New User 390 Piston Question
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New User
Joined: Feb 2006
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New User 390 Piston Question
I am new to this group and to FE engines. I have a 1976 F250 with a 360 in it. The engine was rebuilt at one time, ran well, but smoked. When I pulled it apart, I found that one of the wrist pins came loose and machined a deep groove into one of the cylinder walls. I was able to get the bottom end of a 390 from a 1965 T-bird for $99. My question is this:
The pistons in the 360 have two indents that line up with the valves on the head. The pistons in the 390 are flat on top without any indents. Why the difference? If I end up getting new pistons what type should I get?
Thank you for any advice.
Paul
The pistons in the 360 have two indents that line up with the valves on the head. The pistons in the 390 are flat on top without any indents. Why the difference? If I end up getting new pistons what type should I get?
Thank you for any advice.
Paul
Cargo Master
Joined: Aug 2000
Posts: 2,931
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From: SW Michigan
pistons
Paul, sounds like you got a good deal on the 390 stuff. The notches in the top of the pistons are for clearance for the valves. Lots of factory cams don't need them, but most pistons have them anyways. The factory is leaving you the room to add a bigger camshaft if you want. The flat pistons you 390 has will be fine with a factory 360 cam from a truck. But you might very well want to get new pistons anyways. The flattopped 390 pistons would give almost 10 to 1 compression with the D2TE-AA heads that you 360 probably has. I would check to bores for wear, overbore only if there is a need, and use SpeedPro H304P pistons. The H304P is a 1.76 tall piston that has a smal dish in the center. It will give you good quench and the 8 1/2 to 1 ish compression that a truck needs. You might also consider the KB 150 pistons, which have a D-cup and step on the top. DF, @ work, sorta
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Post Fiend
Joined: Dec 2003
Posts: 6,658
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From: "Islander"
D-cups work for me every time but must have a waist and long thin legs to complement the top. sorry.
I would go with KB 150's, the only question is can they be had with a taller top so they can be machined later for zero deck clearance?
.....=o&o>.....
I would go with KB 150's, the only question is can they be had with a taller top so they can be machined later for zero deck clearance?
.....=o&o>.....
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New User
Joined: Feb 2006
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Cam and Pistons
Thanks for you reply. What is the difference between the truck and car cam? Would the truck cam from the 360 be a better choice? Both are in good shape.
Originally Posted by Dino@his Dad's
Paul, sounds like you got a good deal on the 390 stuff. The notches in the top of the pistons are for clearance for the valves. Lots of factory cams don't need them, but most pistons have them anyways. The factory is leaving you the room to add a bigger camshaft if you want. The flat pistons you 390 has will be fine with a factory 360 cam from a truck. But you might very well want to get new pistons anyways. The flattopped 390 pistons would give almost 10 to 1 compression with the D2TE-AA heads that you 360 probably has. I would check to bores for wear, overbore only if there is a need, and use SpeedPro H304P pistons. The H304P is a 1.76 tall piston that has a smal dish in the center. It will give you good quench and the 8 1/2 to 1 ish compression that a truck needs. You might also consider the KB 150 pistons, which have a D-cup and step on the top. DF, @ work, sorta
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New User
Joined: Feb 2006
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Another Piston Question
I have another question about pistons. I was looking around and noticed many pistons have years stated with them (ex. Ford 390 1966-1970, etc.). What is the difference between the years. I am using a 65 block and newer heads. Sorry for all the questions, but I want to put this engine together correctly.
Postmaster
Joined: Nov 2002
Posts: 3,447
Likes: 1
From: Littleton, CO
Get a new cam and lifters that will work with your build.... There is no issue with the year differences, the car line dropped the use of the FE engine after 70, but the trucks kept using them. I agree that the true flat-top 390 pistons would be a little much on todays octane, but running something like the 360 piston with the fly-cut reliefs will be fine. I went with the 360 pistons in my 390 and used a crane 901 grind cam. Works pretty well so far at 5200 ft above sea level 
--Mike
--Mike
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