Im thinking of buying a JDM B20 Block and going from a b18c1 to a b20vtec. Is it necessary to build the block before swapping it in. By build I mean Rods, Pistons . Or could I just do a straight up swap . Is this safe ?


Modified by 2000Plus at 2:05 PM 11/9/2006

 

You'll get a lot of different opinions on this, but my personal opinion is at least drop some higher CR pistons and upgrade the rod bolts with ARP ones. You could drop the B16A head onto the B20 block stock as-is, but I personally would not feel good about it lasting for the long haul.

 

one more question . How do I identify my head ? I bought my car at a auction and its a GSR motor but im positive the head is not a GSR it says PR3-2 and it has a different intake manifold from my regular b16a2. It looks much bigger .

 

b20 weak walls get a block gaurd for sure if you need anymore answers feel free to ask i have a built b20 myself high comp so shoot

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2000Plus &raquo;</TD></TR><TR><TD CLASS="quote">one more question . How do I identify my head ? I bought my car at a auction and its a GSR motor but im positive the head is not a GSR it says PR3-2 and it has a different intake manifold from my regular b16a2. It looks much bigger .</TD></TR></TABLE>

Hell PR3 head is either B16A or Type R, and there's not really a good way to tell exactly which one it is. It's definately not a GS-R head, because they say "P72" on them rather than PR3.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eg-owns you &raquo;</TD></TR><TR><TD CLASS="quote">b20 weak walls get a block gaurd for sure if you need anymore answers feel free to ask i have a built b20 myself high comp so shoot</TD></TR></TABLE>

Like I said this topic will bring out a ton of different opinions.

Personally I don't like block guards unless you're going to have the block sent to a machine shop to install the guard and then rebore the cylinders, because the tops get pinched up some with the block guard in place, which creates hot spots at the tops of the cylinders, excessive wear, etc.

Make sure if you get a block guard to get one that doesn't fit crazy tight, because once they heat up think about how much it will expand and press in on the tops of the cylinder walls.

 

What would your prefer PR3 or P72

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2000Plus &raquo;</TD></TR><TR><TD CLASS="quote">What would your prefer PR3 or P72</TD></TR></TABLE>

For a stock B20 bottom end? P72 only because it raises the CR more due to its smaller combustion chambers.

If you plan on swapping pistons out for custom ones to get the CR up anways keep the PR3 head since you've got it already. The PR3 and P72 flow similiarly stock or worked, and the P72 is actually harder to find as many aftermarket intake manifolds for it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18C5-EH2 &raquo;</TD></TR><TR><TD CLASS="quote">For a stock B20 bottom end? P72 only because it raises the CR more due to its smaller combustion chambers.

If you plan on swapping pistons out for custom ones to get the CR up anways keep the PR3 head since you've got it already. The PR3 and P72 flow similiarly stock or worked, and the P72 is actually harder to find as many aftermarket intake manifolds for it.</TD></TR></TABLE>

Thank both of you guys for your help and my noob questions .

 

I have a question? I have a b20a5 block and I have a 91 integra will that block bolt up in it and if so will a ls tranny bolt up as well

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Holderb20 &raquo;</TD></TR><TR><TD CLASS="quote">I have a question? I have a b20a5 block and I have a 91 integra will that block bolt up in it and if so will a ls tranny bolt up as well</TD></TR></TABLE>

Ditch that motor, it is a early prelude motor, and not worth pretty much anything.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eg-owns you &raquo;</TD></TR><TR><TD CLASS="quote">b20 weak walls get a block gaurd for sure if you need anymore answers feel free to ask i have a built b20 myself high comp so shoot</TD></TR></TABLE>

That's hear say, it's got teh same walls as the LS motor, only difference between the LS and B20 blocks is obviously the displacement size.

As for whether you need to upgrade internals or not, I'd say "no" - others say "better safe than sorry." Maybe some forged rods, while ur in there big higher comp pistosn and some ARP studs and you'd definately be set...

 

what's wrong with your b18c1? why not just build that?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Syndacate &raquo;</TD></TR><TR><TD CLASS="quote">

That's hear say, it's got teh same walls as the LS motor, only difference between the LS and B20 blocks is obviously the displacement size.
</TD></TR></TABLE>

actually b20's have a different sleeve design than other b series

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by that one doood &raquo;</TD></TR><TR><TD CLASS="quote">actually b20's have a different sleeve design than other b series</TD></TR></TABLE>

True with that, here is a little write up explaining it.

http://dwolsten.tripod.com/articles/jan96a.html

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by my_slow_civic &raquo;</TD></TR><TR><TD CLASS="quote">

True with that, here is a little write up explaining it.

http://dwolsten.tripod.com/articles/jan96a.html</TD></TR></TABLE>

good ****

 

Well my b18 is fine it has 300,000 on it and I needed a motor to put in it so I got the b20a5 but i didnt know that it was not the same as a b20b/z. I need a nother motor to put in my ls because i need a car for work

 

300k? jeez that's a ton.

anyway, you could just try to find a used b18a block and swap that in.

 

If you want to brace the cylinder walls of the B20 without boring it, maybe look into installing some Endyn block posts instead of a blockguard...
Other than that of course some ARP bolts are mandatory.
I'm just getting going on my B20 VTEC build. Whether you really need to change pistons depends on whether you have the B20B or the B20Z, which have 8.8 and 9.6 c\r, respectively. The PR3 head will raise it to around 9.9, just shy of stock GSR compression. A GSR head will get you 10.1 c/r.
Milling the block or head will get you even more so if you have a Z block as I do you can get away without an expensive set of pistons if you're planning a mild build with cams that aren't very crazy.

 

ya and the motor dont even smoke. Where would I find a block

 

Ok I have a b16 head and I have the oil tap that ties in at the oil pump a vtec controler what all do I need to make it work on a ls block

 

Umm....first off, what are you intending to drop in into?

Believe it or not, you're not the first person to think of this. It won't work as easy as you think. First of all, a B16 head doesn't just bolt up to a B20A* motor and work properly. The B20A/21A motors are the bastard children of the B series and only came in 3g Preludes. B20B/Z are newer and came in CRV's. They are completely different.

Very few bits and pieces are interchangeable between B16/18 and B20A/21A. It LOOKS like it will work, eyeballing it, but application is something else entirely. There is some extensive (and costly) custom work to be done to make everything line up the way it should. Second of all, the cylinder walls aren't weak, it's just that the B20A/21A motors were not designed to rev high enough to make VTEC a practical option. That article that was posted above from Tripod only applies to the B21A1, not the B20A*, and is a remnant of Honda's famous use of the Prelude as a testbed for new technologies in development (4ws for example--too bad they didn't keep that and use it more, cause it's awesome!). All H22's also used this material for cylinder sleeves, and most newer Honda motors. The B20A* all had steel sleeves. Regardless, they're both low revvers in comparison to newer Honda motors. A B20A/21A *might* survive one trip to 8 grand rpm. MIGHT. It certainly wouldn't survive as many as 5 trips there before a rod came sailing out the block. Once again, extensive custom work must be involved, probably in a set of custom cams that allow the VTEC to kick in at a much lower rpm. If you're determined to follow through with it, it can make a killer setup that would even be very turbo-friendly, but cost effectiveness goes down the toilet. This is not to say that the B20A/21A is worthless. Just because it doesn't have VTEC doesn't make it so, although plenty of people here may think that. Far from it, actually. Both of these motors are torquey in stock form, not to mention extremely turbo friendly, and I've seen a couple that boasted better than 380whp. That'd toast most people that think they're hot stuff just because they have VTEC, and believe it or not, it'd probably cost less to go that route with one of these. However, although the B20A/B21A are very buildable, they received very little aftermarket support, and you'll be hard pressed to find any goodies for it except in the used market, and even that contains very few. Most serious performance mods for this motor are DIY, as in "Design it yourself".
On top of that, there's a fitment issue here. The B20A/B21A block is taller than other B series by some ways. In the 3g Prelude, it's laid over some 18-25 degrees or so, and Civics and Integras sit straight up, so clearance is an issue, and the motor mounts might also be. They'll fit just fine in certain other models, but a civic or a teggy - not without some modifications. I don't mean to rain on your parade, but you really do need to do some serious research to undertake this project. There ARE some people who have done it, however, and with documentation, which can be found at http://www.preludepower.com. Use the search function on their site and look it up. You can find some answers there. But seriously? Give it up. VTEC's a lost cause here. The block's great for turbo. Go that way with it if you decide to use it.


Modified by tjcross at 2:56 AM 5/20/2007


Modified by tjcross at 3:04 AM 5/20/2007


Modified by tjcross at 3:08 AM 5/20/2007