I have a '78 F150 with a 400. I would like to increase the hp and torque, but I want to avoid replacing the pistons with the higher-comp ones it really needs. It already has an Edelbrock 600, 4bbl manifold, and Headman hedders. What kind of gains can I expect with a mild performace cam and head porting? What about altering the heads to use larger valves?
Your stock heads flow pretty good now. Higher compression (with pistons or shaving the heads) is the next logical step. Port work will help, but not as much as compression.
I guess we need to know a little more about your plans. Are you trying to get away with not rebuilding the the bottom end? Just doing a top end rebuild is pretty risky on a high mileage motor. You could shave the heads to build compression and put in the bigger valves but you may end up with excessive blowby if you don't "tighten up" the bottom end as well.
>I guess we need to know
>a little more about your
>plans. Are you trying to
>get away with not rebuilding
>the the bottom end? Just
>doing a top end rebuild
>is pretty risky on a
>high mileage motor. You could
>shave the heads to build
>compression and put in the
>bigger valves but you may
>end up with excessive blowby
>if you don't "tighten up"
>the bottom end as well.
>
I was hoping to get away with leaving the bottom end in tact, but you're probaly right - it needs the rebuild, too.
How high can I raise the compression and still run on 87 octane gas? I was considering using stock pistons and only shaving the heads about .02"
With the current gas prices, that 87 octane is about all I can afford!
I've had a lot of expierience with this and here are some thoughts. If you go with a flat top at about 9:1 it will be to far down in the hole and lead to preigition etc. They definitly need the help though. My machine shop had J.W. piston make up a set that are dished and the outside ring (edge of the piston)comes very close to the top of the cy1inder. That solves the problem. I don't have spark knock problems anymore but I do have 175/180 PSI static compression! That must be close to 10:1. They cost a bout $500. but it was well spent.
1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything
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1977 F-100 Ranger XLT,400,C6,GV
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heres a phone number for some 10:1 cast pistons (with 76cc heads) the part number is #400-100f (badger pistons) they come with pins pressed in for $144
I had the heads on my 400 shaved .030" with no noticeable difference, am going with pistons next
>heres a phone number for some
>10:1 cast pistons (with 76cc
>heads) the part number is
>#400-100f (badger pistons)
fozzy,
The only Badger number I can find close to that is the 400-10F. Those pistons are actually made by Ohio Piston & Pin (same as their part number 1282P), and they are good for about 9.0-9.1:1 in a 400 M-block.
I've been having a conversation over on usenet about these pistons and I discovered that if you plug the numbers into a comp calculator such as the one at: http://www.jersey.net/~rforceno/crs/crs.htm
you can get between 9.25:1 and 10:1 depending on how much you take off the block. I realize this isn't a huge revelation but the #s I put in for my motor gave me almost 9.5:1 (9.48) with those pistons. I did have .008 taken off of the heads. Take .020 off either the heads or block and you're right at 10:1.
I have an Excel spreadsheet with the same formulas. When I plug in the numbers using the stock bore (4.0") and stock deck height (10.297") in my spreadsheet, I get 9.02:1 with those pistons (1.640" comp height and 4cc valve relief). That number agrees with the web site calculator.
I don't have a set of those pistons to measure, but it's common practice for piston makers to adjust the piston top relief clearance to maintain a specified compression ratio at different oversizes.
If you change the numbers for bore to 4.030" and drop the deck height by 0.020" and keep the same 4cc relief volume, the CR comes out to 9.459:1 on my spreadsheet and 9.469:1 on that web site calculator. (Probably because they just use a deck clearance number input rather than calculating the deck clearance in the formula.)
If you assume that the relief volume is adjusted for overbore, using the stock bore numbers is a more reliable calculation, especially when the manufacturer specifies only one relief volume.
Reducing the deck height by 0.008" and using the stock bore (4.0"), the CR comes out to 9.154:1.
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1977 Ford F150 XLT Ranger 2wd 400 
1-626-869-0270
