Which CAM should I use in my 351m/400 6.6?
 

Hello all,

Simple question, which CAM should I use for my 1979 Ford F150 Ranger? Either this:
32-221-3 - High Energy? Hydraulic Flat Tappet Camshafts

or

32-206-3 - Dual Energy? Hydraulic Flat Tappet Camshafts

or

32-207-3 - Dual Energy? Hydraulic Flat Tappet Camshafts

or

another suggestion?

The engine is a 1978 351m/400 6.6. I would use this truck for 70% on road, 20% off road, and 10% towing. I plan on keeping the truck mostly stock. I would also buy the kit for either of the cams, a new intake, and a new holley carb. The goal is to have excellent / good torgue and "average to below average" fuel economy. I will most likely not buy new pistons at this time.

Please help, thanks!

. A 351M/400 is usually a 351"/5.7L... but if it says 6.6L it could be the 400" size...

. If not increasing the 7's:1 compression ratio for now, need to keep cam small like a Summit 5200:

http://www.summitracing.com/parts/sum-k5200
.

The motor says 351m/400 6.6 on it. From what I gathered the compression ratio should be 8.4 from stock.

To increase the compression ratio, do you recommend replacing the headers (302C 2 AUS) or milling? I am looking to get a decent power increase but not break my wallet.

One thing to note, this is my first build so I am open to all suggestions. :)

Shorter duration and higher lift. More stuff in quicker with less bleed off = higher cylinder pressures which result in more power.

Post 2 lists such a cam:

https://www.ford-trucks.com/forums/1...am-choice.html

With the low compression, you do not want a lumpy performance cam.

So I guess the next question, what is the accurate compression ratio for a 1978 351m/400 (That's the model on the engine) 6.6L engine. From what I think I know, this engine is a 400.

From what I've read, it should be 8.4:1. Please advise.

The motor doesn't say it is a 351M/400 on it. The label on the radiator support may say that, but all that means is that the specs shown on the label apply to both engines. It physically cannot be both a 351 cubic inch and a 400 cubic inch engine at the same time.

As for increasing the compression, you are pretty much stuck with about 8:1 compression with a 351M since you cannot get pistons with which to raise the compression. However, if your engine is a 400 you can get good pistons from Tim Meyer that will give you 9.5:1 with stock heads.

So now you need to figure out what your engine really is - a 351M or a 400. And that is tough to do from the outside as the only reliable way to do so is the measure the stroke - 3.5" for a 351M and 4.0" for a 400.

It was on the side of the engine (similar label from google, both the Google label and the label on my engine show 351m/400, 6.6L, and 400CID).

http://i70.servimg.com/u/f70/17/32/68/90/img_8512.jpg

The guy I bought the engine from stated it was a 400... but I could be wrong. I thought all 6.6L 351m/400's were the 400 model since the 351 is a 5.7L. It also does say 400CID next to it.

Thoughts?

What year is the 400 ? 351m is a de-stroke 400 where the name 351m came in 1975. Before 75 only 400. The first year in 1971(if m'y memory'sur good) the 400 came with more compression.

The year of the motor is 1978.

Well, that will teach me to forget that this isn't the 80-86 forum. Ford put that label on the radiator support in 80-86, but that's on the valve cover. My bad. However, it says "Engine Family" and then says "351M/400", which are two of the three engines in the 335 Series family. Note it doesn't say 400M, but 351M and 400. They are also known as a 5.8L and 6.6L engine, respectively.

Where does it say 400 CID? I believe you but just can't pick it out.

Next to the engine displacement line on the tag, it says: 6.6L 400CID

This is right under the Engine / Family line on the tag. Hope this helps.

Got it. Yes, it says it is a 400. So, let's start over. Are you rebuilding the engine, replacing the cam only, or??? I ask because the original cam is adequate, but the timing set probably has the cam retarded something like 8 degrees. So if your cam isn't flat, meaning the lobes are ok, you can replace the timing set and get a big boost with much less expense than a cam and lifters. Plus, you will need the new timing set anyway even if you install a new cam.

I am open to all suggestions. I originally was going to replace the cam with a cam + cam kit, carb, and intake.

I am open to just getting the kit to replace the chain if it were to make more sense.

I've heard from others that the original cams weren't bad from a lift and duration standpoint. It was just that they were badly retarded, making the engines gutless. If that is the case, and if the retard was in the timing set, then a simple swap of the timing set would be the best bang for the buck. And easiest as well. I would suggest letting someone like Buzz respond as I think he knows the answer to the question of where the timing retard was done - cam or timing set. Others may know that as well, but don't myself.

Sounds good, I will wait for a response from Buzz.

One thing I did notice though is that it is difficult to tell the difference between a 351m/400 motor. I know it says 400CID on my motor but is it really the 400 version? Several posts in this forum discussed it but I never really saw a straight answer.