Hello I’m new to your forum and love the site! I have a 1975 for F150 4X4 with a 400 with C6 tranny.
I am wanting to put a cam kit in the motor but nothing super extreme.
I was thinking about the thumper cam but would I have to change my torque converter if I add this cam?
Thanks.

 

Are you sure it is a 400? If it is, it won't be original to the truck. The 351m/400 were available in 77 and up.

 

Post some pictures of the engine if you are not sure, though it is pretty easy to tell the difference between the two. If the valve cover covers up part of the intake as well, you have a FE engine (most likely a 360 if original), as a 75 should. Also, if you could post a link to the cam you are talking about. Probably the most important thing with a cam upgrade is whether it will work with the stock valve springs, more so than the torque converter. Without knowing the spec of the cam, as long as it is a mild upgrade only, then the stock torque converter should be fine I would think.

 

With a name like "Thumper", yeah I'd imagine you'd have to change the torque converter. Read cam descriptions and think about idle quality. If it won't idle at around 650 rpm, you'll need a looser than stock (higher stall) converter. And there are other considerations with high lift and extra overlap camshafts. Low vacuum being one of the biggest. Air flow also. Your stock cylinder heads won't flow enough on the intake or exhaust side to see much benefit from a hot camshaft

 

A thumper cam would be a joke in a stock 400 forget it. the convertor would only be a part of what you need to change.

Figure out what engine you have first, if it's really a 400 someone went to a lot of work to go backwards.

 

X2 on this post.....

The 351M/400M is a merely designed very torquey 2 barrel head with limited potential as you cannot really build it for horsepower.

Choice of cam selection upmost importance is it needs to match with a set of valve springs that will handle the cam specs, followed by what kind of cylinder heads are capable of flowing air in and out to increase it's performance potential, and what one really wants for performance if venturing beyond the stock or mild build zone (beyond 260 advertised duration or beyond 210 duration at .050 lift).... which means modifying other components while sacrificing engine vacuum, fuel efficiency, $$$$$$$$$$, etc.

I don't see much benefit of a radical cam on a 400M either unless it is a seriously modified cylinder head of sorts.

What are the cam specs of this "thumper' cam ?

 

First of all unless someone swapped one in, your 1975 truck doesn't have the 351M or 400 engine. If you are lucky, it's an FE 390 or 460, if you want power. Post the VIN and you will find out.

Second, it's a surprise that people here jumped on the 400 so quickly. 400 variants have won or placed in Enginemasters more than once. Tim Meyer has a handle on building 400hp 400s, that should be enough power for most folks. Think 351Cleveland's big brother.

The stock M head flows enough to support 400hp. The critics don't understand camshafts, either. Using a longer duration camshaft is a common way to crutch a low-flowing head. Modern engines are making 1hp/cubic inch with 0.050 lift durations of around 210 degrees. That's because the heads are so good. Older heads with which we are familiar might need up to 240 degrees at 0.050 lift to make 1hp/cubic inch. So saying a head doesn't flow enough to use a larger cam is nonsense.

R.

 

Please don't suggest to this member that he can make more than double his horsepower on a stock 400 with only a camshaft swap.