425 Engine Rebuild - How would you do it?

[acaciaavenue]

Starting to gather notes on what I will need to do to get 400hp out of rebuilding my 425. Looking to build a street rod that will roast the tires and generally be low-maintenance - not a dragster.

I've got the top end handled (dual 4 intake, 2 425cfms, Accel HEI distributor) now I just need the bottom end. I split the chores due to the cost of parts and rebuild, which is why I have the top end on right now, with the bottom end coming soon.

I gather that .040 over is a good bore, but does anyone have any insights/suggestions for modifications to the heads or any other useful information?

Swapping to a 472/500 is not an option.

http://jasonbeamstudios.com/Hearse2005.jpg

[Al from MTS]

It won't be too much different than building a bigger brother. Just run you a few bucks more due to piston availablity. You will also have to spin the 425 harder to make the same power as big brothers.
Your 425 heads can be ported, polished, and big valved etc. If you decide to raise compression it will require a custom forging. Cam choice will be a key factor too.
I'm sure your tired of everyone beating you up about using the 472/500. My guess is one reason is that you have your intake adapter fit to your 425 heads already.

[acaciaavenue]

Yeah, the issue is the cost of the adapter and distributor (that fits the clearance of the adapter and intake) - by the time you factor that in, it might be at a break-even point and there's still the hassle of swapping motors.

So you're suggestion is to give special attention to the heads and cam? I was also thinking .040 over would be a good start as well.

I don't think I want to go the route of custom-forged pistons, I'd like to keep it all above-the-counter (although, I don't mind having to hunt around) and still be able to obtain 400hp.

Anyone else have suggestions?

[Al from MTS]

In the case of your car there is zero hassle to swap engines. No tougher than changing a 60 watt bulb for a 100 watt bulb. Unscrew one and screw in the other. All your stuff will bolt right back.
Your coach would love the extra torque the cubes would bring. If you used a 500 short block we could reuse your heads if the budget requires.
Whoops! Looks like I've joined the pack and want to lean you twoards building a 472/500. You would not regret it one bit!

[shakedog]

Al.
Are you saying he could use his 425 heads? I have heard some say its OK to do and others say it would cause the risk of head gasket problems.What approximate compression would this bring with an engine that already has 120cc heads, and is it for stock bore only? Coming from you, it would be easier to trust. Are there any tricks you would have him do, like a special head gasket?
Thanks, ~SHAKEDOG~

[acaciaavenue]

So, let me see if I have this straight - I could use a 500 short block, port and polish my existing 425 heads and my manifold and adapter will bolt on?

Or could I get a long block 500 with heads and still use my intake and adpater?

I'm asking because I'm all over putting a 500 Cad motor in my hearse, and I don't want to get my hopes up before I learn a bit more about the swap.

As usual, thanks Al for all the help.