BP-4W Build? Thoughts?
#1
BP-4W Build? Thoughts?
Hey guys haven't been on here in a while. Sold my 95 na a few years back to much rust. A few months ago picked up a 99 nb and she's healthy and up to date on maintenance. Just couldn't stay away.
Anyway was browsing my local Craigslist and came across a bp4w engine, flywheels, clutches, and a 10AE dash with airbag all for 100 bucks.
The motor spun #4 rod bearing and I think it might be salvageable but I don't know yet. The head looks clean but the guy said it has the "exhintake" cam and I don't know if its right has the 197.5* hole drilled in the cam gear but I am not sure if its correct
Anyway I plan to build the motor and head up for boost and really want it to be able to rev out to 8k. Looking to pick your brains for ideas on the build. I've got an idea, again just want to hear your thoughts on it. Anything is appriciated
Anyway was browsing my local Craigslist and came across a bp4w engine, flywheels, clutches, and a 10AE dash with airbag all for 100 bucks.
The motor spun #4 rod bearing and I think it might be salvageable but I don't know yet. The head looks clean but the guy said it has the "exhintake" cam and I don't know if its right has the 197.5* hole drilled in the cam gear but I am not sure if its correct
Anyway I plan to build the motor and head up for boost and really want it to be able to rev out to 8k. Looking to pick your brains for ideas on the build. I've got an idea, again just want to hear your thoughts on it. Anything is appriciated
#7
I second the finding a second crank. You have to pay to get it ground down and polished, then you pay again when you get it balanced. By the time you've done that, you could have just gotten a good (used) crank in the first place.
I found out the hard way that, when sourcing oversized bearings (for the undersized crank), you run into problems if you need to have the option to have slightly odd bearing sizes (1mil under or over). Especially if you have your blocks mains bored/honed out and need slightly oversized (1mil) bearings. You can't get both oversized (1mil) and 20mil undersized at the same time.
I found out the hard way that, when sourcing oversized bearings (for the undersized crank), you run into problems if you need to have the option to have slightly odd bearing sizes (1mil under or over). Especially if you have your blocks mains bored/honed out and need slightly oversized (1mil) bearings. You can't get both oversized (1mil) and 20mil undersized at the same time.
#8
I second the finding a second crank. You have to pay to get it ground down and polished, then you pay again when you get it balanced. By the time you've done that, you could have just gotten a good (used) crank in the first place. Ifound out the hard way that, when sourcing oversized bearings (for the undersized crank), you run into problems if you need to have the option to have slightly odd bearing sizes (1mil under or over). Especially if you have your blocks mains bored/honed out and need slightly oversized (1mil) bearings. You can't get both oversized (1mil) <em>and</em> 20mil undersized at the same time.
Taking 0.001 off the rod journals would need rebalance?
So you are saying all the journals need to be the same size?
#9
I never knew about the over/under limitations. I guess those who ever run billet mains and have it line bored, have otherwise pristine cranks.
Last edited by psyber_0ptix; 07-24-2018 at 09:13 AM.
#11
Boost Pope
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Any time you touch the rod journals, you re-balance the crank.
And, no, the journals don't all have to be the same. You can always mix-n-match bearings from different sets. It's just that if you do, some future engine-builder will find you what you did the hard way, and hire a witch to place a curse on you. Now, admittedly, there are a lot of incompetent witches out there, but is that a chance you want to take?
I wouldn't personally switch to a Protege crankshaft. No personal experience, just a gut feeling that there's a reason you rarely hear about people breaking stock Miata crankshafts even in engines making 2-3x the original torque.