well i'm confused now (two different answers) Dino told me that they used 390 pistons on the 352 crank and rods....does that mean that 360 pistons don't exist??? what about my machinist that gave me my engine assembly back...did he give me new 390 pistons to put back in or 360 pistons that exist today?? also if i give you guys the numbers that you want (head gasket thickness,bore, stroke, headcasting number) will you be able to tell me the compression ratio i will have after doing all of this?? i don't want to go a spend $1000 to get a true 390 and then end up running premium for the rest of my life!!?? thanks guys...tough call^_^

 

also dino, i now see that you said i can use the assembly that i have and get custom pistons. where could i get these and how do i know what kind to get?? what will this do for me? thanks so much!

 

TRW-L2291F30 This part number will get you forged .30 over speed pro pistons from summit that yeild around 9.5-10 compression iirc. Replace the last two digits with the over size you need. There are cast and hyper style pistons for way less depending on your budget and needs. Here is a current thread you should check out it may help you alittle https://www.ford-trucks.com/forums/s...d.php?t=403830 There are so many threads here with helpful info on your motor. You really don't need custom pistons I run TRW pistons in my 390 and I love them. I have the edelbrock alum heads and I have about an 8-8.5 compression. What are ou wanting to do with the truck? You want to smoke tires all day long or just be able to bark them on command?

 

If you use those pistons you will have to run premium gas.

 

ya i don't want to smoke tires all day or else that will just cause other problems...just bark on command like you said. my 360 is so weak...slow as crap on takeoff and drinks the gas. plus i saw a thread a few days ago and a guy said he was running a 460 in his pickup and getting 15mpg!!! If i'm only getting 8...whats that tell you?!?!? i've done everything i know to do with what i have to get the best mileage. what dino@hisdads said made sense and lines up with the performance i get or don't get. i'm just really confused at this point as to what to do. i've got the money to throw a 390 crank and rods and pistons in but i don't want to do all this and then run premium forever...that'd be more expensive than just getting bad mileage with 87oct. thanks guys...tough call

 

I guess I should have been more clear when I posted part numbers. I meant that summit and other companies have off the shelf pistons for what you want. I used those pistons numbers because they were a readily avail part number just to give you an idea. My 390 block had cast pistons in it when I got it brand new. I pulled them for forged replacments. I would offer them to you but I gave them to the guy who did the majority of the piston/rod reassembly for his time. There are 87 octane friendly pistons out there. You could have the heads done to lower compression if you can't find a piston you want. I doubt you will have to do that but the possibilities are endless as long as you have the funds. I just picked up a recon crate short block for like $900 plus core then pulled the stock pistons and replaced them with TRW's. I also changed a few other things but you get the idea. Maybe a new short block? Have you checked compression to see if there may be a problem there? What kind of budget you have will decide what you do. By the way FE's don't get good milage or so I have read in the sticky at the top of the thread lists. Maybe someone could do an FE poll to see what the avarge gas milage is. I'm guessing about 10 city and maybe 13 highway.

 

Replacing the 2bl manifold with a 4bl will help performance. If you don't hotrod the 4bl you can get about 12mpg. 10 -14 mpg is about the norm for FE blocks.

 

well guys this coming monday i'm gonna get on the phone with my machinist that did all the work for me on the entire motor. I'm gonna ask him what pistons he gave me to put back in, the thickness of the headgasket set he gave me if available, and if he knows anything about the 352 crank and rods and what i can do with what i have...only he knows what i have b/c i just put together what he gave me. i'm also gonna try and get the casting numbers off the heads to give ya'll some numbers to play with. thanks for everything guys!

 

what about plaining the heads on the 360? i am currently building a 360 that i had no knowledge about before digging into it and found out a week or two later after putting $1300 into the bottom end with getting the 360 crank ground and 360 rods reconditioned that i should have got 390 crank and rods so i talked to my local shop and they said they could plain my heads and give me about a half a point higher compression, unfortunately i havent gotten the motor finished to tell you the results lol

 

If you cut the heads you need to also get all 3 machined surfaces on the intake cut the appropiate amount for a proper mating of the surfaces for a good seal.

 

well guys i found my answer and let me tell you its not what i wanted to see. took a compression reading of my #1 and #5 cylinders and both are dead set on 105psi!!! if that don't make you sick i don't know what will. that explains why my motor has never wound up tight like my dads old 390 used to when i'd punch it. i guess that .040 difference in throw between the 360 and 390 components makes a big difference compression wise. just for grins i took a compression reading of the #2 cylinder on my dads '68 mustang with an inline 200 and got 190psi!! i still can't believe it but i guess now i know something. gonna try and talk to my machinist this week and see if he can come up with a 390 crank and rods for me. I also pulled the invoice from my machinist and got you the part number for the pistons. 1131-30 Silvolite thanks guys!!

 

alright just took a look at my drivers side head and between the #6 and #7 spark plugs it says DT2AA?? that do anything for anyone out there?? is that the number that identifies what cc heads i got?? thanks guys

 

'73, the 1131 silvolites are what is called for in a 360, but as you have already found out, they don't give much power. You can use them in your 390 job if you want, but flattops and the 390 crank might give more compression than you want in a truck engine. The silvolite 1116, 1131, and sealed power H304P all give an approximate 1.75~6 pin height and have a small dish in the top. Very nice pickup truck pistons. Just make sure you don't use a S/P 381P or Sil 1139s, those slugs will give you less than 8 to 1 in a 390. DF

 

Is there anyone who can confirm this?? thanks

 

Someone asked about MPG. I have a 1976 F250 4x4 with a rebuilt 390. Stock engine with Edelbrock Performer, 600 cfm Holley, MSD 6A, Blaster SS coil, dual exhaust. The engine has about 2500 miles on it and I get 10 MPG on the highway with a large ATV in the bed. MSD Pro-Billet FE Distributor is next project. Thinking about headers.