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I have a 1973 Ford F100 with a stock 390/C6. How can I find the factory engine specifications? How much improvement can I expect by rebuilding/boring .030 over/4 barrel intake, carb/ a bit of a cam/ headers?
I have a 1973 Ford F100 with a stock 390/C6. How can I find the factory engine specifications? How much improvement can I expect by rebuilding/boring .030 over/4 barrel intake, carb/ a bit of a cam/ headers?
OK gotta disagree. Even with stock compression, adding a 4bbl, manifold, headers and slight cam increase can make it run circles around it's old self. If you are boring .030, you need pistons anyway, so bump the compression to whatever you feel is safe for your intended use. It will be the icing on the cake.
Just finished my first FE 390 in a 74 F250 and the combination of bumping the cam up a couple steps (Meling dual pattern, 214/224 maybe??), headers (Hooker), Holley Street Avenger carb, and an overall rebuild kicked things up a LOT. I also spend a couple of weeks porting (myself, with bits and pieces picked up off of the web and various forums, D2TE heads if I remember right). Fun rebuild, work great. HP a bit higher in the range than the C6 likes to shift for. (FYI, I am up in the Denver area, so I may be a bit higher altitude than you. Makes some difference in timing, cam timing, etc.).
Unfortunately I've already purchased the pistons....stock top 4.080" (.030 over). How about a thinner head gasket to up the compression....or shave the heads???
Can you return and exchange 'em? I really think you'll be happier with higher compression, particularly with a bigger than stock cam. I mean, you've got .112" deck clearance with those 390 truck pistons! When you figure up compression ratio you'll see what I mean.
Unfortunately I've already purchased the pistons....stock top 4.080" (.030 over). How about a thinner head gasket to up the compression....or shave the heads???
Thanks for the info.
You may be alright if they are for a car 390. Are the piston tops flat with little eyebrows cut in the top for the valve clearance? you really don't want to shave the heads, that leads to other issues...
Welcome aboard! --Mike
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Mike G
The Ford related items representing 1/3 of what's in the garage....
1965 F100 LWB 401FE power and C6
1968 Cougar XR7 (wife's toy)
2001 F350 Long-Crew-Dual-4x4-7.3L TD Hoss
I don't know. I ordered the FE 390 rebuild kit from Summit Racing....pt #FEM-MKP601M-300. that includes .030 over pistons for a ford 390. I don't have them yet but they are to be delivered today. I had planned to take them to the machine shop today so they can check and do the boring. Maybe I should call summit and see about shipping just the pistons back and replacing them...I'm anxious to get this thing back together. If I get the 360 pistons what does that change the compression ratio to?
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Mike G
The Ford related items representing 1/3 of what's in the garage....
1965 F100 LWB 401FE power and C6
1968 Cougar XR7 (wife's toy)
2001 F350 Long-Crew-Dual-4x4-7.3L TD Hoss
Summit says the pistons I've ordered are stock replacement pistons...That 360 pistons are ..116" higher in the cylinder and will stick up past the deck....which doesn't make sense to me because I thought that the 360 and 390 blocks are identical. Also they said if I did change to 360 pistons that I wouldn't be able to run on pump gas because compression ratio would be 10.6 to 1. Help!!!
The 360 pistons in a 390 will NOT stick above the deck, you'll have .012" deck clearance (I measured mine when I built my 390). They're just the right deck height. Plus, they will NOT give you 10.6:1 compression. If you figure 10cc valve reliefs, 72cc chambers, and .012" deck clearance, in a .030" overbored 390, with a .043" thick fel-pro permatorque head gasket, you'll get 9.511:1 compression. That's not too bad IMO.
The compression height of truck 390 pistons is 1.680"
The compression height of 360 pistons is 1.776"
The difference is .096"
So Rusty are you saying another way to build a 390 up for more compression instead of spending money on head work, would be to drop 360 pistons into a 390 block on 390 rods and crank?
The 360 pistons in a 390 will NOT stick above the deck, you'll have .012" deck clearance (I measured mine when I built my 390). They're just the right deck height. Plus, they will NOT give you 10.6:1 compression. If you figure 10cc valve reliefs, 72cc chambers, and .012" deck clearance, in a .030" overbored 390, with a .043" thick fel-pro permatorque head gasket, you'll get 9.511:1 compression. That's not too bad IMO.
The compression height of truck 390 pistons is 1.680"
The compression height of 360 pistons is 1.776"
The difference is .096"
They've got their numbers wrong.
Problem with the measurements on decks is that this is all on paper, untill you put the slugs in the cylinder, you don't know. I think they have to CTA... I have 360's in mine and they extend past the top of the deck, if I recall correctly, about .010". The diffference was made up by using a copper shim with the regular FelPro.
--Mike
__________________
Mike G
The Ford related items representing 1/3 of what's in the garage....
1965 F100 LWB 401FE power and C6
1968 Cougar XR7 (wife's toy)
2001 F350 Long-Crew-Dual-4x4-7.3L TD Hoss
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