C6 vs c4 fmx

Big dog

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Hi

I have 72 Mach 1 351c with c6 that is leaking and will need a rebuild am I better keeping this or changing for c4 or Fmx engine I believe is stock at the moment

I will look to change inlet manifold carb and headers plus exhaust to gain more horses

Regards Perrie

 

TommyK

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For simplicity sake I would say rebuild the C6.

 

Big dog

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If only issue is the leak fix it and don't bother to rebuild. Most drag racers prefer the c-4 but the C-6 has always been stronger.
Proberly the safest bet

Do the new rebuild kits create less drag than the original,as been told c6 robs horse power

And seems not many headers available I have 351c 2v

 

mjlan

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A generic rebuild kit will only include clutches, steels and soft parts, nothing exotic.

If your build is primarily a street car, I don't think the parasitic losses of one automatic trans vs. Another are worth swapping for.

Now if you were drag racing with a once a week trip for ice cream with the family, then spending $3k on a heavily modified C4 to reduce losses might make sense.

Hopefully I'm not coming across as a dick, I have a tendency to overthink things, and the internet is a great enabler of that.

My $0.02- if you have a running car with an old trans that works but just needs some attention, and you are not after knocking off each tenth of your ET, just keep the C6. It was Ford's HD trans for many years and is good unit...

 
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Big dog

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A generic rebuild kit will only include clutches, steels and soft parts, nothing exotic.

If your build is primarily a street car, I don't think the parasitic losses of one automatic trans vs. Another are worth swapping for.

Now if you were drag racing with a once a week trip for ice cream with the family, then spending $3k on a heavily modified C4 to reduce losses might make sense.

Hopefully I'm not coming across as a dick, I have a tendency to overthink things, and the internet is a great enabler of that.

My $0.02- if you have a running car with an old trans that works but just needs some attention, and you are not after knocking off each tenth of your ET, just keep the C6. It was Ford's HD trans for many years and is good unit...
Thx for comment

I was concerned that as my 72 is H code 351c 2v could be low Hp I would be disappointed if gearbox dragged it back,I want it for street use going to my local meets tearing up the street a bit and just looking good

I will up grade carb and inlet manifold to elderbroke

And headers in the future

It's a 72 built late 71 what is most likely Hp

 

Big dog

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Also any info on comp cam 238 is it suitable for street use with my engine as above

 

secluff

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Agree with mjlan. Unless your building an all out quarter mile assault car where every tenth of a second counts, for simplicity's sake I would stay with the C6. Our shop trans tech built a lot of C4's for the local Ford drag racer's who wanted a lighter transmission with less parasitic losses and didn't want to run a GM Poweglide. To them everything they could do to lighten the vehicle and not long term longevity was their primary concern.

The C6 was a very robust (and heavy) transmission that Ford used in a multitude of vehicles and industrial equipment including the F600 medium duty trucks.

As others have posted, I would repair the C6 and not have to worry with dealing with different driveshaft's and neutral safety switch.

 

Don C

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Advertised horsepower was 266, down from 280 in 1971 due to pollution controls, and may have been a little optimistic.

The drag racers are looking for ways to shave a few hundredths of a second off their E.T.s wherever they can. The C4 helps in two ways, lighter weight and less drag. The only way you would ever be able to tell the difference would be to run it down the track with your C6 and then with a C4 and measure the times. I doubt if you would be able to tell the difference by "seat of the pants".

The general reason a C6 has more losses is due to larger gears and bearings, which have more friction than those in the C4.

Unless you rebuild it yourself, or know a good rebuilder, I would just take care of the leaks, as long as it is running OK. Other than the pan gasket the most common leak is from the shifter shaft seal, which can be a challenge to replace while the transmission is in the car, but doable.

 

Big dog

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All sounds good advice and has put my mind at rest I will keep the c6

It has a b&m mega shift kit i like the look of it in the car who likes them here

Or would you go back to original, I do not have original shifter so would need to purchase the parts

 

mustang7173

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Big dog,

How many miles are logged on the odometer? If it is the original engine, then the timing chain, plastic gears, could be suspect of loose chain. I am with the other members, if you can tell where it is leaking, get it repaired.

IMO, I would spring for the exhaust headers, dual exhaust with a cross over first. This will open up the engine to breathe better. Then get the Edelbrock 2V performer with a 600 cfm carb.

mustang7173

 

Big dog

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Big dog,

How many miles are logged on the odometer? If it is the original engine, then the timing chain, plastic gears, could be suspect of loose chain. I am with the other members, if you can tell where it is leaking, get it repaired.

IMO, I would spring for the exhaust headers, dual exhaust with a cross over first. This will open up the engine to breathe better. Then get the Edelbrock 2V performer with a 600 cfm carb.

mustang7173
Looks original starts up good ticks over nice don't know what it's like under load as not on the road yet shows 98000 miles

 
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