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Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial

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Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial

Old 06-18-2013, 10:43 AM
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Default Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial

I just concluded negotiating a refund for an internally damaged FA450R3D radial that I bought over on RCG.

I am using (new) parts from FA180, FA220 & FG57T engines to rebuild the FA450R3D W/a .035" case deck reduction. I am building a 5.12 Cu. In. 3 cylinder radial W/12.2:1 CR, & induction improvement including a modified back plate & a 12mm FA220 carburetor as well as C&H CDI to light things off in a consistant manner.

I will use a modified FA180 intake manifold similar to the one pictured below on Hobbsy's FA150. The back plate will have to be machined for the larger gland nut. The engine will be run on 20mm standoffs & the firewall might have to have a small hole for clearing the velocity stack on the FA220 BB carburetor. It might help power to pull cooler air from the fuselage rather than the hot cowl area.




If the engine responds as well as the FA180HC CDI BBC engine did, W/similar modifications, I should see over 7HP, perhaps 7 1/2 HP on 15% Cool Power.

Stay tuned.
Old 06-18-2013, 10:49 AM
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Default RE: Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial

looking forward to this Subscribed!
Old 06-18-2013, 11:10 AM
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Default RE: Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial

I learned a few interesting facts along the way.

1. The FA180 pots will drop right into the FA450R3D case W/O modification. There is no "step" like in an FA150 case.

2. The FG57T pistons are .016" taller in compression height compared to the FA180 pistons. On an FA450R3D rod they are the same hieght above the deck as a stock FA180 piston in an FA180 engine. That means the combustion chamber volume will still be 3.4cc & even W/O a case deck reduction they yeild 9.24:1 CR on the FA450R3D bottom end. W/a .035" case deck reduction the chambers shrink to 2.5cc. With the slightly shorter 150 stroke of the FA450R3D, (27.98cc per cylinder compared to an FA180 volume of 29.1cc) that computes to 12.2:1 CR.
Old 06-26-2013, 08:52 AM
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Default RE: Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial

Have you done any port work to the saitos? There used to be a guy that would port the YS 120s and it would make quite the difference in top end power.
Old 06-26-2013, 11:14 AM
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Default RE: Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial

ORIGINAL: JeffH

Have you done any port work to the saitos? There used to be a guy that would port the YS 120s and it would make quite the difference in top end power.
No, but on an FA180 that I built on an FA150 case to raise CR to 12.8:1 responded very well to a ported intake manifold W/a 12mm FA220 Big Bore Carburetor.

W/the CDI set @ 35° BTDC total spark advance lighting off 15% Cool Power fuel, it spun an 18 X 8 prop @ 8450 RPM making 3.45 HP. That was a 250 RPM improvement over the same engine W/the stock 11mm Carburetor. & manifold

I'm hoping for similar power improvements W/the 180 pots/FG57 pistons on the 450 case.

There are several parts on backorder until the 1st week of July so further posts about the build on this thread will be delayed until I get all the parts in hand.
Old 06-27-2013, 08:57 AM
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Default RE: Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial

I am thinking about copying your work on a 150/180 to put in a Yellow Aircraft Cap 10B.
Old 06-27-2013, 06:22 PM
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Default RE: Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial


ORIGINAL: JeffH

I am thinking about copying your work on a 150/180 to put in a Yellow Aircraft Cap 10B.
You can bolt the 180 pot on the 150 case & use the 150 crank & rod W/the FG57 piston & have a 9.24:1 CR FA171.

Use the FG57 piston in an otherwise stock FA180 & you wll have a 10.7:1 CR FA180 (1.775 actually)

I'll be going over the various combinations when I get all the parts in hand.
Old 06-28-2013, 10:01 AM
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Default RE: Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial

Now the FG57 Piston sounds like an easy upgrade along with the ignition. I may have to start scouting out a 180 that needs some love.
Old 06-28-2013, 01:32 PM
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Default RE: Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial


ORIGINAL: JeffH

Now the FG57 Piston sounds like an easy upgrade along with the ignition. I may have to start scouting out a 180 that needs some love.
The FG57 & .020" deck reduction on an FA180 case will get you in the 12.8:1 CR range.

I just bought the last 12mm FA220 Big Bore carburetor from Horizon.

I have 3 of them now. The HC FA180 W/CDI really responds to the 12mm carburetor on a ported manifold.
Old 07-01-2013, 10:31 AM
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Default RE: Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial

What do you do about pushrods? I think you mentioned it in the other thread, but damn if I can remember. I know the ends are hardened, and if you take too much off past the hardening, things will go poorly. Do you reharden, or is there enough hardened material there to work with?
Old 07-01-2013, 11:58 AM
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Default RE: Building a 12.2:1 CR 7 1/2 HP SAITO FA512R3D Radial





ORIGINAL: JeffH

What do you do about pushrods? I think you mentioned it in the other thread, but damn if I can remember. I know the ends are hardened, and if you take too much off past the hardening, things will go poorly. Do you reharden, or is there enough hardened material there to work with?
Pushrods for FA150 & FA180 are the same.(FA120 parts actually SAI120S139)There is enough adjustment in the rockers to compensate.

The FA150 case deck is about .055" shorter than the FA180 case, but the cylinder is the same hieght. I ended up W/a net reduction in case deck of .035" by using a .020" C&H cylinder base spacer under the cylinder.

The best way to get a 12.8: CR FA180 is to either use the stock FA180 piston & mill the case deck .035" or use the FG57 piston & mill the deck .020".

In either case you will have to check valve to piston crown clearance. I had to relieve the intake valve pocket on the 180 piston slightly.

I'm hoping that the FA450R3D W/its much longer pushrod has enough adjustment left @ the rocker arms to compensate for the shortened case deck.

The backordered FA450R3D parts are due in on 7-11-13 so I'll be getting some PIX & clearance check results posted soon after that.

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