Block is disassembled, so no way for me to measure...

Just need to know what the original measurement was between stock 455 pistons and deck was?

Purely for planning purposes at this point, but I need some numbers to punch into compression calculators and stock is a good place to start.

Also...
Are there any issues with running the thinner comtec headgaskets (like the .02x and .03x gaskets) on summits site it mentions something about needing O rings? what the heck is that referring to?

Thanks-
Ben

 

You could put the crank in with just the end bearings and mock it up.
But with the stock dished pistons .040 is probably a good estimate.

Some gaskets are made to be run with o rings, others aren't. Just make sure you get the right ones. When in doubt call the manufacturer.

 

Iirc, .025"

 

Thanks guys!

 

Almost all that I have taken apart have been between .025 and .030, some even more. Your best bet is to moch up your new pistons and see where they are, to give you better info. If you get dished pistons, be sure to measure the "CC's" in them for a more accurate reading. You should have the block square deck and then take your measurements. I have found some blocks have different reading from side to side and front to rear.

Gene

 

Good advice Gene I have found the same thing

 

Assuming the crankshaft, connecting rod, compression height, and deck height were machined to blueprint specs, .025" would be correct.

Norm

 

Just wanted to have a ballpark number to punch into my neighbors dyno software to work up SCR & DCR.
in retrospect, .25 - .35 really doesn't change it a whole lot. .45 + a .40 head gasket would be pretty big though, but there is wiggle room because i can deck the block, shave the heads or get fatter or thinner head gaskets. like i said, at this point, I just wanted the ball park.

(btw it came back at 9.4:1 SCR, and using XE268 specs to stand in for whatever cam I eventually pick, DCR came back at 7.7:1 So i'm pretty happy with those numbers for an iron headed motor.


Once the crank & Rods are back, and the block is bored & honed I will mock up piston height and get exact metrics before i decide if the block needs to be cut down or the heads shaved. But for planning purposes I think i'm headed the right way.

 

You need to add a zero to your numbers, its .025-.035 not .25-35 and so on.

Hate to throw a wrench in your plan but if you're going to do the machining process the right way you first align hone the block, then square deck it, then bore it by locating off the deck and main saddles as a reference, then hone it with a torque plate. It's very difficult to locate off of an unmachined deck accurately. After a mock up you may have to have it decked again or take a guess and live with the deck height you end up with then use the size head gasket you need to get your desired piston to head distance.
Just my .02.

Are your heads ported? Valve sizes? Intake?

 

sorry, meant .0x

I'm still learning the machining process. I know most of the terminology, but using it & undetstanding it are still a challenge.
I think you are spot on.. the block will be fully squared, bored, honed- then test assembled, then if additional is needed, it'll get taken apart again and the additional taken off.

I have a line on a set of Small valve C heads and a set of big valve E heads. Until I get them and strip to inspect i won't know for sure which i will run. If i run the C's they will likly be modified for the large valves.

Heads will get some basic port cleanup and the edelbrock crossover plugs inserted, but not much more than that. Intake will be a performer or performer RPM & will be port matched to the heads.

 

Then imo you need a different cam. Don't have to buy one from me, and I know I'll catch hell for it, but the Xtreme stuff, although more correct than the VooDoo stuff for your application, still isn't the right one in my opinion. Something a little slower with more exhaust side would be of more benefit. If you had well ported heads and/or lower compression I'd say go for the Comp Xtreme, but you don't. You need more off the seat time. Jmo.

 

No worries... still a long way from the cam decision. The XE series would not be my choice anyway, but i was using its numbers becuase i was trying to get my friends desktop dyno stuff configured for olds... i was using the car craft 455 build from last year as a baseline. The numbers came in pretty close to what they had reported. Did not mean i was planning to run that cam.

I actually do like the voodoo grinds and was considering the 60803 or 60804, but had not had time to enter them into the software to take a look at the curves.. plus a lot of other stuff inthe software is still wonky since it does not have any canned Olds stuff, it all has to be entered manually....

what are some other grinds you'd recommend?

Basically the goal for this motor is 98% street fun 2% track.
I would like to be able to run high to mid 12's (pending traction) & still have a early & flat torque curve for the street. Doable?

also, as far as porting the heads, i've got a lot of time on my hands before this motor will be together, so if i can get some good info on what do do(beyond just polishing) while porting i will try some additional work, its only time...
appreciate any input i can get.