1973 Mach 1 H-code Question

Also check the centrifugal timing limit under the breaker plate. It should be in the "13L" slot. This limits the advance to 26 crank degrees. The initial advance can then be set for 10 crank degrees for a total of 36 degrees.

Roland said:

that does work? with the same cam?

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Yes, I never changed cams

351c1971 said:

Also consider the fact that the 1973 and later heads have induction hardened valve seats for more durability with unleaded gas.

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I did not know the 73 and later heads had/have hardened steel valve seats. Iive. learn, share... Vey cool. Was that on only the 73 351C, or did Ford do that with all engines beginning in 1969?

mrgmhale said:

I did not know the 73 and later heads had/have hardened steel valve seats. Ilve. learn, share... Vey cool. Was that on only the 73 351C, or did Ford do that with all engines beginning in 1969?

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There is so much conflicting information on this that I'm not sure anyone really knows anymore. My '73C is in the shop right now and has hardened seats.

I believe it was all engines to compensate for the unleaded gas only requirement.

The 73 models actually had an "Unleaded Gas Only" decal on the rear bumper. This was used before the fuel nozzle opening was redesigned for the newer fuel nozzles.

born2cruze said:

A good intake and 4 barrel carb should do well for that car.
In 73 the timing was retarded 4degrees, if you add a new timing gear set and set it to 0 it tends to wake up the Cleveland , sure helped my Q code

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I assume the q-code in 1972 was also retarded, isn‘t it?

I do not recall any timing specs for the replacement timing chains. We’re they all “0” degrees?

Rock Auto lists the same timing chain for 71 & 72. 73 is different. My 71 chain was Melling 3494SB. This was also listed for 72. My guess is that the 71 & 72 were not retarded. At least for the "H" code Cleveland engines.

The Cloyes Timing Set for the 351c engines, does not differentiate between a "straight-up', or "retarded' timing set. The "retarded' cam timing was done by Ford to help with emissions. Cloyes has always been the best aftermarket timing set, almost the Standard of the industry for performance timing sets, therefore, doesn't make a "retarded" timing set. I realise that most hobbiests don't have the experience to degree-in their camshafts,......however, we all know it should be done, at least checked. I leau of checking, rest assured that installing your performance timing set "straight-up", or, dot-to-dot, will yield a decent install. Know, as well, that many camshaft manufacturers today, will grind their cams with 4 degrees advance built in, and is how most are recommended to be installed. Don't worry, a 4 degree advanced cam will give you a bit more grunt on the bottom end, and over time, as the timing chain stretches ( it will, they all do ), the worst thing that will happen, is your cam timing will retard to approximately "straight -up", so don't worry about the new aftermarket cam's built in 4 degrees advance. Back to the post, my "H" code is stock, and has run pretty darned good for many years.

Roland said:

I assume the q-code in 1972 was also retarded, isn‘t it?

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Yes it is, As Spike stated most new sets will set at 0 degrees dot to dot, just install a good double roller set