What vehicle would have a 425 with flat top pistons? Did they leave the factory like this?

 

Interesting. There were no factory flattop pistons used in the 425s. Even the 10.5:1 Starfire/Toro motors got pistons with a slight dish. The E-block 400 motors used flattops, but those are for a 4.000 bore vs. 4.125. Does the ad show the block casting number?

 

It looks like #8 has a slight dish. Could it be a really heavy carbon buildup on those pistons.

Scott

 

the ad says the casting number is 389244D . I asked the seller to measure the lifter dia for me
i think its been rebuilt as it has 3A 350 heads with it….maybe those have a larger chamber than the 425’s?

 

I was wondering about that.

 

75-ish CCs and smaller valves and ports than the originals (which had 80-ish CC chambers). Not my first choice.

 

So i was able to buy this fairly cheap. Can anyone tell me what i brought home? 425/455 mixmaster? Pistons are flat but come up short of the deck I “think” its a39* cba. Gonna pull it apart to get some casting numbers

 

Yes, not factory pistons. The Hobbs switch tied into the oil pressure tap was likely used as a safety switch for an electric fuel pump. And once again proof that the mold number by the distributor is NOT directly related to the calendar year (it's hard to have a "5" for a block that was only produced in three calendar years).

 

Casting number 389244D is a ‘66-‘67 425.

Scott

 

Would an industrial use be possible? Heavy cast iron pulley and fabricated looking engine mounts are odd

 

Yes it would, but still not factory flattops

 

This is really interesting. A cast iron three groove crank pulley??? Note the late model plastic timing tab also.

 

Anyone recognize this cam logo and grind number? CD 300 H

 

Cam Dynamics, perhaps? I think they may be part of Comp Cams now.

 

Pistons are OEM someone cut the crowns to reduce CR for some reason

 

Not uncommon in the dark days of the mid-70s oil crises.