Stock 351 HO questions

[wesjr]

I am running a stock 351 HO, T5 and 4.10 posi rear

The car seems to float the valves when pushed over 5k rpm's I assumed the engine could handle 6-7k redline, anyone have a clue

[wilf leek]

Is it valve float, or just the engine reaching the end of it's normal powerband?

I would have thought that a 7k redline was ambitious, 6k tops, and it would probably stop pulling well before that.

[DAVID GAGNARD]

Wes;

What is your valve spring pressure?????? This has a lot to do with valve float.....Stock enignes do not have a lot of spring pressure and 5k for a stock 351 sounds right to me.....Also,your camshaft is a limiting factor in the rpms turned and 5k for a "stock" cam is correct....

I have found on 351-W's,you need at least 125 pounds of spring pressure to turn 6000 to 6500 rpm's without valve float,a little more would be better,but that would be my minimum....

I have also seen stock 351's with as little as 70 pounds of spring pressure from the factory,hardly enough to turn any kind of rpms over 4500.....

David

[wesjr]

whats best way to push the max rpm up, some new valve springs, or should I go with a beefed up cam?

[DAVID GAGNARD]

If your running a "stock cam and springs" you will need both..... Springs depend on cam lift for application..... Decide on what lift cam you want and then order the corresponding springs for that lift..... When you install them,check the pring pressure and adjust accordingly.....

David

[PSB]

There's really no such thing as a 351 HO. I assume you mean a 351W. Most 351Ws were truck engines and thus, in stock form, were set up for low end torque, not high rpm power.

Your engine most likely has hydraulic lifters, which will cause it to top out at about 6000-6500 rpm.

What year is your 351? What did it come out of?


Pete

[wesjr]

84 bronco, the paperwork say 351w HO, was a longblock crate motor

[PSB]

So was it the stock motor from the Bronco, or was it an aftermarket crate motor?

If it's the stock Bronco motor, a cam change would wake it up considerably. The truck cams are really set up for low end.

If it's an aftermarket crate motor, then who knows what you've got.


Pete

[Rick Parker]

The 351 HO was the name give to the production engine that replaced the Boss 351 in 1972. It was Cleveland style head on Cleveland (non Windsor) block. I believe it was a hydraulic cam motor instead of more powerfull solid lifter Boss 351 from the prior year. This signaled the downturn of performance in Ford showrooms after the heyday of the Boss 302 & Boss 429 of 1969 & 1970, and a 1 Year run of Boss 351 in 1971. As I recall we only had the 351 HO available in the (new larger) Mustang and perhaps the Cougar Eliminator (??). Couldn't give them away.
Ford performace was dead at this point.

Rick

[wesjr]

well I installed some new hipro valve springs and I can push 6k rpm now w/ no valve float

[blykins]

Is it still making power at that point?

[wesjr]

seems to, 5700 rpm seems to be the best shift point