Dish Pistons + 64cc head = ??

[C20-67_N_MO]

Okay I am gathering parts for my Small Block Chevy 406 Build.

And came across a nice set of 4.155 (.30 over) pistion that are dished.

My question is what would the compression ratio be with 64cc heads? If too low I might need to sell them for flat tops.

Thanks for any help you could offer.

[swb85]

Depends how big the dish is.......

[Captainfab]

Yep, Need to know how many CC's in the dish.

Originally Posted by swb85

Depends how big the dish is.......

[Marv D]

I don't think your going to need to worry about too LOW.

If those pistons are a 22cc dish, and you have a stock 0.025" deck, the 64cc heads will net 9.3:1

Deck the block to 9.000 and you have 9.8:1

If those are a 11cc "D" dish as is typical in most aftermarket 400 pistons, you start at 10.3:1,, deck the block and it's up to 11:1, cut 0.020" off the heads to 'clean them up' and your up to 11.3,,, it get's out of hand REAL quick with the big bore.

Here's an example. The sbc in my Nova I run a 12cc dish custom JE piston. Had to to get compression DOWN to 13.2:1 (4" stroke, 4.165" bore, zero decked, 53cc chamber)

Don't depend on any 'advertised' or assumption. Get EVERY component measured so you know EXACTLY what your dealing with

[C20-67_N_MO]

Originally Posted by Marv D

I don't think your going to need to worry about too LOW.

If those pistons are a 22cc dish, and you have a stock 0.025" deck, the 64cc heads will net 9.3:1

Deck the block to 9.000 and you have 9.8:1

If those are a 11cc "D" dish as is typical in most aftermarket 400 pistons, you start at 10.3:1,, deck the block and it's up to 11:1, cut 0.020" off the heads to 'clean them up' and your up to 11.3,,, it get's out of hand REAL quick with the big bore.

Here's an example. The sbc in my Nova I run a 12cc dish custom JE piston. Had to to get compression DOWN to 13.2:1 (4" stroke, 4.165" bore, zero decked, 53cc chamber)

Don't depend on any 'advertised' or assumption. Get EVERY component measured so you know EXACTLY what your dealing with

So if I get one of those Turkey Basker that have the CC on the suckion markers on the clear plastic I could get an idea of how much CCs the pistons are correct?

From what I have been reading, I would need a camshaft that has higher than stock compression ratio to make the cam and timing work correctly.

Will be tearing down the engine this weekend and hoping it has not been rebuilt so the bore can be machined to .30 (4.155 for the pistons I have).

Great info so far guys! Keep em coming.

[Marv D]

Turkey baster will give you a 'very rough' Idea,, get some clear plexiglas, a jar of vasaline, and a cc dropper from any friend that has kids. Childrens medicines have a cc dropper that is quite accurate.
Drill a 3/8" hole in the plexiglass, seal it to the chamber / piston or whatever with a generous smear of vasaline, tip the item slightly and position the 3/8" hole the at the uphill most area,, fill and count, fill and count. You can get a VERY acurate volume that way.
You can have your machinist measure compression height and deck height to get the deck clearance, OR,, move the piston exactly 1" down the bore (using a dial indicator) and use your plexiglass to measure the volume the bore holds. subtract the volume of the bore x 1" and you have piston to deck volume, valve reliev volume, CH, everything all in one measurement.

Piston to deck volume
plus gasket bore volume
plus head chamber volume...
all of that PLUS swept volume (bore and stroke volume ,, pi x R ^2 x stroke), you have everything you need to calculate EXACT compression ratio.

Cam suggestion is a lot more than compression. But without compression you don't have a starting point. One you know your compression (or just post the measurements and plenty of people here that can calc it all for you)
and tell us all the details,, trans, convertor, rear tire, use (race, street, towing ????) THEN you can get a rational cam suggestion. Untill then,, it's just a shot in the dark and a guess.

[dave brode]

You can buy a decent syinge cheap from any farm store [used for animals]. Good enough for the hobby guy imo. I paid $5 for a 60cc version.

Dave

[C20-67_N_MO]

Originally Posted by dave brode

You can buy a decent syinge cheap from any farm store [used for animals]. Good enough for the hobby guy imo. I paid $5 for a 60cc version.

Dave

Hey! Good idea.

Will have to check into that at my local farm store.