I'm not sure but have a hunch that the difference between the 390 and 428 is crank, pistons and cylinder heads. Please I would like to know because my next project vehicle is going to be a 69 mach 1 and I would like to put a 428 CJ under the hood.
390 has a 4.05 bore and a 3.78 stroke, where as the 428 has a 4.13 bore and a 4.98 stroke. The externals on the blocks are identical and the stock 428s used 390 heads and cams. The 428s really worked better wiht the 427 hot rod stuff mainly because of the bigger inches.
LOL...I hope theyour 428 doesn't have a 4.98 stroke!! I think you mean 3.98!!
Also if you are putting it in a Mustang you need GT heads with the dual bolt pattern.
Ok, see what you get when you don't proof read and have fast but fat fingers. Make that 3.98 for the stroke. FYI fomocofan, the 428CJ heads have the same staggered exhaust bolt pattern as a the GT heads and that's the only 428 that was available in the Mustangs. If you want a 428 to really sing you need the CJ upgrades anyway.
I know, I guess I read his post wrong...We all make mistakes!
I was just saying if you put together a non CJ motor and you want to put it in a Mustang you need the GT style heads with the dual pattern because as you know, its the only way they will fit in a Stang..
I guess also it was directed at your comment that 390 and 428's were they same heads...As you know they are not always..as there are 390 and 390GT heads and 428 and 428PI/CJ heads.
And that there are different cam grinds for 390's and 428's.
Last edited by fomocofan : 06-04-2006 at 04:13 PM.
I know, I guess I read his post wrong...We all make mistakes!
I was just saying if you put together a non CJ motor and you want to put it in a Mustang you need the GT style heads with the dual pattern because as you know, its the only way they will fit in a Stang..
I guess also it was directed at your comment that 390 and 428's were they same heads...As you know they are not always..as there are 390 and 390GT heads and 428 and 428PI/CJ heads.
And that there are different cam grinds for 390's and 428's.
It's the only way the will fit in the mid and late 60's Fairlanes and Torinos too. In fact that's where the design came from, the '66 Fairlanes had to have those exhaust manifolds for the GT engine to fit. The Mustang got the 390 in '67.
It all depends on what relatively stock means..
But assuming you still have stock pistons and cams...you would not benefit much from the improved flow and valve sizes...not only that, you may loose compression unless you change pistons or mill the heads.
However, if you go with Edelbrock Aluminum heads, you would atleast have a weight savings, but there are much better and cheaper ways to improve power.
It all depends on what relatively stock means..
But assuming you still have stock pistons and cams...you would not benefit much from the improved flow and valve sizes...not only that, you may loose compression unless you change pistons or mill the heads.
However, if you go with Edelbrock Aluminum heads, you would atleast have a weight savings, but there are much better and cheaper ways to improve power.
Agreed, The heads have bigger valves and ports but need a cam change and intake change to really be worth the effort. Plus of course the pistons to bump the compression back up.
www.ford428.com is a pretty new site that sells 428 parts. I've never dealt with them so i really don't know how they are. A good research and reading site is www.428cobrajet.org. Some original CJ parts are off the hook price wise so shop wisely. The aftermarket is thriving with good new parts if you don't have to have original parts. Sounds like a cool project....
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Difference between 390 and 428
