Ok here's what I got

1-.018
3-.023
5-.023
7-.025

2-.020
4-.025
6-.025
8-.025

These are how far into the hole my pistons are. I have had the block (350) deck plate bored and honed and had the rotating assembly balanced.

Is there anything I can do to get these more in line before I have the block decked? Or can the machine shop do something for this?

Or is it just what it is and I have them cut .015" off and that's as good as it gets?

 

4 things affect deck clearance:

Block true
Piston pin height match
Crank journal true (90 degrees between journals, journals the same offset)
Rod length

Any or all of those could be your issue.

Measure and correct.

Yours looks like the block, but ... MEASURE before doing anything to anything.

 

SO I should swap around pistons and rods to see if that has any affect and if it doesn't then the block is the issue?

If it ends up being the block, can the machine shop fix the issue?
If its the rods or pistons then I have to buy different ones or is there another fix?

 

Yes you could swap stuff, but a micrometer is quicker and eeeeeeeeezier.

Yes a machine shop can fix the block, IFF they can MEASURE the height from crank centerline to deck, and cut accordingly. Most corner parts store type shops can't or won't do this. Any real racing machine shop however, does it daily as a matter of course.

This is MEASURED from crank CL to deck surface.

Stock deck height in the SBC is 9.025", -.000" and +.015" or so. Unbelievably sloppy.

"Ideal" is 9.000" -.000" and +.003" or better.

If they're going to cut it (99.999% likely) have them make sure that it's perpendicular to the crank from side to side as well as parallel from front to rear.

Then when you get it bored, have them bore perfectly perpendicular to the crank CL, and all 4 on each side in a straight line and 90 degrees apart. Stock, this is also usually a disaster, and most "on the wear" el cheeeeeeeeepo bore jobs just make it even worse.

Did I use the word MEASURE enough times?

 

Did you check this with a feeler gauge or did you check it with a dial indicator running the piston to the top and back down and measuring in the center of the piston also checking piston rock to see if it changes the readings?

It could end up costing you a lot of money in machine work for little to no gains.

I ran a 350" with .013" pistons down the hole Flat tops with 5.5cc reliefs .
I ran the steel .015" head gasket and milled 186 casting heads that finished at 54cc chambers.
270H magnum cam 224@ .050 It had 245 psi cranking pressure.
35,000 miles later I stuck .038" head gaskets on it.
Ran the same ET and MPH.
I ran 41 total timing with 93 octane.
38 total timing with 91 octane.

When summer temps got into the 95+ area I had to pull timing from the thin head gasket engine.
The thicker engine was not as finicky on the tune.

I really would not sweat the difference unless you are building a max effort deal.
Did you cc all the chambers on the heads?
Do all the intake and ex ports flow exactly the same and have the same swirl.

I have built many engines and all ran excellent and lived a long time and some were off more than yours.
When you have your next crank ground ask if they can index grind it.
When you have your rods resized make sure they can make them all the same center to center.

And like was stated pistons can play a part also.

It could be just the deck height issue with the block like you said.. But I would run it if it was just a driver and not a competition deal where you are looking for the last hundredth of a second.

 

I used a dial indicator to check them all and I checked them at the center of the piston. I haven't cc'd anything but this is just a driver so I'm glad to hear I'm trying too hard and can live with it being off.
I swapped around some pistons and remeasured everything but it didn't change any of the numbers so like sofakingdom said its probably in the block.
I didn't know any better to ask for all of that from the machine shop. It's all a learning experience for next time!
I won't sweat it then. How much would you guys tell me to have decked? I'm now thinking just .010" to clean it up and use a .030" head gasket.

 

I've run at both ends of the spectrum.
Original 350 (new with zero miles) had decks that were off as far as yours. That was with the stock crank, rods and aftermarket pistons (to replace the OEM castings).
Ran fine with a composite head gasket and about 10:1. Cranking pressures varied between cylinders but for the application, which was mostly street and some drag racing, the engine ran fine and practically forever.
Next block was treated to additional machine work. GM forged crank, aftermarket rods (massive Elgins), aftermarket pistons all added up to an even deck with the pistons .014" down. Added a .026" gasket for around 10:1.
This engine ran as well as the previous one or I should say the other way around.
As was pointed out, depending on the application, the decks as you have them will be fine. If you want to go the extra and spend more on good machining, then the block can be decked and squared but it may be for very little gain.


.028" piston to head clearance! Wow. That's tight.
245 PSI cranking pressure!

This sounds like a Super Stock drag racing engine....

 

Yeah, I think I don't know enough to get it perfect but I also don't know enough to know whats acceptable in this case.
Thanks for the info.

 

I grew up around drag racers, My uncle raced against the King Richard petty and all the others many years.
So a lot of stuff was stuffed down my throat since i was able to play with hot wheels.

Port the heads get the air in and out .. compress it as much as you can get by with.
If you do not have 12:1 compression then it is probably your grandmothers car.

224 @ .050 cam needs 11:1 compression.. all that old school stuff.

The above being True or Not that .028" piston to head was my 2nd SBC to build.
I used it in my daily driver 78 nova and put that 35,000 miles on it in about 7 months time.
I pulled trailers with cars on them and pulled my bayliner to the lake 160 miles away.

I loaned the Nova and trailer it to a buddy that needed to move out of his house.
2 days later i get it back.
I head to work that Monday and of course run it through first gear as hard as it will go.
I hear BAM BAM! and the car shook , I thought I ran something over..nothing in the rear view mirror.
OH well hit the throttle again BAM BOOM!
White smoke following me.. car shaking really bad.. I coast into a gas station and call someone to drag me home.
Call in to work at the same time (Pay phone).
I have it all apart less than 2 hours and one cylinder has 3 cracks in it and part of the top ring land on the cast piston (345NP) is gone.

Off to the machine shop to get sleeved.. back in the car running 2 days later with the thicker head gasket.

I found out my buddy filled the tank a couple times for me while he had it.
Yep 87 octane!
No little ping ping sound from low octane this was brutal BAM!

I have built another recently with a smaller cam and a tad less compression 260H I used Hypereutectic (H345np)pistons.
That will not happen ever again..I was building it for a MPG test.
Those are not stronger than the old USA cast.
I was rewarded with NO piston left on the connecting rod and what looked like gravel in the oil pan.
It had less timing and less cranking pressure than the other one.
My current 350 is the sleeved one with 11+ compression and a 268H with a very early closing intake lobe .. earlier than the 260H cam.
It gets 18 MPg in my 1957 4 door chevy brick with NO OD .

Not fast though just 14.40's and 225 psi cranking pressure.
But it gets 18 MPG pulling trailers or not, city or highway.. does not really care.

Sorry long winded.

 

Best case in my experience is usually zoo deck clearance, .039" gaskets, smaller rather than larger head chambers carefully worked to get rid of any sharp edges, and "reverse dome" pistons if necessary to lower the compression. Keep in mind that aluminum heads REQUIRE between half and a full point more CR to achieve the same power as otherwise identical iron ones.

And of course, consistency among cyls, and correct geometry.

 

So have them take .018"? Then .039" head gasket is the best way to go?
The machine shop said they dont have the equipment to square the deck to the crank bore. So I don't think I have the best shop around and I'm out of luck seeing that they have already been paid.

The things you learn the first time you do something................

 

Hey it has happened to many of us.. no big deal.
You learn to ask specific questions as you learn more.

I learned coarse cylinder wall finish will in fact chip the molly from the molly faced top rings and power will be down in about 20,000 miles or less.

Most of the small local machine shops finish the cylinders to 240 grit.
I need 400 or finer ..Usually 600 with a plateau hone.

Quote.
Plateau honing is a process that improves cylinder wall surface finish by removing tiny peaks of torn or folded material and increasing bearing area. This type of finish allows lubricant to collect in the remaining valleys, improving lubrication control and retention. It also extends the life of components such as piston rings and seals because there are no peaks of material for them to remove during initial break-in.

All those little things really start stacking up when building for max power and longevity.

My first time I had a rod knocking in a 350 oldsmobile.
I took the rod and piston out that had a stacked bearing and I knocked the rod bolts out of it and began rubbing the rod and rod cap mating end on the concrete to reduce the clearance.
Stuck it back together with a new bearing and it still knocked.. but had better oil pressure.. a week later i purchased a crank kit and a set of rods and pistons from another engine. at 5 bucks each.
Live and learn..
I was a little poor back then and would try anything.
You will be amazed what you can get by with.

I had one head that had only 1 2.02" valve the rest were 1.94"

When a boat engine (2 stroke) scalds a cylinder you do not mess with the other cylinders you fix that one and go a small over size and stick it back together.
I have done many of those.

I have seen a few V8 car engines with different size cylinders.
I have seen inline 6 cylinders missing the rod and piston in 1 hole and the rockers and lifters etc removed from that hole.
Run great .. never know until you pull them apart.


Think about unequal length header tubes.. I actually like that.. as it makes each cylinder peak at a different RPM giving you a broader torque curve.

 

There IS NO "take off .xxx" ".

What you need is, take off the metal that makes the deck surface not parallel front-to-rear, and not perpendicular left-to-right. Odds are, it's a different amount at every point. If they "take off .xxx", all you get is, a block that's a little smaller, but retains its current crookedness.

After of course, MEASURING everything, so that you know that the block is the thing you need to be working on, and not the rods or crank (pistons are less likely).

 

What are your plans for this engine?
If they are anything like mine were (a few, few years ago) then the stock block with a stock crank and rods will do the job.
So will the stock factory machining.
It did for me for tens of thousands of miles and hundreds if not thousands of red-line shifts drag racing (or getting groceries).
In all seriousness, there is little to be gained if the engine isn't a maximum (or nearly so) effort.
I only say this with past experiences to look back on.
If the machined surfaces are sound, in this case that would be the block deck, then leave them alone.

 

That's true, to a point...

If all that's being built is a slap-together I-have-this-laying-around what's-the-cheeeeepest-[fill in the blank critical part]-I-can-find type of build, then... slap it together out of what you have laying around plus the leeeeeeest possible amount of the cheeeeeeeepest chinesium crap it takes to plug the gaps.

If on the other hand, you DON'T want to be one of those guys that lays out the cubic bucks for some elaborate parts list, and then is underwhelmed by the results (like, you get the usual 275 HP out of a certain well-known build that's "advertised" as 420 HP), then ATTENTION TO DETAIL pays off YUUUUUJJJJJE.

So to skinny's point, do the level of machine work that's appropriate to the results you expect. Being realistic and not all starry-eyed about buying acoupla high-zoot go-fast goodies here and there and then them not making any real difference to the end product. Or, putting lipstick on a pig, and expecting it to turn into a supermodel.

Personally, I have prided myself for decades on being the kind of builder that can take a BOM that looks "normal" and "frugal", and handing abuncha "big hat no cattle" types their a$$ on a silver platter, by way of the BOO. ATTENTION TO DETAIL is how that is done.

 

Sofa I totally agree with what you are saying. The goal here is more power for weekend driver. I wish I had the know how you do. I wasn't even planning a rebuild actually just a cam swap until I saw the cam bearings.

I have stock vortec heads ported TPI top end and Dyno Don headers. I'm definitely not shooting for the moon in the power department. I don't think my current situation/goals warrant finding another machine shop (or should I say "real engine builder") to square up the deck. Then finding whatever else will be wrong to get everything perfect. I definitely started in that direction and knew waaaaaay too little to actually get there.

At this point (sad to say) I'm looking to get a bottom end put together that will be a little better than stock and won't let me down before my next project.