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Old 11-05-2022, 04:43 PM   #1
sc0terdad
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Default b21a internals, same as b21ft?

maybe stupid question, but I have mostly only heard of people talk about the internals and strength of the b21f/ b21ft, I have a carbed 81 b21a and I am considoring the prospect of doing a +t, does it make any sense to do this? I have not found much in terms of info about b21a's

I think I might recall someone posting something like this at one point but there was only one source of info responding to the question.
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Old 11-05-2022, 05:45 PM   #2
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Yes, same internals. And M-rods.
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Old 11-05-2022, 05:47 PM   #3
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Similar internals (the pistons are different on the turbo for lower compression ratio)
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Old 11-05-2022, 06:58 PM   #4
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And, the exhaust valves are sodium filled valves for the turbo models to for heat control.

Volvo used to sell an Rsport blow through carburator setup. Are you staying carb or going to injection? I would go with injection. Just swap to a whole injected turbo engine is the best bet for longetivity.
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Old 11-06-2022, 03:09 PM   #5
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Quote:
Originally Posted by dl242gt View Post
And, the exhaust valves are sodium filled valves for the turbo models to for heat control.

Volvo used to sell an Rsport blow through carburator setup. Are you staying carb or going to injection? I would go with injection. Just swap to a whole injected turbo engine is the best bet for longetivity.
I figure that I would have gone the injection route as blow through setups seem to be pretty shoddy. performance and reliability wise.

in terms of a turbo build would it be best to keep the rods and crank for use in a b230f+t setup, or is there any major differences that would make this not worth while?
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Old 11-06-2022, 03:15 PM   #6
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You cannot use B21 parts in a B230.

The cranks are differently sized

I would just start with what everyone else does, buy a B230 and rebuild it
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Old 11-06-2022, 03:19 PM   #7
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If you were only closer. I'd have a B21FT for you to rebuild. Your engine should have an A cam in it. That's a decent cam to use with turbo.
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Old 11-06-2022, 03:21 PM   #8
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Quote:
Originally Posted by hessam69 View Post
You cannot use B21 parts in a B230.

The cranks are differently sized

I would just start with what everyone else does, buy a B230 and rebuild it
ah alright, thanks.
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Old 11-06-2022, 03:24 PM   #9
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Quote:
Originally Posted by dl242gt View Post
If you were only closer. I'd have a B21FT for you to rebuild. Your engine should have an A cam in it. That's a decent cam to use with turbo.
I will definitely be sure to remember that about the cam.
thanks though
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Old 11-06-2022, 03:34 PM   #10
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I like the idea of a +t B21. The higher compression will give you a more responsive turbo engine and have potentially better off boost economy. If I recall correctly the engine is either 8.5 or 9.1 compression. the 8.5 being a very good way to go.

Nowadays good off boost economy is helpful. Gas isn't going to truly get cheaper. lol.
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Old 11-06-2022, 04:06 PM   #11
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I +T'd a B21A, it was fine .
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Old 11-06-2022, 04:33 PM   #12
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Quote:
Originally Posted by dl242gt View Post
And, the exhaust valves are sodium filled valves for the turbo models to for heat control.

Volvo used to sell an Rsport blow through carburator setup. Are you staying carb or going to injection? I would go with injection. Just swap to a whole injected turbo engine is the best bet for longetivity.
on this topic, are the b230 530/531 etc heads interchangeable with the b21?
the later heads have sodium filled valves right?
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Old 11-06-2022, 07:06 PM   #13
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The heads interchange.
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Old 11-06-2022, 07:23 PM   #14
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Quote:
Originally Posted by sc0terdad View Post
on this topic, are the b230 530/531 etc heads interchangeable with the b21?
the later heads have sodium filled valves right?
No, only turbo heads used the sodium valves. The stock valves are fine for a +t
that you aren't planning on pushing the limits too far.

If you do put a later 530/531 head on your car. Get the STS timing plate to make it
easier align the cam timing.
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Old 11-07-2022, 12:18 PM   #15
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Quote:
Originally Posted by Broke4speed View Post
I +T'd a B21A, it was fine .
can you give me a rundown as to what it was like, did it drive well, how much power did it make, what setup did you use, were there any problems you found while doing it?
it would be very helpful, thanks.
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Old 11-08-2022, 10:00 PM   #16
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I believe the B21A had different piston dish depth- this created an 8.5:1 ratio VS the 7.5 turbo and 9.1ish non-turbo.
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Old 11-09-2022, 07:52 AM   #17
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Volvo used to sell a R sport Turbo kit to bolt onto the B19a and B21a using a blow through turbo carb. Great in its time but as EFI is so no now there is no good reason to stay carb
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