1. You don't really need to remove the heads unless you do plan to make upgrades.
2. The best you can do is ball park compression unless you remove the heads to measure the bore, stroke, cc the heads, etc.
3+4.  To some degree this will depend on the cam.  If it can't make use of the additional flow potential of the large port, large valve heads then replacing what you have may not be a benefit in that respect.  However, everything else equal you will gain about 1 point of compression and that will help everywhere in the operating range of the engine.  However, if anything has been done to optimize compression, they could increase it beyond what is manageable with pump gas.  So if it has a smaller cam and domed pistons, maybe not a good idea.  But if it has a bigger cam and or flat tops, there should be some noticeable benefit.


Lawrenceville, GA

Hi to everyone!
I have just come home with a 56 Ford F100 from California that is in great shape... very little rust. The questions I have are around the Y-block that came with it.
It was in some state of rebuild with no information on what was done (and now way of asking). I've torn it back down to the block and heads and this is what I have found:
Block - ECG
Heads - ECL-A
ECZ 9425-B Manifold
Older Holley 4 Barrel Carb
New water Pump
New Fuel Pump​
The block was cleaned and it appears that new bearings and seals have been installed as well as Pistons and a new Timing Chain and Gears… I can’t tell if the cam is new but I would assume so, but I have no idea on what the specs are or manufacturer. But from what I can see from the bottom side is it appears that the cylinders have been bored and the pistons look new.
The heads I see are low compression with the smaller valves... I have not removed the heads to inspect the bore or any work that might have been done to the heads.
I'm not looking for a Hot Rod here... just a mild performance Y-block... something that performs well and has some get up and go when you put your foot into it. I’m planning on restoring the truck with a few modern upgrades… not a lowered street rod.
My questions are:
1. Should I remove the heads to determine what has been done as far as bore and what pistons have been installed as well as what work has been done to the heads, if any?
2. Is there a way to determine the compression without removing the heads?
3. Are the ECL-A heads even worth keeping? Should I replace them with the larger valve ECZ-G heads?
4. Is there any value to keeping the ECL-A heads? Will they be a large loss of power/performance? Will I even notice??
Thanks,
Kevin