NOS 308 Head thickness and chamber CC measurments

Kdancy

Ok, I've always read and been told that new stepdown heads were 2.00" thick. I've measured a few dozen and some of them were low mileage and had never been off the motor. Here is an NOS 308 head that Don Crane sent me. I carefully cleaned the light surface rust off and mic'ed the head at several points.
I still have not measured a full 2" on a Hudson head.

bob ward

Ignoring for the moment what the thickness of the head should be, you would imagine that the top and bottom surfaces would be machined parallel, but that isn't the case looking at those caliper readings.

Glowplug

Bob did you see the post on the linkage end availablity?

Kdancy

Bob, that is another thing, I've never measured the same readings all across any stock head I've mic'ed.

RL Chilton

Agreed.  I have not seen a head that was of a uniform thickness, either.  Nor do I believe they were cast with that intention.  

Kdancy

Ken, I've done the same thing with cc'ing the combustion chambers. A lot of work for a stock engine where you would never see it, but a must for a performance engine where you are trying to get the last ounce of performance for that quarter mile or whatever kind of racing.

But you do bring up something with that, I'll check the cc's on this one to see how much variance there is.  

Kdancy

Ok, just CC'd three chambers on the NOS 308
110.5 CC for that one. (NOS head mic'ed at 1.975)
Then CC'd one on a newly surfaced 262
 94 CC for it.  Head mic'ed at 1.941

Per

Kerry,

     What is your procedure for cc'ing a combustion chamber?

                    Per

Kdancy

I use clay to fill the spark plug hole even with the combustion chamber. Use a light coat of grease around the chamber to seal the flat plexiglass pressed on the head surface and covering the combustion chamber. I have a 1/4 hole drilled into the plexiglass where I insert the pyrex tube (burette) with millimeter markings. Fill tube with food colored water then let flow into the chamber thru the 1/4 hole in plexiglass until chamber is full with colored water and no air bubbles. Read descending graduated markings on tube to determine how many millimeters/CC's were used.
http://www.merkurxr4ti.com/chambervolume.html
http://www.nmradigital.com/2012/07/31/ccing-combustion-chamber/

Kdancy

Thought I'd put all info in one post for easier look.

Hudson head  CC volumn

1-     
1951
Hornet H-145 head with the aluminum tag, this head was made to cover
for the Aluminum head until more aluminum head production. Was supposed to be
more compression that standard Iron head from what I read.

  It CC'd out at 103cc and the
head thickness was 1.960" (this
one had been surfaced.)

2-     
 NOS 308 Head       just
CC'd three chambers

110.5 CC for that one. (NOS head mic'd at 1.975)

 

3-     
Then CC'd one on a newly surfaced 262

 94 CC for it.  Head mic'd
at 1.941

 

4-     
Another just surfaced 262 head

It took .030 off to re-surface it properly.

It averaged right under  94
CC, so it was right on target

with the other 262 that I had CC'd.

It now checks out at 1.950
thick.

 5-     
Rudy Bennett and Chuck Fellows designed,
new aluminum head with improvements.

   It CC'd at 80cc,
this was after some smoothing of the chambers.

Thickness of new head is 2.15"

 6-     
Clifford Aluminum head

90CC (I didn’t cc this one)

 7-     
Gibson-Banks aluminum two piece head

???

 

Glowplug

 

Glowplug

Kerry, I have pictures of a Clifford head I bought from Rudy. The pictures show the combustion chambers, all were 90 cc. 

Glowplug

For all the time I have been driving and fix-in Hudson engines, there have been several "facts" that I have been told over and over but some how I was never ever able to verify those "facts" in Hudson literature.   The thickness of a new Hudson 232/263/308 head was one of those "facts".  

Today while looking for the pictures posted in the previous comment, I thought I would check a Back in the Day, Jack Clifford catalog.   Sure enough on page 2 of the catalog under Hudson Tuning Tips is Head Milling Limits, "All heads are 2" thick when new and will take a milling of 0.60" safely, do not go more than .100".   The text goes on to discuss the results of milling beyond the recommendations as well as the compression ratio of the various stock heads mounted on different engine displacements.

I am leaning toward this being the SOURCE of the 2" "fact" for new Hudson heads.   

I was fortunate to know Bernie Siegfried and during my discussions and visits to his shop I do not remember ever being told NEW heads were all 2" thick.  I do remember being told that to make the engine preform, all cylinders should have the same volume (ie cc each combustion chamber, including assuring piston rods were straight, pin bosses equal and the pin placement in each piston was the same).    I know Bernie had unconventional ideas about engine building such as shimming bearings, reuse of head gaskets and stacking them to create a compression ratio.  There were steel sheet gaskets in his shop that were used to "create" the bigger combustion chambers ... to work with his cam/valve timing needs.   

Any way... is 2" factory truth or round up fiction made fact?  I sure don't know.... but Jack Clifford was sure enough to publish that as "fact" in his early catalogs.

Kdancy

Well, the "fact" is, this NOS 308 Hudson head that was still in the factory packaging did not measure a full 2".
So much for Hudson "facts" !
Ken, can you post or send me a copy of those compression ratio's info?

Per

Kerry,

     Thank you for describing the method!

     For ordinary use, what seems to be a good compression ratio to aim for?  Walt Mordenti says that if it is too high, it will be necessary to retard the timing to avoid excessive pinging.  I had an experience which seems to confirm this:

     On a '47 Hudson 212 cubic inch engine, I once put a head from a '42 Hudson Traveler (175 cubic inch engine).  The Traveler's compression ratio was 7.25.  The compression ratio of the 212 with the traveler head was about 8.7.

Even with high-test gas, I could not push the gas pedal down very far without getting pinging, with the timing set as it had been with the original head.  I eventually took the Traveler head off, put the original head back on, and used regular gas again.

                  Per

Kdancy

Per, that depends on a couple of things.
Gas quality here has become a big issue as it is now 10% or more whiskey gas! I try to find non ethanol gas locally and it's usually 89 octane.
Combustion chamber design, electronic ignition and gas feed type all make a difference on how much timing can safely be run for street use.
Normaly, as you go up in compression ratio, timing will need to be retarded some, sounds like you needed to do that on your 212 motor.
There are far more experienced guys on here than me, but as a general rule for stock setup,I think it's considered desirable to install a 262 head on a 308, which gives one around 8 to 8.25 according to Clifford's info.
My experience with actually finding a good "in spec" 262 head after surfacing, for a 308, led me down this path of questioning.

Per

Kerry,

Thanks  for the information.  Yes, I did have to retard it quite a lot.  As a result I didn't get the combination of a little more power and improved gas mileage that I was expecting.

                              Per

KTRON

I'll probably get flamed for this, but in my Hall-Scott engine book, the first Hudson built engines did not meet Hall-Scotts stringent standards, and were melted down despite the military's call for more engines. Hall-Scott shipped a "million pounds" of machinery from Berkeley, California to Detroit, Michigan. Hall-Scott doubled their staff of inspectors and trained machinists in the Hudson plant, to meet their stringent demands when building engines. Quality in the Detroit plant never matched what Hall-Scott could achieve in their own factory, due in part to Hudson's foundry.  Hudson demanded that their name be cast into the water jacket covers and valve cover of this successful engine, a ploy later used by Hall-Scott to distinguish how much better their Berkeley built engines were. Although the Hudson Invaders and Hall-Scott Invaders look the same to most, within the Hall-Scott community the Hudson built engines are looked down upon as "lessers" to their Berkeley built brothers.

I hope this sheds some light on your quest to determine the quality and accuracy of some of Hudson's figures!

I certainly would not overlook how your new cylinder head was stored all of these years. Cast iron creeps as it ages, enough that new old stock parts will have to be machined true again prior to use. You will probably find this to be the reason behind your varying measurements,

Chris

Kdancy

Chris, thanks for your info, never heard or read that before.
Always new stuff to learn. That would help explain why I've never gotten the same measurements
All the way around on any Hudson head I've ever measured.
This also makes me wonder if Hudson made improvements to their casting-machining tools and
methods after WW2 for the new stepdown? Surely the techniques learned from Hall Scott would
have hand some carry over.

KTRON

I do not think Hudson could afford to machine let alone build engines like Hall-Scott did. Hall-Scott machined every part in three passes, (a rough, intermediary and final cut), between every pass the cutter was discarded and a new one fit. From what I am told their machine shop ran like clockwork, and when bought by ACF in the 1930's they sought to streamline Hall-Scotts wasteful machine practice, but they could not. Elbert Hall did not want his name slandered with failure from poor machining, so he made sure every part which left the factory was perfect. Every engine was run on a dynamometer not once but twice. After the first eight hour run, the engines were completely dismantled, inspected (including the magnaflux of the crankshafts & heads), new bearings and rings installed, and then reassembled. It was not until after the completion of their second eight hour run that the engines were painted, palleted and shipped to the customer. Good machining practice, inspection and thorough testing nearly eliminated engine failure for the first five hundred thousand miles the engines ran! Their pricing was astronomical, but you knew as a customer that you were buying the finest high speed engine built! Many 6 cylinder models before and after WWII sold in excess of $10,000, more than 3x what Hudson sold their complete Hornets for a decade later! They did not build near the number of engines that a large automobile manufacturer like Hudson needed to supply, but they satisfied their small niche of the market well up until the 1960's.

Chris

Kdancy

https://en.m.wikipedia.org/wiki/Hall-Scott
Don't know of any auto manufactures that could stay in business trying to make a profit at that level of manufacturing. Even Hall-Scott couldn't do it. Very admirable, just not sustainable.

Kdancy

Ok, just cc'd another one, a 262 head I just got back from the machine shop.
It took .030 off to re-surface it properly.
It now checks out at 1.950 thick.
It averaged 94 CC so it was right on target with the other 262 that I had CC'd.