I fail to see the logic of increasing the rocker ratio and bumping the valve lift on the exhaust side if the problem with the exhaust is a restriction in the port itself, if the intention is to let more hot gases flood the already overcrowded exhaust port then please explain how increasing valve lift is going to help, i am literally dying to know..

 

It's simple really, these small block ford heads are undersized for the displacement and flow poorly but even then the stock cams don't fully utilize the flow potential that exists so there are substantial gains to be realized with added valve lift and duration on both the intake and exhaust sides. And if you knew anything about engines at all you would realize that if you can't get exhaust out of the motor then it really doesn't matter how much you can get into the motor.

 

Goodness, thought i knew a thing or two about engines, guess you proved me wrong, lol..
If we could talk without you adding insulting comments we might be able to have an intelligent conversation, but i see that's not possible..

 

Stock E7 heads flow 110.8 cfm @ .400" lift and 114.2 cfm @ .500" lift. Board Navigation

Is an additional 3 cfm really good bang for the bucks?

The added ratio also helps get valves off the seat a bit faster, which is good, but once again you're only talking about making the awful (from a performance standpoint) stock cam ramps marginally better.

Most any Ford that came with a carb (can't say for sure about the factory EFI cam specs) came with a cam ground ~6° retarded. Rockers do nothing to change that. You'd feel more seat of the pants increase with a timing set that bumped the cam ahead 6° than new rockers.

Higher ratio rockers are the last thing I'd do if I was looking for more power. Even then only if testing and tuning demonstrated a need for more flow and the theoretical increase in valve lift would affect flow enough to make a difference. Anyone who spends $250 bucks on rockers and thinks they're gonna feel a real kick in the **** will get a rude awakening.

 

It's already been well documented that just switching from standard rockers to full rollers is worth its weight in gold, but your right about not spending $250 on rockers, i would spend $300 on some quality rollers. I will look into the cam timing and see if there are gains to be had with the EFI cam..

 

Higher ratio rockers produce a noticable(from the drivers seat) gain on one of the HO motors(351HO, 5.0HO) or the late model '94+ truck motor but that's because these motors are close to having an optimal cam. The other EFI motors had cams that only produced 0.379/0.395" lift and 244/266 degrees duration seat to seat with 1.6 rockers so these motors need more than a little more cam lift and benefit more from a wholesale cam change, and if you do that it makes sense to get a cam that produces enough lift and duration with the stock 1.6 rockers.
For the record my idea of an "optimum cam" is one that allows the motor to produce roughly equal quantities of HP and TQ assuming there is enough intake and head flow. For the 5.0 that is something in the 250deg(seat to seat) range, for the 5.8 it's into the 260ish range, and the 7.5 needs something in the 270deg range.

 

Hey Paul, is that .379/.395 the measured lobe lift or valve lift ?

 

That's got to be valve lift, .395 * 1.6 = .632" valve lift.

 

That's the same conclusion i came too and checked my math, twice..
That cam is way too small to work with, i realize that now. High ratio rockers are out of ther question now, thought i had more lift to work with but i don't. So, the manifold and front end/timing cover have to come off, might as well pull the heads and replace them so now i will start post about chamber size and design with stock pistons.. Thank you.

 

I installed higher ratio rockers on my 87 5.0 HO (1.6 to 1.7), but I'm not sure I felt any significant difference in my seat. I'm told that aftermarket aluminum rockers with full rollers reduce friction from the stock rockers, and are supposed to flex less. I would go for an upgrade if even half of that is true. And if I were upgrading, a set of 1.7 is often going to cost the same or not much more than 1.6 rockers.

 

I will upgrade to full rollers, after the cam is changed out..

 

Comp makes the camshaft for the job, #35-255-5 will bump the lift from .379/.395 to .478/.485, that'll scrape a little more varnish off the valve stem as the rocker pushes it down in the guide another .100" or so..

 

just for reference: Installing 1.72's on a 351W such as mine with the smaller camshaft will bump the lift from .379/.395" up to .404/.424"
.379" vlave lift / 1.6 rocker ratio = .236" lobe lift x 1.72 = .404", etc..

 

No they won't make a significant difference they will make a subtle just noticable difference but... this version of the motor needs an improved intake system on it first before any other mods will be of any benefit.

 

Yeah that's the total valve lift not cam lobe lift.. pretty sad isn't it. I can tell you that swapping the Comp 35-349-8 roller cam into my '90 5.0 truck motor produced startling power gains. If you have an early(pre '94) 351 flat tappet motor the cam to use is the Crane 444232, again startling power gains across the board including healthy gains at lower rpms with longtube headers.