Thread: Got the rotating assembly / Now what heads?

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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. This measurement will allow me to compute the actual compression.

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?

No, you can use deck height for that computation, with a 0 deck height your pistons are 10:4 with a 64cc head. You would only need to calculate if you didn't know your piston part number or they didn't have it listed in their chart. Dart does make that head in 72cc I'll calculate that for you post it in a bit.

"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

Originally posted by camaro_fever68
No, you can use deck height for that computation, with a 0 deck height your pistons are 10:4 with a 64cc head. You would only need to calculate if you didn't know your piston part number or they didn't have it listed in their chart. Dart does make that head in 72cc I'll calculate that for you post it in a bit.

A good estimate would be around 9.5 to 1.

Originally posted by dcoffield
Do I need to use the new pistons and crank to check the deck
height?

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

OK, I CHECKED YOUR COMPRESSION HEIGHT AGAIST A STANDARD DECK HEIGHT. YOU CAN FIT FIRST TO MAKE SURE BUT YOU NEED A 9.0 DECK HEIGHT YOUR PISTONS ARE 0.025 DOWN THE BORE. AND I CALCULATED COMPRESSION WITH THE DART 72CC HEADS TO BE 9.58 AND SOME CHANGE

Originally posted by erik erikson
He never say's anything about (the squish).I think you might of read to much into it.

YOUR RIGHT BUT WHY WOULD I CONFUSE A FIRST TIME BUILDER WITH QUENCH WHEN I TOLD HIM HOW TO DO INSTEAD AND TOLD HIM WHAT IT DOES READ THE ARTICLE

Originally posted by camaro_fever68
OK, I CHECKED YOUR COMPRESSION HEIGHT AGAIST A STANDARD DECK HEIGHT. YOU CAN FIT FIRST TO MAKE SURE BUT YOU NEED A 9.0 DECK HEIGHT YOUR PISTONS ARE 0.025 DOWN THE BORE. AND I CALCULATED COMPRESSION WITH THE DART 72CC HEADS TO BE 9.58 AND SOME CHANGE

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?

Originally posted by camaro_fever68
YOUR RIGHT BUT WHY WOULD I CONFUSE A FIRST TIME BUILDER WITH QUENCH WHEN I TOLD HIM HOW TO DO INSTEAD AND TOLD HIM WHAT IT DOES READ THE ARTICLE

I think you are right on this one.Maybe all the terms are confusing to a first time builder.How did you know he was a first time builder?

o.k., here's how I see the static c.r. of the combination.
cylinder cc's 784...(.7854 x 4.03 x 4.03 x 3.75 x 16.387)
chamber cc's 72
gasket cc's...about 9
piston valve relief cc's....about 4

Add all of 'em up and you get 869 cc's. Divide that by the compressed cc's (chamber, gasket and reliefs) and you get 10.22:1.

Now there are a couple of questions.
1. can you run 10.22:1 on pump gas with iron heads? Yes, with a good tight squish.
2. Will you be able to tolerate the long cam that will be required at this level of compression? (low vacuum, little bottom end power)

With a 2,500-2,800 stall converter, this is the type of cam you'd want to run. Maybe not this specific cam, but a cam with numbers close to these.
http://www.cranecams.com/?show=brows...tType=camshaft

Originally posted by erik erikson
I think you are right on this one.Maybe all the terms are confusing to a first time builder.How did you know he was a first time builder?I guess the post before this one answers the question.

[QUOTE]Originally posted by erik erikson

Originally posted by camaro_fever68
Boy, Boy, Boy, Had me fooled, making enough HP to bust 400 blocks, giving advice on everything etc.. and then giving me heat about my Big E huffer. Thought you knew what was up!!!

BUT THEN YOU COME IN HERE AND SAY THERE IS NO ADVANTAGES T0 A ZERO DECK HEIGHT ENGINE ON THE STREET. WOW.....

IT IS A GOOD IDEA TO ZERO DECK ANY PERFORMANCE ENGINE BECAUSE IT MAXIMIZES A GOOD QUENCH AREA TO PUSH THE AIR FUEL MIXTURE INTO THE CHAMBER, CREATING DRAMATIC MIXTURE MOVEMENT THAT CREATES A MUCH BETTER AIR FUEL MIXTURE IN THE SPACE OF THE CHAMBER ABOVE THE PISTON, AND TO TOP THAT OFF, A BETTER MIX OF AIR FUEL IN THE COMBUSTION CHAMBER CREATES AND ENGINE THAT IS LESS SUSCEPTIBLE TO DETONATION. THE SAFEST PISTON TO HEAD CLEARANCE FOR OPTIMAL QUENCH AREA IS .037-.039. MY SUGGESTION TO THIS FACT IS THAT UNLESS YOU HAVE EXTREMELY TIGHT TOLERANCES GO WITH THE 0 DECK AND FELPRO PERFORMANCE HEAD GASKET WITH A COMPRESSED HEIGHT OF .039


ERIK, DO YOUR HOMEWORK AND INVESTIGATE THE MATTER BEFORE YOU COME BACK ON ME AND HAVE A PROVABLE THEORY WHY I AM WRONG. ALL I HAVE JUST SAID HAS COME TRUE ON DYNO AND EVERYDAY DRIVING. [/QUOTE WHY DON'T YOU GO BACK AND READ MY QUOTE.I NEVER SAID THERE WAS NO ADVANTAGE TO A ZERO DECK HEIGHT ENGINE.YOU CAN CHANGE HEAD GASKET'S OR COMBUSTION CHAMBER SIZES.WHY DECK A BLOCK WHEN THERE ARE OTHER WAYS TO OBTAIN THIS.PLEASE READ MY POSTS AND TRY AND QUOTE ME A LITTLE MORE CLOSELY.

I READ YOUR QUOTE, YOU HAD NO IDEA WHAT WAS BEHIND THE CONCEPT CR WAS NO WHERE ON MY AGENDA, THE REASON I DON'T LIKE TO DO WITH GASKETS AND SHIMS IS BECAUSE THE CYLINDER WALL RUN INTERFERANCE WITH SWIRL ITS MORE EFFECTIVE IN MY EXPERIECE AND YOU DON'T SET QUENCH WITH COMBUSTION CHAMBER SIZE.

Originally posted by techinspector1
o.k., here's how I see the static c.r. of the combination.
cylinder cc's 784...(.7854 x 4.03 x 4.03 x 3.75 x 16.387)
chamber cc's 72
gasket cc's...about 9
piston valve relief cc's....about 4

Add all of 'em up and you get 869 cc's. Divide that by the compressed cc's (chamber, gasket and reliefs) and you get 10.22:1.

Now there are a couple of questions.
1. can you run 10.22:1 on pump gas with iron heads? Yes, with a good tight squish.
2. Will you be able to tolerate the long cam that will be required at this level of compression? (low vacuum, little bottom end power)

I DON'T ALWAYS AGREE WITH CAMARO FEVER 68 BUT WHY IS IT WE BOTH CAME UP WITH ABOUT 9.5 TO 1?I ROUNDED MINE DOWN TO MAKE IT EASIER.

Originally posted by techinspector1
o.k., here's how I see the static c.r. of the combination.
cylinder cc's 784...(.7854 x 4.03 x 4.03 x 3.75 x 16.387)
chamber cc's 72
gasket cc's...about 9
piston valve relief cc's....about 4

Add all of 'em up and you get 869 cc's. Divide that by the compressed cc's (chamber, gasket and reliefs) and you get 10.22:1.

Now there are a couple of questions.
1. can you run 10.22:1 on pump gas with iron heads? Yes, with a good tight squish.
2. Will you be able to tolerate the long cam that will be required at this level of compression? (low vacuum, little bottom end power)

TECH,
something's nt right that piston part no. says 10.4:1 w/64cc head and 5.7 rod

well, I don't know how you guys are figuring c.r., but I'll offer up a paper I wrote based on 50 years of experience....
http://streetmachinesoftablerock.com...opic.php?t=124

Originally posted by camaro_fever68
TECH,
something's nt right that piston part no. says 10.4:1 w/64cc head and 5.7 rod

I think it is 10.2 with a 64cc combustion chamber.

Federal Mogul has a c r calculator at

http://www.21cgt.com/FMWebCatalog/frmConversion4.aspx