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Harry Ferguson Tractors Discussion Forum
Show Parts for Model:

Intake manifold differences.

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Jason S.

11-09-2013 17:07:47
174.237.10.74



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I"ve got two extra intake manifolds laying around. One original and one aftermarket. I had them laying next to each other and noticed there is quite a bit of difference between the two. The opening where the carb bolts on is quite a bit bigger on the aftermarket manifold than the original one. The ports are also bigger on the aftermarket one than the original. From my observations the aftermarket manifolds will reduce the low end torque on a TO-20. They key to building low end torque is small ports which keeps up velocity in the air/fuel charge. The aftermarket one will hurt the low end performance on the smaller cubic inch Z120 engine. The aftermarket manifold would be ok on a Z129 or Z134 engine because of their increased displacement and better breathing because of their larger intake valve. I am going to measure tomorrow and give you all some numbers. Also by the design the aftermarket manifold will cause the exhaust to be louder than the originals.

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ShadetreeRet

11-10-2013 18:43:51
76.3.100.234



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 Re: Intake manifold differences. in reply to Jason S., 11-09-2013 17:07:47  
If an intake manifold has larger ports, yet the ports in the head remain the same, I fail to see how the size of the ports on the manifold would have much effect.



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Jason S.

11-11-2013 08:54:12
192.43.65.245



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 Re: Intake manifold differences. in reply to ShadetreeRet, 11-10-2013 18:43:51  
If the port in the head is smaller than the port in the intake then there will be an overhang all the way around the port and the effect would be like turning a fan against a wall. The air and fuel would hit the overhang in the opening and it would go back into the intake. Part of the air fuel mix would flow through fine but around the edges it would constantly blow back into the intake which is bad. Ideally you want both port sizes to be the same or have the port in the head bigger than the one coming out of the intake so there is no disruption in flow.

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Jason S.

11-10-2013 18:17:34
174.237.2.148



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 Re: Intake manifold differences. in reply to Charles in Aus., 11-09-2013 17:07:47  
Quoting Removed, click Modern View to see



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Jerry/MT

11-09-2013 22:02:38
206.183.116.145



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 Re: Intake manifold differences. in reply to Jason S., 11-09-2013 17:07:47  
Smaller ports mean higher velocities that limit max power and torque. Remember the power curves you see are WOT operation so that"s the max airflow for any given rpm.
The reason the torque curve drops off with increasing rpm (or converely increases with decreasing rpm)is due to increased induction system losses(pressure losses due to both manifold friction and losses across the valves). The peak torque occurs at low rpms because the losses are a function of the dynamic pressure ~V^2 and V increases with increasing airflow which increases with rpm. I believe there is an issue of requiring certain velocity levels to prevent fuel droplets from dropping out of suspension in the air stream and screwing up the mixture distribution so there is likely some lower limit on runner velocity for carburetion effects. These are more likely second order effects.
Runner lengths influence the torque curve also due to wave effects but that"s not germain to tractor applications except possibly for the guys running pullers.

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Jason S.

11-10-2013 05:29:36
174.237.2.148



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 Re: Intake manifold differences. in reply to Jerry/MT, 11-09-2013 22:02:38  
I can't agree with all of that. Runner lengths are important to any engine regardless of the application. You also have to remember that the Z120 had a longer duration camshaft than the Z129 or Z134 which would make the Z120 even more sensitive to plenum and runner size.



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Jerry/MT

11-10-2013 10:58:42
206.183.116.145



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 Re: Intake manifold differences. in reply to Jason S., 11-10-2013 05:29:36  
Runner L/D is important for performance improvements that will occur in a vey narrow range of rpms. These engines are designed for operation over a wide range of rpms.

Further, as I recall, the lower the rpm the greater the required L/D to get an induction improvement. It might be practical for a racing application at 6000+ rpm but for a tractor operating between 1200 and 2200 rpm it would be difficult to fit in the allowable space envelope.

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Jason S.

11-10-2013 18:07:41
174.237.2.148



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 Re: Intake manifold differences. in reply to Jerry/MT, 11-10-2013 10:58:42  
I copied this out of engine building 101

Intake Port Area
Unlike intake runner length which effects power over a narrow rpm range, the size (area) of the runner will affect power over the entire rpm range. If the port is too small it will restrict top-end flow and flow, and if it's too large velocity will be reduced and it will hurt low-end power. The larger the port is, the less strength the pressure waves will have.

There you go, it is the runner length that effects power over a narrow rpm range but the port area effects power over the entire rpm range which is what I'm saying. It would be like putting a large plenum large runner intake on a dump truck motor. Low end torque would suffer because the engine was not designed to move the amount of air and run the rpms that it takes to keep velocity up in that style of intake. There is an old rule of thumb that you never want to have the port size bigger than the intake valve diameter. The original intakes plenum and runner was 1.00" as I measured today. The aftermarket was 1.25" which is closer in size to the 1.14" intake valve size of the Z129 and Z134 engines. Also adding plenum volume raises the rpm that peak torque would would occur at. Look at the picture not only is the aftermarket a 1/4" bigger in diameter look how much longer it is which is adding plenum volume to the intake that only high rpms or added cubic inches could benefit from.

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