I have a 351M and just sent it to get new cam bearrings and a dip done on it.Ihave a coulple of questions?

1)exhaust "ports" what do oyu mean by that and how would you grind them out
2)cam setting it stait-up?do taht when you put on the timing chain our when you install the cam?

thanks Richard

 

Well first of all make sure you have it hot tanked before you have the new cam bearings put in

Exhaust ports are the area of the head behind the exhaust valves and before the manifolds/header where the exhaust exits the heads. In the 335 series heads there are bumps in the heads where the A.I.R. system injects air into the exhaust stream. These are the first things you want to grind out of the heads to improve flow. You can also increase flow by removing the casting flash from inside the "pocket" which is just behind the valves and smoothing the port as much as possible. If you really want to improve flow then you can remove most or all of the valve boss that extends down into the pocket as well.

In a "perfect" head the exahust gases would have a straight shot out of the head into the headers which is why some hi-po aftermarket heads "raise" the exhaust ports to provide a smoother path for the gases to flow. The limitations of the engine compartment determine the shape of the exhaust ports in factory heads which is why you end up with a "dogleg" port from the combustion chamber to the header. On some heads there's enough metal that some of the "floor" of the exhaust port can be removed making the flow path straighter. If you remove too much you end up cutting into a water jacket. This is generally referred to as a V.B.T. (Very Bad Thing) and results in some very large paperweights.

Straight up cam timing refers to the timing of the camshaft relative to the crankshaft. In an effort to reduce emissions in the mid 70's Ford built a 4 deg timing retard into the factory motors. Putting in a good aftermarket timing set and determining the piston position relative to the valve timing, commonly know as "degreeing" the camshaft will ensure that you get the most performance out of whatever camshaft you decide to install.

In order to degree a camshaft you need the cam, the timing set and the #1 piston installed. You'll also need a degree wheel. There are plenty of "how to" guides on the 'net which'll walk you thru the process.

 

Thanks for the help do you have any sites with cam degree on them?and what is a degree wheel can you get that at alocal tool place or is it a special order thing?maybe i will just get Armstrongs to do it(thats where i sent it to)

 

You can get degree wheels at auto parts stores, speed shops, and some tool stores. You will also need a piston stop that screws into the spark plug hole and a dial indicator with a magnetic base.

Cam degree information is on the cam card that comes with a new cam. You can also look up the cam card specs on the manufacturer's websites.

 

My 78 351m did not have the AIR INJECTION SYSTEM. So it depends on which heads you have!

 

The 78 heads would still have the air passage and the bumps in the exhaust ports even if it did not have the air pump.