FORD 351W LONG ROD STROKER KIT

Very interested in running this in tandem with afr 165s, edelbrock efi truck upper&lower, and longtubes. Kickass rod ratio of 1.88:1, should make lotsa torque and decent mileage. Thinking about running dished hypereutectic pistons to keep the compression reasonable with the 60cc chambers.

Anybody done a long rod 351 or know someone who has?

Speedomotive hasn't been very responsive to my questions yet, but I'm nowhere near purchasing just yet.

 

I'm a person who concerns himself with rod ratio but I'm also a realist. The rod ratio will have an incremental effect. If it is properly matched with intake and head runner size and cam LSA the combination can be a reasonable addition, but in and of itself, rod ratio is not a big variable.

The long stroke and the long tube headers will have WAY more positive effect than the rod ratio.

 

As far as I know, a higher rod ratio should equate to less sideloading, more piston dwell (supposedly better burn efficiency), and better longevity when compared to 351 strokers whose rod ratios are generally right at the stock 1.7 or less. Granted, it won't have as much power as a motor with 30-50 more cubes, but I think it should be plenty with 4:56's and 35's.

The stroke remains at stock 3.5", rods are longer, and compression height is different to compensate for additional rod length.

I figured the plan above (twin 56mm tb, eddy efi intake, 165 afrs, 1.5" primary longtubes) was about right for a torquey and reasonably efficient lifted bronco. Haven't made up my mind on a computer compatible cam yet.

What would you say is a proper runner size and LSA for a SFI 351w longrod motor.

 

You are indeed correct as rod ratio effects engine longevity. The higher rod ratios do indeed decrease thrust side piston/cylinder loading.

My point was that power wise, rod ratio is a small factor. If it is properly matched to the intake runner volume and the lobe separation angle it can be a helpful combination. In and of itself, moving from a 1.7 to a 1.8 rod ratio is virtually insignificant in the power department.

The first I ever read about rod ratio was written by Bill (Grumpy) Jenkins in the mid seventies. He was (is) an educated mechanical engineer and engine builder par excellance. His take on rod ratio at the time was that a SHORTER rod ratio matched up with smaller runner volume and shorter lobe separation angles gave better low speed torque.

When you analyze his take on it, however, you need to put it into the proper context. He was a drag engine pioneer of the day and his concepts applied to high RPM drag engines. I have read differing theories on the subject of rod ratio since that time in which a longer rod tended to help low speed torque, but I think that this is in the context of low speed torque being something less than 2,000 RPM. To Grumpy I think low speed torque in his pro stock car was in the context of 4,000 RPM for a launch.

My $0.02,

 

I'm with the Doc here.. the rod ratio increase in itself would have about the same effect on power production as a few degrees advance on the camshaft.. in other words you probably need a dyno to see the difference you couldn't feel the diff from the drivers seat.. all else being equal. The combo you selected should produce outstanding TQ I think you'll be very impressed. Don't be afraid to run CR up to 9.5:1 or even 10:1 either, my 351 was running some rediculous advance(17 initial with up to 30 deg more added by the computer) with no problem at all, that was with iron heads and 9:1 CR. Sequential injection means all cylinders get the same fuel so detonation resistance is much better than the batch fire system.

 

I'm thinking a 9.5-9.7 static CR on that motor, my dynamic CR should be around 9.3-9.5. I gotta talk to some engine builders and decide if its better to add dish to pistons or remove material from combustion chambers to get the compression I want.

SO, if the power difference isnt that great between a stock 351w and a long rod 351w, whats gonna be the difference in longevity all else equal?

With a responsible right foot, would I get better gas mileage with a longrod 351 or a 372 stroker? There is still cost/benefit analysis to be done.

I've heard things like you can run lotsa timing and decent compression with longrod combos, in some of the posts I've read on other forums.

 

I don't think engine life will be any different, it will have more to do with maintenance and driving habits. One thing I know from experience is that short trips kill motors. It doesn't give the engine time to warm up and boil off any moisture that finds it way inside, and it also means the motor spends a larger percentage of it's life running in open loop mode.. which is rich. This tends to wash oil from the cylinder walls which accelerates cylinder and ring wear, and also contaminates the oil faster.

As for the pistons, select some flattops with valve eyebrows to guarantee valve clearance, my calculations for example indicate the ones I have will produce about 9.3:1 with the 62cc Dart heads.

Milage. City will be worse the bigger the motor, a big motor revs just as much as a smaller motor when running through the gears(assuming an auto tranny), so fuel consumption will be higher. Highway milage is where this reverses, a bigger motor makes more TQ and doesn't need to downshift as much to maintain speed and climb grades, so it has the potential to get better milage. My 5.8 motor regularly produced 17-18mpg(US) cruising at 70mph, it made enough TQ that it rarely downshifted from OD even up some big hills, I was continually amazed at what it could climb without loosing speed or downshifting. The AOD tranny helped in this, it requires quite a bit of throttle to provoke a downshift.. unlike the electronic trannys that downshift at the slightest change in speed or throttle.

 

So I've abandoned the 383 idea in favor of either a 357 longrod or a 372 stroker.

Thankfully I've got an e40d, I was looking into a ZF swap but I don't think I'll be able to get that truck manual to shift as fast as an electronic auto tranny.

My buddys got a 91 with an AOD that sucks! Its been rebuilt less than 15k ago but we can't get it to downshift easily under power without it clunking into gear late and lugging the motor as it comes to stops. Its got a lift an 33s and a 302. I was able to get my e40d to work nicely with a bigger lift and bigger tires but it can be racalibrated electronically for tires/gears. AODs get a speed signal mechanically correct?

How do you go about recalibrating an AOD to shift correctly with bigger tires and gears? I was told by the tranny guy that AODs have a governor that determines when shifts happen. Can this mechanical device be modified, recalibrated for his truck? The tv cable has been adjusted a few times and hasnt fixed the clunking.

 

Yes everything is mechanical with the AOD and tires and gears should have no effect whatsoever on shifting. Sticking and leaking governors is an issue, but the TV cable regulates the holding pressure behind all major parts in the tranny so proper adjustment is critical. I suggest you try adjusting it again and keep releasing preload until the problem goes away or the tranny starts to upshift very early. If you get this far and the downshift problem is still happening then there is something sticking inside the tranny. See this site for all things AOD.. Ford-AOD.com the ultimate AOD Transmission Perfromance Website

 

What are the symptoms of a sticking governor?

A leaking governor?

Hes had the tv cable adjusted by a mechanic 3 times and the problem hasn't gotten better. Had the valve body and governor checked/cleaned and it still did the clunky engine bogging late downshift. It only happens in OD and will only happen after the trucks gotten to top gear.

I'll have to check your link and see if theres anything like what we're describing.

 

That's because the mechanics will set the line pressure to the published spec, but every tranny is different and this one may require a little less static pressure to operate smoothly. Adjusting the TV cable is easy and there is NO DANGER of toasting the tranny as long as the cable has at least some preload. Why are people so afraid to touch these things, the adjustment I'm talking about here is very small, just 1 notch on the preload adjuster, an easy 10sec thing.

I recently replaced the TV cable on my truck becaue the clip at the TB linkage was broken(NOTE: is just slides off if you grab the connector and pull straight forward on the cable while holding the throttle linkage stationary). Anyway.. I tried to match the preload setting I had on the old cable but I got it a bit too tight because now my truck does exactly what you friends truck does.. holds OD and bogs the motor when slowing down. But it didn't do this before the cable change, so I'm 100% certain I can eliminate this problem on my truck by adjusting the TV cable.. it's the only thing that changed.

 

Let me know what your fix is. Ill relay what you've said to my friend.

 

Dunno if this is going to be helpful, considering the age of this thread, but here is a link to a thread referencing the long-rod 351W.

Here is an article about lessons learned in building a long-rod 351W.

Don't forget to visit Colt 351 for more info and photos.