[LStathas]

Just wondering why are rods or pistons are not available in variants to achieve zero deck height. It just seems silly to deck a block any more than it needs to be true to achieve zero deck. It can't be that hard to make a few sets per run +.010 or +.020. any thoughts?

[steve25]

You’ve never been in the manufacturing world have you?

[steve25]

One option would be to have rods resized as that would allow you to change the C to C by some + or - .015”.

[PAUL K]

First issue is most mass produced Pontiac blocks vary in height from front to back and left to right.

[PunchT37]

Originally Posted by PAUL K

First issue is most mass produced Pontiac blocks vary in height from front to back and left to right.

And, they ain’t the only blocks.

[AG]

You can measure your deck height on the four corners and knowing the stroke and C-C distance of your rods , you can order custom pistons and adjust the compression height to reduce how much you have to deck the block. For example, Butler sells Ross pistons with a 1.295" CH for a 4.25" stroke crank and 6.800" rods. On several motors I have ordered pistons with 1.305" CH.

[JLMounce]

You can definitely do it with custom pistons and there are several variants of BBC rods that can be used as well if you're turning the crank down to a BBC rod journal size.

At the end of the day though, after crank grinding where necessary and any up-charge for custom pin height pistons, it's typically cheaper to deck the block.

I just had my engine done in 2024 and the block was decked/squared on a BHJ fixture. I want to say the cost was $275 for the service and I have a known flat deck now. Previously I had 2 thousandths of verifiable taper front to rear. The machine shop set the deck to leave the pistons .003 in the hole. This gives enough deck left for one more cut if the engine needs rebuilt again in 20+ years.

[mgarblik]

Pontiac blocks from the factory are pretty square from what I have seen. +-.003-.005 at the 4 corners. But the overall height can be high or low by .015-.020". SBC blocks made in Mexico are the worst blocks I have ever had to square up. Had one a few years ago that was twisted and out of square .024". !!

[LStathas]

Originally Posted by steve25

You’ve never been in the manufacturing world have you?

Actually I have. I was a machinist for over 30 years.

[Formulabruce]

deck the block, then Mill the heads to match and then mill the intake to fit and have a 1 OFF engine...... nah.... not the way... work with the stock height IMHO.

[scott70]

I made the mistake once of ordering some forged pistons and never checking the compression height of them (1.47). By the time the engine was assembled it was then I found out the pistons were around. 036 in the hole. At that point I threw on some .027 cometic head gaskets to help with the quench. Next time I needed pistons I just ordered custom compression heights.

[VCho455]

Originally Posted by Formulabruce

deck the block, then Mill the heads to match and then mill the intake to fit and have a 1 OFF engine...... nah.... not the way... work with the stock height IMHO.

In a perfect world......
Yeah.

[grivera]

With factory blocks being all over the map, what is the margin for good enough vs absolutely needs to be decked? Let's say a piston is .020 in the hole and using a .039 gasket like a 1016 - is that ok on a performance build?

[JLMounce]

Originally Posted by grivera

With factory blocks being all over the map, what is the margin for good enough vs absolutely needs to be decked? Let's say a piston is .020 in the hole and using a .039 gasket like a 1016 - is that ok on a performance build?

Probably depends on the person.

To me an actual performance build will pay attention to things like quench distances.

If you want a factory type engine, there's probably no real need to worry about getting the deck perfectly flat and minimizing quench distances.

The previous build on my 455 was very basic. When it gave up the ghost on me and I tore it down, the tolerances were all over the place. That said, it still ran good, made good power and at it's death I estimated the engine build was around 25 years old. It was in the car when I purchased it, but supposedly fairly fresh at that time.

It's rebirth has consistent tolerances, good parts with a lot of attention to detail, including getting the deck and quench distances set optimally. It makes quite a bit more power and in many ways is also more tame than the previous engine was.

[hurryinhoosier62]

Originally Posted by PAUL K

First issue is most mass produced Pontiac blocks vary in height from front to back and left to right.

Yep; as much as .015 or more.

[hurryinhoosier62]

Originally Posted by Formulabruce

deck the block, then Mill the heads to match and then mill the intake to fit and have a 1 OFF engine...... nah.... not the way... work with the stock height IMHO.

Bruce, or align hone and deck the block so both decks are the same height, then measure the rod c-to-c, ensure the crank is “on” stroke. These are the variables too many people leave out when attempting to zero deck a block.

[KEN CROCIE]

In response to Steve25s manufacturing comment: Let's say that a piston mfg. wanted to satisfy a market that needed several pin heights to let a customer adjust the piston to head clearance. The mfg. decides that four .010" increments of pin height would be a good idea. That means the mfg. would have to quadruple his piston inventory in every bore size and every C/R that he has available. There would be a lot of dead inventory in order to satisfy the guy who wants a .020" over piston with a .030" shorter pin height.
Personally, I have my machine shop cut the block to 10.230" then order the pistons with the pin height appropriate for the rod length and stroke I am using.