Hmmmmm, if it accelerates on the flat per expectations then perhaps you're back to perception of what the engine is capable of. My aforementioned brother also owned a hilarious looking 55 F5 with the 256 Yblock, you couldn't help but burst out laughing as you looked at the front of that ugly bulldog of a truck. That 7K# truck served it's patient master for over 50 years hauling loads of apple boxes to market. When it came time to drive it over the Cascades to Seattle it was no surprise my brother was down to 30mph on the steep grades. That dead stock truck was shipped a year ago to a Swedish car collector.



In any case, as the guys are saying, if you simply change the simple bits like 1957 intake, 113 or G heads, cheap but very good long tube truck headers, mech advance dist from 1957 up, also very cheap, and you've got good compression, power may come up some 20-25%. That leaves the cam as the weak link, which also brings to mind making sure you don't have some flat lobes. If you choose to pull the cam have it and lifters re-ground to good lift. But where do you stop? Complete rebuild with 292 or 312 crank, re-pistoned etc? If so suggest leaving those decks .04 over the pistons to avoid detonation. Complete Yblock top quality rebuilds cost me a bit over $3K. If you choose to go with FE block you would get serious power upgrade but you'd never see much better than 10mpg. Before you toss em check your original heads to see if they're 471s.

Dan in Seattle

There's no advantage to putting a 292 crank in a 272, they're the same stroke.  The 312 crank is a different horse though.

John - "The Hoosier Hurricane"

Got me there all right.

Dan in Seattle

RE avoiding detonation, with unmilled G heads, a 272 will have compression just above 8:1 if about .040 is left between the piston and the head. When building the engine, about .040 is what you want. It will not be in danger of detonation due to compression.



A 292 with the same setup will be just above 8.5:1, and a 312 will be just above 9:1. You can see that the displacement just isn't there to allow compression high enough to worry about detonation in most cases. Forget what they posted in manuals and advertising, it's all lies. The compression figures, as assembled by Ford are even lower in '57



Looking at these numbers, with the late small valve truck heads, and the fact that his pistons are probably in the hole, he might not even have 7:1 for compression. A compression increase will be a huge step in the right direction and regular fuel can still be used.


Lawrenceville, GA

Charlie, I actually was hoping for some info about what I did to my engines in regards to compression. I'm new here so perhaps you could start another... uh, what do you call these lines of communications, threads? in tech section?

Dan in Seattle

As Charlie said I think with a lower comp height piston, comp gaskets, + small valve heads have added to the problem.  I will probably leave the engine in the truck and take the heads off.  If the piston in the hole distance is more than stock should I put the thinner steel stock gaskets on?  I didn't really want to plane the heads down in that there are unposted.  

Start a new thread with your inquiry. Tell us the modifications you made and we should be able to come up with a ball park figure.







If you had your block and heads surfaced at the time of the rebuild and the pistons are at least .030 in the hole, then use the shim gaskets. If they are less than .030, or the block/heads were not surfaced, then use composition gaskets.

If your heads are the late small valve truck heads, then they should be posted. Milling is an option. Heavy milling usually costs more than a clean up cut, and the intake surface will have to be cut which adds to the cost. I'd find out how much it will cost to mill your current heads, see how it compares to having the G heads reworked. If it's not much difference, then I'd go ahead and do the Gs. I think you will find more compression by swapping the Gs than you will by milling the truck heads. Ted says its about .0064" per cc for the G heads. If it's close to the same, you will have to remove about .045 to get the same compression as the Gs. That's why I've suggested swapping before milling.


Lawrenceville, GA

Thanks again for the info.  I will keep you informed as to how it is going.

My vote is for g heads, 57 4bbl intake and either stock 312 carb or 500 cfm Holley. Dual exhausts with crossover pipe and good turbo mufflers. Headers optional. All this will work great with 292 or 312 if you decide to upgrade latter to more cubes.

Running a cranking compression check on all the cylinders and insuring that they are all within 10% of each other from the lowest reading to the highest would be at the top of the list.  This insures that the engine is mechanically in good condition while also giving a rough idea what the dynamic compression ratio is.  155-160 lbs of cranking compression would be considered a good number for a good running 272.

 

From the descriptions you give on the performance of the engine, I suspect you do have cranking compression readings that will be on the low side which would simply indicate a compression ratio that’s also on the low side.  This would explain the lack of power going up those hills.  Even if you’re going forward with a head and/or head gasket swap, I’d still recommend that a compression check be performed prior to pulling the heads so that those values can be compared to the numbers obtained after boosting the compression ratio.

Lorena, Texas (South of Waco)