whats the stock, uncut height of a cyl. head as measured from the deck to where the valve cover bolts to?i just wanna know so i can measure and make sure my machinist cuts the correct amout off.about 0.090 should give me about 9-9.5 compression right?

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1975 Plymouth Duster,225/6 2bbl. and duels, 904, 7 1/4
1986 Dodge Charger Shelby, 2.2 Turbo I, A525

Not necassarily, Measure the chamber CC, the deck hight, and gasket thickness and go from there. Can't stress it enough. MEASURE, MEASURE, MEASURE.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Yep, what Charlie said. Production tolerances varied way too much for their to be a standard measurement.

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Official Cookie and Mater Tormentor.

so how can i tell if the head has or has not already been machined?

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1975 Plymouth Duster,225/6 2bbl. and duels, 904, 7 1/4
1986 Dodge Charger Shelby, 2.2 Turbo I, A525

Like I said before, MEASURE the CC's.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

You really can't by just looking, what Charlie is referring to is measuring the size of the combustion chamber to see it's size and tell if it's "small" (then it may have been machined), or untouched (or really big due to bad tolerances at the foundry/etc...)...With this number you can plug it into a formula or program to compute your final compression ratio and tell your machinist how much needs to come off...(make sure to include the head gasket in the calc)

A quick and dirty chamber volume measuring proceedure on a used head:

Need a 7"x7" peice of lexan or plexiglass or clear plastic
Go to a farm veteranarian office and ask for a Horse Catherter (about 60CC is a good size)

With the head chambers facing the ceiling, the milled surface should be 'level' on your work bench. (make sure it can't fall over or tilt)

I pick a couple of chambers to measure (something like 2,3 and 6) so I can get an "average".

Clean the carbon out of the chamber as best as possible (or have it hot tanked, previous to procedure)

I smear a little swipe of grease around the edge of the closed valve heads in case I have one that has gone bad and isn't seated tight anymore (makes a nice slow leak).

Take plexi glas and drill two 1/4" hole in it somewhere near the center a couple inches apart.

smear a thin continuous film of grease around the chamber to be measured (the flat machined surface).

Push the plexiglass on making sure the grease has sealed all around the chamber.

Get a cup of water put a little of your mom's food coloring in it so it's not clear.

Fill the Horse syringe up to max size with the water and make sure there's no air in it... stick nose of syringe into one of the holes and...

Fill the chamber slowly...as you get to the top of the plastic slowly drip water in until it gets to the edge of the fill hole and stop....(if you overfill, pull plastic drain...do it again and pay closer attention).

Note the amount of water left in the syringe/catheter (say 7cc...)

So you take max size minus the remains....(say 60cc - 7cc....so that chamber is 53cc...)


If your 3 chambers come out to be 52-58 cc's it's probably original, there are a few out there especially the early heads that are bigger (up to 68cc)...if closer to 50cc and under it's been cut already, so you can do some calculator figuring and see if it's still useable in your rebuild plans...




good luck,

-D.Idiot

We need a tech article doing a step by step on this one...

Thanks Duster, for the explaination on how to CC the heads. Very well written.

To follow that up, here is a link to a good article on calculating compression ratio based on your head measurements plus a little more...


http://www.imperialclub.com/Repair/Engi ... ession.htm

-Mac

Just to answer your original question, I measured 3 most likely uncut heads. They were between 3.610 and 3.620 inches. I also measured a cut head, that has a NHRA legal stock CC's and it was 3.560. Don't remember the CC's without looking it up. Also don't forget, the factory used a "shim" gasket at about .022 thick, and most replacement gaskets are about .040 thick, so that makes a difference, also.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Thanks again for making this post D.I and Charlie I am going to copy and print these directions and will be using them soon! ( Hopefully )