Since that cracked exhaust manifold came out to replace it with a new one, decided to continue on taking Dixie, the '27 Touring on apart. Had purchased a new 'P' high compression head this summer, so thought it was a good day to remove the existing 'Z' head and see if the new 'P' has more performance
So removed the 'Z' and found some bit of carbon in the cylinders, this head has been on for 7 years, or about 15K miles without a good scrub for the piston tops and compression chamber.
Also, at that time added to the water outlet the anode to sacrifice itself with the dis-similar alum head and the iron block. As you can see, that thing has deformed and shrunk some by sacrifice
Didn't see anything that was hurt on the old 'Z' head against a copper gasket and iron block. So think that having an anode is just a waste of time, leaving it out now.
Cleaned up the engine top of the carbon with tools, and some gasoline, all shiny now again.
Important too to use a jet of compressed air in each bolt hole to get out debris prior to replacing head bolts!
And also to check the new high compression head prior to gasket and bolting it on.
Just a few bolts placed to center the head, then turn the engine over many times and be sure there is no piston strikes, do this without the gasket. Then with the gasket, no worries of any contact.
Will be interesting to see if the new 'P' head has more ump-th to it compared to the 'Z'.
The compression chamber has more squeeze area over the pistons with the 'P' head, the 'Z' is great, hope this new one is greater
Isn't that what an anode is supposed to do? If it wasn't doing something it'd be in pristine condition.
Dan, I am interested to see how the head gasket fits on the P head versus the Z head. I have a Z head, but there is so much exposed gasket material in the combustion chamber, I am afraid to use the Z head.
Could you take a photo a head gasket on the P head and post it?
Looks like it should have a lot more compression! It would be interesting to know the volume of each head.
By the looks of it the Prus head should give lots more power due to higher compression and more efficient combustion chamber but may be harder - much harder - to crank by hand, or with a starter.
Wish one of them would make a low head version. I sure miss Ralph Reeder.
I think you'll like it. I know I sure do!
However, I went from a stock slightly milled head to the "P" head.
I used the copper gasket and it fit fine.
Have two T's with 'Z' heads and always use the copper gaskets without any problems.
The gaskets go seam side on the head, the un-seamed side on the block. That way that 'seam' is squeezed by the head when bolting down. Probably make no difference, but works for me.
And you can see the 'seam' lines formed in the soft alum head, and that there is lots of clearance, can't see where any gasket would be in the compression chamber, or be where the pistons or valves could hit gasket.
Note the 'lines' made by the copper seam fold that is in the gasket face.
Copper gasket that was on this head.
The copper gasket fits the 'Z' head just fine, and will fit the same on the 'P' head too
Dan -- I notice that your Z head's spark plug holes are centered between the valves. I recently acquired a Haibe Giant Power head and was comparing it to a Z, which is patterned after the Haibe. The spark plug holes in the Haibe are centered, as yours are, but the ones in my Z head are above the intake valves. I wonder why and when the Z folks changed that. I'll take some pics tomorrow and post them.
I agree with Royce in that I wish the "Z" head was also made in a low head configuration.
I now have a Reeder head from Chaffins on my '14, but before that I had a "Z" head on it and it performed much better with the "Z" head.
I changed to the Reeder head because I didn't like the bend in the upper radiator hose and I wanted the low head so it would look original.
Dan, do you still have the Prus head loose?
It would be interesting to compare the compression chamber volume in the Z head with the current production Prus head. Just put a spark plug in one chamber of each head, arrange them level on a bench and fill water with a measuring cup from the kitchen. I suspect they're very close in volume, that's what earlier measures has shown - The Tulsa Model T club measured a Z head to about 203cc or 12.4 cui years ago, Dean Yoder measured his Prus head from the first production run to about 225-230cc and I measured mine to about 210cc before milling, 185cc after milling 0.100".
If you don't have any use for your Z head now, then I would be interested in buying it
Low end torque will likely be about the same with your new Prus head compared to the Z, but the Prus head gave 2hp more at the top end in Tom Grahams dyno test in 2012 = 28hp versus 26hp for the Z head. The compression is about equal for both heads but the Prus head follows the Ricardo priciple better by concentrating the compression volume over the valves - that's the likely cause for the difference.
Lucky....came in from the garage and saw your post. Was just letting the copper head gasket dry after coating with Copper Spray, and was going to clean out the bolt holes again using a bottom tap to be sure no debris.
So, placed the two heads on the workbench and leveled them each up. The new Prus'P' head on front, and the 'Z' head behind.
Now my scientific instruments for this testing were the wife's turkey baster and measuring cup in ml. As one ml = one cubic centimeters, easy to convert for cc's test of each chamber.
For the fluid, had drained the radiator, so why use water with a bit of antifreeze! Green color for contrast
Filled each chamber to right at the top, tried to be very accurate in filling. Each plug hole was capped with plastic pipe plug, so the spark hole is negligible.
Then sucked each chamber dry, one at a time, putting the fluid into the measuring cup.
Results for the Prus 'P' high compression head.
Just over 200ml
Did the same for the 'Z' head.
Results for the 'Z' high compression head.
Right at 250ml.
So, my quality assured garage workbench cc'd testing shows:
Prus 'P' Head 210cc
'Z' Head 250cc
...now gotta go clean out Mimi's turkey baster and measuring cup from the anti-freeze, won't be good on Turkey day unless these things are CLEAN
That's great, Dan
So the Z head measured by the Tulsa club was very different from yours - their 203 cc corresponded to 5.3:1 in compression while 250cc gives just 4.3:1 - much lower than the 5.1:1 with your new Prus head.
So you will likely get noticeably better punch in Dixie with her new head
Think those numbers are just rough estimates.
True CC'd would include the reduction in the head chamber from the piston rise. The piston does go up into the chamber a bit. That would reduce displacement some more.
I know the flat top pistons stick up past the block, had to shave some alum from another 'Z' head install, as that pop-up of those flat top pistons hit the top of the head chamber
So there may be considerable differences between Z heads, while Prus heds are machined in the area above the pistons for better safety against unwanted piston contact.
The calculations I used comes from the Tulsa site and takes care of the volume corrections from the piston rise and the gasket:
" A stock high head has a volume of about 294 cc or 17.9 cu in. The volume is reduced by 2.8 cu in because the piston rises 5/16 inch above the deck. The volume is increased about 0.8 cu in due to the head gasket. For a stock head, the combustion chamber volume is 17.9 - 2.8 + 0.8 = 15.9 cu in. An engine with stock bore and stroke has 44.2 cu in displacement per cylinder, so the total volume when the piston is at the bottom of its stroke is 44.2 + 15.9, and the compression ratio is (44.2 + 15.9)/15.9 = 3.8"
(Message edited by Roger K on November 21, 2014)
It's going to be like adding a fifth cylinder in terms of increased torque. Should be more efficient too. Likely will use less gas per mile.
I tell everyone that a better cylinder head is the single easiest improvement you can make to a Model T. 89 octane gasoline is nearly double the octane of gas that was available when T's were new.
Royce - Here in the PNW where I live, 89 octane is "mid-grade" in most major brands.
Regular .......87 octane
In Texas, is your 89 octane regular or mid-grade?
Royce, you are correct sir! Feels like a 5-cylinder Ford! About like a Model A!! Woohoo!
Bolted on the new Prus 'P' head and finished up the new manifold and got all the pieces back.
Wouldn't fire up right off the bat. Think again I used too much heavy grease on the Anderson flapper again, seems to cause that. Anyway after cranking quite a bit, fired up, ran ruff at first and then smoothed right up again. Set the carb, let it idle. Snugged up the pack nut again on the exhaust manifold.
Then off for a run. Oh My!
Initial launch in low is really something, think I could scratch off the tires if I tried.
Out on the road into high, and greater pulling than the 'Z' head. Really could tell.
New nice road speed is now 35, used to be 31-32, but the motor seems real smooth at 35.
And now there is a whale of a lot of power band from 35 to 40, pull on the lever, and real quick to 40. Big difference.
Only offset is the spark, now if retarded where I run about 25-30 speed, pings are happening, that 'Z' never did ping. So have to keep the spark advanced. But that is not a problem now.
Love the new power and pulling, can really feel a difference.
Now hills will be conquered in high gear
After you get a few miles on the new set-up, let us know how the "ping" situation is on those hills Dan. You might have to switch to "high octane" gasoline, huh? Ha, ha,.....harold
Wait a minute! Hills? In Florida? The flattest state in the USA?
Dan's posts above got me interested in how my "new" Haibe Giant Power head compares. So I did the same cc test with it. When I first got the head, I measured the combustion chamber depth in several places, and compared those measurements with those of the Z head which I had been running on my car. The Haibe and Z combustion chambers are similar in shape, but the Haibe's were pretty uniformly 1/8" deeper. So I had 1/8" milled off the Haibe. Its chambers now hold a bit less than 250 ml, about 240 I'd say. (I used the same accurate measurement methods Dan did. ) So I expect the engine's performance will be about the same as with the Z head. But that's OK, since it screams "GIANT POWER HEAD" in large letters across the top, so it looks WAY cooler.
I did need to take a die grinder and dress a few spots down a bit, since they were touching the pistons without a head gasket. But after getting those up to snuff, everything should be hunky-dory.
Yes, I painted it red.
I've never understood folks who put Z heads on their cars and grind the Z off. When I pay $300+ for a head, I want people to see the Z! I've always painted them black to match the rest of the engine, but I left the Z.
I bought this Haibe from a fellow on eBay for $350 with free shipping. "What a deal!" I thought. Then I took it to my local machine shop and had it "baked" to remove all the rust build-up inside, blasted with stainless steel shot to clean up the outside, and milled 1/8". I now have $530 in this head, so it'll be RED for sure!
Newbie question - what is the compressed thickness of the stock copper head gasket?
For comparison, measured the used copper gasket just replaced.
Measured at the 'bridge' narrow section that goes between the cylinders.
Used and compressed: .465"
Thanks! You probably mean 0.0695 and 0.0465, right?
Measured it ok, just didn't type it in the post correctly
Used and compressed: .0465"
Spell Check won't work on math