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390 Piston Height Information Needed
I'm planning on building a 410 this summer and I'm figuring out piston heights between a couple 390s that I have. I have a book by Steve Christ How to Rebuild Big Block Ford Engines which I get a lot of information from. There is a chart in the book on deck height and a formula on figuring out the deck height for mix matching parts. One thing that is holding me up is that has a couple different pin heights. One of the 390s that I have is a 69 which the pin height is
1.775 and the other is a 70 which has the same. It also shows for a 390 68-76 the pin height is 1.680. I will be able to use a 390 piston that has a pin height of 1.680 and have .012 deck clearance. Could the two different heights be for a 2V and the other 4V, or is it between a car and a truck? My 69 390 came out of a truck and is a 2bbl motor the 70 came out of a car and I'm guessing it came with a 2bbl, I got the motor without an intake. I would like to build this engine with stock parts. Is there a piston chart that has the pin heights for all FE's a guy could get? Anyone have any info on this? |
all 390 compression heights should fall between 1.778 and 1.782 are you sure your not confusing 360 motor specs? although a piston manufacturer can make any comp height you wish.
fred |
1 Attachment(s)
it was converted from html so its a little difficult to follow but here you go.
looks like the 410 height is closest to what you need. the file will open with msword i have the page saved i will try to find the source and post a link |
My spec book lists between 1.775 and 1.7915 with various stops in between. It is primarily for various compression ratios and depends on year as well as combustion chamber size. As long as you build the engine around the piston used it is probably not a big deal. It was also well known that the FE engines tended to vary from side to side, one( can't recall which) had more clearance than the other and was usually corrected when blueprinting......at least according to Dyno Don....I will yield to his superior and wider experience.
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here's the link much easier to read.....
http://www.mercurystuff.com/fe-engine-specs.html the 410 and the 428 seem to share the compression height you desire 1.680, note they share this because their cranks have the same stroke, what crank stroke are you spec'ing |
The 390's in 1969 & 1970 in both passenger car and truck were 2 bbl.
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Several of the 390 engines built for trucks used a very short 410/428 pin height - put the piston waaay down the hole and had like 7.5:1 compression. Replacement pistons for those like the F-M 304NP or Silvolite 1139 - can be used to built budget strokers with a 428 crank.
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I missed that it was a 410 build, the comments on the 410/428 pin height are correct.They use the same crank and rod length. |
390 Piston Height Information Needed
The crank is out of a 410. The guy rebuilt the motor and he said he put 390 pistons in it and it brought the piston all the way to the top of the bore. The 390 that I have which came out of a truck has C8ae-h heads on it and had a two bbl intake on it. I guess the only way to tell what the height is to either tear the motor apart or peal the heads off and measure the clearance that way.
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There's a 0.20 difference in stroke(0.10 at the top & 0.10 bottom), I think you would have to have a really tall block or the pistons would require cutting to keep them from whacking the heads. The 410 variations should be available from several sources, I wouldn't try screwing with 390 pistons to get the correct height...that's a pretty thin piston top after that much machining, IMO.
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The 381NP has the lower pin height needed for the 410/428 conversion which uses a 1.66 pin height. The Silvolite 1139 list as the 1.66" pin height. Not saying your wrong, just want to be sure... |
No - you are likely right - I just typed that out from memory....
The punchline is that some 390 pistons can make a 410, but it'll be a cast piston cruiser. |
Thanks Barry.
I was just reading on another forum that some have used the SP 2291 for 390 and milled them for use with a 3.98 crank. Here's my situation. I've got a mirror105 block that was a 360. It was rebuilt, bored .030 over and they used the 2291 forged pistons. Now the bores and pistons are good, i've got 390 rods, 3.98 crank. Is it worth it to make these parts work or should I go with the new pistons. Budget build for a 2wd 68 F100.. |
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