And on the dyno.

427 bore/stroke/piston issues.
 

4.250 bore on a 427 is actually a .017 over bore. Due to the thin wall casting of a 427 it's pretty common to bore in .003 increments. 4.250 pistons can be purchased via the web, no special order required, in various dome/dish configurations to allow for various compression ratios. Typcial 428 crank in a 427 block (stroke 3.980) requires a piston with a non stock pin height, also readily available via the web.

4.25 bore/3.980 stroke = about 454 cubes.

Nice motor!

NOT saying THIS motor is stroked, just a typcial application found in a lot of 427's.

Thanks excaliber, I corrected the post. I'm terrible at math. Thank god for GPS or I would get lost while I am flying......
On a normal rebuild, without damage, just wear, what would be the average they would remove? .003?
This engine has the steel Lemans crank not the cast 428 crank so I think it is still at 427 cubic inches.

Reading your other post regarding upgrading the ECM on your system, and reading your post above...

something to the effect you want a new ECM because they could never get all the bugs out on the dyno with the original one...
That's probably when they went from 50lb injectors to 36lb ones. Too much fuel at idle and they probably couldn't ratchet it down enough with the 50lb-ers so they went with the 36's. Everyone thinks they can get 600HP with a little tuning, but think about it: you've got a naturally aspirated 430-something displacement engine. In order to get to 600HP it'll have to be putting out something close to 1.5HP/cu inch. Yeah, you can make it do that by spinning it to high rpms, but do you want to drive that on the street? That's what I remember, and see, from the dyno graph on the engine...very peaky, very skewed to the right.

You need to ask yourself what purpose will this engine serve? What type of usage are you planning for it?
Drag racing, 50lb injectors, av-gas, and why not just convert the Hilborn units back to mechanical?
Street use in a heavy Mustang? You want more low end, maybe time to swap cams.
Street use in a light Cobra? It should work the way it's set up. You'll probably want to be running av-gas (and this is probably why they never got the max performance out of it: detonation).
36lb injectors should support 500HP or so, depends on your fuel pressure. And that's where they're at.

What new ECM? Depending on your planned usage: Racing, something simple. Street: something with a lot of control over blocks of rpms, like the 500-1100 block for idling, 1100-2500 for most driving, 2500++ for heavy throttle applications. You also want to have control over parameters other than how much fuel to provide, when. You also need control, in the same rpm-blocks, over timing. And that control should be able to rely on not just throttle position, but ambient air temperature, barometric pressure, and allow for things like enrichments at lower operating temperatures (cold starts vs warm starts vs hot starts).

I don't know that individual cylinder trimming is that important though if it comes with everything else it's obviously nice to have. And I think the newer Accel's have all of the above now.

You need to make a check list:
What vehicle is this engine going in?
REALISTICALLY, what type of driving will I be doing in that vehicle?
Read up on current efi systems, and list the control features you'd like to have.

Then put you money down.

Compression is one "key" to big horse power, but a streetability cost.

My 427 FE was 667 horse, with 12.5 to 1 c.r., a radical solid roller cam, high riser (HUGE) heads and matching twin four barrel alloy intake and open headers at 6000 rpm. 660 cfm full drag race Holley carbs.

On the track I would shift at 6000 or 6500 but there was essentially no difference in the time slip. At 6500 I'd finish in 3rd, at 6000 in 4th gear.

It was "to much". I have the engine out reducing compression, milder cam, smaller carbs, more streetability. I'm pretty sure 500 horse will still be "enough". :D

Oh,,,, .017 bore with 428 crank and 72 cc heads.