Technical Increasing compression on '53 Nash head

Great info and pictures. Looking at the pictures of the two heads I might not be able to up the compression much without if affecting the flow. There is definitely room to smooth things out on the "new" head to improve flow.
I think it is going to be best if I wait to swap heads until the winter when it's in storage for the season. Then I can accurately compare the cc's of both heads and look at areas on the block and the head to smooth out.

 

The '56 Statesman with 130hp is the OHV motor

I've seen different spec's listed for the '53-'55 Statesman motors. 100hp or 110hp with the 2v, 120hp with the 2x1v

The confusing thing is the 1956 date casting, but all the specs for the '56 lists every motor as an OHV
If it's a '54 or '55 head, it should be 8.5:1
if it's a '53 like it was advertised, it's only 7.45:1

Hopefully it is a 8.5:1 head

 

Back at it!

I finally pulled my head. Motor looks pretty good inside!

My first very unscientific measurement of the head volumes show my stock 1959 1V head to be about 50cc
The 1953? Nash 2V head is about 60cc. So it appears to be the lower compression ‘53 head versus the 8:1 compression ‘54 head. Of course my ‘59 motor could also have different piston height than they used in ‘53/54.

At first inspection of both heads, it looks like I have pretty significant room on the ‘53 2V head to take off material and maintain the same valve clearance.

Also I purchased two different head gaskets. The newer Fel-Pro 7802B gasket is significantly thinner that the older looking Fel-Pro 7802A that I got. The head gasket I removed looks like the 7802A.

So my next steps are accurately measuring the volume of each head. And checking valve clearance on each for comparison.

My initial thoughts are that I will have room to machine the ‘53 head to get be back towards the 8:1 compression and use the newer thinner 7802B gasket.
Just need to figure out how much material I can and need to remove.

 

Here's what I've come up with.

Rambler American 1959 1V head = 55cc (8.0:1)
Nash Statesman 1953 2V head = 63cc (7.45:1)

I checked valve clearance of '59 head with the old gasket and it was pretty much identical to the '53 head with no gasket, average at .1300".
Compressed gasket thickness of my new FelPro 7802B is listed as .0535>.0625
So I think I'm going to take .0650" off of the '53 head. Add the gasket thickness back in, and I still should have adequate valve clearance, ~.1175"+
Mapping the area of the funky head shape, I came up with 61.25cm2
So taking off .0650" should equate to about 10cc of volume
If the machined head finishes out at 53cc, that would bump me to 8.2:1

Time to get it down to the machine shop in Denver!

 

The problem with skimming an L head is you get diminishing returns. The less room above the valve and you restrict flow around the port. You are significantly reducing the crossectional area the gas has to get in and out of the combustion chamber. High compression heads often have a different combustion chamber shape AND sometimes even have to move the spark plug hole. You may not get the results you are expecting.

 

Did anyone else notice that 2 head bolts go through the channel of the cast in intake manifold. Thus restricting airflow to the end cylinders. I would try porting the one barrel head and make the two bbl carb fit. Try opening up the head around the head bolt going through the port, and rounding the passages that feed the valves. If you wreck the one bbl head you still have the 2 bbl head to use.

 

For true, there are tradeoffs. Milling the head .060" will increase the compression ratio that much and increase low-to-medium torque. It also decreases the transfer area, limiting top end power to about the same as you had originally.

jack vines.

 

Glad you are making progress!
What is the valve clearance of the '59 head, without the gasket?
Are you considering radiusing the "ports" under the carb or any improvement on the intake groove?

Would relieving above the valves help mitigate this?
I.E. mill head .060, then cut a relief above each valve .050-.070, of course with an appropriate radius. Obviously this wouldn't increase compression as much, but would it bring back enough flow to counter the negative effects of milling?

 

Think about how the gas gets in and out of the valves, clearance directly above the valve would make no difference. Compression ratios in the 7's is high compression for an L head. It would take a lot of work to make a head flow at 8:1 even starting from scratch. Volumetric efficiency has a bigger effect on power output than compression ratio.

 

Those are vacuum ports, not head bolt holes.

I don't see how adapting the 1bbl head to a 2bbl carb would do anything. The AF mix has to squeeze through the same size single hole. The two ports for the 2bbl are 30% larger than the 1bbl port.

I chose the 2bbl head based on the performance numbers of the stock engines that used this head, 100/110 hp over my 90hp.

 

I did do some smoothing out of the intake runner and softened the sharp edge of the intake ports. I also smoothed out the combustion chamber of the head, and removed material at the valve reliefs. That was before my PlayDoh valve clearance check.

I didn't check the '59 head without the gasket. I could do that tonight and add back the gasket thickness.
I was curious how tight it was stock, so I used the old compressed gasket and only snugged a few head bolts.

 

I was thinking the same thing about flow above the valve, doesn't seem like that would make much difference. But with side valves I guess if it can't flow around the "backside" of the valve very easily you will have some flow over the top. Probably more on exhaust stroke than intake.

 

Head after some smoothing

 

I see that they are vacuum ports now. I was not thinking of just adapting the 2 bbl carb, but boring out the holes to match the carb base. If you didn't hit a water jacket you would end up with an 8 to 1 head with a 2 bbl carb.

 

The mounting flange and carb stud pattern is different as well. I didn't see a good way to make the 1V head fit a @V carb. So I bought the NOS 2V head.
Comparing the depth and volumes of the two heads, and knowing they all used flat top pistons with almost no deck. They had to be machining the head surface to change the compression ratio using the same head casting from '53>'55. I'm sure a company as budget as Nash didn't cast a different chamber shape for the one year only, 1954 motor with 8.0:1 & 110hp

I'm trying to make my 1953 7.4:1 head into the 1954 head

 

Gizmo;
"Think about how the gas gets in and out of the valves, clearance directly above the valve would make no difference."

Ed Winfield has stated it much differently. In an interview w/Tom Senter in ~ '77, 1001Rod&CustomIdeas mag, he stated that in a flathead, a/f mix goes around, & over the valve head. For proper breathing, these can't be constricted. IIRC, he stated that the area extending(horizontally) around the valve edge, must have at least the same area as the valve-curtain(Height of the valve fully open, x the circumference of that valve. & the same for over the valve. Over the valve flow being very important.
As you mentioned: "Volumetric efficiency has a bigger effect on power output than compression ratio."
What a lot of the old banger guys found(even back to Winfields' day), is that hi(er) compression gave real quick acceleration for stoplight to stoplight & choked off the mill at higher rpms, but the low(er) compression gave much more top-end, due to better breathing.

Breck;
You'd do well, if you can, to finish relieving the block for better breathing. Also if possible, to get ~.045->.060 squish for the pistontops. But I realize this means the mill has to come apart. + maybe a junk head to section, so's you can measure the available room to port the head around the valves & the valve-tops.
Something to consider if the squish is ~.100, is the Singh Grooves. Creates a lot of turbulence & a/f mixing on compression, = better combustion. But, it's abit controversial.
If you have another cheap used head, you could bore out desired carb-locations & sleeve them w/tubing. Mig, braze, or preferably silicon-braze them in place. If it doesn't work, you're not out that much.
& of course, there's always super(or turbo - although around here, that's sorta a dirty word) charging for a nice decent increase, + the "wow" factor. . Can be quite "period" if you want that.

A few years ago, Dick Datson did a compilation-booklet on amc engines, from a series of newsletters he put out over the years. Might find a copy on ebay or amazon. Maybe in one of the amc clubs? Covered v-8s & sixes, might be worth your time?
Nice project. .
Marcus...

 

If you look at the carbon deposits on the block you can see where the choke point is, it looks to be roughly where the spark plug hole is. If you put a strait edge accross the head at that point the gap is where the gasses have to get through. It may be why some historic high prrformance heads resort to moving the spark plug location.

You can calculate the reduction in crossectional area of that gap with a 60 thou skim on the head

 

The pistons are very close to the deck at TDC, hard to even measure a gap. So the squish is essentially the head gasket thickness. All I can find for a spec on my gasket is a range, .0535">.0625". I'm going to use the newer Fel-Pro gasket that measures .0640", I would imagine it will compress to under .0600"

The NOS 2V head does have a larger squish area above the piston. And has a larger relief above part of the valves extending down to the spark plug. Looks like it will flow better between the valves and the cylinder.
The valve relief on the '59 heads cover almost all of the valve, and then has the round crater shape relief around the spark plug, it actually bulges up more right at the transition from the valve area to the cylinder. Seems like its an obvious restriction point for flow between the valves and cylinder.

I'll have to read up more on the Somender Singh groove theory.

 

You you can't clay the top of the piston?

 

Got the head back from the machine shop, they removed .065”
Measured two of the chambers and they are right on 55>55.5cc matching the volume of the stock ‘59 head. So it should maintain the 8.0:1 compression.
I’m going to do another head to head comparison of valve clearance on every cylinder without a gasket to get a solid comparison.

If everything is looking good I’ll be ready to assemble with my new head gasket and ARP studs.

 

Got it installed and fired up!
Too snowy still at 10,000’ to drive it, but dang she sounds great and the throttle response is off the charts!
Can’t wait for dry roads so I can take her out.

 

What was the result so far as driving it?