RPM Range of Stock Intake?

[colnago]

Sorry, all, I really don't want to mire the forum in yet one more manifold thread, but I've looked everywhere and found nothing. Does anyone know the operable RPM range for the stock iron 4BBL manifold, or have a link to the info?

Thanks,

Joseph

[1972hiboy]

to my understanding, the factory manifold is supposed to be fords ideal compromise across the spectrum based on their projected use of the engine. In a stock engine i think the valves would float before you run out of air flow through the intake manifold.but in design be the best compromise of low end drive-ability , high rpm ability and economy. now say you have an engine can can really breathe, ie, compression, cam etc etc, the stock manifold might become a bottleneck im guessing at 5 grand neighborhood? Maybe somebody who deals with high performance aspects could chime in.

[colnago]

Five grand? Heck, my back-of-the-envelope numbers say that I'm turning 3K at 65MPH. This means that I would be well above 100MPH at 5K. My breathing will stop first, just keeping the old girl on pavement! As boring as it sounds, I'm more interested in the low end, and I've heard that you don't want your cam to be "lower" than the intake.

I'd suggest that Fordification just take up a collection and buy me a Performer 390, just to shut me up about intake manifolds, but then I'd just find something else to whine about.

Joseph

[DuckRyder]

Well, I said I should pick up Jay’s book and I did.

I’ve not deep dived into it and I have no intention of divulging a great amount of information from it since he cleary put a lot of money and time into it and the best way to compensate him is to buy the book, so if you’re super interested in learning about intake and exhaust you should probably pony up the cost of admission.

I do think he posted some early information on the FE Forum, which is now part of TapaTalk

I’ll say a couple of things, his engines were higher performance than you are talking about, though one of them did have a 941 cam. They were all 428 or larger so the loss of nearly 40 cubes to a 390 might change the results a little... but still theres good info in it for you.

I’ll also say that based on my preliminary perusal - I think you’ve been given good advice so far...

[colnago]

Well, I said I should pick up Jay’s book and I did.

I've been tempted, but I've understood he didn't really hit the lower RPMs. But I should, anyway, just to support Jay.

I’ll also say that based on my preliminary perusal - I think you’ve been given good advice so far...

Joseph

[Ranchero50]

I think we should combine all of these threads to keep the conversation relevant...

[colnago]

I think we should combine all of these threads to keep the conversation relevant...

I have no objection to a single thread. I really, truly, did NOT mean to keep coming up with questions on Intake manifolds. The mods probably think I'm beating a dead horse. But I've just been "given the opportunity" to not use my truck for the next two months. That opens up everything!

Getting back on topic, is it up to the mods to combine the threads? I could probably do it this weekend, but it may end up looking ugly (combined, but ugly).

Joseph

[DuckRyder]

I think we should combine all of these threads to keep the conversation relevant...

I have no objection to a single thread. I really, truly, did NOT mean to keep coming up with questions on Intake manifolds. The mods probably think I'm beating a dead horse. But I've just been "given the opportunity" to not use my truck for the next two months. That opens up everything!

Getting back on topic, is it up to the mods to combine the threads? I could probably do it this weekend, but it may end up looking ugly (combined, but ugly).

Joseph

I don’t have an issue with that, though it might read a bit outa sync.

Joseph, we (me or Jamie) will have to do it I don’t believe you can.

Should we decide to, I’d sy delete the parts where we are talking about doing it....

[DuckRyder]

I've been tempted, but I've understood he didn't really hit the lower RPMs. But I should, anyway, just to support Jay.

Joseph

That is true it appears, in fact I would pay for a book 2 that dealt with smaller and milder engines.

Still he does talk about how some of the picks might perform on different engines based on the test he did do...

[Jacksdad]

Five grand? Heck, my back-of-the-envelope numbers say that I'm turning 3K at 65MPH. This means that I would be well above 100MPH at 5K. My breathing will stop first, just keeping the old girl on pavement! As boring as it sounds, I'm more interested in the low end, and I've heard that you don't want your cam to be "lower" than the intake.

That's not necessarily going to be an issue in top gear. It's how much you need to rev it in lower gears given the situation, say climbing a steep incline or getting a heavy load moving. Or proving a point to the guy in the Prius that's trying to get around you.

I'd suggest that Fordification just take up a collection and buy me a Performer 390, just to shut me up about intake manifolds, but then I'd just find something else to whine about.

Joseph

[colnago]

A Prius? Bite your tongue! My truck eats 'em for lunch!



Joseph

[8ton]

I run a "S" intake with a 2* advanced stock cam on a 360 with C8ae-h heads, with a 450 Quick fuel carb on top. Exhaust goes out 428cj valves into flowtech long tube headers and a 2 1/2 dual pipes.

The runners took a bit of enlarging to match to the heads, and had a moderate amount of casting flash that you wouldn't see on a 'Performance' intake. It pulls strong from idle-4700 or so, by 5300 it is on the far side of the power curve. True power peak is likely a bit lower, maybe 4400. Does it give out because of the cam, small carb, or intake? There is no knowing, but I get 12-13 mpg running through a mountain pass and through a small town to my work.
I blame the giant piston to head clearance (quench, squish, whatever) for not getting better mileage. Ideal is .035-.045.

You state that your goals are good mileage, towing power and reliability. Keep it simple and don't get sold high dollar race parts just because. Remember that high port velocity, above average fuel atomization, low friction, and efficient combustion in the range of 1200-4000 is what you are after. If a stock intake costs you 30hp at 5500, you will never know the difference.

[cep62]

A Prius? Bite your tongue! My truck eats 'em for lunch!



Joseph

Did you ever see the Prius on Jay Leno's Garage ?
We'll see if this link works.

https://www.youtube.com/watch?v=gFbvYeFO8w4

[colnago]

"I don't think it's stock." What a hoot! Thanks for posting.

Joseph