j200pruf

iTrader: (4)

Hey all, hopefully someone here can answer this for me. My friend is got me thinking a little bit about throwing a 5.0 or other american SB in my FC. My question is if one were to put a cam that has a basic range of ~4000rpm-7000rpm, what parts would need to be upgraded to keep one of these motors together at a 7K-7.5k RPM shift point?

bigj50

good flowing heads and intake...... valve springs/ roller rockers arms....... also stonger push rods......... then u should be good ..... but this is a very basic list......i'm sure someone can get more detaled with it.

digitalsolo

iTrader: (2)

Three things.

1.) You have no need for a 7000-7500+ RPM shift point. I'm building an LS1 with ~600 RWHP that shifts between 6600-6700 RPM.

2.) With a SBF, you'll probably want at LEAST rod bolts, springs, retainers, pushrods, lifters, and rocker arms. Lighter valves wouldn't hurt any either. That's considering a 7500 RPM shift, and a long trouble free lifespan though. You can do it on stock parts as well... if you want rotary reliability.

3.) You have no need for a 7000-7500+ RPM shift point.

peejay

Errr....

Roller rockers - not required. Nice for valve guide longevity (pissing into the wind here) but not required. They were running 8k on road courses, 10k on the dragstrip, with stock stamped-steel or cast iron rockers in the 60's.

"Stronger push rods" - depends on your cam selection, rocker ratio, and valvespringing! An old timey loooong-duration, mild lift cam can make do with even stock type pushrods. A modern roller cam with shortish duration but plenty of lift, or especially looong duration and skyscraper type lift (if you're only shooting for a 7k shiftpoint this is NOT required) the mondo valvesprings to deal with that, and higher ratio rockers, will require beefier pushrods. Probably also a stud girdle.

The bottom end would be my main focus, and THAT depends on the engine itself. Some engines have mondo-beefy rods from the factory that can handle abuse (AHEM Chrysler, Chevy) but others have really weak compressed-garbage rods (AHEM Pontiac).

rarson

That's exactly what I was thinking.

V8Mongrel

I am having someone who is very knowledgable building my Ford small block and I can pass on what he says. Please note, this is not stuff I know, but info I am passing on.

The bottom end in a late model engine is good to bursts of 7000 rpm. With good rod bolts and proper attention to bearing clearances, you might be able to get away with 7000 on every shift. Either way, you will need a stronger oil pump shaft. As indicated, the valvetrain is the biggest problem. Pushrods, lifters, cam ramps, spring tension and valve weight all play their part. If you have to ask, you probably should just call the engine builder of your choice and see what they say. Why do you want such a high RPM? On the Ford engine, 6500 is a the 'right' redline if you want the engine to deliver good power without having to uprate everything.

Nihilanthic

Youre too hung up on hp/liter and high rev stuff dude.

Yes, you can build a v8 to that kind of powerband if you want, and yes, it will rip ROAR around. But the problem is that its harder on parts and more expensive to get the same hp youd get from boost and/or stroking it out.

HP/liter means nothing! HP/weight means EVERYTHING. Turbos add negligeable weight to the whole car and stroking the engine out and/or boring AFAIK adds basically nothing. Im sure you also have heard that broader powerbands (aka torqueyness) makes the car faster down the line and out of corners as well, right?

Now, that said, revs are a means to an end, just like forced induction and adding displacement. However, generally, the only reason to go with revs instead of more displacement or higher manifold pressure is if youre racing in a class that doesnt allow it, or, if you have basically a nerfed motor that can rev higher without adding a lot of cost by cheap upgrades to help it breathe better.

What Im basically saying is exhaust cheaper methods first, especially the possibilities of adding displacement and forced induction, before going over about 6500 - bigger powerbands, easier driveability, and more ponies for your dollar would be why.

Now, if you really wanna go through with it, and have the money and knowledge of what you're getting into, youre going to want to find some heads that were already ported out really good, and if not find some heads (most 5.0 guys swear by Twisted Wedge Trick flows) and have them ported, then go shop around for some light, strong rotating assemblies (have them balanced!) and upgraded valvetrain kits.

Now just as an aside, the 5.0 block likes to split down the middle over 500 whp... dont get too crazy now, or youll need to go find yourself a Dart or FMS block that can handle the abuse. No, Im not sure about its ability to stand up to revs, but you should go find out.

Anyway, if you have the money to do it, and REALLY know what you're getting into, go ahead! It will be a very fun ride, and with a good exhaust system will scare the crap outta anyone who hears it. And keep us posted, it should be fun to see that going around circle tracks or generally tearing **** up

peejay

Block breaking is more of a factor of torque, not power. I worked with someone who was running *damned* fast (low 11's/high 10's? been a while) with a Fox-body GT Convertible. The heaviest Fox Mustang you could get. Naturally aspirated, manual trans, stockblock, stock displacement.

He never had it on a dyno, but he was shifting at 9800... Probably well over the often-quoted 450 crank horsepower (for blower motors). The only time he mentioned block problems, was that one of the umpteenth times he was putting the heads back on, the threads started pulling out of the deck. Studs are nice for saving the block, but they are a hardcore pain to deal with when pulling the heads in-chassis.

Merc63

I went for high rpms on my Ford small block due to the abysmally short gearing the RX7 has, and the short tires (23" tall), and the single OD gear in the trans. Letting it rev to 7500 allowed a similar powerband to the rotary, giving the same speeds in gears (but getting there much quicker). It's a valid goal with stock gearing. If it was cheap to put 3.23s or 3.55s in there, then yeah, you can get away with a lower peak rpm.

A friend used to build up DZ302 Chevys for street/autocross/track day use, and I had a clone to put in a Porsche 914. These were 9k rpm street engines. Not a lot of power down low, especially in a 3400 lb '69 Camaro Z/28, but more than adequate for a light car like a 914, 240Z, or RX7. 9k rpm in my car would have added close to 20 top end mph AND made it quicker, even at the same hp, as it was completely gearing limited.

The lower low end torque is easier on driveline parts unless you're dumping the clutch at 6-7k rpm+...

digitalsolo

iTrader: (2)

So a ~10K RPM redline for ~550-600 HP? Sounds like he needed someone who knew how to put together a well balanced engine package.

Nihilanthic

The problem is the pricetag for that is going to be nearly as much as the redline

V8Mongrel

DING! We have a winner.

Accepting that everyone here is smart enough to recognize that HP is what we are after (maximum average over the operating range you need) then we also realize that horsepower being an expression of torque and RPM will be increase when either one of the two contributors is increased. Domestic V8s have a reputation for providing cheap horsepower. It is because of the torque part of the equation, not the RPM portion. So, if you want your V8 HP on the cheap, make the most of the torque while using the least RPM possible.

While Merc63 illustrates that more RPM = more HP = more speed, that is the harder way to do it. The DZ302 output could most likely have been made more economically with a good 383 or 406, with little to no weight penalty. There is obviously an element of personal preference involved (some like the screamer engine) but always remember that there are two ways to get HP, and generally speaking, for domestic V8s, looking to increase torque is cheaper than looking to increase RPM.

So, if you are looking for an RPM range, which as indicated might just be your preference, be aware that you are not playing to the strengths of most American V8s. If you are actually looking at the RPM to try and get horsepower, consider the other way to get it if you are on a budget.

peejay

But before 1970, the Trans-Am rules did not permit changing the stroke from the street engine, thus the DZ-302. When destroking was permitted for 1970, Chevy nixed the 302 and came out with the LT-1 engine, which was a 350. As much power, but realistic powerband.

Yah, and the torque characteristics can be partially defined by the chassis, too. A lightweight car doesn't *need* bottom end to get moving, and lots of lowend torque can actually make the car harder to drive, as far as keeping the rear tires in some sort of agreement with the ground is concerned.

V8Mongrel

No doubt. If you have to live by a rule book, once you are maximum torque, you are stuck pulling off the RPM pipe. See Formula 1 today.
Too much power?!? Blasphemy!

You are correct, however, I would rather live with the 'problem' of too much torque and wheelspin than the reverse!

Merc63

You're correct about the rulebook scenario. It still made for a wonderful engine, however, and one that can be duplicated rather inexpensively. And the sound of a smallblock cranking at 9k is incredible. Since the slight reduction in low end power isn't really a penalty in a light car, it's a valid choice to build for fun. I love those engie in cars like the 914 and RX7. I wasnted to build one and stuff it into a RWD converted '93-95 Civic coupe, with a license plate that read "9K RPM" and do it with pushrods to **** off the ricers that say pushrod dinosaurs are ONLY good for low rpm truck motors. Yeah, well this one revs higher than your ITR...

While all your "the best way to build it is for torque" talk is valid, and the reason we love these engines, is there yet a cheap way of getting gearing that takes advantage of that? 4.10 final drives with short tires is NOT the best combo for an engine that won't rev past 5-6k, especially if 70 mph is equating to 3500 rpm. IN a Mustang/Camaro/Corvette with 2.73-3.23 gears, it's not much of an issue. But woudl you put typical 4.11s behind a low rpm engine in one of those cars?

It would be silly to use "lower rpm costs less" as the excuse for going that route if you have to spend a bunch extra to re-engineer the rear end to get lower gears to take advantage of that lower rpm torque production, OR spend more money on a dual overdrive 6 speed gearbox. Sorry, but my 7500 rpm Ford engine cost considerably less than the purchase price of a 6 speed trans...

V8Mongrel

The gearing is a problem, no doubt.
If you follow this link to an Excel file you can see I know full well the problem. The only rear gearset I currently have for my RX-7 is 4.875! Thankfully it is being built as a track car, so cruise RPM isn't much of a worry, but the fact that the T5 ratios were just never designed for that sort of rear is a problem.

You bring up an excellent point. The whole package has to be considered. As you pointed out, gearing is an issue, as was shown earlier, chassis weight is a consideration. Engines are part of the package that must work with everything else.

What you intend to do with the car is also a big part of it. Believe me, the 4.875s will be sweet in a hillclimb where only the very fastest cars reach 100mph.

peejay

Matter of taste. I find big-blocks with 4-speeds to be quite annoying to drive, even in a heavy car. Very difficult to drive smoothly, when 1st is 2.2 and 4th is 1:1. Have to shift *very* fast so the revs don't drop more than 400-500rpm, because if they do, you get all bouncy and lurchy and look/feel like a fool.

On the other hand, if you have decent gearing, like say some 3.91's, just start off in *fourth* gear

V8Mongrel

I agree with you that a typical big-block type torque output and a close ratio trans are just a really stupid combination.

wingsfan

You know better than to make such blanket statements. It's all dependent on available gearing and application. A lot of the LS1 FD guys that drag race are out of gear when they trap, even with 28" tall tires and the 3.9 ratio. A couple hundred more RPM would benefit them imensely. Now, getting the motor to breathe in that range is the kicker.

wingsfan

Nice disclaimer. Afraid someone will latch onto the most trivial of details and then hound you for a couple of days?

V8Mongrel

Afraid? No. If I am not sure of something, it wouldn't be right for me to present it as fact. Something that is lost on some others.

wingsfan

Apparently the humor went right over your head.

V8Mongrel

Haven't we already gone over the fact that we have different senses of humor?

wingsfan

Clearly.

I find it humorous that someone "here for fun" has a big disclaimer in front of their post. I would think you'd welcome any and all responses (flames included), since you've already made it abundantly clear that you A) don't take forums seriously, and B) are just around this forum to yank on people's chains. Given those criteria why would you need a disclaimer?

V8Mongrel

No, I don't find misleading people fun, no matter the medium or the message.