1996 MAF 351 to 393 question
 

Hey guys,

I intro'd myself in the new user area and have a couple of questions.

I am currently sitting in Germany (Army) and my dad is working with a friend of the family who own's a shop to get my Bronco ready for when I get home this summer. We discussed pulling the engine to freshen everything up and the idea of stroking it to 393 came up. I have wanted to do this in the past, but as the Bronco was my DD for the last 6-7 years I never had the chance to do a major operation like that. There is a ton of information on this topic, obviously, but nothing that answers the question I have.

What I am looking to do is stroke my 351 up to 393. That's it; no heads, no injectors, no high flow fuel rails or fuel pump. I have a MAF roller 351 in my 1996 Bronco and am willing to get a custom tune, but want to know what problems I may run into driving it with the factory set up. All the other things are going to be done in the future, and I will re-tune the truck then, but I don't want this to turn into too much of a project right now. When I get home I am only going to have about 6 months before I deploy again and want to enjoy my truck in that time (camping, fishing and hunting in the backwoods of Louisiana). I know I am not going to get the full benefit of 40 more cubes if I don't do anything else, but what I am worried about is running lean. Do you guys think that is possible? My stock heads probably don't flow enough air to really cause a problem, haha, but I want to know if anyone else has ever dropped a 393 short block under a factory everything else, and if so what the results were.

The ONLY reason I am considering this is because the motor is going to come out anyway (leaking rear main seal plus some other work forcing the motor to be pulled), and this seems like the perfect time to stroke the short block so it is ready for my other stuff in the future. I can change heads in a day, swap fuel rails and injectors, etc, no problem in another year or so, but this is the major operation I want to do while the truck is down.

Let me know what you guys think - again, I am aware I am not going to see a huge HP/TQ gain without upgrading other components, but that's not what I am after right now - just it running as close to normal as possible.

PS - I may drop an RV cam in, but haven't got that far yet, and again, don't want to have to tweak anything else right now.

Thanks!
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Justin

I managed to find an old post referencing a 395 stroker. Must have missed it when I searched for 393 stroker.

One of the responses mentions "several members who have used 393 short blocks with stock top ends" and no problems.

I would love if someone could chime in and let me know how that worked out for them personally. That is exactly what I am looking to do.

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Justin

I have a 96 E150 van with the roller 351 and M/A and after doing a GT40 head swap, combined with Cobra 1.7 roller rockers, shorty headers and a full 3" single exhaust it never really has adapted to those changes. I have had several issues ever since one of which I still have problems with and have yet to figure out why it does what it does. I too had thought about stroking it too, but since doing the changes I did, I shelved that idea.The roller 351 already has an RV cam in it. Specs are 256/266 advertised duration. Lift with 1.6 rockers is .422/.445, LSA is 116* Add 1.7 rockers and the lift goes to .445/.473. I would leave it alone and enjoy your time off. And Thanks for what you do.

Thanks for the info. I didn't know what cam was already in my 1996. I have run the motor stock up to this point (ignition upgraded to MSD but that's it) save for replacing a few things that have failed (water pump, etc) but always with OEM replacements.

Have you had your ECM tuned or is it still factory? The only thing I am interested in doing at this point is having a custom tune done but want to keep everything stock otherwise (not counting, of course, the stroked short block).

My pleasure - I love my job.

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Justin

Hate to say it but that MSD was a waste of dollars. The stock ignition is equal to that. My ECM is still as it came from Ford. I was told it could handle the changes. Adding 40 more cubes will likely require larger injectors as well in addition to the custom tune. The only other change I made was adding an adjustable fuel pressure regulator. Currently the problem I have now is it spits sputters and backfires when you suddenly nail the go pedal at low speeds, otherwise everything's fine. This also started after changing the rear gear ratio from 3.55 to 4.10.

My ignition failed so I replaced it with an upgrade from stock. Note expecting performance gains, I just figured it couldn't hurt.

Could your lag when mashing the accelerator be due to the fuel regulator not keeping up with a sudden change in requirements? I can't see how changing gears could have any effect on that at all.

Cheers,
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Justin

No, it did this with the stock regulator and the new adjustable aftermarket unit. I've replaced everything but the M/A sensor and the IAT so far in an effort to fix this. As long as you refrain from putting your foot into it at low speeds it's fine. I had one guy tell me he experienced this too in a Fox body Stang after a gear swap. M/A calculates fuel curves off of several inputs from the various sensors, including vehicle speed and rpms, so this could be the result of this.

Wrong forum bud

Put an adjustable fuel regulator in it and bump the fuel pressur a little , that's my only adjustment on my Speed density 86 .should get rid of the splutter.

Didn't affect mine. Even reprogrammed it yesterday, still there.

Aftermarket ECU ,and bigger injectors .. ! :-) make sure all the basics are ok , no vacuum leaks , I added a accel replacement coil and it made a huge difference. Good earths.

Done all that.