify the pp/disc bolted up to our flywheels.

So i will keep you guys posted on any new information i come across.

-Ok i decided to go measure my B20A flywheel and if im not a mistaken i converted the mm to inches and it comes out as:
210mm=8.4 inches
220mm=8.8 inches

and i came up with 8 1/2 inches=8.4 on the flywheel so that would be right that we have a 210mm flywheel which is the 88-89.

**hoppy** · 12-06-2003, 12:13 PM

I have a JDM B20a flywheel. I''ll let it go for $80 CDN.

Do you want it? I'm not sure what shipping will be

-Sean

**RobT5580** · 12-07-2003, 01:16 PM

Ok just a little more info from carotman, he said the 88-89 B20A5 is identical to the B20A flywheel except the ring gear location. So im gonna pursue my research on the B16 flywheel because that would open more doors for us.

**88LXi68** · 12-07-2003, 07:21 PM

Rob there are a couple of guys on Hondatech selling an LS flywheel for cheap like $40.

**RobT5580** · 12-07-2003, 07:36 PM

Thanks steve iv been finding more and more about this all week but it looks like mike lee used the 90-91 B20A5 flywheel which was the problem with it hitting the bell housing since it is 10mm's larger than the 88-89. The do make the fidanza for the 88-89 but they dont make the clutch kit i want/really need for my setup w/o me going into a 4 or 6 puck which i really dont want. When i get some time i want to look furthur into it but im gonna just have to try the flywheel if thats the case. So i may just use the 88-89 and try to find a clutch that will work or call ACT to see if they can help me out.

***carotman*** · 12-07-2003, 09:25 PM

Ok, I've been away for a couple of days and Missed a bit of this thread (tough I took the time to answer Rob's questions hehe)

I got my hands on a B20A5 (88-89) flywheel and I compared it to the JDM B20A wheel. Everything on those flywheel is identical except that the ring gear on the B20A5 if located more towards the tranny case, which causes a bit of rubbing. Everything else is the same (thickness, diameter offset)

The 90-91 are larger and even without measuring them you can tell right away.

I haven't tried yet to install the B20A5 flywheel on the engine to see if it rubs ben when I test-fit it on the Tranny it sure rubs. Howeverm the JDM B20A flywheel also rubs when placed on the tranny but does not rub when bolted to the engine. I will get my hands on a spare B20A engine soon and I'll be able to make more tests.

Feel free to do those tests before me :D

**RobT5580** · 12-08-2003, 12:37 PM

Im thinking when the B20A5 is bolted up it would be fine because if the B20A one rubs when not bolted up then it cant be in the proper location. One of my B20A's came complete with clutch and all so i know it fits.

I guess the only question i have for you carot is do you think the A20A3 Auto starter will mate with the ring gear when assembled? Is the ring gear closer to the transmission or the engine?

I dont think this is gonna be a problem cause one of the guys in California that did it used the B20A5 (assuming the 88-89) and said it worked perfect.

***carotman*** · 12-08-2003, 02:22 PM

Yeah I think the starter will work fine.

I really got to try the flywheel bolted to the engine.

I'm sure that some of they guys here didn't know that the B20A starter (auto or manual) is the S-A-M-E as the Auto A20A tranny

**RobT5580** · 12-08-2003, 03:46 PM

I have a B20A starter but when they ripped the cable off they broke open the housing and took the terminal with it. So im just gonna get a new Auto A20A3 starter since everything else is gonna be new. The starters is somewhat different from the 5spd starter so i tried swapping parts out but dont remember where i left off with that other than i didnt finish it.

**Gregg86DX** · 12-09-2003, 12:19 PM

If the ring gear does turn out to be an issue, I wonder how hard it would be to actually move the ring gear. It would be interesting to compare them side-by-side and see if the ring gear could be moved or even slightly milled.

The pictures I saw of the B20A transmission that had been ground for clearence (the one Yasu had), was clearly interfering with the pressure plate, not the ring gear. That tells me there is a thickness issue, either with the flywheel or the pressure plate. In either case, the position of the ring gear should not matter.

Hoppy, I would like to buy your flywheel, and if I do, I'll try to track down a B20A5 flywheel and do some comparing and testing. I also have a buddy that is going to give me a B16 flywheel to play with.

Gregg

Originally posted by RobT5580
Ok just a little more info from carotman, he said the 88-89 B20A5 is identical to the B20A flywheel except the ring gear location. So im gonna pursue my research on the B16 flywheel because that would open more doors for us.

**mykwikcoupe** · 12-09-2003, 07:32 PM

If the findanza weighs in at 7.5 lbs for the 88-89 lude. How much does the stock b20a or b20a5 weight in at. Dont have access to one thanks guys.

**Gregg86DX** · 01-20-2004, 12:46 PM

I just wanted to update this thread since I don't want to leave it hanging. Based on the info provided and other research I have done (mostly on the internet), I have decided to go with the 1988-1989 Prelude 2.0si (B20A5) flywheel. I bought a used one yesterday for $40 and I will be ordering a clutch soon. I'll post the final results of this, once I have all the parts assembled and tested.

**Gregg86DX** · 01-30-2004, 09:51 PM

Ok, I bought a clutch (Exedy for an 88 prelude SI) and bolted everything together. The bad news: it rubs. The good news: it's just a slight rub that should be easy to clearance. I have attached some pics to show the area that rubs.

The blue line inside the orange box is where the pressure plate rubs the bellhousing. It was actually pretty minor. The PP gouged the aluminum about 1 mm when I rotated the engine. It would probably clearance itself fine if the engine was started this way. As it is, I will probably just shave down that area just a bit to make room.

Here is a pic of where it rubs on the PP.

After I do a little clearancing, I will put everything back together and use clay to see exactly how much clearance I have.

Gregg

**RobT5580** · 01-31-2004, 06:43 AM

I think its odd that some people have this problem while others dont. Maybe there is a difference in the F2K5 and the B2K5 bell housings? Or maybe its the design of the pressure plate some are using.

I guess i should ask which tranny you have to see if maybe thats the reason why some have not had this problem. I also think the lightened flywheel will solve this w/o grinding the housing since the pp will be pulled closer to the engine. Least you didnt have to grind much off like Mike Lee did.