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64studeavanti
07-12-2014, 08:51 PM
This started on another thread about piston clearance and kind of grew from there. While trying to fit .060 pistons, the discussion turned to maintaining a decent squish for proper quench. Well, to my surprise, when I measured the combustion chamber on my heads, I get 59cc! this is very confusing as I thought the specified size is 54.5cc. I measured 3 times on each head thinking I was doing something wrong, but always the same result. Can anyone shed any light on this?

PackardV8
07-12-2014, 09:40 PM
1. Post a photo of the combustion chamber. I've seen many modified heads. If yours is 59cc, something is going on.

2. On the other hand, the difference between 54.5 and 59 is only an 8.25% increase and quite a bit less than that % of the total deck, gasket and chamber volume. For comparison, the 13.7cc difference between the R1 and R2 heads is a 25% larger chamber and drops the compression 1.25 C.R. points

3. Measure the height of the head from the gasket surface to the rocker cover rail. Let's start with first principles.

jack vines

64studeavanti
07-12-2014, 09:50 PM
This is a picture of the 2 heads I have. The one on the left is "stock", the one on the right is ported, polished with R3 intake and exhaust valves. I do have another set of R1 heads I can check. I measure the head height in the morning.

Mike Van Veghten
07-12-2014, 10:31 PM
Two things...one from the picture one from your comment.

1. Picture - It "appears" that you are using a "J" series spark plug, (or they are a coupla turns from tight...) .
Either use "H" series plugs or have your heads machined for the "J" series spark plugs for the best combustion action.

2. Comment - Just to clarify, the quench distance doesn't depend on the chamber size what so-ever. Unless you remove a LOT from the deck to get rid of some of that dumb angle Stude engineers designed into the heads.
In some cases (other brand, modern heads) depending on the chamber side wall shape, machining the deck can expose a little more "ledge" to the overhang, increasing the quench "area".
Increasing or decreasing the quench distance comes from the distance of the heads "overhang" into the bore, by the gasket thickness and the amount the piston is down in the bore from the block deck surface.

Gasket thickness + piston deck distance down in the bore from the block deck = quench distance.

Mike

64studeavanti
07-12-2014, 10:56 PM
Using J plugs. IMHO, there is no difference in the machining for either plug. I base this on the fact that Studebaker had the exact same part number for both. Additionally, The head on the left is from an Avanti and the one on the right is from a regular 1963 289. Of course, over the years, Avanti heads could have been swapped for regular heads and vice versa and my assumptions based upon the part number may be all wet. However, I would be curious as to how the parts department was able to handle different machining with the same part number.

I'm not looking for the size of the combustion chamber for squish, but I am trying to find a combustion chamber that will allow me to maintain a decent squish as well as a livable compression ratio. In the morning, I will measure each head again just to ensure that there is no problem in my technique. I has been almost 50 years since I have cc'd a head - I am a little rusty. While I am at it, I do have another set of Avanti heads I will measure just to check myself. I will also measure the height of the heads as I have no idea how much has been shaved off any of these heads.

64studeavanti
07-13-2014, 10:35 AM
Ok, I measured the third set of heads, this one from a 1963 Avanti and I still get just under 59cc. Whatever I am doing wrong, at least I am consistent. For kicks and grins, I measured the cups in the valves and the recess in the spark plug hole, and got approx 4cc. So it looks like most of the discrepancy could be accounted for. Throw in a little valve seat recession and some measuring error, and I think I have got it. Unless anyone has anything different, that is the size of combustion chamber I will use in my compression calculations. This does beg the question as to how Studebaker arrived at a 10.25 compression ratio. In order to get the same, I used a 58cc combustion chamber, a .015 head gasket and a .020 piston deck clearance in the compression ratio calculator.

BTW, the spark plug is recessed about the same as in the other two heads.

64studeavanti
07-13-2014, 01:37 PM
I found this comment below on an old forum thread. So if the piston deck clearance on an 'R' engine is .019 and the gasket is .017, the combustion chamber must be around 58cc in order to get the 10.25 compression ratio.

Chicken Hawk
12-12-2011, 11:26 PM
Specs I have for the 259 deck is.082"; the standard 289 .031"; the R 1 and R 2 .019". R 3 .011" to +/- .023". NHRA lists the R3 as .017" (which is right in the middle of the .011" and .023"), and for the R 4 +.227" which would be the dome on the piston.

Get this: The deck on the 232 engine is .109" and they don't run too bad for what they are. I'm guessing on this but I think the 259 deck of .082" is so the 259 and 289 will have the same compression with the same heads used on either.

Ted

11SecAvanti
07-13-2014, 02:43 PM
Are you using a class A burette?

Mike Van Veghten
07-13-2014, 03:03 PM
64studeavanti wrote -
Using J plugs. IMHO, there is no difference in the machining for either plug.

It's NOT opinion here...! It's simple fact. The spark plug gasket seat IS....machined different for the "J" series plug...period.

This is getting funny...!

Mike

64studeavanti
07-13-2014, 03:54 PM
Not sure what a class A burette is. The one I am using is from Comp Cams. http://www.summitracing.com/parts/cca-4974/overview/

PlainBrownR2
07-13-2014, 06:09 PM
I have a feeling not many people here may know what a Class A burette is, even I had to look that one up. I know what a burette is, but never heard it called by its formal name. :cool:

http://www.sigmaaldrich.com/catalog/product/aldrich/cls2103100?lang=en&region=US

Anyway, that's a Class A burette. These guys would usually carry something like that, which is basically the same glassware as Comp Cams carries. :cool:

On a separate note, I always wondered myself on why heads that looked the same, used two different versions of the spark plugs between the regular and Avanti and JTS engines, now I know! :D

Chicken Hawk
07-13-2014, 08:10 PM
This can be a little confusing when it is said the R engines use one plug and non R's use another when some trucks used the same heads as the R 2 (1557582) and then some '63 standard cars used the same heads as the R 1 (1557570).

Ted

64studeavanti
07-14-2014, 06:16 AM
Mike, Ted, anyone, how do I tell? As I said, I have 2 sets of "R" heads and one set of "P" heads. The "P" heads are the ones that have been ported and polished with the larger valves. In all six heads, the "J" spark plugs seem to be recessed about the same with the "P" heads marginally less (I assume due to the polishing). If I wind up using the "P" heads, should I use "H" plugs?

rkapteyn
07-14-2014, 11:26 AM
The "H" plugs are a little longer and the heads have no exposed thread to glow and cause
preignition.
The later H14Y plug is not as rugged as the originals and were actually some other plug
that was stamped H14Y. they are dinky compared to the originals.
The H10 was used earlier and on most trucks and the electrodes did not extend into the head as much as the H14Y.

Robert Kapteyn

64studeavanti
07-15-2014, 08:59 AM
Ok, found a previous post on the chamber size. It appears that my measurements are not far off. I am a happy camper!

http://forum.studebakerdriversclub.com/archive/index.php?t-47355.html


Chicken Hawk

12-28-2010, 08:10 PM

The 570 heads I have cc'd come out to about 58 if valves have not been ground or the heads milled. For every .010" you mill the heads you will lose about 1.5 cc's. To tell if your heads have been milled, measure the thickness of the head from the machined surface that sets on the block to the machined surface where the valve cover gasket sets. Stock thickness is 3.563".

Since your heads average about 60 cc's if you mill them about .013" that would put them at about 58 cc's and with a beaded steel gasket would give you about 8.0 compression. If you mill them .040" to get them to about 54 cc's this would put your compression at about 8.5.

The 259 piston deck is about .082" and the beaded steel gasket is about 3.5 cc's. Double check me and if my figures are wrong, let me know. I make a lot more mistakes than I used to.

Ted

Mike Van Veghten
07-15-2014, 11:01 AM
64stude -

Assuming (?) that your heads are not on a block...just install a spark plug. At this point, either will do.
1. If you install an "H" series plug, and no threads protrude into the chamber, you need the "H" series spark plug.
2. If you install an "H" series plug, and it protrudes by about 2-1/2 threads, you need the "J" series plug.
3. If you install a "J" series plug, and it does NOT fully engauge all of the threads in the head, you need the "H" serise spark plug.

Hope that helps

Mike

P.s. - Like Ted says, just because a set of 570 heads are on an "R" series engine...does not mean that the heads were on that engine as it came from the factory. A LOT of years have past since these engines were built. Many have been rebuilt in some form or another.