I have a f22 block crank and rods. I want to use f20b pistons in this motor. I know the compression height is different between f22a and f20b pistons by .45mm. I want to take a set of f20b pistons and shave .025 off the top of the crown. I'm not touching the dome just the outer edges of the piston. What I need to know is whats the thickness of the top ring land on a f20b piston before I go spending the cash on a set.

 

I'm going to use a a6 head and custom h23 manifold with 2 60mm throttle bodies on this motor. I'm just looking for a cheap high compression setup. Pirate mcfred can I get a little insight on these motors and what I can actually do with stock parts. I've watched this forum a lot for building b series motors I know putting an f series together can't be to much harder.

 

you could try and measure it from the pic since you know the pin diameter


if i'd where you i'd just run a thicker HG! less hassle, less risk...
at least clay the setup!

piston is a heavy ****** tough

 

Do you know if the valves in F22 and the F20B have the same angle?

If they don't there is a big chance the valves will hit the pistons when using a big cam.

 

I have access to a rotary table and bridgeport mill. The pin is the same at .866. Is the under side of the piston dished or flat could I shave some weight from there. This motor will only see 7500 to 7800 rpm.

 

The angle I don't know about but the valves are the same size. I do know the combustion chamber is smaller on the f22a head

 

wait, i notice room for c-clips in the pistons, can you say floating wrist pins.

the f22 units are press fit are they.....?

 

So do the f20b rods have a bushing in the pin bore? Dose it even matter because the pin presses into the f22 rod?

 

My thread shows the f20b pistons on f22b1 rods yeah they are floating wrist pin but you can still put it on it's on the hybrid section they stick out the block at 0.020" but it wont touch the h22/f20b head. The oem headgasket is 0.026 at crush so a little clearance there.

 

How did they do it? Press the wrist pins in and not use the locking rings in the piston. That's how it looks in your build thread, kind of hard to see though.

 

Lol they put the locking rings on i thought he wasn't going to but he did. The guy said it was going to be a bit** but he did it he used the wrist pin from the f20b pistons.

 

So did he bush the F22B1 piston end of the rod or are they press fit?

 

With a pressed pin there's no reason for the clips. They have the same pin and pin bore as the f22 piston. I figured the piston would come up past the top of the bore but only by .010. Most of the hondas I've worked on the piston sat .015 to .025 in the hole. What do you guys think about shaving the head like .030 to .060 thou for more compression.

 

Honestly they are the same wrist pin so with some observation i looked at the difference between the two and the f20b piston wrist pin moves in and out with the piston instead of the rod moving with the wrist pin. It's weird but that's how you can tell they are full floating.

 

Let me know how that piston/head combo works out for you with the .030 or the .060 milling of the head along with the pistons sticking out .020" out of the hole these pistons do have a 4.70cc dome and a compression height of 31 instead of 30.5 like the stock f22a1 setup.

 

That's why I am wondering how they did it. The F22B1 rod is a press fit wrist pin. If the machine shop has now made them a full floating rod...did they put a busing in there or did they just hone it and throw the wrist pin in.

reason I'm asking is because 4 years ago I took my F22B2 rods (same as F22B1/H23A1) in to have the piston end honed and bushed to use them as full floating. the machine shop said that they would not warranty the rod after honing them out and adding the bushing. Something about having to remove too much material????? I'm not a machinist....just going by what I was told.

 

Well maybe they did just press fit them in i will ask them to see if they did. I still have the other f20b rods they do have the bushings in.

 

I'm going to shave the tops of the pistons to keep them in the hole by .010 to. 015 thou.

 

You don't get it the outer edge is where the piston sticks out to where it will touch the head in your case if you mill the head it will go into it. If you don't mill the head you will be alright you will yield 12.3:1 compression with those pistons in there or more cause the f22 head has a 50.5cc combustion chamber. .020" is the deck to piston height not the dome top dome/dish doesn't matter. Not trying to bash you or anything it's just your gonna be pissed when you start to turn it and it won't turn by hand.

 

He mentioned that he was going to be shaving the piston face (outer edge) not the dome.

 

Oh ok if he does that would be better but still iffy about the mill. lets see what happens there is always a way to make something work.

 

I would definitely clay the combustion chambers before starting it up!

 

He should know to clay the motor before start up i think he will see his whole life flash ahead of him if he just turned it over when finished lol.

 

Ill be claying the motor to determine how much I can shave the head.

 

Yeah give some updates on it i will post vids of mine when i'm done it's in the hybrid section and it's almost done. I'm using an f22a1 block and an f20b head man did it move the first time i did it felt like the original f20b motor but with more torque. Then it gradually started dying on me hence the rebuild.