V-8 Cylinder Head Chamber Volume Question

[t1003nl]

I'm rebuilding a '64 259 V-8 that has 1557570 cylinder head castings. I've read several posts on the forum regarding chamber volume and I expected these to be around 54-55cc's. I cc'd all 8 chambers and got between 59.6 - 60.8 cc's. These numbers seem high to me and I want to see if anyone has measured 570 heads and found chambers this big. I'm using a 100 ml graduated burette with a 1/4" thick clear plastic plate. I seal the plate to the head with thin grease. I'm not detecting any leakage past the valves or spark plug. The valves and seats have been cut and the springs had to be shimmed 0.015" so some of the volume may be from valve recession. I will probably have the heads cut to make up part of the volume but I want to make sure the numbers I'm measuring seem reasonable. I haven't reshaped the combustion chamber, only deburred the edges. Any suggestions on how much to cut the deck are appreciated.

Neil

[studebaker-R2-4-me]

Good Question.

http://www.studebaker-info.org/Headcasting.html

Allen

[Chicken Hawk]

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

I'm rebuilding a '64 259 V-8 that has 1557570 cylinder head castings. I've read several posts on the forum regarding chamber volume and I expected these to be around 54-55cc's. I cc'd all 8 chambers and got between 59.6 - 60.8 cc's. These numbers seem high to me and I want to see if anyone has measured 570 heads and found chambers this big. I'm using a 100 ml graduated burette with a 1/4" thick clear plastic plate. I seal the plate to the head with thin grease. I'm not detecting any leakage past the valves or spark plug. The valves and seats have been cut and the springs had to be shimmed 0.015" so some of the volume may be from valve recession. I will probably have the heads cut to make up part of the volume but I want to make sure the numbers I'm measuring seem reasonable. I haven't reshaped the combustion chamber, only deburred the edges. Any suggestions on how much to cut the deck are appreciated.

Neil

[DEEPNHOCK]

In addition to what Ted said, Jack Vines has also done some of this work...
One thread about it is over on Sonny's Racing Studebakers site at:

http://www.racingstudebakers.com/foo/viewtopic.php?f=1&t=2148&p=23034&hilit=CC+heads#p23034

[t1003nl]

Thanks for the feedback.

I should have mentioned in my original post that I am converting this to a 289 displacement. I bought a used 289 crank and had it ground 0.010"/0.010" u/s and balanced. I had the block bored 0.030" o/s and have a set of 1/2 dish 289 pistons. I'm also using the thin shim steel head gaskets. I had estimated the gasket volume at 3.6cc based on a measured 0.020" compressed thickness but will update that to 3.5cc based on Ted's comment.

I measured the deck to valve cover height per Ted's comment and got between 3.558" - 3.562" (caliper measurement) so I'm inclined to believe that these heads have not been cut in the past.

A 0.040" deck cut makes sense so I'm going to send the heads out and have that done. I will recheck the chamber volumes when they come back and will update this post.

Should I have any concern about push rod length, piston to valve clearance or valve train geometry with a 0.040" cut? I'm running a stock 259/289 cam, stock rocker arms, stock valve sizes... With the valves recessed 0.015" will I have enough adjustment in the rockers to allow me to use the stock push rods?

Thanks again everyone for the help. It's nice to be able to bounce numbers off people who have experience with these things.

[Mike Van Veghten]

At .040" cut off of the deck, you'll be close to screwing with the rocker geometry. On one hand...many have done it...on the other hand, if it throws the rocker geometry off too much, you will loose some lift.
Personally...I'd check it.

The cubic inch (longer stroke) will not screw up the static compression, but it will raise the dynamic compression ratio. The larger bore will lower the static ratio. It "may" end up being a wash as for changing the dynamic ratio...which is what does the work for you.

Now...a thought.
You are going to all of this work...and you've said nothing about any port work. Some clean up right around and below (inside) the valve seat.
I'd also most definatly (even with a slight loss in ststic compression..), at least lay the wall (top of the heart) adjcent to the valves back a little. I normally use a 45 degree angle. In your case, I'd at least go to a 30 or so degree angle and put a large radius on the corner that's left.
It's worth low/mid lift flow in the air flow bench. Low and mid lift are more inportant than high lift flow in case of the low lift Stude cams.....

A couple of us have spent a lot of time on the flow bench with Stude heads...the above is well worth are well worth the effort.

Mike

[t1003nl]

Mike,

Thanks for the input. It helps to know what others have tried that works.

I could reduce the deck cut to 0.030". I don't want to cause a valve train issue trying to squeeze a bit more C.R.

I've done some cleanup in the bowl area under the valve seats, especially where the head bolt boss comes through. Just some smoothing and blending while removing some of the boss. I'm surprised at how rough Studebaker's castings are. I tried to keep the port geometry stock except for port matching and cleaning up the rough cast surface. I don't have a flow bench and it would be easy for me to do more harm than good.

I've got copies of the posts showing the wall around the valves laid back. Any idea how much chamber volume I would add doing the full 45 degree modification? I would be doing this by hand (very slow) and would probably just remove a portion of the walls.

My goal is to go after the tried and proven ideas. I appreciate all the help and input.

[Mike Van Veghten]

Neil -

Go here to get some idea what I do. The "Stude cylinder head porting" folder. Double click to enlarge pictures.

http://public.fotki.com/-Mike-/

No, it's been a "long time" since I measured the finished volume. I don't recall the numbers. But what I did was to zero deck the block and use flat top pistons to help keep the compression up.
But like I said, cut the "heart" wall back to about a 30 degree angle. This should give the best compromise on flow vs. compression loss. This is a major blockage to fuel/air comming into the cylinder.

As for the rest of the port...two things that will make the biggest difference for the least work....using the shim intake gasket as a guide -
1. Straighten the wall nearest the pushrod. That is, scribe the location of the gasket on the gasket surface and grind this wall so it's 90 degrees to the gasket surface, then put a large radius around the back of the pushrod area.
Note - stay about .030" clear of a full cleanup on straightening this wall. That is, make a template with a 90 degree angle cut into it. Use it as a guide to tell you where you are. Keep the template about .030" from the scribe mark you made to help keep the wall thick.

2. Remove the strange casting marks from the port. Espicially the roof (top) of the port. The roof should be nice and smooth...NOT...polished.

Both these things are easy to do and will help the entire rpm range.

Mike

[Rosstude]

This is the kind stuff I love about this forum. I really enjoy "listening" into these conversations, and knowing it’s here for future reference if I ever needed it.
Thanks guys.

[t1003nl]

I dropped the heads off at the machine shop today. I will recheck the volume with the stock chamber and will then lay back the wall around the valves. Mike's comments about laying the wall back make sense for low to mid lift flow. Taking a close look at a stock chamber with the valve at low lift the air flow around half of the valve has to squeeze between the valve margin and the chamber wall. I will probably make some paper templates to help me mark the radius and the 30 deg slope. I'll be doing this by hand so it may take a while before I can report the final chamber volumes.

I should have cc'd the chambers before ordering my pistons. I agree that flat top pistons would have been a better choice here to make up some volume due to the larger chambers and to allow some stock removal in the chamber to deshroud the valves. Hopefully I will still be between 8.5 and 9.0:1 CR when done.

I'll send out an update when I get the heads back.

[PackardV8]

You might want to hold off cutting the head surface until you look at your piston height. When you get your pistons, mock up the short block and verify the piston-to-block-deck height. I always like to get my pistons to within .040"-.050" of the cylinder head. This gives the best quench/squish. Good squish allows more compression without ping. Machining the block deck also gives a much greater increase in compression than does removing the same amount from the cylinder head. Get an old head gasket of the type you will be using, lay it on the block, put a piston at TDC and with a depth micrometer, check the total deck height and cut the block to get within the range.

jack vines

[Mike Van Veghten]

Neil -

If you are doing the whole engine, reread what Jack said, and what I mentioned earlier, cut the deck of the block from +.005" to +.010" of the piston tops. Unless your shop is good...I normally go to +.002"/.003".
Actually, per Jacks note...if you are using the thick composition gasket...you can actially have the piston "out" of the block .005" or so to both raise the compression AND to limit the quench area.

Note: A large quench area, will do several things...all bad...!
1. It will contain mostly unburnt gas...bad
2. It will promote detionation (pinging)...bad.
3. It will raise the "NOx" (oxides of nitrogen) comming out of the tail pipe...bad.

Mike

[t1003nl]

Jack + Mike,

The block's decks have already been cut. With #1 piston at TDC the top of the piston is below deck by 0.017". I'm using the thin shim head gaskets and my used ones measure 0.020" compressed. That should put the top of my pistons below the cylinder head deck by 0.037".

[PackardV8]

That should put the top of my pistons below the cylinder head deck by 0.037".

Perfect

jack vines

[t1003nl]

I got the heads back from the machine shop. I had 0.020" cut off the deck to reduce the chamber volume a bit. I cc'd the combustion chambers after the deck cut and they were 4cc's smaller on average. I need to measure the deck to valve cover distance to see how close the shop was to a 0.020" cut. Then I laid back the heart wall around the valves. I've tried to attach before and after photos below. I was pleased with how they came out considering I did them by hand and I'm a rookie at this. I cc'd all chambers after this modification and the chambers got bigger by around 1.2cc's on average. My finished chambers came out around 57.7cc. I cc'd a piston in a bore at TDC and calculated a compression ratio of 8.82:1 for this build. I'm happy with that.

I had previously cleaned up the ports to remove lumps and bumps plus a l opened up the bowl areas under the valve seats. It's surprising how much the wall between the intake and exhaust valves sticks into the bowl area blocking air flow. I removed some of this. Any idea how much of this wall can safely be removed? Is there a water passage between the valves?

I'm looking forward to seeing how this engine responds to these changes. Thanks everyone for the help and advise.