8000rpm redline?

[Trakrat]

I'm looking at building out my engine to be able to safely rev to 8000 rpm.
(FYI... I don't actually plan on shifting at 8k, but in the rare instance I wind it up to 8k, I want the engine to be able to handle it)

I've already purchased ARP rod bolts and case studs, Aasco springs, titanium retainers, etc...


Also looking into Carrillo and Pauter rods. (can't decide on which yet)


Is there anything else that I should be looking into... reinforcing?

[BURN-BROS]

Anything above 7500 rpm I run a Carrillo for strength and weight reduction. a 100 grams of weight reduction on the reciprocating weight removes about 800 lbs off of the rod bearing @ 8000 rpm. aside from that, the AASCO spring and Ti retainers are about all that is required.

[smokintr6]

The engine air pump works as a system. A head / cam combo that still makes power at 8k will need to be run near that speed to make power. You either are, or are not building an 8k rpm engine. If you don't plan on shifting there, don't build for that. Pick your head and cam package, and then decide what bottom end you need. If you target normal shifting at 6500, and you wind it to 8k every now and then, you'll just be making noise and look like a complete idiot. if you build an 8k engine and shift at 6500 all the time, you'll never make any power.

You must build an engine as a complete package.

[Trakrat]

Originally Posted by smokintr6

The engine air pump works as a system. A head / cam combo that still makes power at 8k will need to be run near that speed to make power. You either are, or are not building an 8k rpm engine. If you don't plan on shifting there, don't build for that. Pick your head and cam package, and then decide what bottom end you need. If you target normal shifting at 6500, and you wind it to 8k every now and then, you'll just be making noise and look like a complete idiot. if you build an 8k engine and shift at 6500 all the time, you'll never make any power.

You must build an engine as a complete package.

You are correct on all counts... I am NOT building an 8k rpm engine and will never make any power at 8k RPM and I will look like a complete idiot shifting over 7k RPM.

I just want to make sure my engine is more idiot proof than I am...

[Trakrat]

Originally Posted by BURN-BROS

Anything above 7500 rpm I run a Carrillo for strength and weight reduction. a 100 grams of weight reduction on the reciprocating weight removes about 800 lbs off of the rod bearing @ 8000 rpm. aside from that, the AASCO spring and Ti retainers are about all that is required.

That's good to know... I wasn't sure if I needed to change anything with the oil delivery to the engine internals.

[Bob Kontak]

Originally Posted by Trakrat

That's good to know... I wasn't sure if I needed to change anything with the oil delivery to the engine internals.

Lots of pressure from stock oil pump at high rpm. Wish I knew more about the dynamics at that high of rpm.

Pretty cool info from Burn Bros

[spuggy]

Originally Posted by Trakrat

I've already purchased ARP rod bolts and case studs, Aasco springs, titanium retainers, etc...

Also looking into Carrillo and Pauter rods. (can't decide on which yet)

Pretty sure both of those already come with ARP rod bolts. I know my Pauter rods did.

I did much the same; not because I plan to rev to 8K often/at all, but because a turbo revving to 7K with the wastegate open sounds like Armageddon - sometimes I just do that because a) I can & b) I like the noise - and safety margin is good...

Lightweight clutches also very worthwhile; every # you can save on rotating mass helps. Those springs/retainers much improve valve control over stock, I'm told.

Difference in willingness to rev is very noticeable; you might find you have to re-train your right foot when pulling away off idle...

[BURN-BROS]

Originally Posted by spuggy

Pretty sure both of those already come with ARP rod bolts. I know my Pauter rods did.

I did much the same; not because I plan to rev to 8K often/at all, but because a turbo revving to 7K with the wastegate open sounds like Armageddon - sometimes I just do that because a) I can & b) I like the noise - and safety margin is good...

Lightweight clutches also very worthwhile; every # you can save on rotating mass helps. Those springs/retainers much improve valve control over stock, I'm told.

Difference in willingness to rev is very noticeable; you might find you have to re-train your right foot when pulling away off idle...

Carrillo has their own equivalent bolt for their rods.

Clutches...I use stock flywheels and a light weight pressure plate for street duty.

I built a motor that ran an aluminum flywheel and a 5.25" twin disk clutch...throttle response was outstanding. However, the alternator mass would shear the crank pulley pin and throw alternator belts and the engine would stall on decel. It needed a damper to slowly close the throttle to solve the problem. Too many issues when you go too light .

[KTL]

Yep Aaron is correct on the Carrillo bolts. They use either their basic WMC bolts or CARR SPS bolts for a bit extra strength and cost. Most Pauters use at least ARP 2000 bolts. Both rods use threaded caps (which technically makes the fasteners screws- actual bolts use nuts) where the factory Porsche rods are through-bolted w/nuts on the rod end.

Wow that's interesting on the issue with the crank pulley dowel pin & throwing belts. I never considered that the fan + alternator drag/inertia would exceed that of the clutch + flywheel and cause problems like that! Maybe it's a blessing that I have yet to put my WEVO superlite clutch (which uses a compact Tilton 5.5" twin disc clutch and their impressively "windowed" flywheel into use on the stillborn racecar project.

[Trakrat]

Originally Posted by BURN-BROS

I built a motor that ran an aluminum flywheel and a 5.25" twin disk clutch...throttle response was outstanding. However, the alternator mass would shear the crank pulley pin and throw alternator belts and the engine would stall on decel. It needed a damper to slowly close the throttle to solve the problem. Too many issues when you go too light .

I don't think I'd want to drive something on the street that has a mod to 'SLOWLY' close the throttle.

[BURN-BROS]

Originally Posted by KTL

Wow that's interesting on the issue with the crank pulley dowel pin & throwing belts. I never considered that the fan + alternator drag/inertia would exceed that of the clutch + flywheel and cause problems like that! Maybe it's a blessing that I have yet to put my WEVO superlite clutch (which uses a compact Tilton 5.5" twin disc clutch and their impressively "windowed" flywheel into use on the stillborn racecar project.

I think the best way to do it is to run the alt off one of the cams...that way the fan belt can focus on one duty. And you could ratio the alternator to be the most efficient @ rpm. Just gut an alternator for the shaft, bearings and housings to use at the fan.

That Tilton setup is nice for sure!


There are benefits to running the lighter rod for track motors that do not see 8000 rpm. you will see improved service life of the crank and bearings.

[47silver]

cis engines at least my 75, use a deceration valve that slowy reduces rpm when you remove decelerate (say when shifting).

[faapgar]

I run a gutted alternator on one of my cars for the last 40 years.Alt.runs off the camshaft with toothed belt for no slippage.Only downside is there is no charging until 1800 rpm as the cam spins at 1/2 crankshaft speed.Fan belt issues are solved and engine runs cooler.Wayne Baker ran his alt.off the inner CV joint on his IMSA 914-4.Fred

[chrisbalich]

Originally Posted by faapgar

I run a gutted alternator on one of my cars for the last 40 years.Alt.runs off the camshaft with toothed belt for no slippage.Only downside is there is no charging until 1800 rpm as the cam spins at 1/2 crankshaft speed.Fan belt issues are solved and engine runs cooler.Wayne Baker ran his alt.off the inner CV joint on his IMSA 914-4.Fred

do you have a picture or two of your setup?

[Quicksilver]

Originally Posted by Trakrat

I don't think I'd want to drive something on the street that has a mod to 'SLOWLY' close the throttle.

That is a standard emissions reduction system. A quick drop of throttle causes a NOX spike so a huge quantity of auto manufacturers design their cars this way and have been since long before electronic engine management.

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To get an 8000 redline "safety margin" you need to hold the rotating assembly together and you need to keep the valve train together. Tension is where the problem lies as loading something in compression is always stronger. All this works together so I'd talk to a builder with a lot of race prep experience.

The valve train is all about lightness, spring tension, cam profile acceleration, and the one people forget about: spring cooling.

The rotating assembly needs to be able to deal with the tension of trying to stop the piston at the top of the stroke. The rod and piston are much stronger in compression then in tension. Under a tensile load the big end is distorted oblong and to make things worse that distortion causes the parting line to squeeze inwards and actually squeegee the oil film off of the crank. Pauter and Carrillo are quality knee jerk answers but the most interesting take on this I've seen comes from Henry at Supertec. He says that rod failures using well prepped 3.0l rods just don't happen. He also claims that Carrillo and Pauter have more small end failures. And to use the 3.0l rods the 3.2 crank has to be ground down which means you can have a larger fillet radius on the journal and it actually makes the crank stronger.

The piston strength is mostly related to material, weight and how well the pin bosses are designed. (Closer to the rod is stronger but that has trade offs.)

In all of this I would talk to someone who builds a lot of race engines. Henry at Supertec, Dave at TRE Motorsports, Steve at Rennsport Systems, Jerry Woods at Jerry Woods Enterprises, John Walker, etc. (And after you pick their brains be nice enough to buy some parts and services from them!)

[cabmandone]

Why not just build it for the power and torque you want and set your rev limiter on your ECM accordingly?

[chrisbalich]

Originally Posted by cabmando

Why not just build it for the power and torque you want and set your rev limiter on your ECM accordingly?

Because a revlimiter won’t save you from a mis-shift or missed shift at WOT.

[cabmandone]

Originally Posted by chrisbalich

Because a revlimiter won’t save you from a mis-shift or missed shift at WOT.

Wouldn't you be screwed either way then? What I mean is if you miss a shift or go from 4-1 somehow by accident wouldn't you be hoping you only hit 8K if that's what you designed the engine for? I have never missed a shift and don't track my car since it's a cab but it seems in the scenario you mention you'd just be hoping you built it strong enough.

[chrisbalich]

Originally Posted by cabmando

Wouldn't you be screwed either way then? What I mean is if you miss a shift or go from 4-1 somehow by accident wouldn't you be hoping you only hit 8K if that's what you designed the engine for? I have never missed a shift and don't track my car since it's a cab but it seems in the scenario you mention you'd just be hoping you built it strong enough.

it's my understanding that what the OP is looking for is a little extra protection. i've gone 4-3 at WOT and managed to keep my valves their original shape with a quick stab of the clutch. but the engine and my heart definitely got over the 7200 my redline was set to. (my old LS powered M3, not my 911)

there is no absolute safety measure for an over-rev. but you can build in a little extra durability to help lessen the odds of valve/piston contact if you do spin too high.

[cabmandone]

I follow you. I guess I just mistook him saying in the rare instance he ends up at 8K for meaning he wasn't paying attention the R's and where to shift rather than accidentally missing a shift.