Don's (Pebcak) 351 upgrade Project

Yes, I agree - use those heads.  But like Jim said, even better pistons can get you whatever compression you want.  And you have to have new pistons, so get some that put you in the 9+ range.

There's a balance between compression and cam.  Too little compression and too much cam is a bad combo.  But as you go up in compression you can use more and more cam.  In fact, there's a difference between static and dynamic compression ratio, with static being what is calculated using bore, stroke, and piston & head recesses.

But dynamic is closer to actual as the cam leaves the valves open during part of the compression stroke and you lose some compression.  And the longer the duration of the cam the more is lost.  So some people go up closer to 10:1 and dial in more cam to kill some of it.

ArdWrknTrk wrote

Taller pistons
Deck the block
Stroker crank

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All I get from that is that I could start to go down a rabbit hole.

When I was talking to the first engine shop the owner told me that there are a lot of "little" things they could do while redoing the engine for me to increase HP here and there.  Little upgrades where all together it could make a difference without breaking the bank. Is that kinda what you're meaning above?

Gary Lewis wrote

And you have to have new pistons, so get some that put you in the 9+ range.

Ahhh  I didn't see your post cause it was on page 6.  

I'll add this to the list when I'm talking to the new shop.  That way I can get the 35-283-3 cam kit on order.

I'm not sure I'd order the cam before talking to the engine builder.  He might have suggestions that you want to consider.

On the pistons, you'll find hyper eutectic and forged.  You don't need forged.  Go for the hyper eutectic ones.

So if you go to the engine builder and tell him what your plans are for using the truck and then say you think you want this cam and about 9 - 9.5:1 compression you give him a chance to provide suggestions.  In the long run, having him bought in is good.

Pebcak wrote

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Static compression is the ratio of cylinder + combustion chamber volume at the bottom of the stroke (BDC) V/S top of the stroke (Top Dead Center)

Taller pistons come closer to completely filling the cylinder (even exceeding, if a high crown)
So, less space left at the top of the stroke.

Decking the block cuts down the cylinder height instead of using pistons with a greater height.
(This is sometimes better because you can have more quench, which reduces knocking)

A stroker crank increases compression by making the bottom of the stroke farther down the hole.
Two fold increase of compression and displacement.

ArdWrknTrk wrote

Static compression is the ratio of cylinder + combustion chamber volume at the bottom of the stroke (BDC) V/S top of the stroke (Top Dead Center)

Taller pistons come closer to completely filling the cylinder (even exceeding, if a high crown)
So, less space left at the top of the stroke.

Decking the block cuts down the cylinder height instead of using pistons with a greater height.
(This is sometimes better because you can have more quench, which reduces knocking)

A stroker crank increases compression by making the bottom of the stroke farther down the hole.
Two fold increase of compression and displacement.

Thank You for the explanation!  I gotcha now.  I'll ask this stuff when I call.

Gary Lewis wrote

Go for the hyper eutectic ones.

So if you go to the engine builder and tell him what your plans are for using the truck and then say you think you want this cam and about 9 - 9.5:1 compression you give him a chance to provide suggestions.  In the long run, having him bought in is good.

Got that on the list to discuss too.  Will get with them to get their opinion before I order stuff.

Thanks!!!!

Your engine has a bore of 4.000" and a stroke of 3.500".
If you take the volume of a cylinder and multiply by eight you arrive at engine displacement.
Your engine is a positive displacement pump and would move this volume every two revolutions (4 stroke, or Otto cycle engine)

Taller pistons or lower decks do nothing to change this, but increasing the stroke by increasing crank pin offset makes your 3.500" into something else (say 3.750") by the time you multiplied that 1/4" by eight you have a substantial increase in displacement AND you have a new higher compression ratio, because zero is always zero.