How much HP can a stock 390 take?

[George vega]

From all my research I have a garden variety C6ME 390 short block. I've decided to just rebuild it and use all the components from my 428 to complete the engine, then I can get back to racing. In the meantime I can check out why the 428 mixes water and oil.
The 390 although having a stock short block will make decent HP. What's a safe rpm that I can shift it without stressing the stock pistons, rods and crank? Thanks.

[Joe-JDC]

I've heard of Stock Eliminator 390s making ~565 hp, turning 7200 rpms with all the necessary preparations to meet the class rules.  Joe-JDC

[George vega]

Joe, Hopefully the stock bottom end will last until I find out if my 428 block is repairable and how much. The bore is 4.050, the cast pistons are the 4 eye brow without the raised area in the middle. Maybe 10.1 comp. Good for pump gas. Milidon 8qt oil pan and high volume pump caps the bottom with all the oiling mods. A crane solid roller with 596/620 lift cam is turned by a rollerized roll master timing set at straight up. The short block is topped with a set of ported to CJ heads with 2.15 intake /1.72 exh d's valves w/5 angle cut. The springs are matched to the cam with titanium retainers. The intake is a victor that has been ported to the heads with a 950 hp on top. A empire electric water pump and a Griffin radiator to keep it cool and hooked full race headers with 2 1/8 tubes wrapped to the slip on collectors. MSD dust and crank trigger. How would you run this combo to try and not hurt it if that's possible. With the 428 block, this combo with 12 to 1 pistons ran 10.20/130 @ 6700 rpm.

[George vega]

I guess the general consensus is to keep it below 6000 rpm for stock bottom end. I'm thinking 5800.

[cjshaker]

I think the cast pistons are the weak point in your engine. I've ran 390's with a similar set-up for years and years with no bearing or piston issues, but always kept it under 6000 like you said. With good clearances, machine work and good oiling, I wouldn't hesitate to do what you are suggesting.

[George vega]

I have done all the oiling mods and have cleaned and painted the block. I'm taking it to a machine shop for final cyl measurements. If it can stay standard, I'll leave it standard, I'll have it honed. If it needs to be bored, I'll bore it .030 and buy 410 pistons and use my good rods and crank and cross bolt it.

[George vega]

I have done all the oiling mods and have cleaned and painted the block. I'm taking it to a machine shop for final cyl measurements. If it can stay standard, I'll leave it standard, I'll have it honed. If it needs to be bored, I'll bore it .030 and buy 410 pistons and use my good rods and crank and cross bolt it.

[e philpott]

Will the 1.72 exhaust valve clear the 4.08 bore ?

[Nightmist66]

Will the 1.72 exhaust valve clear the 4.08 bore ?

Don't think so. Not long ago, I was looking at some parts I had laying around and checked with my 390 block and some old iron CJ heads. The block was 4.080" and the heads had 1.75" exh valves. I sat the heads on the bare block, no gasket, and moved the valve while watching from underneath. The valve only made it about .450"ish lift before smashing into the bore. I suppose you would get a little more lift with the gasket in place, but not much. How would someone make that 1.72" valve work in a 4.050" bore with any kind of lift? 

[KMcCullah]

I do know with iron heads and a 4.05 bore, a 1.65 exhaust valve just BARELY clears the cylinder wall. At .680 lift or so. A 1.72 exhaust valve with a moderate scallop on the top of the cylinder might work. It would take some mockin up and messin around on a scrap block to see.   

[jayb]

Hmmmm, I got 1.71 valves to clear on my 4.09" bore 390 block, with a 0.640" cam.  That was with a 0.041" head gasket, and Edelbrock heads.  Maybe you just have to mock up each individual case to see for sure...

[George vega]

I was just going to say that Jay made it work at 4.09 that's why I went with that combo if my block can't stay standard. The reason I prefer to stay standard bore is for strength of the block since this is a garden variety block at the bottom of the list of blocks to use for a performance build.
I would still do the preliminary checks of valve clearance at the piston and cyl wall.
I appreciate any comments. Thsnks

[scott foxwell]

I was just going to say that Jay made it work at 4.09 that's why I went with that combo if my block can't stay standard. The reason I prefer to stay standard bore is for strength of the block since this is a garden variety block at the bottom of the list of blocks to use for a performance build.
I would still do the preliminary checks of valve clearance at the piston and cyl wall.
I appreciate any comments. Thsnks

Did you see my sonic check? Maybe there's something useful for you there. Seems like even with some pretty severe core shift these blocks are good for .060 pretty safely. I don't think the C6ME blocks are "garden variety". I think they have thicker cylinders than the typical 390.

[fryedaddy]

 I don't think the C6ME blocks are "garden variety". I think they have thicker cylinders than the typical 390.
[/quote]i think you are right.i have subscribed to many ford and muscle magazines over the years,in one of them i read that the 66-c6me block had thicker walls and that the c6me-a aint bad either,but i cant find the article and i got laughed at by many members who thought i must be crazy. i posted a topic on it when i first joined the forum,absolutely nobody agreed with me. i wish i could find the article.the guy who wrote it had blocks all over the floor,looked to be dozens,and it was an old mag from the late 80s-early 90s.back then i was so obsessed with fe engines i bought every mag-book i could find with fe fords in them

[George vega]

. I agree, the thicker cyl will add strenth as long as you don't bore it. That's why im trying to keep my block standard bore. What I was referring to things like extra webbing, cross bolts, ribbs or high nickel content.