I recently got my hands on a '91 F150 with a 351 Windsor. I've been looking into some options for mods and have been amazed by what's available for these motors. The general opinion seems to be that the heads are flow-impaired boat anchors, and stroker kits are too cheap to even try fooling around with other parts of the truck to build horsepower. So, while looking deeper into options I found a 408 stroker kit that adds 1/2 inch of stroke if I remember correctly, bringing the oversquare 351 to a more square configuration
I'm looking at the 800hp kit, not because I'm expecting that kind of power, but because of the forged over cast crankshaft. I also want to go with headers and a higher flowing intake if there is one (edelbrock?) So, my question for all of you are:
What heads work well on these motors (bang for buck)
Is the 408 stroker too large? Am I just begging for constant rebuilding? (Will likely need at least .030" bore)
What intake would you recommend?
What is a good brand of headers? (i've heard horror stories of headers cracking, bolts backing off constantly, is this a common problem or just a symptom of cheap headers?)
What cams would compliment this heavy breathing engine? I'm looking for something to be able to use as a daily driver but still blow the doors off these annoying little ricers
And last, flat or dished top pistons? I'm willing to run premium as it won't be my main truck but I would like it to be somewhat reliable and I'm not planning on forced induction
The stock EFI system in these trucks can accommodate a mild upgrade(to about 300hp) but after that it gets real complicated and expensive if your truck has an auto trans because the PCM controls both the engine and transmission. So if you want the type of power even a mild 408 can make(400-500hp) you got a choice to make..
A)Stay with EFI and budget for the necessary upgrades to that system $2000-$4000 extra
B)Convert to a carb and swap in a non computer controlled transmission $1000-$2000 extra
C)Just do a mild buildup of the 5.8 $0 extra
I am in the middle of the build of a 351w myself. As far as intakes edelbrock does make one 3881 for 5.8 efi. its 609 on ebay, 629 summit. Throttle body for that would be bbk 56mm dual plane. I am trying to find numbers right now to see how much flow you actually will get with that set up over stock. I have an email in with edelbrock. If your interested I will let you know. If its not ridiculously better flow, at that price point I am planning on just having my intake ported and port matched from TB to Head.
update.. Edelbrock does not publish flow numbers. He tried to get pretty creative with the reason why. Saying there are a lot of variables that could change how the manifold flows so the numbers dont matter blah blah blah, I asked flat out. So the base numbers are not available to see what gains are being made in the manifold over the stock one. He said no. So at the price of over 600 dollars I am going to pass. I think the inflated numbers of 36lbs of torque do not justify the cost. Spend your money else where or look into taking some meat out of the stock one. Just be careful and make sure the machinist can identify where the water is running through that manifold.
The word directly from Edelbrock about this intake is that it was designed as an upgrade for an all stock motor and not at all suitable for a high reving 5.8(4000rpm+) or a stroker of any kind. This was a reply to an inquiry by one of our moderators here after experiencing less than spectacular results with one on a 393 stroker he built. This agrees with general design principles in that for any given displacement the higher the HP peak the shorter the intake runners should be, and also the intake runners should increase in size(cross section) proportionally with engine displacement. This is why I always suggest the relatively short runner single throttlebody Performer or Typhoon instead of the truck version for most 5.0 and 5.8 builds here and would also suggest a TFS R-Series intake for a stroker.
Does switching to one of those single plane TBs place the intake on the opposite side? if so do you need to relocate the battery, extend throttle cables, electrical wiring and so on? I was thinking about doing this myself but if its going to be more work than its worth I would pass on it and just open up the stock one a bit.
The upper portion of many of the single TB intakes(performer, typhoon, GT40) is reversable so the intake plumbing can go to either side, a different throttle cable will have to be used as well because the attachment at the TB is different.