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b21a internals, same as b21ft?

sc0terdad

sc0terdad

Active member
Joined
May 1, 2020
Location
Victoria, Bc
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.
 
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.
 
dl242gt said:
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.
Click to expand...

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?
 
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
 
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 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.
 
dl242gt said:
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.
Click to expand...

on this topic, are the b230 530/531 etc heads interchangeable with the b21?
the later heads have sodium filled valves right?
 
sc0terdad said:
on this topic, are the b230 530/531 etc heads interchangeable with the b21?
the later heads have sodium filled valves right?
Click to expand...

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.
 
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.
 
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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