/4 shortblock assembly + HP limits, case, crank and rods....how much abuse?? Options

[Mueller]

Let's say we take the stock heads and cylinders out of the picture and use heads/cylinders that are overkill and robust....

what is the next weak link in the motor?

are the rods going to fail once we start hitting the 200+hp mark?

will the stock crank turn to putty at 7000rpm?

what about the case??


at what HP range before it cannot hold everything together and gives up scatering it's internals all over???

[Brett W]

Mike,

HP limits will depend on what type of aspiration is used. If you are going to a NA high hp motor then the rods are way to heavy to be turning the RPMs needed to make the power up high. The crank is plenty strong. Long strokes in conjunction with high rpms will cause case walk and pounding of the main tunnel. Unfortunately VW didn't put a 5 main crank and case to this package.

If you go with a boosted application then the stock rods should be alright with good bolts. The stock crank can handle 600+hp. Ask Dave Sadler. He was running stock based bottom end at 30lbs of boost. Stock crank, probably aftermarket rods, 94mm bore and Pauter heads.

[Bleyseng]

(IMG:style_emoticons/default/agree.gif)
In anything over 120 hp the rods are the problem, too heavy and the bolts. So they will break and fail away inside doing lots of damage.
Geoff

[airsix]

I saw the title of this thread and thought "I bet I can guess what he's thinking!" I bet it has something to do with nickies and Subaru DOHC heads. Am I close? (Warped minds think alike)

-Ben M.

[Mark Henry]

Cam and lifters, go with ceramics.

For 200hp it's a stroker/nickies anyways, don't skimp on the rods. Balance everything.
7000rpm is a lot, most cams will drop off before that anyways, so your just asking for problems.

A done right 78X96 with 150ish/hp should last almost as long as a stocker with proper head maintance.

[Brett W]

Guys horsepower does not kill parts. 120 hp will not kill the factory rods or bolts. If you use new rod nuts the stock rods (assuming properly balanced) will more than adequately handle that power level. RPM kills parts not HP.

If horsepower kills parts how can Winston Cup engines run zero wieght oil, at 10lbs of oil pressure per 100hp? The old rule has gone the way of the dinosaur. No more 10lbs per 1000rpm. These guys are turning 9600 rpms and making close to 800 hp. Alot of them run less than 60psi. Obviously this is not a perfect rule for the street, this just strengthens my argument that HP does not kill parts.

In anything over a sustained 6500-7000 rpm the stock rods are not strong enough. The rods in my engine which made 138 at the flywheel runs stock rods, polished, lightened by 60 grams, ARP bolts, and shotpeened. I watched my tach come back through 7000 after a missed shift at 80mph that was 10k miles ago. Never had a problem. I am running a piston that weighs 394 grams much lighter than the stock piston. Less reciprocating weight means less stress on the rods. Thus longer life for stock rods.

[davep]

I remember Chuck Stoddard say that the case needed work for anything over 120 HP. Basically pinning the case halves. And that is just the start.

[john rogers]

I tried running the 200 HP stroker four for several years and finally broke a Pauter forged rod. Problem was the long stroke of the crank coupled with short rods put too much stress on even really great rods and one failed on the front straight of the CA Speedway. I'd say use stock stroke with a forged crank and rods and go with larger bore and very very good heads that flow well and you'll get an engine that will last a little longer. I'd also recommend a dry sump system, not for the cooling but the huge increase of oil supply you'll get at 6000RPM or more should lengthen the engine life. Use at least a two stage pump and three stage is even better. But I gave up and put in a six and life is much better now!!!

[Jake Raby]

The case is good for 250HP with the correct work (not pinning- don't need it)
The case is hellaciously strong!

The crank is super strong, I know of a slat flat racer that turns a destroker to 17,000 RPM! I don't like the stock 2.0 rod journals as they are way too tiny to hold bearing stresses, we only use them on bus engines and 2056 low ball engines, everything else gets TI, Buick, or a certain Honda size that we save for our high revvers.

The weak point is the stock rods. They are too heavy, 750-800 gr!!!)

too short and because of the weight they snap rod bolts. The stock rod is good for 130BHP,(with better bolts) but not for a super high revver. I'm not fond of the Pauter rods at all, every one I have seen has had an issue and caused a failure. The stock length rod is inadequate for any added stroke, it creates a powerband that is totally out of whacjk for a stroker.... The Ricardo rule laughs at those rod ratios!

I'm working on rods now that can be bought for the same price as rebuilt stockers. They have an H beam design, various big and small end sizes. One of them is a 100% stock replacement with ARP 2000 bolts..... Another is a stock replacement that is .300 longer, the way it should be!

I started making my big power when we tossed out the stock rods and opted for H beams with TI characteristics.

The other weak link is the stock lifters, they weigh in at 140 gr....

Its all in the combo!

I would have to say that weak link #1 is rods, especially 2.0.. I have 90% MORE 2.0 rod bearing failures than I have 1.7/1.8 rod bearing failures. Odd thing is that we tear down more 1.7/1.8s than we do 2.0s because the cases are BETTER for what we are doing with them....

BTW, Higher RPM does not need more oil pressure! The centrifugal force of the crank will feed the bearings much better at high RPM... Just keep the mains fed and the crank will do the work for you. Extra pressure just pulls down HP and bumps up the flow of oil to the valve covers through the pushrods.... Thats why guys have oil pressure problems on the track!

Too much pressure and using a stock windage tray will put atleast a quart in each valve cover and the tray keeps it from GETTING BACK TO THE PICK UP TUBE!

It doesn't take extra parts to make this engine good, it takes extra thought- more later when I don't have one hot on the dyno!

[ArtechnikA]

...I'm not fond of the Pauter rods at all, every one I have seen has had an issue and caused a failure...

me either, but i have nothing more than intuition to base it on. interestingly, Bruce & Jerry don't like Pauter rods in 911 configurations either...

but i notice you don't mention Carrillo's...

opinions here have been hot and cold on Carrillo's, wondered what yours is.

(any application i'd have for them is so far from 'extreme' that a nice shot-peened stocker would probably be just fine, but i'm curious what your experience has led you to...)

[Jeff Bonanno]

wassa shotpeened?

[Brett W]

I haven't heard anyone say that Pauter rods aren't anything but problems. I prefer Crower for most engines, Eagles aren't bad but not available for our motors. I agree on the Carillo statement, heard both sides. Heard good things about Oliver and Cunningham. My SOHC honda engine runs a 1.77 rod journal, much smaller than the factory 2.0 journal size. It turns 7000rpm on a daily basis without any problems.

Haven't decided who to go with for this 1.9 monster. The 1.8 has a rod ratio of 1.95 while the stock 2.0 has a rod ratio of 1.84. If the engine is stroked to 2270 with 78 crank and the stock rod, the rod ratio goes to 1.678. Although not really bad it is a little below optimal. Some factory production motors are running 1.55 rod ratios with much smaller rods than what the factory put on our motors.

I would like to use something in the 1.75 range (115mm rod) on the 1.9 but I may just work a factory rod over and see what happens. The factory ports aren't big enough to support a shorter rod ratio. I am afraid dropping the factory rod ratio that much will cause the engine to lose power due to the lack of breathing area. we'll see though.