Thread: Got the rotating assembly / Now what heads?

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Originally posted by erik erikson
I think it is 10.2 with a 64cc combustion chamber.

I LOOKED IT UP AGAIN 10.4:1 IN JEG'S W/64CC HEAD

Originally posted by camaro_fever68
I LOOKED IT UP AGAIN 10.4:1 IN JEG'S W/64CC HEAD

IN THE SPEED PRO CATALOG IT SAYS 10.2 WITH A 64CC HEAD.I STILL DON'T KNOW WHY WE BOTH CAME UP WITH THE SAME COMP. RATIO AND TECH'S WAS SO MUCH HIGHER?

Originally posted by erik erikson
IN THE SPEED PRO CATALOG IT SAYS 10.2 WITH A 64CC HEAD.I STILL DON'T KNOW WHY WE BOTH CAME UP WITH THE SAME COMP. RATIO AND TECH'S WAS SO MUCH HIGHER?

I think it has something to do with piston like it may not be a true flat top. may have some bowl to it

o.k., I can see you guys are gonna be hard-headed, so I'm moving on to other threads. I will say this.....BOTH OF YOU ARE WRONG AND ANYBODY ELSE WHO SAYS A 0.030" over 350 block with a 3.75" stroke, zero deck, 72 cc heads, 9 cc gasket (0.039" compressed) and pistons with 4 cc's of valve relief isn't 10.22:1 is WRONG.

A 383 with 64 cc chambers will yield 11.8:1. Use these calculators and see for yourself if you don't want to take the time to figure it out yourselves.

http://www.turbofast.com.au/Tfcomp.html
http://falconperformance.sundog.net/compcalculator.asp

Originally posted by techinspector1
o.k., I can see you guys are gonna be hard-headed, so I'm moving on to other threads. I will say this.....BOTH OF YOU ARE WRONG AND ANYBODY ELSE WHO SAYS A 0.030" over 350 block with a 3.75" stroke, 72 cc heads, 9 cc gasket (0.039" compressed) and pistons with 4 cc's of valve relief isn't 10.22:1 is WRONG.

A 383 with 64 cc chambers will yield 11.8:1. Use these calculators and see for yourself if you don't want to take the time to figure it out yourselves.

http://www.turbofast.com.au/Tfcomp.html
http://falconperformance.sundog.net/compcalculator.asp

I LOOKED AT SEVERAL PISTON CATALOGS AND THERE SEEMS TO BE SOME DIFFERENCE.A ROSS PISTON WITH 2-VALVE RELIEFS THIS SET -UP WOULD GIVE THE 10.22 TO 1 COMP RATIO.THE SPEED PRO BOOK SAYS AGOUT 9.5 TO 9.6.ARE THE VALVE RELIEFS LARGER AND DEEPER ON THE SPEED PRO PISTONS?MAYBE THIS WOULD ACCOUNT FOR SOME OF THE DIFFERENCE.

Originally posted by dcoffield
I didn't completely follow this. What does 9.0 deck height mean? 9cc? Do I want a 9 deck height?

Will my new 30 over pistons fit in the cylinders before machining?

Are you putting this together? If so let me tell you the process.

1. Take your block, pistons, and rods to the machine shop. Get the block cleaned and checked out. Have it bored for your pistons. Then if you have press fit rods, have them fit em to the rods.

2. You have a choice (1) You can bring the block back home and assemble it and mark where it has to be clearanced and when you do that measure your piston height in the bore. Then take it back apart and deck it and clearance it. Clearancing means makeing enough room for the bigger crank to swing.
(2) Your other choice is to let the machine shop do the measuring and clearancing of the block. They can either assemble it for you or just mock it up and do the machine work and let you come and get it and put it together at home.

Small block chevys have a 9.025 deck height. That is the distance from the crank centerline to the flat surface of the block.
Your pistons are exactly 0.025 below the surface of the deck. Zero deck height would mean getting rid of extra 0.025 so that your piston would reach the top of the bore.

WHEN YOU CALL UP A MACHINE SHOP YOU TELL THEM YOU NEED YOUR BLOCK CLEANED CHECKED BORED 0.030 AND TORQUE PLATE HONED, THEN YOU WANT IT DECKED PARELLEL TO THE MAINS TO 9.0. THAT'S ABOUT $325.00 I THINK THEY WILL CLEARANCE ALSO FOR ANOTHER $50 AND IF YOU HAVE PRESS FIT RODS I THINK THAT IS ABOUT $30 I DON'T KNOW WHAT THEY WOULD CHARGE TO DO ALL THE MACHING AND COMPLETLY ASSEMBLE IT FOR YOU. THEY CAN TORQUE IT ALL AND CHECK ALL YOUR CLEARANCES FOR YOU AND CHECK CAM CLEARANCE TO ROD FOR YOU ALSO.

ONE THING THAT IS OFTEN OVER LOOKED WHEN BUILDING A 383 IS THE OIL PAN.IF YOU USE YOUR STOCK 350 PAN MAKE SURE THE CRANK WEIGHT DOES NOT HIT THE PAN.THIS MIGHT HAPPEN ON THE PAN ON THE FRONT PART OF IT CLOSEST TO THE TIMING COVER.A QUICK FIX IS TO USE THE 400 OIL PAN OR BUY AN AFTERMARKET PAN.THE 400 OIL PAN HAS A LARGER (BUMP) TOWARDS THE FRONT OF THE PAN.

I couldn't find volume figures for the H860CP piston, guesstimated relief volume after looking at photo. I figure 7 cc's for a 4-relief piston, so a 2-relief piston oughta figure out around 4 cc's. http://www.racersauction.com/auction...fm?lotID=62885

Originally posted by techinspector1
o.k., I can see you guys are gonna be hard-headed, so I'm moving on to other threads. I will say this.....BOTH OF YOU ARE WRONG AND ANYBODY ELSE WHO SAYS A 0.030" over 350 block with a 3.75" stroke, zero deck, 72 cc heads, 9 cc gasket (0.039" compressed) and pistons with 4 cc's of valve relief isn't 10.22:1 is WRONG.

A 383 with 64 cc chambers will yield 11.8:1. Use these calculators and see for yourself if you don't want to take the time to figure it out yourselves.

http://www.turbofast.com.au/Tfcomp.html
http://falconperformance.sundog.net/compcalculator.asp

I WENT AND PLAYED WITH THE CALCULATOR AT CAMBELL ENTERPRISES.

4.030 BORE
3.750 STROKE
72CC HEAD
0.039 HEAD GASKET
0.000 DECK HEIGHT
-6cc VALVE RELIEF
8 CYLINDERS


EQUALS----10.1:1CR----382.67

BUILD TO THESE SPECS WITH THAT 270H CAMSHAFT.

Originally posted by camaro_fever68
I WENT AND PLAYED WITH THE CALCULATOR AT CAMBELL ENTERPRISES.

4.030 BORE
3.750 STROKE
72CC HEAD
0.039 HEAD GASKET
0.000 DECK HEIGHT
-6cc VALVE RELIEF
8 CYLINDERS


EQUALS----10.1:1CR----382.67

BUILD TO THESE SPECS WITH THAT 270H CAMSHAFT.

YES,BUT HE USED -4CC IN THE VALVE RELIEF VOLUME.

Originally posted by erik erikson
YES,BUT HE USED -4CC IN THE VALVE RELIEF VOLUME.

IF YOU GO TO A CALCULATOR AND USE -6CC AND 0.025 DECK HEIGHT IT COMES OUT TO 10.4:1 W/64cc THROW OUT THE DECK HEIGHT AND ADD IN THE 72cc CHAMBER AND IT COMES TO 10.1:1

Originally posted by camaro_fever68
IF YOU GO TO A CALCULATOR AND USE -6CC AND 0.025 DECK HEIGHT IT COMES OUT TO 10.4:1 W/64cc THROW OUT THE DECK HEIGHT AND ADD IN THE 72cc CHAMBER AND IT COMES TO 10.1:1

NOW I AM STARTING TO GET A HEADACHE.I SAY WE TAKE .005 OFF THE DECK AND CALL IT GOOD.JUST KIDDING.YOU BOTH ARE RIGHT.IT DEPENDS IF YOU ROUND UP OR DOWN ON THE NUMBERS.

Originally posted by erik erikson
YES,BUT HE USED -4CC IN THE VALVE RELIEF VOLUME.

4.030 BORE
3.750 STROKE
64cc HEAD
0.025 DECK
-4cc RELIEF
0.039 GASKET

EQUALS 10.63:1

4.030 BORE
3.750 STROKE
72cc HEAD
0.000 DECK
-4 RELIEF
0.039 GASKET

EQUAL 10.3:1

Originally posted by dcoffield
So, if I understand what you are saying (before the conversation got 'squishy' ):

I should get the rotating assembly, fit the crank and a piston to
be able to measure the height of the deck from the piston at TDC.

Should I do this after the block is machined and decked flat?
Then have the deck machined down to 0 when I have the measurement?

I THINK HE SAY F**K THIS HE'LL BUY A BOOK OR GO DROP IT OFF A ENGINE SHOP LOL

Originally posted by techinspector1
"I should get the rotating assembly, fit the crank and a piston to
be able to measure the height of the deck from the piston at TDC"

yes, use a piston/rod assy on each corner, cylinders 1,2,7 and 8, make sure you have the piston at TDC on each cylinder and measure with a depth mic from the block deck to the crown of the piston. The piston will want to rock on the wrist pin, so measure each piston right at the cylinder wall at the pin location, not toward the intake or exhaust side of the motor. Measure at two locations on each piston, at 3 O'clock and 9 O'clock as you stand at the side of the motor. A different reading on the same piston at 3 and 9 will indicate a bent rod.

"Should I do this after the block is machined and decked flat?
Then have the deck machined down to 0 when I have the measurement?"

Edit: The block has to be bored to fit the new pistons.

"Do I need to use the new pistons and crank to check the deck
height?"

yes

"Can this be done before taking the block in to be machined?"

Edit: You must have the 350 block bored at the machine shop in order for you to establish deck with the new pistons. Have it magnafluxed and bored, but not decked yet. Take the block home and check the deck, then if the decks are all out of whack or you want to deck the block to establish squish, disassemble it and take the block back to the machine shop and have them cut the decks to your specs. Or have the machine shop do the whole thing. I answered this incorrectly originally. CRS

I went back and edited my answers here. I must have been really tired when I first answered, cause the answers were wrong.