I would like some input about throttle response please. I have never built an engine any other way other than stock. I consider myself to be a rookie when it comes to getting more horsepower and torque out of an engine i am rebuilding. I am reading and learning before I actually try to rebuild a more powerful engine. I am preparing to rebuild an '85 Ford 4x4 351M truck engine for more pulling power. A couple of years ago I was at a friends house, he had rebuilt an engine to go into an old panel van he restored. He started the engine while I was there and after it warmed up he would punch the accelerator and the throttle response was instant. I was use to what I would call a relatively slow or normal throttle response from stock engines. His throttle response was more like that of a dragster type engine. Why question is how is this "instant" throttle response accomplished? Is this something that has to be consider through out the entire rebuild or does this mostly come from the intake and carburetor setup? I would ask him but he is no longer with us. I appreciate your input and thank you in advance for sharing your wisdom.

 

First, welcome to FTE. Second, it really is an M and not a W? If so, welcome to the relatively small club. I own two of them - one is stock and is a dog, and the other is rebuilt with an RV cam, 4bbl carb and intake and it runs well. So, do not build a stock M. No way, Jose. The stock cam is retarded as is the stock timing set.

As for throttle response, several things play into that: Good compression; a low RPM cam; proper idle air/fuel mix and distribution; ignition timing; and a good accelerator pump are all on the list. My rebuilt 351M has good throttle response but doesn't really have anything special that makes it so. Here are some of its components:

• Cam: I actually dont know exactly which cam it is, but it pulls strong from idle. Dont go with a high RPM cam.
• Intake: Edelbrock Performer 400
• Carb: Edelbrock Performer 1406
• ignition timing: 16 degrees BTDC
• Heads: Stock
• Exhaust: Stock manifolds and Magnaflow muffler

One thing you might consider if you are going to build an engine is to make it a 400. The difference is just the crank and pistons and you'll have lots of torque.

 

Gary hit it.You need a short duration cam with lots of lift.Higher compression than stock.Lots of initial timing but not so much as to cause detononation or hard starting.Long tube headers with 1 1/2 in primary tubes.A smaller carb w/vac. secondaries.It's hard to be humble when building an engine for torque but that's what you need to move these massive trucks.If you want factory gearing,stock converter and off idle power then you'll have to stay conservative.Tuning everything after you get it running is where you'll really notice the gaines.50 cubes more will be very apparent.400 cranks are not looked at as being desirable so you shoud be able to score a rotating assembly for cheap.Most people scoff at the M engines but they can be built for power.Check out the M engine section in this forum for specifics.The biggest power gaines will come from the proper combination of parts.

 

Thank you gentlemen I really appreciate your input here. The question has been posed to me about whether it is an M or a W and now I am wondering myself, I was sure it was an M but now I'm not so sure. If it is an M I want to rebuild it as a 400 if it is a W I am lost and will have to start all over figuring out how to increase the torque and horsepower. Is there a way to know whether it's an M or a W? If it is a W I will be looking for ways to increase it during the rebuild. Thanks again for the help.

 

8 bolts holding the valve covers on? It's a 351m.

6 bolts holding the valve covers on? It's a 351w.

 

81 was the end of 351M's in the pickups, with the W taking over in 82. So it would be odd for your 85 to have an M as it would have been swapped in. But, it isn't that hard to do so is possible.

 

Thank you gentle men I honestly appreciate your input. I will count the valve cover bolt and see if it's an M or a W. If it's a W then I will start a new thread seeking advice on how to get more horsepower and torque out of a 351W rebuild LOL. Spent all my time researching the M and now I may have to switch and research and ask for advice and input on the W LOL. Thank Again

 

I swapped out my factory ignition box for an MSD 6A and it improved throttle response quite a bit. Prior to this, if I would blip the throttle hard from idle, it would rev pretty slow and stumble alot of times. But with the MSD it revs very quickly and doesn't stumble at all. Idle sounds different and I noticed a power increase.

I removed my factory ignition module from the system entirely, the only factory wire I'm using for the MSD is the key-on power wire. Everything else is new and heavy gauge.

 

Thank you again gentlemen I appreciate your input. I counted the valve cover bolts and it has 6 per cover. I also looked at the exhaust manifold bolts and horizontally they are in a line but each chamber has a short and a long mounting bolt. I don't know if the short and long exhaust manifold bolts have anything to do with anything, I suppose you could say they are staggered in and out but not up and down. So what do I have gentlemen.........a 351W? Thank you in advance for you input and priceless help with this.

 

Sounds like a W, which is what it should have come with. In fact, it is probably an HO with a Holley 4180 4bbl carb.

Another check on the M vs W is the M has the thermostat in the block while the W has it in the intake manifold. But, don't know of an easy check using the exhaust manifolds or bolts.

 

Thanks Gary, I am about 95% certain now it's a 351W instead of an M. I bought this truck from my son who bought it used so I don't know what changes it might have gone through before he bought it. I do know when he bought it, it had a 2 barrel intake and a little 2 barrel carb on it. While he owned it we put an edelbrock high rise and an edelbrock 4 barrel on it trying to help it out a little. I can't remember the size carb we put on it but it has ran really well with the 4 barrel. I had to drill out a broken intake bolt in the head when we did the swap so I pulled the head. I looked at the cylinder walls and to the naked eye they looked pretty good and there were no markings on the piston tops to indicate it had ever been bored. It is now using some oil and leaking some oil plus I am wanting a little more torgue and horsepower out of it for pulling trailers so it is getting a rebuild job soon. Any input on turning up a 351W will be greatly appreciated and I thank all for their help and guidance thus far.

 

An 85 351 Windsor that came with a 2bbl? Are you sure it's DSII and not TFI?

If it's TFI, you won't be getting the most power out of your motor because its probably got the timing locked.

If it's DSII, then the ignition module is under the hood on the driver's side wheel well. If it's TFI, then it'll have the ignition module under the ash tray, in cab.

 

You want a low RPM setup, which means a low-rise intake, medium to small 4bbl, and RV cam. I like the Edelbrock Performer intake and their 1406 carb, although that's their economy carb and the 1405 might get you a bit more power. As for cam, I ran a Comp Cams 252H in a 351W and loved it. Torque came in from idle and it pulled hard right on up.

Compression ratio really helps torque, but w/o going to aftermarket heads you are pretty well stuck at 8.x:1. Thumper sells some stock heads that have been ported and, from what I've read, give good results. And, you can go to later model heads like the Explorer heads. But you have to know what you are doing there as some of them will give you way too much CR. whatever you do don't go with heads that have huge valves and runners as they kill the speed of the incoming charge, which kills low RPM power.

 

Check your oil pressure sending unit. My truck used to lose oil quite regularly until I installed a new sending unit. Now I only have to add a little oil maybe once every month or two.

I have also heard about installing what's called a "straight-up" timing set. From the factory our engines have retard built into the timing set, and a non-retarded set might improve power.

I've never even been inside my own engine much less anyone else's, so I'll leave the big stuff to the pros. haha

 

Thank you gentlemen I appreciate it. To be honest with you I really don't know the answers to some of these questions. Please bear in mind I am a rookie here, the last engine I rebuilt had points and condensor setup. I don't know about the TFI or the DSII sorry but this is over my head. I do know I can twist the distributor and change the timing according to my timing light, please remember it's a 1985 model 4x4. I am honestly not trying to be a smart azz here I am just ingorant. The only Ford motor I have ever rebuilt in my life was in a 1964 truck with a 3 on the tree and the newest I ever rebuilt was a 1974 chevrolet with a 350. Every engine I ever rebuilt had points and condensor so I know less than nothing about electronic ignition and timing locks. I am very willing to read books to learn but I have no idea which books to get to learn about what. Again I thank you for your help and your input and I really thank you for your patience, they are greatly appreciated.