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

Got me there all right.

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"

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

Oh, I forgot to say I did check TDC with #1 piston and is right on the mark.

I can floor it on the flats and it picks up great but when I take a hill it just slows down, it won't maintain speed.  Forget carrying a load.  I did check out the fuel issue, it has new lines, a clean tank, rebuilt fuel pump and rebuilt carb.  I initially found a problem with the rebuilt distributer which I found the centrifugal advance was blocked not allowing advance. Since that fix it runs better.  I checked vacumn and centrifugal and combined advance and was within specs.  I replaced carburetor with a rebuilt one.  My personal feeling is the weight of the truck, low flowing heads, restrictive exhaust are all adding to the problem. I was told by a mechanic to disconnect the muffler and see if it makes a difference.  If it has more power the exhaust could be part of the issue.  Do you think if I disconnected the muffler there would be a chance I would burn a valve?

How about fuel delivery? You may have a blockage the is small and only affects the engine when under a load. What if you run fairly hard through the gears on a flat surface? If it slows then the problem could be in the fuel system. My 56 with a high performance FE pump and a McCullouch supercharger would run out of fuel at high RPM in second gear. I had to put an electric pump on it to keep up.

Not saying you need an electric pump, just that fuel can also cause the loss of power feeling. I've even seen rubber fuel lines with a tear in them that acted like a flapper valve when demand increased. It would pull shut and block the fuel flow.

Try putting a temporary fuel pressure gauge on and run it where you can see if from the cab. That should tell you if the pressure is dropping. It is not recommended to run a fuel pressure gauge in the cab unless you use an Isolator. This keeps actual gas from flowing in the vehicle.

Anyway, I think fuel is worth looking at. Chuck in NH

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

Whoa there, you mean it actually loses power? I'd suggest not spending any more money until you nail this down. The very first thing I'd do is make very certain you have a working mech advance distributor, then make sure the carb works correctly, set everything including timing to stock settings. Don't trust the timing marks either, carefully rotate to #1 TDC and prove the mark.

Dan in Seattle

I checked anything that would drag and couldn't find anything.  It accelerates great on the straight away but put it under a load and it slows right down.  I think total timing, vacumn and centrifugal was in 30's max.  I would have too look again where I wrote them down to make sure though.  I have a stock 58 3/4 ton with a Napco add on axle with a 272 with G heads and I am redoing the brakes then I want to drive it around.  I would like to see how it performs and compare.  I went to the machine shop yesterday  and will take the G-heads down to get cleaned  and checked out next week  to see if they are usable.  The blocks look good, and are 1 inch thick so I don't think they have been machined down.

If his engine has compression and is properly tuned, in stock setup it may make 140/150Hp and 200-220#tq at the tires but his 4 wheel drive truck may weigh near 5K# with him in it so he may be expecting too much. My 57 F100 shorty weighs 3650 with me and my built 292 4 bbl/T85OD/4:11 posi in it and it'll tear yer head off.

Dan in Seattle