Fa20 with Fb25 block. - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

jet86 · 09-04-2013, 08:35 AM

Not sure if it has been looked into enough but I decided to do a comparison with pictures.
The blocks are VERY similar apart from the few things.
One of these differences that could be the potential deal breaker is the fact the fb25 has no starter motor hump due to the gearboxes on the fa20 being sourced by Toyota, this could be sorted by milling out some of the fb25 block and drilling+tapping into hole for the starter motor lower bolt.
Another difference in the block is the huge threaded hole on the top of the block (about m16), the only reason this could give you issues is if you run a sprintex supercharger setup as it uses this hole.
The last and most obvious change is the fact the bores are now 94mm rather than 86mm. You can get around this by enlarging the combustion chamber on the fa20 heads with the use of a Cnc or a very steady porting hand (not recommended). The water jacket ports on the fa20 heads don't have any issues with the fb25 deck.

jet86 · 09-04-2013, 08:45 AM

Pics being uploaded. Don't mind the speed hole in the fa20 block.

jet86 · 09-04-2013, 08:54 AM

jet86 · 09-04-2013, 08:55 AM

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ft_sjo · 09-04-2013, 08:57 AM

Photos aren't working, which is a shame. Bandwidth exceeded errors.

That big bolt hole is probably an M14, not M16, if it's the one the Sprintex s/c fixes to.

jet86 · 09-04-2013, 09:34 AM

Yea yiur probably right. I'm not at home so I can't check, I just remember it was way bigger than m12

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jet86 · 09-04-2013, 09:35 AM

Il upload the pics in the morning, there is about 10 or so including head gasket differences

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ft_sjo · 09-04-2013, 09:39 AM

Thanks, I look forward to the photos and further dialogue.

chadstyle · 09-04-2013, 09:48 AM

Damn, nearly identical!! I'm surprised no one has done a FA25 swap yet...

Sportsguy83 · 09-04-2013, 09:56 AM

@jet86

Sportsguy83 · 09-04-2013, 09:57 AM

@jet86

Sportsguy83 · 09-04-2013, 10:01 AM

Quote:

Originally Posted by jet86

Not sure if it has been looked into enough but I decided to do a comparison with pictures.
The blocks are VERY similar apart from the few things.
One of these differences that could be the potential deal breaker is the fact the fb25 has no starter motor hump due to the gearboxes on the fa20 being sourced by Toyota, this could be sorted by milling out some of the fb25 block and drilling+tapping into hole for the starter motor lower bolt.
Another difference in the block is the huge threaded hole on the top of the block (about m16), the only reason this could give you issues is if you run a sprintex supercharger setup as it uses this hole.
The last and most obvious change is the fact the bores are now 94mm rather than 86mm. You can get around this by enlarging the combustion chamber on the fa20 heads with the use of a Cnc or a very steady porting hand (not recommended). The water jacket ports on the fa20 heads don't have any issues with the fb25 deck.

What would be the advantage of using the FA20 heads and not the FB25 long block altogether?

I understand the Honda frankensteins, you combine the bigger displacement of a non-vtec engine with V-tec heads having the best of both worlds, but what is the advantage here?

OrbitalEllipses · 09-04-2013, 10:14 AM

Quote:

Originally Posted by Sportsguy83

What would be the advantage of using the FA20 heads and not the FB25 long block altogether?

I understand the Honda frankensteins, you combine the bigger displacement of a non-vtec engine with V-tec heads having the best of both worlds, but what is the advantage here?

DI. I didn't think the FB25 had DI.

zooki · 09-04-2013, 10:25 AM

What is the bore spacing difference on the two blocks?

09-04-2013, 09:48 AM	#9
chadstyle Senior Member Join Date: Oct 2012 Drives: 2013 Subaru BR-Z Limited Location: Fort Lauderdale, Florida Posts: 883 Thanks: 407 Thanked 562 Times in 294 Posts Mentioned: 42 Post(s) Tagged: 4 Thread(s)	Damn, nearly identical!! I'm surprised no one has done a FA25 swap yet... __________________ ChadStyle's Build

09-04-2013, 10:25 AM	#14
zooki Senior Member Join Date: Jun 2012 Drives: waiting on a 2021... Location: Texas Posts: 770 Thanks: 190 Thanked 410 Times in 233 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	What is the bore spacing difference on the two blocks? __________________ 2016 4Runner Tail edition 2020 Camry 2020 RAV4 2013 Chevy 3500 4x4 Duramax 1999 Ford F250 Powerstroke, the tow rig 1969 Mustang, the fast car....(:

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09-04-2013, 08:57 AM	#5
ft_sjo Banned Join Date: Oct 2012 Drives: GT86 Location: The Motherland Posts: 1,398 Thanks: 140 Thanked 473 Times in 271 Posts Mentioned: 22 Post(s) Tagged: 0 Thread(s)	Photos aren't working, which is a shame. Bandwidth exceeded errors. That big bolt hole is probably an M14, not M16, if it's the one the Sprintex s/c fixes to.

09-04-2013, 09:39 AM	#8
ft_sjo Banned Join Date: Oct 2012 Drives: GT86 Location: The Motherland Posts: 1,398 Thanks: 140 Thanked 473 Times in 271 Posts Mentioned: 22 Post(s) Tagged: 0 Thread(s)	Thanks, I look forward to the photos and further dialogue.

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