Edelbrock intake differences

[blykins]

Sheesh, doesn't anyone on this thread have my book? 

Well sure, but data is relative and not every engine is a 410 hp 428CJ or a 500 hp 390 stroker with the exact combination of parts that you had.   When looking at data such as this, I consider the entire engine build as a whole and realize that the build just may not be efficient enough in a specific rpm range to take advantage of one intake or another.   

We are zooming in on how well an engine can get a specific volume of air/fuel charge moving, and if a larger intake doesn't show as much hp/torque at a lower rpm as with a smaller intake (but peak numbers are the same), then it just simply means that the engine can't pull hard enough at that rpm to get that specific volume of air/fuel charge moving.  Camshafts play a huge role in that and I would venture to say that if different cams (read smaller) would have been used, the results would have been much different at those lower rpm ranges.  It actually makes perfect sense that an engine with a healthier cam would make more power in a low rpm range with a smaller intake. 

Aside from all of that, the OP's engine is much larger than a 428 or a stroked 390 and the camshaft was only 224° @ .050" duration.  That engine should pull hard on whatever intake is bolted to it and it will make the power as long as the intake manifold's capability is higher than the cylinder head's capability.  Per Joe's point, a 230 cfm intake on a 290 cfm cylinder head will be a bottleneck.

[My427stang]

Sheesh, doesn't anyone on this thread have my book?  The data from 2500-3000 is all in there, Performer vs Performer RPM.  On my 410 HP 428CJ, the Performer makes torque of 389 to 438 lb-ft from 2500 to 3000 RPM, and the Performer RPM makes torque of 340 to 406 lb-ft.  On this engine the Performer is better in this range, and is actually better than the RPM up to 3500 before the RPM takes over and makes a lot more power.  Both intakes peak at nearly the same torque, 485 lb-ft around 3500 RPM. 

On my 500 HP 390 stroker engine, I only tested from 3000 RPM up, but basically the two manifolds behaved the same as the other engine from 3000-3500.  But on that engine the RPM made more peak torque, and caught up with the Performer a little sooner.

I have heard a lot of anecdotal evidence that the Performer RPM is better than the Performer 390 at all engine speeds, but it is all based on the "seat of the pants" dyno, not actual data.  I'll stand by the back-to-back test data in my book, and say that the Performer 390 is better than the Performer RPM up to around 3500 RPM.

I love your book and reference it regularly, but IMHO, and honestly with all the peer respect anyone in the world could muster...it's testing is far from this target.   WOT dyno runs on smaller engines with curve analysis, I think, just doesn't match the part throttle and mileage discussion.  I really don't know, nor does anyone really know how throttle jockey movements will respond between the two.  For me, on a small motor, 390 with 270H and a 600, the Performer 390 was pitiful and a PI and a unmachined SD were both nice to drive.   

That being said, in the end, he is looking for seat of the pants and mileage, so I don't see any reason other than buying and fitting a manifold not to do it, but I cannot imagine it's the right thing

We do have a big inch engine that did exactly this, Turbohunter's truck.  Marc ran a stroker with a Performer and the world didn't end, but on the other end of the spectrum I run a Victor on my 462 and it makes tons of torque, and got 14 mpg with a 3310 before the fuel injection.

I'll admit it's not scientific, but I do think it's going to lose enough power that it will be less effective through each shift.   I say go for it if he wants to try it

[FrozenMerc]

To be clear, the engine is doing just what I want.  I'm wondering why dropping 24% rpms (2900 down to 2200) didn't give me at least a smidge better mpg.

On the highway it takes X amount of horsepower to push your truck through the air at 70 mph.  Semi's with 53' Vans take about 270 Hp, Corvettes take about 35 hp, your truck falls somewhere in the middle.  Your engine has to generate that same horsepower whether it is running 2200 rpms, or 2900 rpms just to push the truck along.  If all other things are equal, and your burning fuel stoichemetrically, then you need to burn the same amount of fuel to generate the same horsepower regardless of engine RPM.

The difference that occurs, is the engine has less rotating resistance at 2200 RPM's, which should help to increase your mileage, because at 2200 rpms you would expect that it only takes X-5 or so horsepower to move the truck down the road.  However, the overdrive robs power, and as you suspect, there is probably some decrease in efficiency in the intake track at the lower rpm, but I would venture to guess the OD is the big killer.  The big truck guys figured it out a while ago that a tall rear axle and one-to-one final on the transmission is more efficient than a deep rear axle paired with an overdrive.

[blykins]

To be clear, the engine is doing just what I want.  I'm wondering why dropping 24% rpms (2900 down to 2200) didn't give me at least a smidge better mpg.

However, the overdrive robs power, and as you suspect....

An excellent point that I didn't consider at first.  Anything that's slapped in between the transmission and rearend will suck some power. 

[frnkeore]

To be clear, the engine is doing just what I want.  I'm wondering why dropping 24% rpms (2900 down to 2200) didn't give me at least a smidge better mpg.

Besides the frictional loss, in the gears, it may also have put the engine, in to a range, where it's less efficient and is "lugging".  A vacuum gauge would help in determining that and a switch to a lower final drive or a higher w/o the Gear Vender.

If your not concern about 3k>, a smaller carb (550-600 cfm) could help. Your engine is only pulling 418 cfm @ 3k. Try to tune it for 14.5-15/1 A/F at lighter throttle cruise and 12.5-13/1 at low vacuum. That's what power valves are for, right?

You could also, advance the cam 2/4° and pick up low end torque. Be careful of to much compression here.

Again, water injection and cool intake air.

When tuning for MPG, a vacuum gauge is very important. Get your O2 sensor going again, too.

[blykins]

Cam needs to stay where it is on this one and advancing the cam doesn't always "pick up low end torque".   Depending on the camshaft and the entire engine combination, it *may* increase throttle response, or it may not.  It *may* push the hp curve down and then again it may not.  There are no absolutes, except for that it will raise cylinder pressure and you don't want that here.

[frnkeore]

Only one way, to find out, for sure.

For his application, I believe he needs ~218 @.050 duration, with the Adv duration, adjusted for DCR, as well as minimum overlap.

You need to get that 3700 rpm, max torque down to 3000/3200 rpm.

One last thing, is to use a carb with annular boosters, if you an find one.

[blykins]

Only one way, to find out, for sure.

For his application, I believe he needs ~218 @.050 duration, with the Adv duration, adjusted for DCR, as well as minimum overlap.

You need to get that 3700 rpm, max torque down to 3000/3200 rpm.

One last thing, is to use a carb with annular boosters, if you an find one.

If you would share the data from your past FE engine builds that would lend themselves to this conclusion, I'd be interested in seeing it.   Mind posting it up?

[frnkeore]

Brent, it doesn't take much, to see that this engine, was not built for what the OP's requirements are and many different things, need to be changed, to meet his current goals.

Simple as that.

[blykins]

Brent, it doesn't take much, to see that this engine, was not built for what the OP's requirements are and many different things, need to be changed, to meet his current goals.

Simple as that.

Oh, when he wrote, "To be clear, the engine is doing just what I want", I kinda took that as it was actually doing what he wanted.   Who would have guessed that the whole thing needed to be replaced?  :facepalm:

[chilly460]

Of course nobody has done a true AB test on this, but I have some data that may help with conclusions.  When I first got my Merc it had a good running 390 in it with Ebrock 600, Perfomer intake, Performer cam.  It got 15 with stock 3.00 gear and a COM

I swapped in another 390 with 224* cam, Performer RPM, 750 Holley, and a T10.  With 3.00s it got 15mpg. 

With 3.50s it got 14, 4.10s it got around 9mpg, and putting in a TKO it gets 17mpg.

So, in my combo of a fairly large ugly Merc, with similar 224* cam, it got decidedly better mileage dropping the rpm.  With extra 100ci with same size cam, can’t see how dropping rpm would cause it to lug to a point it’s losing mpg. 

I’ve had my car on a chassis dyno, it peaked at 3500 and 5400

[chilly460]

Haven’t read every reply, but have you tuned the PV circuit with the OD?  Assuming it’s a Holley.  Lower rpm and more gear mean it’s likely pulling less vacuum at cruise, could be opening the PV sooner on grades. 

I had an M715 with 4.56s but 38” tires and a tall deck 427 bbc bus motor.  It had an Edelbrock 700 on it, I put an AF gauge on it and didn’t change main jetting but changing out the metering rods and springs to lean out the transition netted 2mpg as it was very fat when I’d roll up grades
 

[TJ]

Thanks to all for the ideas. 

Apologies to Jay for not looking at the Comparo:  I have no good excuse.  I tend to believe there is a time and place for the Ebrock 390.

Dizzy:  Yes, I have a vacuum advance and like it.  I think it's fairly well dialed in but going on personal preferences and a stopwatch there.

HP demand:  I get what FrozenMerc is saying about needing X amount of power at a given speed though I figure this much displacement is wasting more gas just by running than it actually needs when the truck is empty.  Lower rpms should permit it to waste less gas. 

Gear vendor:  Maybe it's costing me power and mpg but sure seams like a lot.  I like it if for nothing else than splitting 3rd and 4th and lower rpms on the freeway.  Perhaps it contributes to the overall stacking of tolerances.

Cam change:  Thought crossed my mind but in no hurry to do that because it costs decent amount of money and time.  Plus I think I have a few other things to try first. 

Engine not meeting my needs:  Thought that comment might have been a joke but in case it wasn't...We have a 2002 Duramax we've used it to pull our fifth wheel through 40 of the lower 48.  And we really like it. If that somehow gets fubarred, I'd seriously consider finding an '80s or 90's crewcab to stick this 482 in and pull our camper around the country because I like it that much.  Really, I'm just puzzled why lower rpms didn't help mpg.  Thought intake was something to consider.  Now I'm thinking carb adjustment might benefit. 

Carb PV:  That's something I need to read up on...as well as get a new O2 sensor.  That's sounding like my first thing to check. 

[Joe-JDC]

If you are serious about the Performer 390, I have a new one that is ported and flow balanced that I will swap you even up for your used RPM if you pay shipping both ways.  You get a new Performer 390 intake, $500.00 worth of porting, and it will flow 290 cfm average.  Ship me the RPM and I will send you the ported new Performer 390 in the same box with you paying shipping back to you.  PM me if interested.  Joe-JDC

[Cyclone03]

First Joes offer is very generous and might bridge the gap nicely between a stock for stock intake.

I have a thought on your mileage not improving with the OF.

From my own,insane, cruise carb tuning on a BG 800 on my 433ci FE that got 18mpg with 3.70 gear and TKO .64 At 75mph I can say dropping cruise RPM from 2900 to 2000-2200 puts the carb in a high load condition. Add your truck being much heavier than my Mustang and I bet your running on the main jet AND opening the power valve (Holley?).

If your running 13:1 at cruise,2200rpm that will be costing you 2-3mpg for sure. The problem is that load and engine set up will want a bit more RPM.
With an O2 indicator,Vacuum gauge and tach if you pay attention to minor changes you can actually see the carb circuits stack one on another. I found it interesting how much time the engine runs on the transition circuit NOT the main jet.
What could be happening is at low rpm your actually running on the main because you have the throttle blades opened more than you do at lighter load at 2900RPM where it’s actually running on the transition circuit.
Add the fact that low rpm high load is dropping the vacuum so the PV is open as well.

It might be said your lugging the engine.

At one point my Mustang had a cam in it that caused the car to chug below 2300 rpm, but was smooth at 2600.
With my 3 tools above I could see how messed up the fueling was below 2500rpm.

Paying attention to the vacuum at the same road speed in D and OD then maybe D at the same RPM that the OD drops the engine too (even though it’s a lower speed) may help you understand the load the engine is seeing.

I found it very interesting and rewarding how simple jet ,air bleed ,and IFR charges effect the fuel curves.