Is this a flat top, dish or a dome?

 

Dished, I was thinking you could find tdc clamp a piece of plexiglass on the deck with a hole drilled in it use a heavy oil in a measured ml container and fill keeping track on how much was used... just a thought

 

Try this. You need a jar that is graduated in cc's, some liquid such as alcohol and clay or play-dough. Take theclayand smash it into the dish. Make sure it is filling in all the gaps. Then take a razor and trim the excess so you are left with a flat piston after the clay is in place. Fill the jar to about half. making sure it is even with a number or line. Now, take that clay out (you can ball it up at this point to make it easier to handle) and drop it gently into the liquid. The gain in liquid height is the amount of cc's in the piston dish.

We have found that this is easier than trying to keep liquid running past the rings, etc. It is a lot less messy too.

 

Great idea!! We have alot of graduated glassware at the lab at work I am going to give it a try on monday myself..

 

If it's a stock type dish with 2 small valve reliefs cut into them, then they may be -16cc dish pistons which is what I am running in my 400. With the vortec heads and the fact that you have decked the block, I think your comprssion is going to be higher than you think. Go to campbellenterprises.com, they have math calculator for figuring it out. Just fill int the necessary numbers and it will calculate your numbers. My engine with a -16cc piston, .025" in the hole deck, .038", head gasket and a 62cc head figures out to 9:95:1compression.

 

Something to look at when calculating compression also is some of the pistons dont achieve the .025 deck height I have one now with the replacement dish pistons that is more like .040 (measuring from the highest point)I think they put the pin locationhigher for some reason.

 

this may also be due to the rod center to center being off a little. when they sized the rod they may have ground more of the rod end than the cap and or taken more metal out of the rod end of the hole.or if only one rod was resized. Also if the crank grinder got off just a little on the stroke on one journal it could also throw it off, but ususally that shows up in the two cylinders that share the journal.

either way the compression ratio won't be drastically effected.
G

 

It only works out to .3 on compression, the crank hasnt been turned but the rods were resized, Ive heard that some of the 4 valve relief dish pistons had the pin set for .020 in the hole my concern was that I was trying to maintain the quench distance of .045 to .030 it will not happen unless I deck the block. Really though I wonder if the quench distance really has a bearing on dished pistons anyhow?

 

finally found me a set of vortec heads. taking them to a machine shop today. my question is how much to mill to get more compression. if stock combustion chambers are 64cc and i would like it to be around 60cc. can this even be done with these heads. i know they can answer this there at the machine shop i just like to not sound to silly when talking to them. im told that there are after market retainers available to gain more clearance between valve guide seal and bottom of retainer. thanks 359 PETE

 

I would find a way of measuring the cylinder volume you have now before I would look at increasing the compression you would gain around .5 in compression losing .04 cc of head volume. With 0 deck you could be over 10.5:1 with a 64cc head depending on cam choice you could be approaching the race gas range real quick. For the retainers I would look at having the machine shop cut down the guides you might not need to increase the spring pockets depending on cam choice. The aftermarket retainers either operate with beehive springs$$ or are raised making them heavyer the cost is probably a wash and the machining is the better way to go. We only needed .010 clearance for the cam we have so we ground down the bottom of the retainers if we were really serious about an engine I wouldnt do that. We have our vortec headed budget engine in the car and need to get the wireing and everything else done and then we will see what happens [8D]<center>
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