Hey guys,

I have two questions regarding the installation of a new timing set on my 1978 Ford F-100 351M truck. One was an installation issue and the other was a question on where the dot on the camshaft sprocket should line up on the crankshaft sprocket

Comp Cam timing Set Part no. 2121.

First, I cannot get the dowel in on the cam sprocket to save my life. The dowel slips in the new sprocket fine, slips in the cam slot fine, but will not slip into both the cam slot and cam sprocket at the same time. This is when I either slip it I the cam slot first and put the sprocket on or put the sprocket on then try to put in the dowel in. I called Comp cams and they said it could be a machining issue. I asked the comp cam guy if I got the wrong timing set that was shipped in a 2121 box (I told him some stampings that were on the sprockets to see if he knew if it was the right part), and he said he wouldn't know because comp cam doesn't make their timing sets but put their name on it. Has anyone had this happen to them? I bought it off Summit and they will exchange the item, but I didn't know if I just need to get a wood block and a mallet to tap in the dowel or just wait the week and half for a replacement.

Second, the cam I have is the factory cam with the 4 degrees retard built into it. I am going to install the timing set with the 4 degree advance but wanted to make sure I was doing it right since I haven't done something like this. The crankshaft sprocket has a provision for the 4 degree advance. I saw a forum post from a few years back where this smart guy Tex was talking about how to advance the cam but I wanted to make sure I understood and did right what he was recommending.

Here is the forum:

New guy with a old truck and motor - Page 2 - Ford Muscle Forums : Ford Muscle Cars Tech Forum

I uploaded two pictures, I hope they load. I'll try again if they don't but I wanted to know which label needs to line up with the camshaft dot. On the crankshaft sprocket there is an upside down "A" on the keyway (highlighted in orange) and an upside down "A" on the crankshaft tooth sprocket (labeled red) just to the right of the keyway. Do I line the dot up with the keyway "A" OR the sprocket tooth "A" (which would have the keyway off to the left and I would not be at true TDC)?

Also, I did the thumb on the spark plug hole trick and then used a pencil along with the timing pointer to find TDC.

Any help is much appreciated.

Thanks,

Vos

 

I got a new timing set, I will give it a try to see if the old one was just defective. If anyone knows which way to set it at 4 degrees advanced, let me know. I think the tooth marking needs to be aligned at 12 O'clock with the keyway off set a little to the left but wasn't completely sure.

 

When the crank gear mark is straight up, the cam gear mark should be very slightly clockwise to the left of bottom center for the advanced position. I know (from experience) Edelbrock at one time had some mis-printed instructions regarding this. Been long enough ago I don't remember if it was 400 or 460 double roller set.

 

Hey thanks, I got the timing set installed 4 degrees advanced. For anyone who might know about these symptoms, I am still having troubles (engine runs better than before). I started the truck and it is fine at idle (or at least idling well enough), but the engine consistently fires out the carburetor at 1/3 to half throttle. It stumbles at any speed beyond that. If the peddle is maintained beyond 1/3 to 1/2 throttle, it will continue to backfire and eventually bog down. When in drive, the truck will move in idle to 1/3 throttle without losing power, but once it is more than that throttle, it will give heavy backfire out the carb and bog down.

The motor is at 114,000 miles (I don't think it rolled to 214,000). I've checked my wires and they don't look crossed. I installed a new fuel pump when installing the timing chain. The carburetor is fairly new. I checked the accelerator pump diaphragm by looking down the intake with engine turned off and saw healthy two squirts of gas. I checked the power valve by blowing on it. No leak.

I pulled out a vacuum gauge, and I get 16 in. when at about 12 BTDC, and have to advance it to about 20 BTDC to get about 19-20 in. The thing is, it doesn't hold consistent. It wavers one or two inches. Maybe I need to check again, but I think it will slowly move back and forth with a slight tick one way or the other within that 2 inch range. I tried to set the idle mixture to rule out that vacuum gauge symptom but it didn't change anything.

I pulled the valve covers off and had the engine cranked over while I looked at the rocker arms and there weren't any moving less than any of the other ones (none sticking). Everything was coated in carbon, however.

Could all the lifters/cam be equally worn on a 351M with only 114,000? I really don't know what to do at this point.

The truck used to run terrible before the new timing set. To drive it where it needed to be worked on, I had to advance the distributor and increase the engine to a fast idle and move it at 5-10 mph to get it there. When I pulled the timing cover off, you could slap the chain around on both sides, it was that bad. It would run bad at all speeds but always fell flat after about a third to half throttle.

My brother, who is not mechanically inclined, drove the truck for over 6 months and complained that the truck had started to get a growing hesitation at half throttle. It would be fixed by pumping the pedal once and it would surge past the hesitation. But, it had gotten so bad and that didnt work so he quit driving it. I had thought the timing chain would fix it. If anybody has any ideas, that would be great. Hate for it to be a cam/lifter problem since I was already in the damn motor. If there are other tests to or ideas, let me know. Thanks