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- - Fa20 with Fb25 block. (https://www.ft86club.com/forums/showthread.php?t=45926)

Fa20 with Fb25 block.

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.

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

http://i213.photobucket.com/albums/c...ps5fafc73a.jpg

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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.

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

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

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

Quote:

Originally Posted by jet86 (Post 1187677)

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?

Quote:

Originally Posted by Sportsguy83 (Post 1187763)

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

What is the bore spacing difference on the two blocks?