Hey guys, I've got a set of original aluminum 21 stud heads for my 36' that I'm getting cleaned up and I wanted to see if anyone could weigh in on the combustion chamber size. I purchased these separately off ebay a while back; the left one was pretty clean and looked ready go, the right one was a little rough, but still looked repairable. My machinist took 1/1000th off the left one to level things out and then cc'd the chambers and got 58cc. He did the same on the right head and got 61cc, but he also found a few more small cracks that I'm going to have to weld up before we go any further (highlighted in the photos). The hope here is that we'll be able to clean up whatever welding dips we get in the few /1000ths that still need to come off to get the head down from 61cc to 58cc...to match the left one. This is definitely a bit of a bear to get these old things repaired, but they're pretty hard to find these days in serviceable condition, and that's kind of flatheads in a nutshell anyway...which I love. So, is 58cc ok for the standard combustion chambers...and do these then become high-compression? What's the best way to calculate the combustion ratio at this point...I imagine I'll need to measure the cylinders and get their volume to complete the calculation? Also, at 58cc, am I looking at an acceptable valve clearance, or should I plan to check their clearance with putty? Thanks...I'm a little rusty on my flathead knowledge.
The Blue Ford book list the 40-6049 head as 57 to 62 cc with a compression ratio of 6.3 to 1 I will let others chime in on the integrity of the aluminum heads I had one aluminum and one cast iron head on my ‘34 The aluminum head broke in two trying to remove it I will be going with 68-6049, 50 cast iron heads with domed pistons and head
Those heads are made for the flat top pistons used in the earliest 21 stud flatheads. Your '36 engine should have domed top pistons which will not work with these heads.
Parts with the #40 prefix are for 34 Fords usually...1936 should have a #68 prefix...My dad use to say that folks replaced the original aluminum heads with cast iron during WWII because the price for scrap aluminum was high...
All 21 stud (water pump mounted on head ) heads will interchange BUT flat top pistons go with flat heads and dome pistons go with dome heads
Thanks guys, yeah, I have flat top pistons currently with cast iron heads. I was told at some point that even some early 36 models had flat top still, and it wasn't until later in the year that they moved to the dome top. My grandpa has a later 36 5-wondow and he indeed has the dome top pistons. Rough blue one is mine...a work in progress... 40-6050. The restored stocker is my grandpas...very clean....68-6050.
There are a lot of new pistons out there for the 221ci motors in flat top and dome and different overbore for not a lot of money You can pretty much get pistons to match the heads you want to run I have heard the problem with the old aluminum heads is corrosion that weakens the aluminum Looks like another block in the background in that picture my broken head made into desk top art
Nice desk art for sure, I've got all sorts of odds and ends myself, big fan of desk art! Yeah, that's another block in the background...my spare, if you will. Between my grandpa and I, we've got probably 6 flattys lying around, in various states of disrepair. He was born in 1935 in rural Kansas, where his dad (great grandpa Mac) owned and operated the towns one service station, model Ts and flatheads were really the only things around.
I Used some on mine. 36 flat top. Polished and look great. Still not much over 85 HP with the old Roof intake and a ,couple of 81s but work great.
Ford carried over the late 34 head (40-6049-50) through 35 and then offered it as an option until Feb 36. There were dome top pistons in some of the 35 cars and the production of the flat top and dome top was mixed into early 36. The 35-6 dome top engines used heads 48-6049-50 It was not until late 36 that the 68-6049-50 heads were introduced and used for replacement only. One question for idlewild: Does the one head have Ford script without a part number??
Yes But only the case. I installed a PMG permanent magnet generator from a Kabota in it. It puts out about 25/28 amps and is enough for my use. 12 volts and as it is a PMG it does not need to be excited like an alternator. I left the small round cover on top for effect. No problems yet.
Definitely agree with Oldtmtech, a thread on hot rodded 21-studders would be really nice...I always try and take note when someone has put time into customizing the old 85hp mills. I saw recently that Loveless performance now makes a reproduction Frenzel supercharger, ideal for a 21 stud engine...very cool. https://www.instagram.com/loveless_performance/ And to answer 48-760s question, yes, the head on the left just has just the ford script and no other part number markings. Like 27TV8...I'm seriously considering polishing my heads when I've got them all sorted, I really love the fully polished look of the aluminum 21-stud heads.
The Jalopy Journal
