so far I'm under the impression they are a stock replacement piston for the 410

 

I'd invest $18.95 in the book how to build horsepower Carburetors and intake manifolds by David Vizard. I did.

He talks about cooling the intake and the effect on handling lower grade gas. He has a graph of several brands of gas and how they handle heat.

Polishing the chambers, blocking the exhaust crossover, cooling the carb with plastic spacers and heat shields, running cold air duct work to air cleaner, colder setting on spark plugs, recurved dist, lower temp-high flow thermostat, will all make a big difference. The chamber should look like polished crome and have NO sharp edges anywhere, and don't touch the flat squish pad except at the very edge to blend it in.

Don't think that a certain CR MUST have expensive gas, it's just not true. Thinking like that is just to simplistic. You MUST consider all the engine componets and mods, as well as the engine design.

I run el-cheapo gas in my heavily modified 60 over 410 and it's ran fine for as much as I drove it. I only have about 50 miles on the engine and decided to tear apart the body for painting, so I can't say for sure, but she did do fine on cheap reg gas.

I did run some octane booster on the prior build and didn't see any difference.

Just a quick note about the book, he says you can increase up to 1/2 point in compression just by going to a cold air intake.

I'd sooner get the flat top pistons and run 10.5 than loose the all-important squish effect with drop down pistons. The squish effect can make up for the added CR.

 

Well, I don't know what "stock replacement piston" means, but they don't match the specs for the pistons that Ford originally put in the Mercury 410 engine. Those pistons had a spec compression height of 1.687", whereas the 390/391 "truck" piston had a spec compression height of 1.660". These pistons are the latter.

ksd
69 F100 Explorer lwb 2wd FE 360 C6. WANTED: straight/clean styleside long box w/aux fuel tank for 67-69 F series.

 

 

the 391 piston are the full sqirt type and are not intended for high perfomance
also most of them have a dish of 20 or 30cc for low comp
so unless your goal is all torque low hp i would not go that route

also the 391 piston are intended to be use with the close chamber type head such as c7te
wich are 59cc or 64cc ther ports are also a bit smaller to accomodate the 1.84 valve

smaller ports and smaller valve give greater torque at low rpm
but the hp will suffer accordingly above 4200rpm

im buildling a 396 from a 391 ft block
to fit in a 64 galaxy
the rear end will be a 3.08

i should average 20+ mile a gallon and be able to criuse a light speed