B20B/VTEC Questions
Thread Starter
Junior Member
Joined: Jan 2007
Posts: 219
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From: Clarksville, TN, USA
B20B/VTEC Questions
Ok, I've search quite a bit on the subject, but I still not sold on the pros and cons of the swap.
I found this in the CRX & Civic FAQ Version 2.0 - https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/88-91-crx-ef-civic-frequently-asked-questions-faqs-1508680/
Then under B-Series, *The LS/VTEC Swap Page - http://www.phatwhippincrx.20m.com/custom4.html
It briefly mentions the B20Z, but never goes into the details. I've been searching quite a bit without finding much on the B20B/VTEC swap, so I'm sure I'm not the only one. If you have links about this swap, please post them. If I end up doing the swap and there's not already a write up on it, I'd be happy to create one.
So, I'm debating doing this swap on my B16A 1990 CRX Si , and just trying to get some answers to some of the questions I have. Most of these are in reference to *The LS/VTEC Swap page. The main thing I took away from it was what said about rod to stroke ratio. So, here are a few of the questions I have.
1. First and foremost, what are the pros and cons for the B20B/VTEC over the B16A?
I know the B20B/VTEC has more torque and a lower redline.
2. As for ECU, Transmission, linkage, mounts, etc. What can be used from the B16A and what needs to come from other platforms?
3. Part of the first question, is the B20B/VTEC swap reliable to DD with occasional weekends at the track?
4. Does anyone know the rod to stroke ratio for the B20B/VTEC swap?
5. What's the best motor to start with?
I know about the Integra's B20A and that it's no good for this swap.
I know there's a B20Z (USDM) and as far as the B20B goes there are some, (P8R head,)that are better than others. Here are a few I found.
H-Motors Online has the 96-98 and the 99-00 long block - http://www.hmotorsonline.com/shop/sc...age&item=30028
Tiger Japanese has two versions:
-one with the short intake manifold - http://www.tigerjapanese.com/index.p...mart&Itemid=26
-one with the long intake manifold - http://www.tigerjapanese.com/index.p...mart&Itemid=26
That's all I can think of at this time. Any help would be greatly appreciated!
I found this in the CRX & Civic FAQ Version 2.0 - https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/88-91-crx-ef-civic-frequently-asked-questions-faqs-1508680/
Then under B-Series, *The LS/VTEC Swap Page - http://www.phatwhippincrx.20m.com/custom4.html
It briefly mentions the B20Z, but never goes into the details. I've been searching quite a bit without finding much on the B20B/VTEC swap, so I'm sure I'm not the only one. If you have links about this swap, please post them. If I end up doing the swap and there's not already a write up on it, I'd be happy to create one.
So, I'm debating doing this swap on my B16A 1990 CRX Si , and just trying to get some answers to some of the questions I have. Most of these are in reference to *The LS/VTEC Swap page. The main thing I took away from it was what said about rod to stroke ratio. So, here are a few of the questions I have.
1. First and foremost, what are the pros and cons for the B20B/VTEC over the B16A?
I know the B20B/VTEC has more torque and a lower redline.
2. As for ECU, Transmission, linkage, mounts, etc. What can be used from the B16A and what needs to come from other platforms?
3. Part of the first question, is the B20B/VTEC swap reliable to DD with occasional weekends at the track?
4. Does anyone know the rod to stroke ratio for the B20B/VTEC swap?
5. What's the best motor to start with?
I know about the Integra's B20A and that it's no good for this swap.
I know there's a B20Z (USDM) and as far as the B20B goes there are some, (P8R head,)that are better than others. Here are a few I found.
H-Motors Online has the 96-98 and the 99-00 long block - http://www.hmotorsonline.com/shop/sc...age&item=30028
Tiger Japanese has two versions:
-one with the short intake manifold - http://www.tigerjapanese.com/index.p...mart&Itemid=26
-one with the long intake manifold - http://www.tigerjapanese.com/index.p...mart&Itemid=26
That's all I can think of at this time. Any help would be greatly appreciated!
Honda-Tech Member
Joined: Aug 2005
Posts: 1,690
Likes: 1
From: NE Ohio, USA
Re: B20B/VTEC Questions
1. b20/vtec obviously as you said it gives more bottom end torque while providing good flow with a VTEC head in the upper RPM ranges.
You also don't have to wait until VTEC kicks in to have any power.
Stock b16a makes peak torque late in the powerband and only like 112 ft lbs while the b20 makes very good bottom end torque numbers.
b16 has almost a perfect rod to stroke ratio, then is why it is so "rev happy"
Reliability, you can run stock b20 bottom end but to make it reliable you need to balance and get upgraded rod bolts as the bottom end is not designed to rev to 8k
2. All B-Series swaps are the same. You can use the mounts, linkage, Trans, etc. As for the ECU, you would more than likely want to convert to OBD1 and run a chipped p28 with a basemap for a b20/vtec and then tune it properly.
3. Reliability can be done if you are willing to put the time and money into making it reliable. Here is a link of "How to build a reliable ls/vtec and b20/vtec. https://honda-tech.com/forums/all-motor-naturally-aspirated-44/how-build-%22reliable%22-lsvtec-b20vtec-1676914/
4. Rod to Stroke ratio is ~1.54 in a b20b. As a reference:
As for rod ratio, consider that the B18C5 that you think is so great really does not have a great rod ratio. Like the GSR, it is only 1.58:1. A stock LS or B20 bottom end has a rod ratio that is 1.54:1. This can be improved to 1.58:1 by using a B18C crank. This destrokes the engine by about 50cc. But you will still have over 1900cc displacement - quite a bit more than a B18C5. A B17A crank will give you a 1.74:1 rod ratio. This would be very reliable and GREAT for turbo use. But it will lower displacement to only 1.8 liters. A B16A crank will give you an even better 1.85:1 rod ratio but will lower displacement to 1.7 liters. For allmotor use, I would stick with either the stock B20 crank or go with a B18C crank. If the engine is built competently with good quality internals and the required upgrades, there is no reason why it shouldn't be reliable. B16 and B17 cranks destroke the engine to the point that alot of the advantages of going B20 are negated. I would use oneof these combinations for forced induction only. Not that they couldn;t be used allmotor. There would just be little point.
Taken from https://honda-tech.com/forums/showpo...87&postcount=5
5. As an FYI the b20a comes from a 88-91? Prelude.
The b20z starts out with a little higher compression ~9.6:1 and the b20b starts out with a 8.8:1 compression ratio. This is obviously with a non vtec head. About 9:1 with b20b with b16a head and 9.9:1 with a b20z with b16a head.
I hope this helps you out.
Also if you want to mess around check out the compression calc to give you a rough idea on what your compression will be with whichever combination you decide to go with.
http://www.c-speedracing.com/howto/c...c/compcalc.php
You also don't have to wait until VTEC kicks in to have any power.
Stock b16a makes peak torque late in the powerband and only like 112 ft lbs while the b20 makes very good bottom end torque numbers.
b16 has almost a perfect rod to stroke ratio, then is why it is so "rev happy"
Reliability, you can run stock b20 bottom end but to make it reliable you need to balance and get upgraded rod bolts as the bottom end is not designed to rev to 8k
2. All B-Series swaps are the same. You can use the mounts, linkage, Trans, etc. As for the ECU, you would more than likely want to convert to OBD1 and run a chipped p28 with a basemap for a b20/vtec and then tune it properly.
3. Reliability can be done if you are willing to put the time and money into making it reliable. Here is a link of "How to build a reliable ls/vtec and b20/vtec. https://honda-tech.com/forums/all-motor-naturally-aspirated-44/how-build-%22reliable%22-lsvtec-b20vtec-1676914/
4. Rod to Stroke ratio is ~1.54 in a b20b. As a reference:
As for rod ratio, consider that the B18C5 that you think is so great really does not have a great rod ratio. Like the GSR, it is only 1.58:1. A stock LS or B20 bottom end has a rod ratio that is 1.54:1. This can be improved to 1.58:1 by using a B18C crank. This destrokes the engine by about 50cc. But you will still have over 1900cc displacement - quite a bit more than a B18C5. A B17A crank will give you a 1.74:1 rod ratio. This would be very reliable and GREAT for turbo use. But it will lower displacement to only 1.8 liters. A B16A crank will give you an even better 1.85:1 rod ratio but will lower displacement to 1.7 liters. For allmotor use, I would stick with either the stock B20 crank or go with a B18C crank. If the engine is built competently with good quality internals and the required upgrades, there is no reason why it shouldn't be reliable. B16 and B17 cranks destroke the engine to the point that alot of the advantages of going B20 are negated. I would use oneof these combinations for forced induction only. Not that they couldn;t be used allmotor. There would just be little point.
Taken from https://honda-tech.com/forums/showpo...87&postcount=5
5. As an FYI the b20a comes from a 88-91? Prelude.
The b20z starts out with a little higher compression ~9.6:1 and the b20b starts out with a 8.8:1 compression ratio. This is obviously with a non vtec head. About 9:1 with b20b with b16a head and 9.9:1 with a b20z with b16a head.
I hope this helps you out.
Also if you want to mess around check out the compression calc to give you a rough idea on what your compression will be with whichever combination you decide to go with.
http://www.c-speedracing.com/howto/c...c/compcalc.php
Thread Starter
Junior Member
Joined: Jan 2007
Posts: 219
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From: Clarksville, TN, USA
Re: B20B/VTEC Questions
Thank you for all the info!! 
I plan on reading all the links you included after this. I had a question about...
The specs posted on H-motors Online for the JDM B20B say:
126Hp 131Trq 8.8 Compression(96-98)
146Hp 133Trq 9.6 Compression (99-00)
So would that mean the 99-00 JDM B20B is the same specs as the B20Z? From what I found, the 96-98 doesn't have a knock sensor and the 99-00 does?
I plan on reading all the links you included after this. I had a question about...126Hp 131Trq 8.8 Compression(96-98)
146Hp 133Trq 9.6 Compression (99-00)
So would that mean the 99-00 JDM B20B is the same specs as the B20Z? From what I found, the 96-98 doesn't have a knock sensor and the 99-00 does?
Vietnamese!
Joined: Oct 2008
Posts: 10,262
Likes: 1
From: Orange County, CA
Re: B20B/VTEC Questions
Thank you for all the info!! I plan on reading all the links you included after this. I had a question about...
The specs posted on H-motors Online for the JDM B20B say:
126Hp 131Trq 8.8 Compression(96-98)
146Hp 133Trq 9.6 Compression (99-00)
So would that mean the 99-00 JDM B20B is the same specs as the B20Z? From what I found, the 96-98 doesn't have a knock sensor and the 99-00 does?
I plan on reading all the links you included after this. I had a question about...The specs posted on H-motors Online for the JDM B20B say:
126Hp 131Trq 8.8 Compression(96-98)
146Hp 133Trq 9.6 Compression (99-00)
So would that mean the 99-00 JDM B20B is the same specs as the B20Z? From what I found, the 96-98 doesn't have a knock sensor and the 99-00 does?
Thread Starter
Junior Member
Joined: Jan 2007
Posts: 219
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From: Clarksville, TN, USA
Re: B20B/VTEC Questions
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Thread Starter
Junior Member
Joined: Jan 2007
Posts: 219
Likes: 0
From: Clarksville, TN, USA
Re: B20B/VTEC Questions
The specs posted on H-motors Online for the JDM B20B say:
126Hp 131Trq 8.8 Compression(96-98)
146Hp 133Trq 9.6 Compression (99-00)
So would that mean the 99-00 JDM B20B is the same specs as the B20Z? From what I found, the 96-98 doesn't have a knock sensor and the 99-00 does?
126Hp 131Trq 8.8 Compression(96-98)
146Hp 133Trq 9.6 Compression (99-00)
So would that mean the 99-00 JDM B20B is the same specs as the B20Z? From what I found, the 96-98 doesn't have a knock sensor and the 99-00 does?
B20 non-vtec FAQ Guide
I created this guide for a couple reasons, but mainly for the reason that there is ALOT of misinformation on B20's. This thread should end all of that misinformation and confusion.
How to identify your B20 Motor:
Let's first start off by saying that ALL USDM motors will have a number after the last letter in it's engine code. The Engine code stamp can be found where the transmission and block mate at the front of the motor. The JDM motors do not have this number after the last letter. For example, a B20B1 is a USDM motor, whereas a B20B is a JDM motor.This is important to understand in determining which motor you have.
Next, there weren't any B20Z's in Japan. All the JDM B20's were stamped B20B, regardless of the year. You can tell the year of the motor by checking the year/month the head was cast in. The year is located just above the fourth exhaust runner. It is in a circle with a slash through it. Disregard the slash as it means nothing. For example a circle with a 9/8 is a motor that was made in 1998. Be careful though, as this is not a 100% accurate based solely on the year. You must also look at the month it was made. Again, it is right next to the year and will have the month in a circle with a slash through it. Just like the year, if it says 1/1, that means it was made in november, the eleventh month. I'll show you why the year is not 100% accurate. If a motor was made in 98, but was made in november or december of that year, it is actually a 99 motor. That is because they start making the motors early for the next years vehicles. If the head was made in september/october though, that is a tossup as it may either be the year cast on the head, or the next year, because that is the crossover where they stop making the current years vehicles and start producing the next year's vehicles.
Believe it or not, almost all B20's, regardless of year, come with the 96+ Integra LS P75 head. They are 99% identical. They have the same valves, springs, valve covers, distributors, cam gears, etc. as 96+ USDM/JDM P75 Integra LS heads. The only differences are w/ the variances in camshafts. There is one exception however. The B20 motor was equipped in MANY vehicles in Japan, mainly the SM-X, Step Wagon, CRV, and Orthia. Of the many B20 powered vehicles, three of them came with the P8R head, and only in certain model years. The Orthia, which came out in 1996 was one. The other was the Step Wagon. The orthia came with the P8R head in it's 96-98 model years and the step wagon came with the P8R equipped B20B in it's 96-98 model years. The CRV also came with either the P8R head or P75 head in it's 96-98 model years. The P8R head is a completely different casting than P75 heads which were used on all other B20's. This head came with 84mm combustion chambers and 33mm vtec sized intake valves.
All 99-00 B20's have a knock sensor, regardless of where it comes from, which signifies the high compression 9.6:1 motor. If your B20 does NOT have a knock sensor, it is not the 9.6:1 compression motor. High compression B20's use "PHK" pistons which have a less of a dish them, as the "P3f" pistons found in the low compression B20's do. All B20's have an 84mm Bore and an 89mm stroke regardless of year. They are internally and externally identical to 96+ B18B's, with the exception of the Pistons, sleeves, and in some cases, the intake manifold and cams. They all have an 81mm combustion chamber diameter as well, except for the "P8R" head, which has an 84mm diameter and larger valves, as described above.
Here is a list of the different compression ratios and Power Ratings for B20's, in regards to the year and origin of the motor:
USDM:
96-98 Honda CRV
126 HP, 133 ft/lbs TQ
compression: 8.8:1
99-00 Honda CRV
146 HP, 133 Ft/lbs TQ
compression: 9.6:1
JDM (taken from Japan's Honda website):
96-98 Honda Orthia
143 HP, 132 ft/lbs TQ
9.2:1 compression
96-98 Honda Step Wagon
123 HP,133 ft/lbs TQ
9.2:1 compression
99-00 Honda Step Wagon
134 HP, 136 ft/lbs TQ
9.6:1 compression
96-98 Honda CRV (two variants)
128 HP, 136 ft/lbs TQ
8.8:1 compression
143 HP, 132 ft/lbs TQ
9.2:1 compression
99-00 Honda CRV
148 HP, 136 ft/lbs TQ
9.6:1 compression
96-98 Honda SM-X
128 HP, 135 ft/lbs TQ
8.8:1 compression
99-00 Honda SM-X
138 HP, 137 ft/lbs TQ
9.6:1 compression
These power figures are worthless for you and me, in the sense that these numbers are for these motors in their respective stock vehicles. Take into account that these numbers are with each specific vehicle's stock restrictive header/exhaust, extremely restrictive ECU with it's conservative fuel/ignition tables, restrictive intakes, etc. I've seen multiple B20's dyno in the 125-140 HP range with nothing more than an intake, header, and exhaust, with torque numbers in the 130-140 FT/LBS region. Which is more torque than they are rated at to the flywheel. Based on the factory numbers, these kind of gains shouldn't be made just with an intake and exhaust upgrade. This just goes to show you how underated these motors are from the factory. There is a Rule of thumb that says whp numbers should be about 15-20% lower than flywheel rated horsepower. By using that formula, High compression B20 motors should be rated closer to 160 Hp and low compression B20 motors should be rated closer to 145 horsepower.
BEWARE!! Do NOT let engine importers fool you. Many of them knowingly try to sell you a "JDM" B20B and tell you that ALL JDM B20B's are high compression. As many of you have just learned, this is not true. They tell you this because demand for the low compression motors is alot less than the higher compression B20's. Possibly, many importers just don't know the difference. But don't take that chance. The only REAL way to tell is if the motor has a knock sensor. Also if it is a USDM "B20Z", it is no doubt the 9.6:1 compression motor. So, it may be safer just to find a "B20Z".
I hope this has been a helpful guide for you. If there's anything I've missed at all, please feel free to let me know.
***I'm still trying to find more information on this P8R head. As of now, it appears that all the B20's w/ the P8R head come with a 2 layer headgasket, which is part of the reason the compression ratio on them is 9.2:1. Another reason the compression ratio is 9.2:1 is because the valves are 33mm and not 31mm, which takes up more space in the head, giving it a higher compression ratio than w/ the P75 heads. I would still like to get accurate readings on the volume of the combustion chambers, as well as other dimensions such as the depth of the chambers. I'm hoping to post more info on the different intake manifolds as well, but not until i've done more research. Also, I am currently researching the differences between all the B20 cams. I will update accordingly.
I created this guide for a couple reasons, but mainly for the reason that there is ALOT of misinformation on B20's. This thread should end all of that misinformation and confusion.
How to identify your B20 Motor:
Let's first start off by saying that ALL USDM motors will have a number after the last letter in it's engine code. The Engine code stamp can be found where the transmission and block mate at the front of the motor. The JDM motors do not have this number after the last letter. For example, a B20B1 is a USDM motor, whereas a B20B is a JDM motor.This is important to understand in determining which motor you have.
Next, there weren't any B20Z's in Japan. All the JDM B20's were stamped B20B, regardless of the year. You can tell the year of the motor by checking the year/month the head was cast in. The year is located just above the fourth exhaust runner. It is in a circle with a slash through it. Disregard the slash as it means nothing. For example a circle with a 9/8 is a motor that was made in 1998. Be careful though, as this is not a 100% accurate based solely on the year. You must also look at the month it was made. Again, it is right next to the year and will have the month in a circle with a slash through it. Just like the year, if it says 1/1, that means it was made in november, the eleventh month. I'll show you why the year is not 100% accurate. If a motor was made in 98, but was made in november or december of that year, it is actually a 99 motor. That is because they start making the motors early for the next years vehicles. If the head was made in september/october though, that is a tossup as it may either be the year cast on the head, or the next year, because that is the crossover where they stop making the current years vehicles and start producing the next year's vehicles.
Believe it or not, almost all B20's, regardless of year, come with the 96+ Integra LS P75 head. They are 99% identical. They have the same valves, springs, valve covers, distributors, cam gears, etc. as 96+ USDM/JDM P75 Integra LS heads. The only differences are w/ the variances in camshafts. There is one exception however. The B20 motor was equipped in MANY vehicles in Japan, mainly the SM-X, Step Wagon, CRV, and Orthia. Of the many B20 powered vehicles, three of them came with the P8R head, and only in certain model years. The Orthia, which came out in 1996 was one. The other was the Step Wagon. The orthia came with the P8R head in it's 96-98 model years and the step wagon came with the P8R equipped B20B in it's 96-98 model years. The CRV also came with either the P8R head or P75 head in it's 96-98 model years. The P8R head is a completely different casting than P75 heads which were used on all other B20's. This head came with 84mm combustion chambers and 33mm vtec sized intake valves.
All 99-00 B20's have a knock sensor, regardless of where it comes from, which signifies the high compression 9.6:1 motor. If your B20 does NOT have a knock sensor, it is not the 9.6:1 compression motor. High compression B20's use "PHK" pistons which have a less of a dish them, as the "P3f" pistons found in the low compression B20's do. All B20's have an 84mm Bore and an 89mm stroke regardless of year. They are internally and externally identical to 96+ B18B's, with the exception of the Pistons, sleeves, and in some cases, the intake manifold and cams. They all have an 81mm combustion chamber diameter as well, except for the "P8R" head, which has an 84mm diameter and larger valves, as described above.
Here is a list of the different compression ratios and Power Ratings for B20's, in regards to the year and origin of the motor:
USDM:
96-98 Honda CRV
126 HP, 133 ft/lbs TQ
compression: 8.8:1
99-00 Honda CRV
146 HP, 133 Ft/lbs TQ
compression: 9.6:1
JDM (taken from Japan's Honda website):
96-98 Honda Orthia
143 HP, 132 ft/lbs TQ
9.2:1 compression
96-98 Honda Step Wagon
123 HP,133 ft/lbs TQ
9.2:1 compression
99-00 Honda Step Wagon
134 HP, 136 ft/lbs TQ
9.6:1 compression
96-98 Honda CRV (two variants)
128 HP, 136 ft/lbs TQ
8.8:1 compression
143 HP, 132 ft/lbs TQ
9.2:1 compression
99-00 Honda CRV
148 HP, 136 ft/lbs TQ
9.6:1 compression
96-98 Honda SM-X
128 HP, 135 ft/lbs TQ
8.8:1 compression
99-00 Honda SM-X
138 HP, 137 ft/lbs TQ
9.6:1 compression
These power figures are worthless for you and me, in the sense that these numbers are for these motors in their respective stock vehicles. Take into account that these numbers are with each specific vehicle's stock restrictive header/exhaust, extremely restrictive ECU with it's conservative fuel/ignition tables, restrictive intakes, etc. I've seen multiple B20's dyno in the 125-140 HP range with nothing more than an intake, header, and exhaust, with torque numbers in the 130-140 FT/LBS region. Which is more torque than they are rated at to the flywheel. Based on the factory numbers, these kind of gains shouldn't be made just with an intake and exhaust upgrade. This just goes to show you how underated these motors are from the factory. There is a Rule of thumb that says whp numbers should be about 15-20% lower than flywheel rated horsepower. By using that formula, High compression B20 motors should be rated closer to 160 Hp and low compression B20 motors should be rated closer to 145 horsepower.
BEWARE!! Do NOT let engine importers fool you. Many of them knowingly try to sell you a "JDM" B20B and tell you that ALL JDM B20B's are high compression. As many of you have just learned, this is not true. They tell you this because demand for the low compression motors is alot less than the higher compression B20's. Possibly, many importers just don't know the difference. But don't take that chance. The only REAL way to tell is if the motor has a knock sensor. Also if it is a USDM "B20Z", it is no doubt the 9.6:1 compression motor. So, it may be safer just to find a "B20Z".
I hope this has been a helpful guide for you. If there's anything I've missed at all, please feel free to let me know.
***I'm still trying to find more information on this P8R head. As of now, it appears that all the B20's w/ the P8R head come with a 2 layer headgasket, which is part of the reason the compression ratio on them is 9.2:1. Another reason the compression ratio is 9.2:1 is because the valves are 33mm and not 31mm, which takes up more space in the head, giving it a higher compression ratio than w/ the P75 heads. I would still like to get accurate readings on the volume of the combustion chambers, as well as other dimensions such as the depth of the chambers. I'm hoping to post more info on the different intake manifolds as well, but not until i've done more research. Also, I am currently researching the differences between all the B20 cams. I will update accordingly.
Junior Member
Joined: Oct 2007
Posts: 19
Likes: 0
From: Ulm, Wurttemberg, Germany
Re: B20B/VTEC Questions
How do you do the swap? Do you have to drill the block? 
Is this one the exact same as the ls-vtec swap, just .2 more displacement? Everything seems like it points to that swap instead.
Is this one the exact same as the ls-vtec swap, just .2 more displacement? Everything seems like it points to that swap instead.
Junior Member
Joined: Oct 2007
Posts: 19
Likes: 0
From: Ulm, Wurttemberg, Germany
Honda-Tech Member
Joined: Oct 2009
Posts: 35
Likes: 0
Re: B20B/VTEC Questions
I have a question about the same idea, Would I be able to put the *99 jdm engine* b20b crank and rods into a b18c1!? would they fit... it'd be the same idea as having a stroker engine wouldn't it!? any help!?
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