The hawk decal on the blower said 26* max but these were originally built in the early days of supercharging pleasure boats.
The bottom of the domes look fine, no excessive heat in the tops of the pistons.
I know I sound like a cheap a$$ but just got married in may and I'm buying another house now, had to pay off both trucks, and any cc's to get approved. Money is tight right now. I sold my old blowers and bravo crap and that equalled enough to buy the 420's.
Do you guys think these will live if I open the bores to .0065? Guys are putting decent size whipples on otherwise stock 500efi's and doing ok right?

Thanks dean, Artie and Gerry always speak very highly of you. I'll give you a call tomorrow.

looks like a oiling issue to me...with pistons all scuffed and bearing look like hell...top of pistons and plugs look good...what oil pump, oil , cooler, oil lines ??

What bearings do you see that look like hell? First layer isn't worn or scuffed on any. Only thing I see is a couple very small score lines from aluminum that scuffed off the pistons
Hp500 oil cooler and thermostatic filter head, stock merc hp500 oil lines, high end melling coated and blueprinted oil pump.

Dean is the man!

That's what I hear!

Your running high compression piston in a blower motor on pump gas.....

So what are you saying happened?
I was under the assumption 8.8:1 wasn't high.

Not exactly. With those pistons in a 460 inch motor, he's under 9:1. Depending on the deck height, chamber size, and gasket thickness, 8.75:1 is probably where he is.

Nothing wrong with running that as long as the boost is kept within reason. About a million guys have slapped roots, whipples, or prochargers on stock merc engines with good results over the years. Running the same pistons, heads, etc.

I think he had a couple things against him.

#1 questionable machine work

#2 174 Blowers. They belong on a small block. They do nothing but make heat on a 454 after about 3lbs of boost.

#3 28* of timing. Too little of ignition lead is just a band aid to try to make the engine survive with the heat pump blower up top.

If he goes with a rebuild, the machine work done correctly, all tolerances in spec, the big 420 blower underdriven and around 5lbs of boost, right fuel setup, 32* or so, he'll do just fine. The big blower, dual carbs, added timing, is just flat out gonna run so much cooler.

God I hope so lol
Side note mr.fixxall, mild thunder, adk61, mike tkach, dean, etc thank you all for your experienced and helpful input.