b21A1 swap in a 87 si

i need some expert advise, from someone that really knows what they are talking about.

is it a bolt in swap? how easy would it be?

never heard of a b21, unless it's a B20 bored out.

yeah what car is a b21a1 from?

Well, since no one has heard this engine - I will tell you this, all B series requires a mount kit to be put in your civic. Your car now has a D series, and they don't mix. You have to change tranny's and axles too.

B21A1 is a 90-91 Prelude Si motor.



B20A3 88-91 Prelude S

Carb SOHC 100 HP
-------------------------------
B20A5 88-91 Prelude 2.0Si

PGM-FI DOHC 135 HP
-------------------------------
B21A1 90-91 Prelude Si

PGM-FI DOHC 140 HP

Whoa yeah what was I talkin about anyway. He said SI, and somehow I thought thats a model of a civic when I wrote it. I wasn't smokin crack or anything, just had a brain fart I guess. I have no idea what engine is in in 87 SI prelude so I can no longer comment on what engine fits.

whats the r/s of the B21, is it better or worse than the B20b?

its worse. in fact, ive heard that the b21 is the worst b-series motor ever made. lots of rod problems or something along that lines. my friend has a 90 S that we are converting to fuel injection, and eventually putting a b18c1 or c5 into, depending on his cash flow by then end of the summer.

i think the 87 prelude has and A series motor like the old accords, but dont quote me on that.

is your 87 FI? if so than its a b20a5.. umm and far as the the b20b and b20a.. totally diffrent motor.. another thing is b21a1s have really bad oil burning problems! and for the guy with the 90 and goin to put a b18c or c5-- waste of time! ull be better off with the H22A than either of those cuz the motors sit totally diffrent and then ud definatly have to get custom mounts!

Look at the engine code to find out! it located where the tranny and block meet! pretty easy to see.. its a flat spot!

as for the oil burning, i dont care. if its a new engine, it wont burn for a while. its an 87 SI, with the b20a5 i think. all i want to know, is if i need new motor mounts, a mounting kit, or if it is just a bolt on. thanks for the help everyone, but im not asking for opinions. i just want to know about the procedure.

This wont help your mounting question but I do have some info on the care and feeding of a B21A1. What I gather from browsing posts on preludepower.com is you have to change the oil ever 3000 miles. The piston sleves are made out of some kind of carbon composite and the piston rings chew them up, if I remember right. Supposedly it was an experiment by honda that went horribly wrong.

You might be interested in a JDM B20A

I think its got something like 143HP and a little less torque then the B21A1

hey I am trying to put this little project together. if you guys are saying that the b21a1 motor is bad do you think that I could put another head like the b18c1 on it and make it better?

not gonna work. the head bolt holes dont all line up. neither do all of the coolant passages.

besides, the head isnt the problem on the b21a1. its the block. its got some experimental coating on the cylinder walls that fails with high mileage and causes them to burn oil.

my buddy with a 90 prelude S is building a b20a block with a b21a1 head on it, and then converting the car to fuel injection. probly not gonna bother with a b18c1 now.

i will be back to up date my info shortly

hi i drive a 91 prelude and the b21a1 motor has a lot of balls what ppl dont think about is that its 140horse power with 135foot pounds of torque thats really good power all the way through every rpm but the b21 does eat oil i know i blew one up and had it rebuilt and modded it putting out 190hp with no turbo yet the motor was designed to be turboed the if you look at the set up of a 91 prelude the cold air intake is really complex and when you remove it their is a lot of room for a turbo and intercooler their is also room to install an after market air intake if you move the battery to the trunk you can use a 94 integra after market intake (you need to cut some off) they are about $35 CAD to yor door step off ebay but about the b21 it tranny is really shity in USA in Japan it uses the Type R Integra Tranny with LSD thats what causes the motor to go because the line loose pressure and the tranny slips then the motor eats oil after time and then it blows (you can install a Type R Integra Tranny but it need a lot of work, not recommended) the motor eats a lot of oil because of the cooling system its a bad designe it has 2 fans one is an eletrice and cools the rad not the block when the car is off but what it should have also doen is ran the water pump so if you have a b21 install upgraded rad and everything else like the fan or go all out and install an intercooler then it wont eat oil also the oil pan is in a bad spot the car is really low to begin with and ppl lower it more so the plug on the oil pan hits the road and the threads rip causing it to leak "fuck" thats what happened to me and my fuckin engine blew, im still pissed and that was 4yrs ago the b21 has a low compression ratio because of its designe to be turboed i have been told it puts of 250hp when turboed and N/A (ZEX Kit) [ think about it b21 = 140 shouldnt it be b21 = about 210hp ] [ b17 = 170hp (civic sir)] when an eng has vtec that a form of a turbo from honda because trubos kill engines also ppl drive them to hard honda uses vtec instead of a turbo because it save gas and repair costs honda no. 1 deally is fule e-conime so 93 integra gsr 1.8 (vtec) = 160hp high compression 91 prelude 2.1 (no vtec) = 140hp low compression but if you drop a turbo in it = 190hp - 210hp high compression think about the h22 from the 2001 prelude the type s 2.2L= 223hp vtec thats type s not the s model 2.2L = 200hp vtec the type s is in japan ok so in a nut shell b21 is good if you turbo it and install an intercooler if not check your oil and coolant every week but this becomes expensive and you should have bought an h22 because it about the same price as a b21 and doesnt need a turbo or an intercooler also it has more hp to begin with, and you could always trurbo the h22 and have even more hp (you do the math) so if you turbo it need an intercooler if you add hp you need to upgrade your brakes the Type R integra brake fit but as for 87 its going to be tight and you will need to do some welding for the eng mounts to fit this is all i know for more info go to prelude3.com and go to the links mustard cat has a lot of good info about early gen preludes good luck and lude for life (the integra is a much easier car to do up the just seems to be more parts witch sucks for prelude lovers also the engine is a better design the 92 (gs) 1.8 = 140hp (no vtec) i dont recommend integra/civic swaps to preludes because the engines in preludes lean back causing less stress on the syncro in the tranny. syncro spin all the gears at the same speed allowing smoother shifting but they are not a durable as a b17 tranny pro vs. con) - mikeymackinon

dude you aint got a fucking clue what you are talking about, VTEC is nothing lie a turbo at all, it lets the engine draw more air in, turbo FORCES ALOT more air into the engine, and the trannny causes the engine to burn oil because the line loses presure and the tranny slips. well how does a 5 speed tranny slip, autos slip and fluid pressure in them to shift and stuff, but oin a 5 speed the clutch slips is the only tihng thats gonna slip, unless you chew every tooth off of a certain gear or something. and no the B21 shouldnt be 210HP, the B18 is not, the C5 is higher than 100/liter, the C1 is a bit lower, the B16 can be equall, lower or higher depending on country it came from. the K20 in the base is 160 and in the type S is 200, you cant say an engine should have thois msany HP because 100/liter is the standard, its not. also the way the engine leans hasnt a fucking thing to do with the synchro wearing you damn stooge. the synchro doesnt spin all gears at the same time, it gets the gear and the input shaft (I think, not sure what parts it gets moving exactly) spinning at the same speed before they engage as you shift. and no engine in any honda has been "BUILT FOR TURBO", if itr was built for turbo it would come with a turbo, honda foesnt boost their cars, I doubt they ever wil form the looks of it.

ban this clown, he just gave a years worth of dumb ass information.

type s prelude h22 not type s rsx k20 i know that and the 87 prelude is an an auto didnt you read the original message or did you rip in to me instead of trying to help anyone "ass clown" but what do i know i only rebuilt my own engine and now drive a 97 lude and working a 240sx to silvia s14 conversion with a sr20det engine, have you ever even changed your own oil, ya thanks. as for the k20 2.0L = 200hp so shouldnt a b21 2.1L = 210hp but you did get me on the synchro 'whops' and i said vtec is a cheep version on turbo not vtec is turbo. the way the engine sits does matter because the engine and the tranny sit on rockers and shift in a pair if the block sits in the wrong direction it causes stress on the tranny and they kill one another also h22 are to much power for a civic body design and cause the chassy to warp so if you change the engine also swap the tranny. and i like that ding on the front of your integra nice work, if you talk trash about me again ill kick your dick in the dirt and smack your mouth loose, ok tuffy, so hop along done done because your done. - fuckin' mikeymackinon

you idiot displacement is not proportionate to horsepower!!!
And VTEC ISNT LIKE A TURBO!!!

you idiot displacement is not proportionate to horsepower!!!
And VTEC ISNT LIKE A TURBO!!!


HAHA mikey youre an idiot. I didnt say it was a K20 in the prelude, it was a reference to your "this engine should be 210HP because it’s a 2.1 liter" bullshit you wrote. the prelude is an H22, 2.2 liter, obviously its not a K20 since those are 2.0 engines. and you were the one talking about synchros and the JDM ITR tranny w/ LSD. I didnt know ITR’s came with an automatic, sorry! oh wait I still don’t think they did. and even if an automatic tranny slips, how the hell does that cause the engine to burn oil???

and what the hell are you talking about here?


"im still pissed and that was 4yrs ago the b21 has a low compression ratio because of its designe to be turboed i have been told it puts of 250hp when turboed and N/A (ZEX Kit)"

youve ben told it puts out 250 HP when turboed and normally aspirated. I REALLY hope you mean 250 when boosted and 250 when built NA or I really feel sorry for you. and N02 is sorta considered FI in a sense, so its not technically NA right there, you inject N02 which becomes heated and releases/FORCES more air to be in the cylinder than would normally be in there without it. and if it is built up NA and has the same power as it does when TC'd something is wrong, turbocharged should yield you way more power than NA, and especially across the whole board, maybe you have the same peak number but thats not all that counts, I don’t even think youd have that though.


another thing, the fan pulls air through the radiator, and thats MUCH MUCH MUCH better than blowing it across the block. and nobody cares that it isnt blowing at the engine when the cars off(although it does somewhat since the air doesnt get through the radiator, then through the fan and just STOP dead right there. when the cars off, it isnt going to get hotter so theres no point in having fans blowing all over it. but when the cars sitting idling, what do you think would be better, water INSIDE the engine pulling heat from the engine and being circulated through to the radiator, being cooled and going back to rob more heat from the engine and then come dissipate it to the radiator which gets cooled by the fan and this goes around in a big circle continuously, or the hot water just keep getting hotter and a fan blowing at the block on the outside trying to cool the cylinder walls and everything INSIDE the engine where it’s the hottest. when driving sure you don’t need a fan, but idling you DEFINITELY need a fan.

and you say this,

"cooling system it’s a bad designe it has 2 fans one is an eletrice and cools the rad not the block when the car is off but what it should have also doen is ran the water pump" ,

like you think that all the other cars have water pumps that keep pumping the water through after youve turned off the car and walked away, which, well, cant happen since its driven off the engine and if the engines not running, the pumps not spinning. maybe there is some cars out there with electric water pumps but I havent ever heard that before, not tp say that means they arent out there but A LOT less than mechanical ones for damn sure.

"1 deally is fule e-conime so 93 integra gsr 1.8 (vtec)"

first what the hell does 1 deally is fule e-conime mean???

2nd the 92-93 GSR's had a B17A (1.7 liter), 94 and up are the B18C1's

I love this one

"ok so in a nut shell b21 is good if you turbo it and install an intercooler if not check your oil and coolant every week"

so if I turbo my car, as long as I put an intercooler on it I don’t have to check on things at all, but if I don’t boost it I need to check my oil and water every week? only thing you could have meant different is maybe if you don’t intercool it then check your water and oil every week, but you know the intercooler cools your air, which gores right into the engine, mixes with fuel, gets ignited, gets HOT and then still gets your turbo DAMN hot anyways, so either way the turbos gonna heat your oil and or water, depending on what turbo you got and how its bearings are cooled.

"2001 prelude the type s 2.2L= 223hp vtec thats type s not the s model 2.2L = 200hp vtec "

both of those have the same 200HP 2.2 liter engine. the type SH has 200 HP and the base has 200HP.


I could basically prove you wrong on EVERY SINGLE statement you made in your WHOLE ENTIRE post.