I would like to some opinions on using a Z head. What are the advantages and disadvantageous?
Thank you for your comments.
I'm running a z head on my 25 coupe. I noticed an increase in power but it takes more muscle to hand crank.
Will make the car have more power. Make sure the engine bearings are in good condition before installing one. The extra compression can work on loose fitting bearings. I like mine in 3 of the 4 cars.
Thank you, Tom & John, I just rebuilt my engine and bearings checked out good. I have a re-ground cam with higher lift and had the crank maga-fluxed and polished. Not looking for speed just power.
I have an aluminum high-compression head and now I wonder whether there's any benefit to be gained from making the engine capable of putting out more power than I'd dare put through the crankshaft. -Maybe a Z-head makes sense for someone with a SCAT crank, but for others, I wonder.
I have one on my 14. It improves hill climbing, but I had a lot of quality issues with it. I had to send the first one back, and had to rework the second one. For the 24 I am restoring I bought a Prus head, no problems with this one, high quality product.
I have a Z in my T's and would't leave home without it. Love the extra "ump".
Ups the compression, and really gives the T a boost to move up hills. Unless you always run flat out top speed, can't think the Z or other high compression head will cause motor issues.
Just have your brakes in top shape
Love my Z head!
Buy it direct.
Thanks to all, looks like nothing but positives for using a Z head.
No, not all positives. Without question it will put more stress on a crankshaft barely adequate for the job it has to do. Can you say "two piece crank club" ;o)
Of course you may get lucky .........
The overriding principle is that it is your car to do with as you wish.
You asked for opinions - I would not. No reason to. Can't go fast enough - safely - to stop in time to avoid rumpled metal, and as others have said, it stresses other parts.
Your choice as to where you put your money.
Let's just say you do the head....then you'll want to port it for better airflow, then a better carb, then a distributor....at some point maybe - a different cam - then maybe - a celebration for joining the two piece crank club.
However, the absence of the high compression head does not mean a crank WILL NOT break...several stories and pictures here:
but MY opinion is that at MY age, why push MY luck!
Your money, your game, you get to do with YOUR auto as you want.
I heard early on that joining the 2 piece crank club was a matter of "when" rather than "if" if you actually drive your T. Trailer queens need not worry much.
A Z head will put some additional stress on the crank and other components but they have do provide a nice power boost and have been used for a pretty long time by folks who really drive their cars. I have one on my 26 Coupe with a stock crank and don't lose any sleep. Personally, I would go higher than 6 to 1 compression on a stock crank.
Whatever you choose, make sure your brakes are as good or better than your motor.
The Z or other heads is the best bang for the buck to increase HP.
Thanks again to all for sharing your thoughts. As I have said before, I am not interested in going faster. I know my '26 will do at least 45mph and that is faster than I want to drive. I live here in beautiful southern New Hampshire and we have plenty of steep hills to contend with when out for any dive. I just want to be able to do a better job going up these hills.
ps: just got back from a quick run up to Hopkinton and Seabiscuit run great with no issues !!! maybe it's time to quit while I'm ahead
The advantage is plainly more power, conside a long steep hill one in which your car is straining and often over revving in low just to make to the top.
the same car can often with a Z head will climb that hill in high. With a lot less stress to your motor.
Disadvantage? Well if you run around with a worn out engine a Z head may help you to decide to get it rebuild sooner aka the laud noises from you engine will be more pronounced with more compression. But really who drives around with a worn out engine?
My vote is yes.
As for all the naysayers I have driven my 15'T on my profile,a car that I restored myself, thru three sets of tires and 10 years of constant driving with a Z head with no problems. Ask anyone I don't baby it either. As for the two piece crank club, well when your numbers up it just is. We are not driving new iron here folks.
Speed and hill climbing both benefit from extra HP. Having the capability for more MPH doesn't mean you need to exercise it. If 45 is max comfort level for you, consider the upping the HP will let you maintain more of that speed on the hills. Just don't let the extra power let you get complacent about how well your car handles and the effectiveness of the brakes.
One thing no one mentioned is increased fuel mileage and a cleaner burning engine - less pollution.
And still one more thing, that I learned some time ago on this forum,.......
Due to more power from a given amount of fuel due to more compression, your engine will actually run cooler!
Have 2 now. Benefits are marginal but are there. Keep re torquing after installation. On both of my installations, I found that continued re torquing was necessary to stop the head gaskets from leaking. The 2nd re torquing after installation wasn't enough. I'm suspecting the heads have some kind of a warp that requires continued tightening down to secure a positive seal. Just my opinion for what it's worth. Jerry,
Jerry - I've always suspected two different thermal expansion rates with an aluminum head on an iron block, but then the Z head proponents tell me no,......???
Jerry, I hope you have been re-torquing when stone cold.
Something else to think about is that you MUST use a modern corrosion inhibitor/anti-freeze. But I notice from your profile pic, that you would definitely need it.
Where I live, anti freeze isn't required. But I do run an old fashioned corrosion inhibitor, soluble oil, in the cooling system of my '21 T. If I'd bought a Z head for my speedster project, (instead of the cast iron Waukesha Ricardo), I'd have had to use a modern corrosion inhibitor and anti-freeze. My aim was/is to run the soluble oil in both T's.
It makes sense that when one increases the compression ratio, it improves thermal efficiency. You get more work (=energy) out of the fuel you put in the cylinder. Heat is also energy, so when you get more of it in power output, less is left as heat.
Both of the Z heads I got needed to be milled. The first one I sent back because of to many issues. The other I received I had to have milled, and a lot of die grinding to make it work. If you buy one make sure its flat before you install it or you will have head gasket problems. I've heard of others that had the same issue.
I have two of them and never had a problem. I do not use the modern composition gaskets but use steel or copper gaskets with liberal copper coat sealent applied. Never had a leak and have done several national tours as well as a lot of local running.
If you buy one of these, I should have also pointed out, check the rear water jacket hole. One of them was okay, the other one was half the size it should be and would have the affect of putting a head gasket on backwards.
No one has mentioned another positive benefit--Increased cooling capacity--the Z head adds about another quart (maybe a bit less...) of coolent. I`m happy with the three I`m using. Probably the single best thing you can do for improved performance on a Model T. paul
Another positive effect of an aluminum head in general is it dissipates the heat faster than cast iron. In the Vintage Ford July/August 2013 I did an in-depth article regarding cures for overheating. In the article I wrote about the advantages of an aluminum head. I don't want to come across like I am trashing the Z Head, I am saying on the ones I purchased recently that the quality had dropped. A friend of mine has them on a half a dozen cars the first four were no problem, the last two he had the same issues I had. The last one he sent back. I'm saying if you a buy a Z Head, check it out before you install it. As in any after product, check it before you install it to make sure it doesn't have any issues
Thanks again to everyone who took the time to leave a comment. If I run a 290 cam will I have any problems with clearance due to the extra high lift?
Probably not but when installing any high compression head you need to check the clearance between pistons and head and valves and head without a head gasket in place to make sure. It is not uncommon to find clearance issues on the pistons with the Z head. These can easily be resolved by a bit of grinding or sanding of the high sport in the head.