cam timing

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Nov 21, 2006 | 12:16 PM

muscletruck7379

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From: Harrisburg, NE

cam timing

I read somewhere that the 400's had the cam timing retarded 4 degrees for emmisions, what kind of truth was there behind this and what other effects did it cause?

Nov 21, 2006 | 03:55 PM

Torque1st

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In 71 they were timed properly, after that they were retarded 4° for emissions. The change reduced low RPM performance and increased high RPM performance slightly.

The OEM nylon tooth timing set can fail at any time after 80K miles so it is common practice to replace the timing set with an aftermarket multi-keyway performance timing set. The OEM stock replacement units available in parts stores are retarded 4°.

Nov 23, 2006 | 03:52 PM

supercab78

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From: Ohio

If he buys one for a 1971, 351C or 400 from a real parts store would he still get one thats retarded? Just wondering!

Nov 23, 2006 | 05:29 PM

Torque1st

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Yes, he would still get one that is retarded 4°. Just like if you go in and buy a set of replacement pistons for a 1971 you would still get the dished pistons for a later engine.

Nov 23, 2006 | 05:32 PM

monsterbaby

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From: iowa

best bet is to buy one of the aftermarket roller timing sets that usually have 3 keyways and then degree the cam to the straight up position.

Nov 24, 2006 | 10:38 PM

grclark351

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From: chicago burbs

all stock cams are not created equal either. look at the D5 camshaft, the intake opening is significantly retarded from all the others. other timing events are also different.
http://home.earthlink.net/~bubbaf250/parts/parts03.html

just as the "2 piece valve" has recently been questioned , having never done a study of the timing sets myself, how do we really KNOW that the timing set is where the retard is built in? Bubba's info shows the cam to be retarded.

Nov 25, 2006 | 01:47 AM

Torque1st

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Every OEM timing set I have examined has been retarded. It is possible to see the 4° built into the crank sprocket.

From that link:

Quote:

When the 400 was introduced in the 1971 model year, it used the same timing set (camshaft and crankshaft sprockets and timing chain) as the 351C engines. The camshaft sprocket and timing chain were both designed originally for the 351C engine (with D0AE part numbers), and the crankshaft sprocket was originally designed for the 1968 Thunderbird 429 engine (with a C8SE part number).

In the 1973 model year, Ford retarded the camshaft timing in 351C 2V and 400 engines for emissions control. To do this, they redesigned the camshaft timing set.

The new D3AE timing set used narrower sprockets (13/32" vs. 1/2") for the camshaft and crankshaft, and a narrower 4-plate chain instead of the earlier 5-plate chain. The actual camshaft timing retard was implemented by changing the alignment of the keyway and “index” tooth on the crankshaft sprocket.

Last edited by Torque1st; Nov 25, 2006 at 03:55 PM.