Hey everyone, I have a '76 F-100 with a 390 in it. Im getting ready to rebuild it, I want the motor to simply be a reliable yet powerful street motor for my truck. I plan on going to a 4 barrel, a mild cam, and headers, with stock heads, One thing I am confused about is the compression ratio, I know these engines had fairly low compression from the factory and i cant seem to find pistons anywhere, the only set i have found is in my summit catalog, the forged TRW's L2219's or something like that, trouble is, im unsure how much compression ratio these pistons would give me with totally stock d2te heads? I would like to have around 9.1 compression, and i think these pistons are closer to 10.1. Are there any other pistons available for the 390 that would give a 9.1 compression ratio with the stock d2 heads? I really dont need a forged piston, A good cast piston would be just fine for what i am gonna do with the motor, and the less expense of a cast piston would be nice as well. Could you guys please help me out, are there any pistons out there like what i am looking for? if so where can i get em and how much? By the way guys, Im planning on using the crane 941 cam with the stock heads and a adjustable rocker setup with solid spacers from dsc motorsports, A 750cfm 4 barrel and intake which i am undecided on still. So if any of you guys could help me out with my question i would really appreciate it, If you guys have any other recommendations you think i should hear regarding my engine build, Im all ears, Thanks guys

 

I'll have to check my notes, as C.R.S. disease has made a joke of my memory, but I think you want silvolite 1131s. Those will give you the 9 to 1 you're looking for. DF

 

dinosaurfan, thanks alot for the speedy reply, I appreciate it, Anybody have any idea where i can get these pistons and how much they cost? Thanks

 

What's wrong with a 10.5 to 1 comp ratio? I'm running that in a 390 with a Crane Energizer cam and it runs fine on 87 octane pump gas.

 

I know nobody else with your kinda luck there man!

 

Must be that sub-terrain altitude (sorry, we are suck'in wind at 3000 ft) ....


--Mike G

 

This is actually the second 390 that I've had that would run on cheap gas with a 10.5 to 1 ratio. The first was a GT 390 that I built in the 80's with TRW forged flattops, and a Cam Dynamics 296 degree/ .523 lift cam. I ran it in the 67 Stang I had back then, then later after displacing it in favor of a lowriser 427, put it into a 70 F100 and ran it a number of years afterward. I drove it all over from here in Louisiana out to Utah and Nevada and it ran on cheap gas there too.

 

According to the 2000 Speed Pro catalog(TRW) the CR with L2291F pistons is between 9.24:1 and 9.48:1 with a 74 cc combustion chamber. They are typically rated optimistic on the comp ratio. It helps sell hi-po parts. The deck height is listed at .015, which is hard to get in a stock block. HTH!

Putt

 

That may be the current compression ratio for the pistons now produced, but the set I had was purchased in 1981 or thereabouts. They were rated at 10 to 1 with 67 cc chambers.

 

The 390 I'm now running has all the original cast flattops ( std size) that it came with in my 68 Merc Monterey. Heads are C8AE-H's with 67 cc chambers. It was rated at 10.5 to 1, but is now a little less with the Felpro Permatorque blue head gaskets that are .020-22 thousanths thicker than the original .020 steel shim gaskets it came with.

 

It's the same piston, they are rated at 10:1 with a .030 overbore and 67 cc heads. According tp my books the C8AE-H has a 68.1-71.1 cc chamber, unless you mill them of course. Usually the cc listed for a head is also on the small size, and the head will measure at the top end of the range. I also used the L2291F at .040 in my 390. When I measured all the volumes and computed the CR, it was 9.2:1 without milling, head chamber was 75cc. The book doesn't even show that large of a chamber!!

Putt

 

Formula for a 390 CI Truck Engine

FE Block, 4.050 standard bore with .030 overbore for 4.080 bore 390 + CI
Oil system modifications and restrictiors installed in the head gallery
10/10 crank, balanced, chamfered and polished
Silvolite 1130 pistons 9.5 to 1 CR with moly rings
Crane camshaft 343901 hydraulic
D7AE cylinder heads with new valves, seats, guides, springs and seals
Re-sized connecting rods, weight matched
Clevite bearings (all bearings replaced)
FelPro Gaskets
ARP rod bolts, head and crankshaft studs
ARP oil pump drive shaft
ARP intake bolt set (shiny stuff)
Huge paper air filter with chrome filter housing
Melling HV oil pump
Cloyes true roller timing chain
Ford 4V “T” intake
Edelbrock 4V carburetor 1405 manual choke
Ford distributor with Pertronix Ignitor
Ford flat cap and 8mm plug wires with autolite 45’s
Stock truck log manifolds into 2 ¼ inch pipes Flowmaster dual 2 ¼ “ in single 3 “out
Adjustable rockers with new pushrods
New belts, hoses, water pump, fuel pump, starter, GM Alternator and 190 thermostat
New fan clutch, huge steel 6 blade Ford fan, stock fan shroud and new Stant radiator cap

You don’t have to do all this at once, but getting the bottom engine right is first and formost. I bought a new engine stand and an 80 dollar block from the Junk Yard. The block included a 390 crank and rods. This was a high mileage engine with Ford script bearings. This crank cleaned up nicely at 10/10. The heads came from the Junk Yard and cost 60 bucks for the pair. This is a pulling high torque motor designed for commuting in traffic, staying cool and getting reasonable fuel mileage on 87 octane. Estimated cost of this engine is around 2500 bucks. I took my time and built it over the winter.

 

Some of the other FE heads had the larger 72-75 cc heads. If I get a chance, I'll cc a couple sets of C8AE-H heads and some D2TE heads I've got laying around. If I have a set of the stock 390 flattops, I'll check the pin height on them too.

 

Nice to see you back around William!

 

So does anyone know where i can get these silvolite 1130's and how much they cost? These will be a 9.1 compression ratio with my stock d2te heads right? Thanks