Hey guys,

I have a question that is best left to the pros to answer. I know that the stock cam timing on the 400's in trucks were retarded 4 degrees from the factory and if you buy a new timing set that is a "stock" replacement it is typically retarded as well. My question is: Was the cam timing retarded in the cars as well?

The reason I ask is that when my 400 (truck) engine was rebuilt 1 1/2 years ago, I had it rebuilt as stock. After reading about the benefits of setting the cam gear "straight up", I tried to find out what set was used in my 400. I can't go to the machine shop that did the work because they no longer exist. But, on my invoice there was a part # listed and I went to a local supply store and the part # listed is for a "car" application. There is a different part # for "truck" and "car" stock timing sets. Are the Cars set at zero??

Sorry this post is so long but I felt I should explain why I'm asking about CARS on a FORD TRUCK site!!!!

Thanks for any input you guys may have....

Jay

 

I think it is the same. When I got a new stock timming chain for my truck it came up as the same number at parts store that I went to.

 

Jay,

Timing was retarded in all 351C 2V and 400s starting in the 1973 model year. Ford designed a new timing set that incorporated cam timing retard and used a narrower chain and gears.

If your timing set was for an early car application ('70-'72 351C 2V or '71-'72 400), or a '70-'74 351C 4V application, then it could be the original spec, wider and non-retarded timing set.

When M-blocks (351M/400) were introduced in trucks in the 1977 model year, Ford went back to the original, wider timing set for truck engines, with a new (retarded) truck crank sprocket.

Lately, I have seen some evidence that persuades me to believe that at least some truck M-blocks did not have retarded cam timing. However, retarded or not, the truck engines used a wider timing chain than post-'73 car engines.

The narrow and wide timing sets are mechanically interchangeable, so some manufacturers may list only one part.

 

a few thoughts on the retarded cam timing. while i was what ifing with the dd2k. i noticed that advancing or retarding the cam timing all it really did was roll the peak power up and down the rpm band. now on a side note, i did also notice that sometimes it made more power a 4 degrees retarded.

hmm i wonder if ford might have known something?????

 

[updated:LAST EDITED ON 11-Oct-02 AT 07:10 AM (EST)]>If your timing set was for an early car application ('70-'72
>351C 2V or '71-'72 400), or a '70-'74 351C 4V application,
>then it could be the original spec, wider and non-retarded
>timing set.

Thanks Bubbaf250,

But the "car" application that is listed is for 1969-1982 Ford Car V8 400 6.6l (I'm in Canada):-X12 The same part # is listed for 1969-1982 Ford Car 351 5.8l(?).

So, do you think maybe they just made one set to cover these years and left it at zero? Knowing that we now have higher octane unleaded gas than was available in the mid 70's?

If there really isn't much difference between straight-up and retarded 4 degrees, then I'm not real concerned with which I have, but from all the posts on this board, it appears to be better.

Thanks,

Jay

 

Hey Bubbaf250,

Thanks to you I've got it figured out! Your info about 1973 being the year Ford started to retard the sprocket made me start to think. So I went to the web site of a part supplier and pretended to do a little "shopping". If I check for a timing set for a 1972 car with a 400 I was getting a Dynagear part # 73005. If I check for a timing set for a 1973 car with a 400 I was getting a Dynagear part # 73009. The part # 73009 is the part # that is on my invoice from 1 1/2 years ago, so I know I have a timing set that is retarded.

The only thing that confuses me is that the part # that comes up for any 77-79 F100 with a 400 is 73005 which wouldn't be retarded.

I know that the 73005 isn't retarded because it's the # that comes up for a 1971 Mustang 351 Cleveland!!

Thanks again!!

Jay

 

Jay,

Some manufacturers of stock replacement, OEM-type timing sets have incorporated the cam timing retard in all their parts. The difference in the Dynagear parts you looked up may just be the width of the chain and gears.

The only way to verify your cam timing is to examine the crank gear, or compare it with a known non-retarded gear.

At any rate, as GT40man correctly pointed out, there is little power difference between OEM-retarded and non-retarded cam timing. The only significant difference occurs at low rpm (under 2K), which is important for acceleration in a truck or heavy car.

Because "horsepower" depends on both torque and speed, as long as the torque curve doesn't drop, spinning more rpm will give more horsepower. Retarding cam timing moves the cam's inherent power band up to higher rpm, and it can produce more horsepower at the expense of some low-rpm torque.

The reason that Ford (and other manufacturers) retarded cam timing in the early '70s was for easy emissions control, not horsepower. Retarding cam timing opens the intake valve later, which reduces the quantity of the fuel/air charge in the cylinder at low rpm. That not only reduces torque, it reduces the emissions at idle and at low rpm, exactly the conditions under which emissions compliance testing was done.