360 Info Please

[Aussie Challenger]

I haven't pulled down my '71  360 yet but am wanting some general info from those that know.   
How far down the bore are the pistons usually, I have heard anywhere from .040" - .080"? I will be using flat top pistons, possibly Keith Black and was wondering if any knew of the part No's for a piston that might have a higher top deck than standard to hopefully bring the piston deck close to the block deck so I don't have to machine too much off the block? This is going to be a strong cruiser engine so I don't want to go for dome pistons, want to keep compression around 9.5:1.   
I will be shifting hopefully in the next few months so don't want to strip the motor down yet but I am trying to get some ideas formulated for the rebuild when it happens.       

[72bluNblu]

There's no real spec on how far down the pistons are, which is kind of the problem. The depth of the piston's seems to vary quite a bit, so you really need to measure your engine. It isn't that hard to measure though. Ideally you'd use a depth gauge, but even using the slide end of a caliper can give you some idea. Your machinist could then get you the exact number if you're going to do any decking.

That said, I believe even the flat-top KB 107's have a slightly taller compression height than stock at 1.675". I know for sure that they're taller than even the Speed Pro Hyper ZH405CP's, at 1.637".

[Aussie Challenger]

Thanks 72bluNblu, I am aware of the problems and as I won't be pulling my motor down for a little while I was trying to get an idea if there was a common number for the piston being down the bore by those who have rebuilt a 360. This will be my first 360 even though I have built many other sizes, thanks for the KB 107 height #, I think they are about .080" higher than stock but again I don't have access to a std 360 piston yet. I build all my own motors, I check original specs and then tell the machinist what I want. If the piston is around .080" down then the KB 107 might be the answer, but I will have to allow for trueing the block deck also.   

[femtnmax]

I have a 360 LA block, and decked the block to fit KB107 hyper pistons.  I don't remember the exact amount that was took of each deck surface, but it was not anything like 0.080 inch, was much less than that.  I had the block decked on one of those CNC machines, had to admit the end result was close to perfect.
I ended up deciding to go with Ross forged pistons.  The Ross pin height is 0.010 inch lower than the KB107, but since I'd set the KB's for 0.005 above deck, the Ross ended up 0.005 below deck.  I rechecked the static and dynamic compression and all still looked good, so did not recut the block decks.
For a 360 mopar, if your looking for a set of 0.03 overbore KB107 pistons and moly rings, new in box, never ran, I have a set listed on the parts for sale section of this forum.  The price has been discounted, and I'm still flexible on final cost.

[Aussie Challenger]

Thanks for that femtnmax, but at the moment due to personal situation and I will be selling house and moving I don't want to commit to anything yet. My motor I have I am fairly certain it is standard but won't know until I dismantle, I am just getting info while I wait on my move to happen as I have never rebuilt a 360 before, plenty of other motors though. I was hoping to go between .030" - .040" max, your pistons were tempting.   
Wouldn't the Ross pistons have placed the piston .015" out if the pin is .010" lower than the KB's?   

[femtnmax]

Wouldn't the Ross pistons have placed the piston .015" out if the pin is .010" lower than the KB's?

My mistake, the Ross piston tops are 0.010 lower than the KB tops, so the Ross pin location is closer to the piston top.
I would not be too concerned about decking your block.  Setting the piston top flush with the block deck makes the most use of "quench", which means having the piston top about 0.040 below the cylinder head surface.  Typical Felpro head gasket is about 0.040 thick which works out real well.  You would need cylinder heads that have a flat portion of the combustion chamber, called a quench pad, that is a surface parallel to the flat top of the piston...most older mopar OEM heads don't have this flat area, so need to check this out first.  If your heads don't have quench pads, then setting the piston top flush with block deck surface is not so important.
Whether you build for use of quench or not, I suggest using KB silvolites compression ratio calculator to verify your build ideas befor you start cutting.

[Aussie Challenger]

Thanks again femtnmax, I am hoping to have the pistons flush, I am aware of different thickness head gaskets and was hoping to use the Felpro .040" thick if possible and there is an outside chance I might be able to get a set of 308 heads. I don't want to take too much off of the block because of inlet manifold alignment. This is why I needed to find out all the different piston heights and if there was any "normal" amount the original pistons could be down the bore.

[moper]

Unfortunately the issue is not the pistons that make it an individualistic deal. It's the block. Most factory blocks are "tall" as compared to the blueprint spec. They are also usually crooked and not parallel with the crank centerline too. The piston manufacturers use the blueprint height to design. So if your block is blueprint, the KB107 should be close to zero deck. If not, it could be anywhere from that to .020 down in the hole. If you are building an engien with modern heads (closed chamber) this is critical to know and set properly. If you are running open chamber heads it's less of a concern and the KB107s will give you more than a full point over the factory ratio, and more importantly they do it with a generous valve relief.

[femtnmax]

Moper is 100% correct of course, and I would not be concerned about intake manifold fit.  Setting everything up correctly is just part of doing a performance engine build.   To check piston deck clearance without CNC machining can take several mockups of the short and long block. 
I will put the same piston/rod in all four corner cylinders of the block, turn the crank over and measure piston top to block deck clearance.  Doing this with an old piston will tell you if the block decks are out of square ( as Moper mentioned...crooked or not parallel), and will also tell you if one deck is higher than another.  I have seen a block where one deck was 0.025 taller than the other. 
So get your decks the same distance from the crank centerline, bored for new pistons, then put one new piston /rod in all four corners again, measure, and then you can take the block back for final decking to fit the pistons for zero deck. 
Then once the block is true, mockup the long block with just block, heads, and intake.  Typically when the amount of material removed from the deck surface is known, then the amount can be determined to remove from the intake manifold side of the cylinder heads. 
Always mockup and recheck everything after it comes back from the machine shop.  I have caught machining errors doing final mockup checks, then its back to the machine shop again.
Takes some time,but is well worth it in my opinion.

[Aussie Challenger]

Thanks Moper, as I haven't rebuilt a 360 I have been searching out any info particular to that motor. I have however built 100's of engines over my 40 + years in the trade, trueing up the deck is one of the early measurements I work on getting right, checking the old pistons first then dismantling and measuring old piston heights against available new pistons. Then of course trial fitting of pistons and so on getting the figures right. I have come across many blocks that not only have taper and different deck heights but some that are not running flat in relation to the crank, that is what you might call twisted. Some machinists don't like me when I tell them how I want the deck machined and how much, I have found a good shop that respect the finer tolerances that I insist on.   

[moper]

There's nothing really unique about 360s. Sounds like you know what homework to do and will do it. that's all you really need to know.
My machinist has commented to mutual friends that he's not real fond of me...lol. Because when I'm measuring and I find something off, I call and ask why. Apparently we are supposed to just accept a word as truth. He's a great guy and runs a very good shop. So I don't care if he hates me. The work is top notch, he can always educate me if I need it, and I'm happy with the results. Knowing the "whys" makes chosing shop or trusting the machinist a lot easier. I have plenty of machinist friends who I won't let near my stuff. They DO like me, are cheaper, but can't give me the quality.