390 questions

glen5574 · #1 (**permalink**) 07-01-2009, 04:28 PM

Hi, i recently picked up a 390 from a guy who claimed that it was from a 1965 Thunderbird. I plan to put together something in the 350-400hp range with good low-end torque. The block has all the oil gallery plugs in the back, but was fitted with a mechanical cam and lifters. It does have adjustable rockers. The block is already 30 over, so my question is, do I have a hydraulic lifter block that some one has put a mechanical cam in? Would this cause problems? The block casting number is C6AE. One more thing- my book claims that the heads are from a 427. Could this be? The numbers are C3AE. Any info is much appreciated.

85e150six4mtod · #2 (**permalink**) 07-01-2009, 04:56 PM

Solids in a hydraulic equipped block are not a problem. A '65 T-bird 390 would have been rated at 300 gross hp, about 240 net (our current standard) and with the stock heads, 9.6:1 CR, if this chart is correct and I'm seeing it correctly:

http://www.woodyg.com/fairlane/finfo/fespechart2.html

That link also has head info, casting numbers etc. I don't see the C3AE, but that doesn't mean anything.

It looks like the 427 heads would have a larger combustion chamber--makes sense with the bigger valves. Since this motor has been gone through, who knows what piston is in it--it could be 11:1 or 9:1.

The big ports and solid lifter cam say high rpm power, but it is a big V8 so it's not like it's going to be a wimp at low revs, maybe just a little rough till it cleans up...

A stock 300 HP T-bird 390, with headers and a larger carb, would hit 300 hp easy. You have a solid basis for well into the 300s methinks.

Next issue here is if the block will clean up with a hone job, or if it needs a bore, will it take the next oversize. Many suggest sonic checks as core shift happens and is not your friend. Thin walls are not your friend either.

Good luck. You will receive more posts with additional info, so stand by. There are a couple of guys here who have forgotten more than I'll ever know about these.

Argess · #3 (**permalink**) 07-01-2009, 05:52 PM

The factory could have installed a solid cam in a block drilled for a hyd unit, but I know that there are blocks with solid cams that wern't drilled.

I'm not sure, but I don't think solid lifter cams were common other than police-interceptor engines or 427s. By the sounds of it, you have an engine someone built out of spare parts.

When I converted my hyd block to a solid cam, I plugged the side oil galleries that feed the lifter oil galleries. But you know, I'm not sure that's necessary. After all, the crank and rods get enough oil with a hyd equipped block when the galleries arn't blocked off. But it's nice to have a little extra oil.......

Anyway, check the center oil gallery under the intake manifold. If they are press-in plugs, the galleries probably arn't blocked off. The normnal technique is to tap for a set screw below the center gallery feed, also tap for a larger set-screw where the press-in plugs normally go.

glen5574 · #4 (**permalink**) 07-01-2009, 08:50 PM

Thanks guys, the engine has been sitting and has some rust in the bores, to top it off there is a hefty ridge, so I'm certain it would have to be 60 over. Is 60 over too risky? Also is a mechanical cam the way to go since I already have the rockers? I'm not afraid of valve adjustment.

85e150six4mtod · #5 (**permalink**) 07-02-2009, 01:05 AM

Sonic check for the block methinks.

Hydraulic cams and cams in general these days have come a long way from the OEM grinds. Depends on what it is, if you like it, etc.

I like hydraulics because I DON"T like adjusting valves.