S code vs. RPM

[averagef250]

The FE's make more low-mid torque than any comparable engine. They have super long rods, and lots of bottom end beef- Monster main bearings and a deep skirt block to handle low RPM lugging. For whatever reason they make the same or more torque down low than engines with 100 more cubic inches. HP is a BS made up term. Torque does the work, and torque where you can use it most is what you want, not top end horsepower at an RPM your truck engine will never see where pushrods bend and pistons come apart. They make an ideal truck engine when you build them right. Built wrong they suck and your 454 and 460 friends will laugh at you. Build it right and you'll be able to accelerate with a 5000 pound trailer as fast as your buddies can empty. The wee little 390's hold their own in pulling power VS the big inch motors.

Those iron intakes work well. FE's have some quirks- Oiling system needs a little help and the intakes take some special attention to seal and keep sealed. When you run an aluminum intake you greatly increase the odds you'll be fighting intake sealing issues down the road. For an engine you want to put together and not pull apart for another 100K the iron intake is the way to go.

[DuckRyder]

I would like to make a couple of points, good discussion and I agree with most of the points made but just to eliminate confusion:

Horsepower is not a made up number it is a calculated number. When comparing two engines if an engine is making more horsepower at a given RPM it is making more torque as well, if it is making more torque at a given RPM it is also making more horsepower, the inverse is also true. Both numbers have value for comparison, but looking at only the peak number either way can be quite misleading. For a street type engine, I look at area under the curve.

You have to remember that cubic inches and other modifications also play a role in the demands made on the intake. A mild 360 might pull to 5000 rpm before the intake is a restriction to the airflow, whereas a mild 428 may only get to 4000 before it is using more air than the intake can provide. Bigger cam, better heads and the restriction may come lower for both engines. On a mild 428 in Jay Browns dynamometer testing the “S” intake was down over 50 horsepower compared to some better intakes. Unfortunately, the graphs themselves are not showing, so we do not know that the curve looked like.

You have to look at the power train as a total package from air cleaner to tires, it all has to match or you will be disappointed.

I ran an "S" on my 360 for a while with a Crane 801 cam, it pulled to 5000 with no problem, but the rest of the engine was tired. I am sure If I put it on my present 390 (396 actually - Which pulls over 7000 with a Blue Thunder) it would fall flat on its face much faster!

[My427stang]

Take whichever advice you guys wish.

I have been doing this for a very long time and truly wouldnt BS you guys, and especially wouldnt roll back in if I didnt think this was a real issue.

I wont argue that FEs run GOOD with an S or T code intake, but they run noticeably BETTER with a better intake, and I have done the swaps 1 for 1 with only tuning changes and have seen great increases across the entire rpm range on everything from 360s to my current 489 FE. My first swap from a regular performer 390 to a 428 PI amazed me.

I have run S and T intakes, Offy, PI, RPM, Performer and just about any other one you can think of over the years on my own and customers vehicles.

If you have to run an iron intake, the T is a smidge better than an S, but no kidding, its giving up power on the curve everywhere but maybe 1000-2000 rpm, and thats a maybe, depending on the combo, the benefit slightly changes but is always the same flavor.

Now my 390 pulls from idle to 5500 with a single plane street dominator and has worked its whole life, more than most anything short of a wrecker, I'd NEVER castrate it with an S or T code, and my 489FE, of course is a whole different animal, but I am still pulling 1400 rpm at the speed limit in 5th and shifting at 6700, and it pulls like a freight train everywhere.

You dont need to give up power to make torque, the idea is to keep a fast port and a good cylinder fill. The S and T codes are not efficient ports, so although volume is low, the ports are inefficient, thats why the RPM works better. Its a med riser port (small) but efficient and fast so it flows at low and high RPM.

[averagef250]

I was very unhappy with the RPM on an idle-4500 RPM 390 I put over 140,000 miles on. Much of that very heavy towing (30K GCVW+). Everyone drives differently and has different ideas how an engine should make power, what gear they like to pull in, etc. I'm a little suprised though that anyone would claim you won't miss a significant power loss below 2000 RPM.

I'm sorry, but with an RPM intake on my 390 with a 600 or 750 holley I had no off idle power. With a performer I had steller off idle power, the S iron intake was a very nice balance. To me the idle to 2000 RPM range is very important.

[My427stang]

Not sure what to say, I dont run them hard at all, more the opposite.

However if you had late cam timing or a slow ignition timing curve I suppose it could have been fussier.

I even ran mine as a daily driver with 3.50 gears and 35 inch radials, so it sure didnt rev high LOL and I could almost count the cylinders when I pulled it down pulling a customers vehicle home or plowing snow.

However, thr truth is, run what you like, thats why we arent all driving Priuses LOL

[Jake11]

That's it. Run what ya like, makes ya happy. Don't be afraid to experiment along the way. Nobody's always right or
wrong. Lots of good advice and smarts on here. Thats a good thang. Jake

[rubiranch]

I missed the "S" results in Jay Browns dynamometer testing, these were the only ones I saw.

Edelbrock Streetmaster: 385.8
Edelbrock Performer RPM: 374.6
Blue Thunder 428CJ: 366.9
Factory Cast iron CJ: 363.0
Factor Police Interceptor: 357.1
Edelbrock F427: 353.6

Did I miss something?

I only see a 10% difference from high to low. The rest of you seem to have experienced bigger gains between "S" and other intakes than what these dyno results showed between the 6 manifolds they tested.

I'll bet that 99% of the time or better very few 390s ever see 5000 rpm. I tow a travel trailer with mine in the mountains at high evevations and I bet mine seldom see's 4000 in 2nd (auto).

[rubiranch]

Dont get caught up in the peak hp numbers

I'm not.

[Jake11]

Most people don't drive wide open throttle. Like on a dyno.

[My427stang]

Most people don't drive wide open throttle. Like on a dyno.

Well, true, but all I can say is I have rode this horse before and was trying to help. My opinion isnt from a single build, I did this to feed my fat belly and put myself through college and still do as a side business. I just tried to back it up by accepted numbers from Jay Brown's stuff when the topic came up and showed big differences.

I dont want to pi$$ anyone off, just passing experience. The biggest issue I have is trying to convey it without sounding like a know it all LOL Posting on a web page is a far cry from comparing two intakes on workbench with a customer or BSing about port/plenum effect over a coffee or a beer.

Bottom line though, when someone comes in for an engine build, or if you call me for one, I would not use an S or T intake unless there was some reason we needed to. It doesnt have to be the RPM either, just not the S or T

Consider the advice worth what you paid for it no problem at all, I am not offended in the least. Just sharing my what I have seen.

[DuckRyder]

I missed the "S" results in Jay Browns dynamometer testing, these were the only ones I saw.

There are at least 5 reports and using at least 2 engines...

Use the search term (with quotes) "Great FE Intake Comparo - Report".

[rubiranch]

I don't think anyone is pissed off, lots of good info and lots of good reading.

[Doug Comer]

My brain hurts now. Really guys thanks for all the input. Doug