what compression ratio
Thread Starter
|
Senior User
Joined: Sep 2004
Posts: 223
Likes: 1
From: Rexburg,Id
what compression ratio
Hey Guys; I'm rebuilding a 390 for my 66 F100. I bought an old truck with a 390, which turned-out to be a reman. engine with a variety of parts. It had a 360 crank, 428 rods, and 390 truck pistons (the ones with the dish and 4 valve reliefs, comoression height-1.78)
I just want something snappy, not pop your neck fast. I've changed to a 390 crank, and wondered what I'll end up with if I use the old pistons and cam (looks like new). I live at about 4800' elevation, and don't want to deal with pinging on unleaded fuel. Heads are ; Int. 2.027, Exh. 1.559, have been milled .010. Holley 600 carb. Thanks, in advance for your help! Brett
I just want something snappy, not pop your neck fast. I've changed to a 390 crank, and wondered what I'll end up with if I use the old pistons and cam (looks like new). I live at about 4800' elevation, and don't want to deal with pinging on unleaded fuel. Heads are ; Int. 2.027, Exh. 1.559, have been milled .010. Holley 600 carb. Thanks, in advance for your help! Brett
Last edited by biggut; Dec 23, 2004 at 06:40 PM.
Post Fiend
Joined: Jan 2003
Posts: 8,600
Likes: 4
From: Iowa
Egad. Lets see, that makes it a 360 with short rods. The compression height of those pistons is 1.776", and they're not 390 truck pistons, they're 390 car pistons and 360 truck pistons.
That would be extremely low compression if they did in fact use 428 rods. You probably have long rods in that motor. (long rods = 6.54" long, short rods = 6.488" long) The 428 used short rods.
If in fact you do have 428 rods and the above pistons the 390 crank will go in without problem. But if it were me, I'd check the deck clearance on the new setup. Get back to us with the deck clearance. Pop one piston and rod combo in it, set that one to TDC and measure it with a straightedge and feeler gauge.
That would be extremely low compression if they did in fact use 428 rods. You probably have long rods in that motor. (long rods = 6.54" long, short rods = 6.488" long) The 428 used short rods.
If in fact you do have 428 rods and the above pistons the 390 crank will go in without problem. But if it were me, I'd check the deck clearance on the new setup. Get back to us with the deck clearance. Pop one piston and rod combo in it, set that one to TDC and measure it with a straightedge and feeler gauge.
Thread Starter
|
Senior User
Joined: Sep 2004
Posts: 223
Likes: 1
From: Rexburg,Id
Annihilator, the bore is.060 over. I hope to get the crank in this week, and then I'll do the deck clearance thing, and let you guys know what it is. Brett
Last edited by biggut; Dec 24, 2004 at 09:41 PM.
Thread Starter
|
Senior User
Joined: Sep 2004
Posts: 223
Likes: 1
From: Rexburg,Id
Put the crank in today; (anyone else get in trouble for being in the shop on Christmas?) ran #1 piston up to TDC, and measured deck clearance with a straight-edge and feeler gage. It is between .019 and .020 to the top edge of the piston. Brett
Post Fiend
Joined: Jan 2003
Posts: 8,600
Likes: 4
From: Iowa
Trending Topics
Thread Starter
|
Senior User
Joined: Sep 2004
Posts: 223
Likes: 1
From: Rexburg,Id
Thanks Rusty, I believe I'll put her together and see how she does. It'll probably be spring before I can put it in the truck, but I'll let you guys know how it works-out. Brett
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
New User
Joined: Dec 2004
Posts: 10
Likes: 0
The truck pistons are the stock flat tops that all truck FE's had. The 428 rods will be the same as any other FE from a 360 to a 428 they all used the same length rod that was a 6.489. The 352 was the only od ball at 6.549. using the stock flat tops should give you somthing around 9.2-9.7:1 depending on the heads. this is enough to run regular unles you are running an agressive timing curve then it require around mid grade.