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Harry Ferguson Tractors Discussion Forum

Z129 block Z120 head

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Daniel Collings

04-30-2007 20:56:19

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I have a tractor with a TO-20 serial number. and a TO-30 gas engine (Z129A) block. There is oil leaking from the front of the enging where the head and block meet. There is enough oil getting into the exhaust that it is coming out of the manifold where the muffler pipe connects. I at first figured that the valve seals were shot and the head needed to to be serviced. I have removed the head according to the service manual and was planning on taking it to a local head shop that I have used several times before. When I got to taking off the valve cover I found something disturbing. There staring me in the face is "Z120A" in the casting of the head. The shop manual stated that the T-20 and T-30 heads are not interchangeable. What now....Do I go ahead and have the head serviced/repaired or find a Z129 head? Question. Do I actually have a T-20 (z120) head on a T-30 (Z129) engine? If so is the service manaul correct about not using T-20 heads on a T-30 block?. If the manual is correct is there a way to make the T-20 head able to work on a T-30 block? Are all the ports the same and it is just a valve size issue or something like that.

Also I found oil in all 4 cylinders. There was a substantial ammount in one and two and not as much in three and four. I have looked for cracks and did not find any. I did find a small ammount of moisture (hardly mentionable) on the block. My questions are 1.)could the wrong head on the block cause this. 2.) If the heads are interchangeable could this just be the result of a bad head job?...ie. not torquing head down proplerly, not using the correct gasket, or something?.....Hopefully someone has run up on this before.....
Thanks in advance Daniel
Proud but po.....Fergy Owner

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Jerry/MT

05-01-2007 15:37:54

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Re: Z129 block Z120 head in reply to Daniel Collings, 04-30-2007 20:56:19

I wonder if the head just has a TO-20 casting number but was machined with the bigger valves ports? You can "mike" the intake valves . The TO-30's are 1.273-1.283 " head diameter whereas the TO-20's are 1.010-1.020 ". You should be able to tell that with the naked eye. the exhaust valves a "pert near" identical with only a change in the face angle (and a number stamped on it) that you couldn't tell without some special measuring tools.
Do some inspection and I'm sure that you'll figure out what you really have.

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Daniel Collings

05-01-2007 20:16:22

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Re: Z129 block Z120 head in reply to Jerry/MT, 05-01-2007 15:37:54

sorry about the picture i'm not sure what i'm doing wrong. The picture is under Tractor Pictures - Help Identify . Heading - "TO20-SN47725 Z129A-SN:600372338 -Head Underside"

I'm going to figure out how to do pictures now.....

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Daniel Collings

05-01-2007 20:09:29

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Re: Z129 block Z120 head in reply to Jerry/MT, 05-01-2007 15:37:54

Hey Jerry. I have already dropped off the head at a local shop. Here is a picture of the head. To me it looks like the valves are the same side but I don't see a number on either one. Could it be covered up by the deposits?

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Jerry/MT

05-01-2007 20:21:41

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Re: Z129 block Z120 head in reply to Daniel Collings, 05-01-2007 20:09:29

For some reason I can't open your picture. call the shop and ask them for a dimension on the valve head diameter. the TO-20's intakes are nominally 1.01"D while the To-30's are 1.23"D

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Jim in OH

05-01-2007 14:16:50

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Re: Z129 block Z120 head in reply to Daniel Collings, 04-30-2007 20:56:19

Hi Daniel.. The "book" says that they are not interchangeable, however, if you search the archives, Chuck (CA) claims to have a TO-30 with a TO-20 head on it (and now you).... Furthermore, I know that Z129 blocks were used to replace Z120 blocks... and all of the hardware (rockers and shaft, and pushrods) are interchangeable (by the book), and we know it will bolt on, so the potential differences are in compression, coolant and oil passages to the top end... Since the current head gasket services both, there may not be that much difference in coolant or oil either, but I would want to verify that, particularly that the Oil passages to the top end are compatible... The TO-20 does has smaller valves, and would be somewhat more "conjested" at higher power.... If you find out more, let us know.. This has come up in the past and has not been definitively answered (except that the book says no).. Jim

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Daniel Collings

05-01-2007 20:43:10

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Re: Z129 block Z120 head in reply to Jim in OH, 05-01-2007 14:16:50

Well while waiting on a response (and being impatient). I contacted three local machine shops. Two basically said that they weren't for sure but that it looked like the head gaskets are the same for the Z120/Z129/Z134. They suggested calling Larry at the third shop. Larry looked up all three motors. After comparing them he said the heads from each motor should be interchangeable with each block. They all use the same gaskett part number. As Jerry stated the differences in the head is the valves. Larry commented that the cams were a little different but the engine will work fine without that change. There would be a slight difference at the top end. I tend to agree with Larry though. I'm working on a tractor not a race car engine. I'm not trying to squeeze evey little drop of horsepower out of the block. I'm just trying to get the enging runniing well and be dependable. (id also like it to not leak oil). He felt that it woudl be better to leave the valves the same instead of machining the head to fit for a larger valve. It will be more importaint for the head to close the valves properly and all the seats and guides be tight so proper compression can be achived. If you want I can try to get the specific information. about the individual part information.

Daniel
Proud but po Fergy owner

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Jim in OH

05-02-2007 07:42:49

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Re: Z129 block Z120 head in reply to Daniel Collings, 05-01-2007 20:43:10

YOu don't need to get the specific information.. As I already stated in the first post to your question, the valve sizes are the only known differences.. and unless you find something more than discussed, it will work. I was just leaving the door open for something unknown. For example, I know the oil passages from the center main bearing are different for the two engines, so I wasn't sure about the oil passages, even though, as I stated, they use the same head gasket... Jim

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Daniel Collings

05-05-2007 07:09:03

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Re: Z129 block Z120 head in reply to Jim in OH, 05-02-2007 07:42:49

Ok....I guess i'm just a worry wart. lol

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TxAllisMan

05-03-2007 12:35:22

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Re: Z129 block Z120 head in reply to Jim in OH, 05-02-2007 07:42:49

Trying to post the pic
Link

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TxAllisMan

05-03-2007 12:36:16

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Re: Z129 block Z120 head in reply to TxAllisMan, 05-03-2007 12:35:22

cant make the pic show

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TxAllisMan

05-03-2007 12:48:42

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Re: Z129 block Z120 head in reply to TxAllisMan, 05-03-2007 12:36:16

Link
Link
http://www.tractorshed.com/gallery/identify/id12556.jpg

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