Cost to rev higher

[BobbyB]

Street/Strip SBC or SBF safely revs to 6000 rpm
How much more money and how much shorter life to build to:
Safely rev to 6500 rpm?
Safely rev to 7000 rpm?
Safely rev to 7500 rpm?
Safely rev to 8000 rpm?

[steve cowan]

Can't really put a price on it I don't think, build to the application.
I think it becomes hard on parts once you get serious and turn engine well past peak at the long end,that's where most failures occur in my opinion.
I think for a street car type of deal you are getting after it once you turn 8000 rpm.
There are alot of engines that turn 500 - 1500rpm past peak before the stripe.

[HQM383]

Street/Strip SBC or SBF safely revs to 6000 rpm
How much more money and how much shorter life to build to:
Safely rev to 6500 rpm?
Safely rev to 7000 rpm?
Safely rev to 7500 rpm?
Safely rev to 8000 rpm?

First - and the answer might be straight forward - how is “safely” defined?

[lefty o]

Street/Strip SBC or SBF safely revs to 6000 rpm
How much more money and how much shorter life to build to:
Safely rev to 6500 rpm?
Safely rev to 7000 rpm?
Safely rev to 7500 rpm?
Safely rev to 8000 rpm?

First - and the answer might be straight forward - how is “safely” defined?

yup, is it where the valves float or when parts come out the oil pan?

[Alaskaracer]

Things to consider, and might help determine cost:

1. Connecting rods. Lightweight is ok to a point, but they give up strength for the weight loss. How much do pistons, pins, rods weigh? They need to be strong enough to hold together at rpm at the weight they are....super lightweight stuff is not always the best choice.
2. Valve train. Number one thing to address to achieve rpm. A lot going on here too. Cam profile needs to be correct to support rpm. Valve springs need to be correct to control valves. Lightweight valves are not an option here, think Ti only, along with Ti retainers and smaller valve stems. Rocker arms. Need to be as rigid as possible not only in construction, but also in mounting. Many racers, myself included, are going back to steel for this reason, and many new head designs are going to one piece steel rocker bars with multiple mounting bolts to reduce/eliminate as much deflection as possible. Not cheap, my new rockers are over $4200 alone. Biggest pushrods you can fit in the engine, with the thickest wall diameter you can for a given size. You cannot get too big of a pushrod in an engine....Just because a certain size may "work", does not mean it's ideal or correct, I don't care what anybody says. Small block? Open up the pushrod holes as large as possible and fit a 7/16 or even 1/2" if you can. Big block, short deck, 7/16 min, 1/2" or larger preferred. I'm going to be running 5/8 on exhaust on my stuff, have to wait and see what will fit on the intakes, but if I'm correct, a 5/8-9/16 single taper may fit and I'll run it if it does.
3. Induction. To turn higher rpms, the engine has to be able to breathe. The induction has to allow this. My head guy told me if you can measure vacuum below the throttle plates at wot, you're leaving power on the table...airflow through the carb and venturi is what draws the fuel, NOT lower pressure below the carb....vacuum below the carb is restriction, period. The booster venturi provide the needed pressure drop to draw fuel.
4. Money....how fast do you want to go? Speed costs money. The faster you want to go, the more it will cost. How much all depends on the combo, rpm, power level, etc...there is no set number.....
5. Exhaust. Just like the intake, the exhaust has to breathe as well......small tube headers will likely not be the best choice....

[PackardV8]

Your question requires a multi-variable regression analysis. Every increase in RPM affects everything else. How much is the question. Valve train has to be able to withstand the increased RPM, as do rods. Heads, induction, block, et al, turning faster, maybe making no more power, doesn't stress them. OTOH, start making more power at the increased RPM and the block goes away.

[289nate]

SBF with a 3” stroke. Stock Mexican block. Going to send it. Drag racing application.

[HQM383]

Street/Strip SBC or SBF safely revs to 6000 rpm
How much more money and how much shorter life to build to:
Safely rev to 6500 rpm?
Safely rev to 7000 rpm?
Safely rev to 7500 rpm?
Safely rev to 8000 rpm?

First - and the answer might be straight forward - how is “safely” defined?

yup, is it where the valves float or when parts come out the oil pan?

That’s the outcome of going beyond safe. Are we able to put an rpm figure on component structural integrity at 500rpm increments and then budget accordingly? And as PackardV8 says horsepower comes into it along with rpm.

So is ‘safely’ defined as pushing the limits to 1 rpm before component failure or within the bounds of no structural integrity compromises of a component with a known qualified failure limit. If it’s the latter then a dollar figure is easier.

[Tom68]

Lifing components was a cost element with endurance race engines, keep putting those Carillo rods back in event after event and you'll break one on an engine that's running perfectly and never over revved.

Any component that's seeing it's modulus of elasticity being called into use has a finite life.

GOOD Valve springs are just bloody amazing.

[BLSTIC]

Just a passing thought, is the car based around reliable horsepower per dollar and not much else? Or is there some kind of theme or rulebook involved?

[skinny z]

Street/Strip SBC or SBF safely revs to 6000 rpm
How much more money and how much shorter life to build to:
Safely rev to 6500 rpm?
Safely rev to 7000 rpm?
Safely rev to 7500 rpm?
Safely rev to 8000 rpm?

Exactly my questions although I'm thinking more about durability vs outright performance as opposed to cost.
I'll say 6500 is all day everyday for a long time with a modest collection of parts. Not endurance racing 6500 but your typical street/strip deal.
I've done it.
Once 7000 RPM entered the picture (cam upgrade and reworked heads), one of those parts, and for the record they had had a hard life previously, a lifter link-bar let go. It may have lasted forever had the RPMs stayed in check.
I can't imagine how long a life even a properly built 8000 RPM pushrod V8 would have if it's driven hard and regularly. "Race"engines require routine preventative maintenance.
Keen to read the opinions.

[Tom Walker]

A significant failure of a component can have a much more impact on damage and cost compared to a less stressed engine that may need just a freshening up to continue.
Engines that are pushed to the edge, are at times pushed over the edge.

[thecarfarmer]

I think the real answer to "how much" would have to be "it depends"

Case-by-case basis...

Modest price aftermarket rods already installed? Not likely to find the limits on them.

O.E. rods, with the original, 40-year-old bolts? You might. Or might not.

How aggressive are the valve events? To use a Harley-Davidson example, the .497" cams used in Buells work just fine with the original valve spring in the 2002 and earlier engines. Until you want to go over 6,000 RPM. They have ramps that are too aggressive to go further with that spring. A smoother, gentler profile may work to 6500 RPM or higher with that same spring.

So, the cam profile from company A may be reliable at a certain RPM, where the cam profile from company B may actually lose valve control at a lower RPM.

I suspect the question to ask would be to put all of the pieces in the planned build out on the board, and ask "what's likely to be the part that will be the limiting factor?"

[PackardV8]

When customers ask about building for higher RPM, I tell them, "Revs are the most expensive horsepower to build and to maintain. Displacement horsepower is cheap to build and cheap to maintain. Unless building to a displacement-limited class, go bigger and turn it slower."

[Bigchief632]

When customers ask about building for higher RPM, I tell them, "Revs are the most expensive horsepower to build and to maintain. Displacement horsepower is cheap to build and cheap to maintain. Unless building to a displacement-limited class, go bigger and turn it slower."

I prefer building a bigger displacement AND turning it more rpm. They make A LOT more power that way.