390 short block ????

[George vega]

 :-\I picked up a c6me 390 short block. I did the drill bit test and the 13/64 bit fit between the cyl. I tried a 17/64 and definitely didn't fit. Do I have a block that can be bored to 4.130 (428)? Or am I better off rebuilding the 390 and installing my ebock heads on it? My heads have 2.15 and 172 valves. Will those valves clear the 4.05 bore? If not what is the minimum bore size that I will need. Thanks

[fekbmax]

id go .030 on the 390, use your heads, should be fine with the valve combo in those at 4.080 . make up your cid with a good stroker kit and have a stout FE.

[George vega]

Thanks

[jayb]

+1 on what Keith said, the drill bit test won't tell you about core shift, only a sonic test will do that.  So, the drill bit test might make you think you have thick enough walls, but if there is core shift involved you could get dangerously thin...

[George vega]

Thanks, I thought about that. .030 over is good for me. I'll have it checked out first.

[George vega]

This is the current engine I want to replace the bock.
It's  making about 600 + hp.

[gdaddy01]

why ?

[George vega]

Because it has 3 sleeves and they are leaking water into the combustion chambs.

[fekbmax]

that be a good reason..

[scott foxwell]

Why not go 4.10 or 4.11? Pistons are available. Take advantage of a bigger bore but don't push it all the way to 4.13. I have the same block and that's my plan. Seems a lot of early 428 blocks used this same enginering number. I will probably have mine sonic checked and even if I can I really don't want to punch it all the way out. I'm shooting for the same HP level and like the idea of a little more wall thickness in the cyls.
JMO

[thatdarncat]

The C6ME casting number is meaningless to determine if it is a 428. A 428 block will have actual 428 cylinder cores. George has a 390 block. In my opinion it would be a better idea to keep the cylinder walls as thick as possible, you get better ring seal, along with the strength. Going from 4.08 ( .030 over ) to 4.10 only gives you 4 more cubic inches, the risk vs reward isn't there. There are better ways to gain a few hp. Again, just my .02

[George vega]

I cleaned the block today and chased all the threaded holes. All the bores were 3.050 and the rod journal's were 2.378. I haven't measured the mains but they look very nice. This block was originally painted light blue and someone else painted it black. It will get the dark blue when I paint it.

[scott foxwell]

The C6ME casting number is meaningless to determine if it is a 428. A 428 block will have actual 428 cylinder cores. George has a 390 block. In my opinion it would be a better idea to keep the cylinder walls as thick as possible, you get better ring seal, along with the strength. Going from 4.08 ( .030 over ) to 4.10 only gives you 4 more cubic inches, the risk vs reward isn't there. There are better ways to gain a few hp. Again, just my .02

Well, now, I didn't say it was a 428 block. The C6ME casting is not meaningless. It's not the holy grail but go back and re-read what I said...a lot of the early 428 blocks had the C6ME engineering number. His block passed the drill bit test which again, isn't the holy grail but another indicator that it has the thicker "428" cylinders. Not a 428 block, but maybe the predecessor? The idea behind going bigger on the bore is not more displacement, it's breathing ability, and going another .050-.060 on the bore can be significant when it comes to breathing and that's one of the best ways to make more than just a few extra HP. -IF- the block can "safely" be bored to 4.13 I still wouldn't do it because I agree...keeping the cylinders thicker is better but there's no reason to not take advantage of the available bore without getting excessive.

[scott foxwell]

I cleaned the block today and chased all the threaded holes. All the bores were 3.050 and the rod journal's were 2.378. I haven't measured the mains but they look very nice. This block was originally painted light blue and someone else painted it black. It will get the dark blue when I paint it.

George, what's your current combination?

[George vega]

My current combo is an early 64 390 block  with the nubs that was cross bolted, filled with hard block and then bored to 4.130 and lined honed. It has an eagle crank, rods, weisco 13 to 1 pistons, Crain roller cam and lifters, ebock heads fully ported, with 2.15 and 1.72 valves, Crain springs, victor intake ported to match the heads, msd ignition. Use a cobrajet c6 with a tci kit and brake. In my mustang it has run 10.19 at 130 mph leaving at 3500 and shifting at 6000.