Casting my own aluminum head

1941 - 1945, MB, GPW modifications, sugestions, and ideas, official MWO's and unofficial WWII field mods NO EBAY or COMMERCIAL SALES.
Seff
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Re: Casting my own aluminum head

Post by Seff » Tue May 24, 2016 2:31 am

Disregard the previous: The RPM counter was faulty.

All I know so far is that I made 55.5 Nm at 1952 RPM with the stock head, and 72.8 Nm at 2016 RPM with the new head. The actual compression was raised from 6.48:1 to 7.84:1 by shaving 2.5 mm off the mounting surface. I measured the stock combustion chamber to 90cc, and the shaved head to 70cc.

I will calculate horsepower and show a power band soon.


ndnile
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Re: Casting my own aluminum head

Post by ndnile » Tue May 24, 2016 8:07 pm

Not my forte, but I was curious. Calculations are from this site: http://www.wentec.com/unipower/calculat ... torque.asp

55.5 nm @ 1952 RPM is 15.2 HP. 72.8 nm @ 2016 RPM is 20.61 HP. Nice gain.
Looking forward to the curves.

Cheers, Doug
Doug
Sacramento Area
1943 Willys MB
1943 GPW-125334 (Sold)
1962 M170
1959 Willys Wagon

Seff
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Re: Casting my own aluminum head

Post by Seff » Tue May 24, 2016 10:40 pm

I found out why it doesn't have more power: The manual throttle cable sleeve (the part the manual throttle cable runs in) keeps the throttle from opening completely - I realized this might be a problem between the two measurements, but the value of comparison meant that I didn't change anything between the two measurements. I will now change it, and do all that I can to increase power and take advantage of the increased compression.

The important thing about this comparison is twofold:
- The peak torque didn't move significantly RPM-band-wise - this means that the engine isn't being choked in any significant degree.
- At the same throttle setting and same timing setting the torque was increased from 55.5 to 72.8 Nm - that's 131% of the starting torque.


I had a tach on the engine for the test, but it showed 6130 RPM at 88.9 km/hour, which I refuse to believe. Assuming that the Hotchkiss M201 has the same 4.88:1 rear end, it should be running 3167 RPM at that speed in high gear tranny and TC. I'm running 6.00x16 NDT tires, with a diameter of 28.6". So I corrected the RPM to adjust it (meaning that the HP measurement from the dyno were incorrect)


Calculating horsepower (and adding the driveline loss to measure engine horsepower instead of wheel horsepower) gave me the following curves:
HP1.jpg
Horsepower corrected for driveline loss
HP1.jpg (68.57 KiB) Viewed 2291 times

And torque, for good measure:
Torque1.jpg
Torque measured
Torque1.jpg (68.98 KiB) Viewed 2291 times

Seff
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Re: Casting my own aluminum head

Post by Seff » Fri Jun 03, 2016 1:48 am

I freed up the throttle body and optimized the ignition. End result: 51 HP@3100 RPM and 134 Nm@2000 RPM. So the engine is tired for whatever reason (age is my guess), and the head shave has moved the peak HP point from 4000 RPM to 3100 RPM. Given that 3100 RPM equals 54 MPH with the standard rear end and gearing, I'm fine with that result. Had I added a 25% overdrive, it would be 72 MPH - or conversely, the overdrive would have me going 47 MPH at 2000 RPM, which is the torque peak (and torque peak is where the break specific fuel consumption is the lowest), so this would be ideal for cruising.

Marty, SoCal
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Re: Casting my own aluminum head

Post by Marty, SoCal » Sat Jun 04, 2016 12:05 pm

Cool! The fastest I've ran mine was 73 mph, verified with a GPS! :shock: It really cruises well at 60-62 or so, though in overdrive. (RPM equals about that at 45 mph stock)

Your test proves that milling the stock head will make an appreciable gain while still looking completely stock. I gained about 1mpg with the higher compression aluminum head.

How much room do you have for the valves and spark plug with the extra milling?
43 Ford GPW 92098
53 Dunbar Kapple M100
Sold: 61 CJ-5, 41 T207 WC-1 Dodge closed cab pickup
MVPA #8266
USMC Tanker (1811, 1812), 85-93
ASE Automotive Master tech, former Chrysler-Jeep Level 4 Mastertech, CA state EA smog license

Seff
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Re: Casting my own aluminum head

Post by Seff » Sun Jun 05, 2016 11:55 am

Where did you get overdrive for the wartime transfer case?

I proved a few things, I think:
- More compression helps this engine a lot.
- Shaving the factory head is easy and shaving quite a bit is possible.
- However, shaving the factory head worsens the flow in the chamber, robbing top end horsepower.


The depth of the factory head at the shallowest end of the chamber (at least the shallowest part over the valves) is 13 mm. Stock valve lift is 8.92 mm. A felpro replacement gasket is around 1 mm thick, and the valves are approximately 1 mm above the block deck when closed. The spark plug does NOT protrude very far into the chamber, however. So, 13 + 1 - 8.92 - 1 - 2.5 = 1.58 mm clearance. Based on that I would NOT shave the head further than 2.5 mm.

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Re: Casting my own aluminum head

Post by ndnile » Sun Jun 05, 2016 2:02 pm

Seff wrote:Where did you get overdrive for the wartime transfer case?
I don't know where Marty got his, but likely from Herm. He has them and he is well respected: http://hermtheoverdriveguy.com/?page_id=883

Here is Marty's write up on his overdrive installation: viewtopic.php?f=10&t=164205

Happiness is a write up from Marty in the Modifications Forum.

Cheers, Doug
Doug
Sacramento Area
1943 Willys MB
1943 GPW-125334 (Sold)
1962 M170
1959 Willys Wagon

Marty, SoCal
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Re: Casting my own aluminum head

Post by Marty, SoCal » Sun Jun 05, 2016 2:40 pm

Yes, Herm was the source I used for a rebuilt overdrive with the proper 27 tooth gear for the WW2 case.

Advance adapters is also selling the 27 tooth overdrive. You can also buy just the gear if you already have an otherwise workable overdrive with the CJ's 26 tooth count.
43 Ford GPW 92098
53 Dunbar Kapple M100
Sold: 61 CJ-5, 41 T207 WC-1 Dodge closed cab pickup
MVPA #8266
USMC Tanker (1811, 1812), 85-93
ASE Automotive Master tech, former Chrysler-Jeep Level 4 Mastertech, CA state EA smog license

Seff
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Re: Casting my own aluminum head

Post by Seff » Mon Jun 06, 2016 6:25 am

I have nothing, but will contact Herm for offers when the time comes. Thanks for the info, gentlemen.


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