A few points to add - the 88-91 Prelude B20A/B21A motors aren't entirely unrelated to the later Integra/Civic/CRV B16/B17/B18/B20 motors. Yes the blocks are cast at that leaning back angle, but a lot of the overall design/size/etc is still the same or nearly the same - especially to the non-VTEC B18A/B (and to an extent the larger bore B20B/Z). Cylinder spacing is identical across them all, as you said the Prelude B20A even has the same 81mm bore as the B16,17 and 18's (all). Camshafts from the non-VTEC B18A/B or B20B/Z drop into the Prelude DOHC B20A/B21A variants though the 'snout' end where the cam gear bolts on is about 5mm longer on the Integra/CRV motors, cam gears are the same size and number of teeth across both old and new B-series (I can't speak for the older JDM-only B20A's in the 2nd gen Prelude or 3g Accord as I never had one - only speaking of 3g Prelude B20A/B21A family). B18A/B and B20B/Z valve covers are also interchangeable onto the B20A/B21A and vice versa. In the early 2000's some Prelude guys on PreludePower.com researched doing a VTEC head swap like LSVTEC/CRVTEC and found that while it is doable due to the cylinder spacing being the same, it's a bit more complicated than using those newer Integra or CRV non-VTEC B18/B20 blocks because the Prelude B20/21 block is a bit narrower side to side so some oil and coolant holes in the VTEC head need to be welded shut, and while the 4 center-most head bolt holes are the same spacing, the 4 outer-most (so the 2 on the front and 2 on the back of the motor - IE transmission side and belt side) are slightly spaced differently requiring slightly opening up the head bolt holes in the VTEC head and then basically requiring a custom head gasket to match the moved head bolt holes etc. I can't remember off hand if the crankshafts have the same size main journals but since the cylinder spacing is the same across both those old B-series and the more mainstream Integra/Civic/CRV B-series I don't imagine they could be much different, though why you would want to put a 95mm stroke crank in a B-series block that didn't come with one I can't answer. But fundamentally, the 88-91 Prelude DOHC motors are actually very very similar to the Integra non-VTEC B18Ax and B18Bx in general design. The intake and exhaust manifold bolt patterns and port shape are different, but the spacing is basically the same, general block and head dimensions internally and externally are either exactly the same or very similar (again, same cylinder spacing, center 4 head bolt holes exactly the same, outer 4 almost the same) etc but the main reason those older B-series weren't popular for swaps is as you said - the angle that the blocks were cast. *edit* also, the SOHC B20A (B20A3 here in the states) block casting is the same as the DOHC B20A (B20A5 here in the states), but the crank in the carbureted engine had smaller connecting rod journals than the DOHC version, and the carbureted engine did not include a factory oil cooler. The oil filter just fit flush directly into the block, whereas on the DOHC motors there was a sandwich plate on the block there with fittings to run oil through a factory oil cooler in front of the radiator. I did see some Civic/Integra people swap B20A5's in the early days but like you said they had to do a lot of janky custom mount work. Making the motor sit straight up like they do in other cars made them very tall, the oil pan, intake and exhaust manifolds were then angled weirdly (since they were shaped to account for the motor leaning backwards in the Prelude), and to use a Civic/Integra B-series transmission required an adapter plate since the bell housings were not the same shapes. Also the Prelude B series were hydraulic clutch and cable shifted. If they tried to use the Prelude transmission, the axle angles would be weird since it was cast to match the backwards lean of the Prelude motor, and then still more custom work to mount the Prelude's cable shifter and on older Civic/Integra chassis custom work to swap from a cable clutch to hydraulic. All in all tons of work just to get a "not that powerful" motor into the car, vs going the much easier and more flexible route of the newer B-series motors which were designed and sold in similar chassis from the get-go.
@@aziangarage hope that helps. I also forgot to add that Integra/Civic B series flywheels will work on the 88-91 Prelude motors as well, but the B20A/B21A's have their ignition timing marks on the flywheel - vs the Civic/Integra that had them on the crank pulley. On my own 88 Prelude with a B20A5, I used an ACT 12lb flywheel meant for those newer B series but had to have a small alignment hole machined into the flywheel to fit over a little pin that sticks out on the Prelude's crankshaft. This is a bit problematic because you lose your timing marks, but if you're smarter than I was at the time you could just lay the new flywheel over the OEM one and paint some bright colored lines on the front and back of the new flywheel that line up properly with where they should be in relation to the alignment pin. The 90-91 Prelude transmissions will work like this with normal B-series clutches for hydraulic clutch model year Civic/Integra. When I did that flywheel swap I also had to swap from my stock 88 transmission to a 90-91 because the 88-89's transmission input shaft is smaller and wouldn't fit. Went with an Exedy clutch kit meant to be an OEM replacement for Integra Type R if I recall.
Thanks for more great information! I had no idea there are so many weird Prelude engines until I saw this video and did some research. I've been a Honda guy my whole life and never heard of the twin cam F22, B21, these odd B20's, etc. I didn't know that some of the JDM 3rd gen Accords came with B20's either. From what I can tell, it looks like the higher end versions of the JDM 3rd gen Accord got the B20 while their base models got the A20 like ours.
I'm happy you enjoyed it. It was definitely was journey for me to learn about the old jdm/edm B20a/B21 engines. A new one I found out about recently was the G20/G25 5 cylinder Honda engine out of a Honda Refaga.
Yup, I always thought the G series was an odd decision. I never understood why Honda went through the trouble and expense of designing it when they already had the C series V6 and the H series I4, both of which making similar or more power. The only thing I can think of is Honda may have wanted an I5 just to stand out and as an attempt to compete with the German 5 cylinders like what powered many VW/Audi and Mercedes Benz models, but then they made those FWD....
Back in the late 90's/2000's 3geez days, you could find the B20 gold top with 5 speed trans 160hp w 160 tq. Like you mentioned its not worth it today due to partsvand accessibility.
Sounds like a great time to be alive. I wish I got to experience the days of these classic Hondas as a teen/young adult while the cars and parts were still at least somewhat available. I completely realize that odd swaps like a B20 into a 3rd gen Accord is far from the most cost effective way to go fast, but to me it's still cool and unique and knowing I can't have something like a B20 swapped 3rd gen almost for any price just makes me want it more LOL
![Honda B Series Engine Best Mods & Upgrades [Tuning]](http://i.ytimg.com/vi/v8KvayMdywI/mqdefault.jpg)
A few points to add - the 88-91 Prelude B20A/B21A motors aren't entirely unrelated to the later Integra/Civic/CRV B16/B17/B18/B20 motors. Yes the blocks are cast at that leaning back angle, but a lot of the overall design/size/etc is still the same or nearly the same - especially to the non-VTEC B18A/B (and to an extent the larger bore B20B/Z). Cylinder spacing is identical across them all, as you said the Prelude B20A even has the same 81mm bore as the B16,17 and 18's (all). Camshafts from the non-VTEC B18A/B or B20B/Z drop into the Prelude DOHC B20A/B21A variants though the 'snout' end where the cam gear bolts on is about 5mm longer on the Integra/CRV motors, cam gears are the same size and number of teeth across both old and new B-series (I can't speak for the older JDM-only B20A's in the 2nd gen Prelude or 3g Accord as I never had one - only speaking of 3g Prelude B20A/B21A family). B18A/B and B20B/Z valve covers are also interchangeable onto the B20A/B21A and vice versa.
In the early 2000's some Prelude guys on PreludePower.com researched doing a VTEC head swap like LSVTEC/CRVTEC and found that while it is doable due to the cylinder spacing being the same, it's a bit more complicated than using those newer Integra or CRV non-VTEC B18/B20 blocks because the Prelude B20/21 block is a bit narrower side to side so some oil and coolant holes in the VTEC head need to be welded shut, and while the 4 center-most head bolt holes are the same spacing, the 4 outer-most (so the 2 on the front and 2 on the back of the motor - IE transmission side and belt side) are slightly spaced differently requiring slightly opening up the head bolt holes in the VTEC head and then basically requiring a custom head gasket to match the moved head bolt holes etc. I can't remember off hand if the crankshafts have the same size main journals but since the cylinder spacing is the same across both those old B-series and the more mainstream Integra/Civic/CRV B-series I don't imagine they could be much different, though why you would want to put a 95mm stroke crank in a B-series block that didn't come with one I can't answer.
But fundamentally, the 88-91 Prelude DOHC motors are actually very very similar to the Integra non-VTEC B18Ax and B18Bx in general design. The intake and exhaust manifold bolt patterns and port shape are different, but the spacing is basically the same, general block and head dimensions internally and externally are either exactly the same or very similar (again, same cylinder spacing, center 4 head bolt holes exactly the same, outer 4 almost the same) etc but the main reason those older B-series weren't popular for swaps is as you said - the angle that the blocks were cast.
*edit* also, the SOHC B20A (B20A3 here in the states) block casting is the same as the DOHC B20A (B20A5 here in the states), but the crank in the carbureted engine had smaller connecting rod journals than the DOHC version, and the carbureted engine did not include a factory oil cooler. The oil filter just fit flush directly into the block, whereas on the DOHC motors there was a sandwich plate on the block there with fittings to run oil through a factory oil cooler in front of the radiator.
I did see some Civic/Integra people swap B20A5's in the early days but like you said they had to do a lot of janky custom mount work. Making the motor sit straight up like they do in other cars made them very tall, the oil pan, intake and exhaust manifolds were then angled weirdly (since they were shaped to account for the motor leaning backwards in the Prelude), and to use a Civic/Integra B-series transmission required an adapter plate since the bell housings were not the same shapes. Also the Prelude B series were hydraulic clutch and cable shifted. If they tried to use the Prelude transmission, the axle angles would be weird since it was cast to match the backwards lean of the Prelude motor, and then still more custom work to mount the Prelude's cable shifter and on older Civic/Integra chassis custom work to swap from a cable clutch to hydraulic. All in all tons of work just to get a "not that powerful" motor into the car, vs going the much easier and more flexible route of the newer B-series motors which were designed and sold in similar chassis from the get-go.
Gold mine of info thank you!
@@aziangarage hope that helps. I also forgot to add that Integra/Civic B series flywheels will work on the 88-91 Prelude motors as well, but the B20A/B21A's have their ignition timing marks on the flywheel - vs the Civic/Integra that had them on the crank pulley. On my own 88 Prelude with a B20A5, I used an ACT 12lb flywheel meant for those newer B series but had to have a small alignment hole machined into the flywheel to fit over a little pin that sticks out on the Prelude's crankshaft. This is a bit problematic because you lose your timing marks, but if you're smarter than I was at the time you could just lay the new flywheel over the OEM one and paint some bright colored lines on the front and back of the new flywheel that line up properly with where they should be in relation to the alignment pin.
The 90-91 Prelude transmissions will work like this with normal B-series clutches for hydraulic clutch model year Civic/Integra. When I did that flywheel swap I also had to swap from my stock 88 transmission to a 90-91 because the 88-89's transmission input shaft is smaller and wouldn't fit. Went with an Exedy clutch kit meant to be an OEM replacement for Integra Type R if I recall.
It's good to know you still make videos.....I remember when you were removing that sunroof on that Civic.
Thanks for more great information! I had no idea there are so many weird Prelude engines until I saw this video and did some research. I've been a Honda guy my whole life and never heard of the twin cam F22, B21, these odd B20's, etc. I didn't know that some of the JDM 3rd gen Accords came with B20's either. From what I can tell, it looks like the higher end versions of the JDM 3rd gen Accord got the B20 while their base models got the A20 like ours.
I'm happy you enjoyed it. It was definitely was journey for me to learn about the old jdm/edm B20a/B21 engines. A new one I found out about recently was the G20/G25 5 cylinder Honda engine out of a Honda Refaga.
Yup, I always thought the G series was an odd decision. I never understood why Honda went through the trouble and expense of designing it when they already had the C series V6 and the H series I4, both of which making similar or more power. The only thing I can think of is Honda may have wanted an I5 just to stand out and as an attempt to compete with the German 5 cylinders like what powered many VW/Audi and Mercedes Benz models, but then they made those FWD....
Back in the late 90's/2000's 3geez days, you could find the B20 gold top with 5 speed trans 160hp w 160 tq. Like you mentioned its not worth it today due to partsvand accessibility.
Wasnt worth it back then as stated above video.
Sounds like a great time to be alive. I wish I got to experience the days of these classic Hondas as a teen/young adult while the cars and parts were still at least somewhat available. I completely realize that odd swaps like a B20 into a 3rd gen Accord is far from the most cost effective way to go fast, but to me it's still cool and unique and knowing I can't have something like a B20 swapped 3rd gen almost for any price just makes me want it more LOL
What notor you recommend for a 2nd gen prelude. If you have a motor in mind, what about axles and wiring harness and ECU?
What is your goal? Nothing wrong with engines the car comes with.
As an '88 owner, I think my path forward is the K-series. I wonder if there's any information on that?
facebook.com/1989akord
Glad to know someone is already trying this, I was considering K-series as well but I wasn't getting nowhere checking 3geez as research
And yes the Ecu from a prelude B20A5 will work👍👍
my man coming in with the video i need lmao
Excellent info.