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MM heads

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GMS

04-14-2000 09:56:51




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I recently purchased a MM G-705 to farm about 200 acres with. After running it for a few weeks, I found I had a cracked head. I did purchases a different head and fixed the tractor, but I have been since told by a number of people that MM's always crack heads. Does anyone know how to keep a MM LP tractor head from cracking? Do MM's crack heads a lot worse than other tractors, any information would be nice.

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No Century

04-16-2000 11:53:21




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 Re: MM heads in reply to GMS, 04-14-2000 09:56:51  
I want a piece of this. 705's used Century LP system. These are a poor system, the load side of the carb doesn't open up 'til 90% of load. That means it runs lean from off idle 'til almost fully loaded. If you are going to invest in new heads then you might as well purchase an Impco mixer and go on. It will work with the Century vaporizer.



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Roger

04-16-2000 17:04:30




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 Re: Re: MM heads in reply to No Century, 04-16-2000 11:53:21  
I will have to disagree with the statment about Century. Impco is a good system, no arguement there. However, you need to look in the inlet end of the Century carb. You will see the metering valve opens as you give the tractor more throttle. I have run Century sytems on 4210 heads for over 10,000 hours. I would not change the carberation in the hopes of stopping cracked heads. I always found that keeping the radiator clean and flushing the cooling system to clean out the blocks helped cooling. I always felt this saved the heads. I am in Kansas, the heart of LP Gas, and Moline country. I base my statments on 40 years of running MM tractors, and 30 years in the LP Gas delivery buissness. I still use MM LP tractors for all my planting, cultivating and haying. 100 degree days are not uncommon here. Keep your heads cool and they will last a long time.

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No Century

04-16-2000 17:54:42




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 Re: Re: Re: MM heads in reply to Roger, 04-16-2000 17:04:30  
We are kinda going in circles here. I am sure you are knowledgeable on the situation. The Ensign and Impco have diaphargm ran enrichment systems that enrichen the air fuel mixture. The Century does not. Like you said the throttle has to move to the metering valve. Engine load can change with the thottle moving. This is the err in the Century system. It needs an economixer valve like the Ensign system to enrichen the mixture at the vaccuum changes.

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Roger

04-18-2000 09:42:12




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 Re: Re: Re: Re: MM heads in reply to No Century, 04-16-2000 17:54:42  
Impco may have a diaphargm in the carberator, but it works on a completly different principle than Ensign. Impco and Century both work on the "Demand" system. The carberator tells the Vaporizor how much fuel to send. Ensign works on a "Balance" system. The Vaporizor and Carberator "Both" decide how much fuel is needed. This was the reason for the balance line, to get them to work together. Impco may use a diaphargm to move the metering valve, but the way it works is still the same as Century. Ensign and Impco should never be compared as working the same.

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No Century

04-18-2000 15:08:56




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 Re: Re: Re: Re: Re: MM heads in reply to Roger, 04-18-2000 09:42:12  
Roger you are missing my point. Ensign and Impco have a part throttle fuel enrichment system the Century doesn't. The Century is a poor system because it does not have one. Vacuum and a diaphragms are the only way to meter fuel on a part throttle basis. The Century has NO way to compensate for engine load with the metering valve being DIRECTLY related to throttle position. Balance lines: An Impco has a 1/8" NPT place on the air horn for a balance line. This is in material to the discussion.

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Roger

04-19-2000 07:14:34




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 Re: Re: Re: Re: Re: Re: MM heads in reply to No Century, 04-18-2000 15:08:56  
I have worked on and sold both Impco and Century. I have no preferance, they are both good systems. Using a diaphragm does not make Impco better. 1. The spring can get weak. 2. Pin holes in the diaphragm, causing a loss of vacuam. 3. Groove worn in metering valve from always seating in the same place. 4. (and worst problem )Turbulance in the Carb. body causes the diaphragm to lift metering valve incorrectly. Any of these things will cause the Impco to meter fuel incorrectly. I have never seen an Impco Carb. yet that was not worn on one side of the metering valve guide worse than the other. This allows the metering valve to cock and drag as the motor is accelerated. The only thing Ensign and Impco have in common is the use of a neopreme diaphragm. They work on 2 completly different ideas. Engine load is compensated for with the use of a govenor. In 1957 Impco started building LP Gas carberation to do away with balance lines. I realize some people use the 1/8 " NPT in the air horn for a balance line. Read the service manual you got when you went to Impco's Carberation school. That opening is used to operate an Impco VFF 30 Fuel Lock/Filter and a supply line for an external electric primer on Impco vaporizers. Balance lines went out 40 years ago. Century is a Poor system ? Are you the Impco salesman ?

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No Century

04-19-2000 17:57:31




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 Re: Re: Re: Re: Re: Re: Re: MM heads in reply to Roger, 04-19-2000 07:14:34  
We have to remember where this discussion began. How many engines have you seen with an Impco have cracked heads. LP 705-8's are known for having cracked heads and they were factory equipped with YOUR Century system. ARE you a Borg Warner salesman?



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Roger

04-19-2000 20:38:47




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 Re: Re: Re: Re: Re: Re: Re: Re: MM heads in reply to No Century, 04-19-2000 17:57:31  
Maybe you didn't read my post correctly. I sell both systems, I don't have a preferance they are both good. As for the original discussion, my statment stands. The cooling sytem has more to do with cracked heads than carberation. Blaming carberation for cracked heads is "coffee shop talk". I have heard it for years. You made the statment that Century does not mix fuel properly from off idle to 90% load. Was this opinion formed using a dynometer, Co2 meter and pyrometer to set your carberation ? Your statment better describes Ensign. Incorrect plugs or timing set to fast will have more effect on engine heat than carberation. I posted 4 facts about Impco carberation, yet you did not respond to any of them. Only that Century Carberation cracks heads. Back it up with some facts. More than likely the tractor was run hot and no one wants to admit it. Since you have not posted your real name or e-mail address, I can't help but think you are someone I know that is just yanking my chain. Once again, I have NO preferance between Century and Impco, I run both.

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No Century

04-21-2000 13:06:33




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 Re: Re: Re: Re: Re: Re: Re: Re: Re: MM heads in reply to Roger, 04-19-2000 20:38:47  
I don't think you've understood my post.
U and G LP's didn't crack heads the way 705's and later MM did. Of course U's and G's didn't use the Century system. I don't have to reveal my sources because I know. You shouldn't sell Century systems they are inferior. YOu should retire to the coffee shop.



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Roger

04-22-2000 02:39:41




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 Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: MM heads in reply to No Century, 04-21-2000 13:06:33  
I understand your post. However, you still haven't backed up anything you have said with facts. Have you ever used a dynometer and Co2 meter to check your carberation to see if it is set correctly ? How many LP systems have you worked on ? How many years experiance do you have in LP Carberation ? I will back up my statments with 30 years of experiance. Up to and including the new EFI computer controled systems. Later model MM's crack heads more often the than early MM's ? I have run MM tractors for 40 years. Everything from R to a G 1355. This includes G705 and G707. I still run 20 MM tractors on my farm. How many MM tractors have you run ? You still haven't given any facts, just that "you know" that Century carberation is not any good. I put Impco carberation on my M5. 1,500 hours later it broke a head. I'm not going to blame Impco Carberation, the motor had 16,500 hours on it. I think age and hours had more to do with it. Seems to me you are the type of person that would blame Goodyear Tire Co. when the ring and pinion goes out on a tractor. You don't even have the courage to back up your statments with a real name or e-mail address. Go back and answer the questions I have asked in my earlier posts. Explain how to fix the 4 things that go wrong with the Impco CA series of Carberator. Do you know how to fix them ? Everyone is intitled to their opinion. When you have some facts, let me know.

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139713

08-06-2004 18:56:23




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 Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: MM hea in reply to Roger, 04-22-2000 02:39:41  

705 mm need to have bigger intake air supply this will help them a lot original to small. The ones I run had the metering valves in the inlet pipe changed from the rotating one to the ones with one-half turn. This solves all problems.




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Harrold Rhodes

04-16-2000 09:47:29




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 Re: MM heads in reply to GMS, 04-14-2000 09:56:51  
I agree with previous about cracking heads. However would add that 4210 head is more prone to crack than most other LP heads. This comes from experience on 605 power units and M5 and 602 tractors. I think it may be because thiey planed more off head to get desired ratio. If your 705 has 4210 heads I think they definitely crack easier. This is only my theory but have stacks of old heads to back it up.

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CharlieL

04-16-2000 19:48:46




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 Re: Re: MM heads in reply to Harrold Rhodes, 04-16-2000 09:47:29  
This post got my attention because I have been looking at an M5 on LP that's for sale and I am sure that one or both heads are cracked, and I 'm curious about what it cost to have heads repaired, I doubt that there are many good used heads around anymore. I have a 4Star that in good shape but I would like to have a larger tractor for heavier work. The M5 if I buy it will probably be a winter project like the 4Star was last winter, but the results are very satisfying. Any info on the M5 will be appreciated.

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Roger

04-16-2000 06:28:28




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 Re: MM heads in reply to GMS, 04-14-2000 09:56:51  
MM heads don't crack any worse than any other brand. For those of you that want to argue the point, come out and help me pull heads off salvege tractors. They all crack heads. It doesn't matter what brand I get in, about half the heads are broke. You can almost tell by the looks of a tractor if the head is going to be broke. A tractor that has been pulled hard and shutt off when hot will crack a head. I have several MM's with over 10,000 hours and never braoke a head. However, I never abused them either.

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GMS

04-17-2000 10:09:08




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 Re: Re: MM heads in reply to Roger, 04-16-2000 06:28:28  
Any recommendattions on how hard to run a tractor, and how long to let it run to cool off? When pullng in the field, my G705 runs between 170 and 180 degrees and I usually let it run 10-15 minutes to cool off. Is this enough. I always thought that if I was pulling a tractor too hard the temperature would increase, it this correct? Any infor would be helpful.

Thanks



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Jeff

04-15-2000 16:12:48




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 Re: MM heads in reply to GMS, 04-14-2000 09:56:51  
MMs crack heads it is a fact of life and all the motors that are cast in pairs have this problem.(not just LP motors) The best thing I can tell you is to make sure the motor is warmed up before working it hard and when done with tractor just don`t turn it off but, let it run a while to cool off. We do this with our MMs and We think it has helped, We have not had a cracked head for sometime(knock on wood)

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