Hey guys, new to the forum here. Alright I got my 351w block basically down to no rods and pistons in it right now and I left the water pump n plate to block on. Rig reemed it, honed the cylinders, new rod bearings ready, re-ringing it when re-assembled. Trying to keep the the price minimal, everyone says that. But I mean it. I really know I should replace the water pump while I do this rebuild but lets get some other facts down first. How big of lift cam can you go safely with this 351w without valve clearance issues? I know a 5.0HO can have a .498 E303 in it without trouble cuz of the valve reliefs, but this isn't that motor. That's the first question I have.

Secondly, I have long tubes already but I could barely accelerate in OD (5 speed HD) at 70mph on the highway right after I bought this 89 250. This is why I'm re-building. There was an oil leakage somewhere. Is it possible to change pistons without having pins pressed or removed, or is this a pressed pin set up stock?

Just want a little more power and I know the speed density system, it just can't read anymore than it knows. How about upping the fuel pressure for the headers and maybe cam to compensate? Anyone... I guess I don't know.

 

Lots of cams to pick from for that motor, clearance is not an issue up beyond 1/2" but the heads don't flow that well, so you want an RV style grind like the Crane 444232 or Comp Cams 35-255-5. These will work with the SD EFI system where the alphabet cams from Ford require mass air. If you are replacing the pistons get flat tops with valve reliefs to raise compression slightly.. the pins are pressed on BTW. Either of these cam will transform this motor... you won't believe the difference.. no problem accelerating in OD from any speed.

 

Thank you for that information. I don't think I will be replacing the pistons in this case. Would throwing a set of nice heads on work better while keeping the stock cam and everything? Or is the cam the cheapest and wisest thing to do at this point? Right now I'm looking for remanufactured stock heads so I can exchange my old ones. But for nearly $400 I could just save and get some that are higher flowing, I don't know, with a cam I'd be spending about $400 less. But with a cam and reman. heads it's like $600, not much more to go for heads.

My head keeps saying heads.

 

You need a cam first, the stock unit is really sad and will cripple any other mods you do. This alone will uncork this motor, lots more power throughout the rev range. The stock heads and intake are fairly well matched and will produce good low rpm TQ with respectable midrange HP. The stock heads are not a complete waste, they flow enough to make nearly 300hp, you just have to supply enough cam and exhaust to let the motor breath. Aftermarket heads may require a piston change because valve clearance becomes a problem with the 2" valves, and most 351 heads will have 2" valves. The stock intake will limit the amount of gains you see from any decent aftermarket head, and combined together, heads, cam and intake will outrun the stock computer and fuel system, so it's at that point things get real expensive. I'm not trying to completely discourage you from buying heads, just leting you know they won't provide massive gains alone on an otherwise stock motor.