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Discussion Starter · #1 ·
Hello all I have been working on putting fuel injection from the original engine in my 91 prelude onto the b20a3 that was put into it. After I got both the dual carb setup and the fuel injection taken off I realized that the fuel injection manifold has 4 pipes and the engine only has two pipes on it. What part do I need to make it fit on the engine?
 

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Head, intake manifold, wiring harness, ecu, all of the fuel lines going to the fuel tank, the fuel tank.

Anything is possible with enough time and money but the fact that you even have to ask what all would need to be done shows that your probably not up for the task.
 

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It's really not that complicated since your car is already fuel injected. You only need the b20a3 short block. That consists of the block, pistons, and crank. Everything else will come from your b20a1.

It would be a lot more work if you were converting a carb'd 3rd gen to fuel injection. But that's not the case here.
 

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Discussion Starter · #6 ·
Head, intake manifold, wiring harness, ecu, all of the fuel lines going to the fuel tank, the fuel tank.

Anything is possible with enough time and money but the fact that you even have to ask what all would need to be done shows that your probably not up for the task.
Well under normal circumstances you would be right but I bought this car for 100 dollars under the impression that it would be a project. I am building this car for the lemons race at sonoma raceway which has rules that the car must be built under 1500 dollars. I chose this car specifically because the body and interior are in nice shape and it has the 4ws parts already installed. I am pretty new to working on cars but I find it fun and would like to learn how to repair more cars, the only ones I have worked on in the past are a 03 toyota 4 runner and a 83 gmc sierra. Say I were to put the heads from the b21a1 onto the b20a3 do you know what the difference in horse power stock would be from either rebuilding the b21a1 or getting a h22a as opposed to upgrading the b20a3. Also would it be more limited in terms of how much I could upgrade it?
 

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Discussion Starter · #7 ·
It's really not that complicated since your car is already fuel injected. You only need the b20a3 short block. That consists of the block, pistons, and crank. Everything else will come from your b20a1.

It would be a lot more work if you were converting a carb'd 3rd gen to fuel injection. But that's not the case here.
Thanks for the information this is quite helpful. What do you think would be the difference in horse power and upgradability between doing this to a b20a3 or rebuilding the b21a1 or getting a h22 engine?
 

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The hp difference would be small compared with the stock b21. The main difference is the b20a3 has thinner rods and smaller rod bearings. It should run fine with stock parts, but there's really no upgrade options for that engine. If you're looking for more power you should go with an h22 or similar swap. Keep in mind that the b20a3 option will be the least expensive by far since there's no real modifications needed. It would be an option if you need to get the up and running quickly. But it's not one that people are lining up to do. You need to decide what your goals are both short term and long term.
 

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Well under normal circumstances you would be right but I bought this car for 100 dollars under the impression that it would be a project. I am building this car for the lemons race at sonoma raceway which has rules that the car must be built under 1500 dollars. I chose this car specifically because the body and interior are in nice shape and it has the 4ws parts already installed. I am pretty new to working on cars but I find it fun and would like to learn how to repair more cars, the only ones I have worked on in the past are a 03 toyota 4 runner and a 83 gmc sierra. Say I were to put the heads from the b21a1 onto the b20a3 do you know what the difference in horse power stock would be from either rebuilding the b21a1 or getting a h22a as opposed to upgrading the b20a3. Also would it be more limited in terms of how much I could upgrade it?
If your build is limited to the $1500 range then the H22 swap is out of the question as it would take $3000 if you did the swap yourself and ordered all the core parts to swap it out.
But if that is the route you want to go, I can assist you in that. Just email me: [email protected]

The B21a1 head on a B20a5 block lowers compression due to having bigger dome on the smaller cylinders.
It will get the car running but you will lose compression which I do not think you want.

Going B21a1 head on a B20a3 block with be the same result, plus what Luzer stated above regarding interal parts.
 

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Discussion Starter · #10 ·
If your build is limited to the $1500 range then the H22 swap is out of the question as it would take $3000 if you did the swap yourself and ordered all the core parts to swap it out.
But if that is the route you want to go, I can assist you in that. Just email me: [email protected]

The B21a1 head on a B20a5 block lowers compression due to having bigger dome on the smaller cylinders.
It will get the car running but you will lose compression which I do not think you want.

Going B21a1 head on a B20a3 block with be the same result, plus what Luzer stated above regarding interal parts.
Ouch thats pretty steep for a self engine swap :sadlike: so unless I got a used engine thats pretty much out of the question I will email you though if I end up finding one. It is good to know though that swapping that head will lower compression. If you were to put an engine in within that budget what would you suggest for the best horsepower and upgradability? I think for now im gonna swap the head on and get it running just so that I can see what works well and what doesnt in the car since it wont cost me any additional money to try.
 

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Discussion Starter · #11 ·
The hp difference would be small compared with the stock b21. The main difference is the b20a3 has thinner rods and smaller rod bearings. It should run fine with stock parts, but there's really no upgrade options for that engine. If you're looking for more power you should go with an h22 or similar swap. Keep in mind that the b20a3 option will be the least expensive by far since there's no real modifications needed. It would be an option if you need to get the up and running quickly. But it's not one that people are lining up to do. You need to decide what your goals are both short term and long term.
Thanks for the information. I thought it over and decided to try the b21 head on the b20 just so that I can see how everything runs. As another person suggested the h22 swap might be out of my budget for the lemons race but in the future its not out of the question. Have you h22 swapped a prelude? If so how did the added weight effect the weight distribution and handling?
 

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... As another person suggested the h22 swap might be out of my budget for the lemons race but in the future its not out of the question. Have you h22 swapped a prelude? If so how did the added weight effect the weight distribution and handling?
I will answer that question since I am the one who not only makes the swap kit I also have done the swap into my own chassis...





As with anything you need to adjust for the added power and geometry that comes with any motor swap.
Example, upgrade to Ksports as well as get my traction bar with skid bar for better suspension handling and help to prevent engine and tranny from bottoming out.

These engines were not designed to sit in out chassis, I got that all figured out and we came up with the most affordable options for this engine to be swapped.

I am currently working a new project to have a custom K-frame to adress the ground height issue and better engine placement but it will be expensive for anyone thinking of going the extra mile for better ground clearance and balance of the engine over the suspension.
 
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