2 valve block in a 3 valve

[Boostaholic]

Did a search and can't find a good answer.

I bought a 2 valve short block with forged internals to replace my low compression 3 valve block .

It has a set if -10.55 dish pistons installed. Do I need a new set of pistons with valve reliefs or will these pistons work? I do have Brenspeed blower cams to go in it. I think the lift is below .500. Just concerned with piston to valve clearance more then the lower compression.

Thanks for any help!

 

[Midlife Crises]

I believe you will need 3 valve specific pistons if your going to use 3 valve heads.

 

[MrBhp]

At one time I think CP made a piston that worked in both motors. I've heard that the 3v heads work fine on a 2v block. I've also heard they don't. I wouldn't take any one's word on it. Just bolt a head down and check ptv clearance. Cause if it don't work you will be f'd. Well not you, just the motor.

 

[Boostaholic]

At one time I think CP made a piston that worked in both motors. I've heard that the 3v heads work fine on a 2v block. I've also heard they don't. I wouldn't take any one's word on it. Just bolt a head down and check ptv clearance. Cause if it don't work you will be f'd. Well not you, just the motor.

Thanks for the info. Just trying to get parts together to save time. I worry about valve clearance even if I bolt a head on and nothing interferes due to the variable timing control.

Probably just going to get new pistons to be safe. Not worth the catastrophic alternative.

 

[Vallee]

I believe you will need 3 valve specific pistons if your going to use 3 valve heads.

That is correct.

 

[Boostaholic]

Can anyone else chime in and give real life experience? I have been told that I can use the 2 valve pistons with the 3 valve heads as long as I lock out the cams. I will be running the Brenspeed blower cams in this motor. I will be upgrading springs, but Brenspeed says you can run these cams with stock springs. Can anyone else verify this or have any good/bad experience. Or am I the first person to try this? Haha

Thanks again!

 

[lwarrior1016]

The problem area is going to be at the very edge of the pistons. I don’t know if anyone is going to know specifically if those cams will work, you’re looking for a very specific combo there and the likely hood of it being done already is going to be pretty slim.

That being said, there is a chance it will work with the cams locked out. With vct though, ford had reliefs in there with stock cams so I would definitely want them with any aftermarket cam.

If you lock them out, you can check piston to valve clearance all the way through the range.

 

[JC SSP]

I would think who every is building your motor or selling you these cams would have an answer.

I don’t know much about 4.6 2v or 3v so let’s start there but I have built and been involved with building several engines (Ford, Pontiac, Olds, Chevy, etc.) in my time.

If your concerned about piston to valve clearance. Mock up the entire motor as if you were ready to start it. Put modeling clay on top of a piston and put the heads on. Make sure you use Head Gaskets and torque to specs. Then rotate the entire assembly a few rotations and remove the head. Check the depth of the indentation on the clay and see how many thousands you have. Make the determination afterwards.

 

[Midlife Crises]

3 valve pistons with 3 valve heads.
10.55-1 compression is a bit high for a supercharger.
The cams you have chosen do not require the phasers being locked out. Don’t lock them out if you don’t have too.
Always run the valve springs that are recommended by the cam manufacture.

 

[hoodoo]

Anyone have any info regarding availability for these? When I talked to Ford Performance last year about control packs for a coyote swap, they suggested this short block which is compatible with the 3v heads and all the 4.6 electrical.
But I’ve never been able to locate one.