Brief Encounter

iTrader: (6)

Has anybody ever attempted to put a flat crank into a LS series engine?

I was thinking about it, and for High RPM's it would make alot of sense.

All one would need to do is, get the Flat crank itself- about the same price as a top of the line 4340 crank, a custom ground cam, and a retune, because the firing order has been altered.

This setup would also be ideal for a turbo, because you now have even exhaust pulses.

And the best part is, It would sound like no other LSx out there.

So what is everybodys opinion on the matter?

Formulated

iTrader: (16)

I think it would be interesting. I'm not sure what the practical benefits would be that would justify the expense, but it would be interesting to see.

I think the crank could be significantly lighter, because you don't need all of the counter weights. The cam might be difficult because of how the blanks are made, but you would have to talk to a cam manufacturer about that.

Do it, and let us know how it goes.

Old SStroker

1. Crank wold have to be billet. Figure 12-16 weeks to get one from a good manufacturer. Also figure the better part of $3K.

2. Vibration is an issue with 180° (flat) crank V8s. Not so bad in a race car but not too nice on the street.

3. Cam core would need to be special, but that's only money. Maybe $300-$500 extra. It could be made during the 3-4 months you were waiting for a crank.

4. I don't believe a turbo cares much about exhaust pulse spacing. All the flow just gets crammed into the spinning turbine wheel. However you can do 4>1 header tuning better on NA even firing banks, so that's an advantage. That's one reason NA open wheel V8 racecars use flat cranks.

5. The NA sound would be cool as long as the exhaust pipes exitied the car near each other. If they came out each side of the car just in front of the rear wheels, it would sound like a big 4-banger from either side of the car.

My $.02

LILS

Which is why you'd probably have to significantly destroke the engine.

chuntington101

i thick its a good idea! vibration can be balanced out. if vw can make a V5 engine (yes with 5 cylinders!!) and it not shake itself to bits then im sure a flat crank LS could be made!

Chris.

Old SStroker

A 180° crank (90° bank angle) V8 is quite a challenge to "balance out". Balance shafts on an LS engine would be a MAJOR problem.

Many engine configurations use split-throw cranks to get even firing for production engines. Not so on race engines.

Ferrari builds 180° crank V8 street cars. Sound is sweet!

Boosted LS1

Afaik you can't balance a flat plane crank properly so you have to live with it. Maybe having a split the plenum would be better for reducing charge contamination.

As for materials, I see know reason why a cast crank shouldn't be used. Nice and tough plus less brittle then a heavy forging.

Boosted.

engineermike

One of my friends, who is a local dirt-track engine builder, built a flat-crank Gen 1 SBC a couple years ago. His comments were, "A bitch to balance and didn't make any more power than comparable conventional crank setups." However, it might actually make sense to have equal length header tubes then. . .

Also, just a correction, forged cranks are tougher and less brittle than cast iron.

Mike

Old SStroker

180° crank V8s balance as well as inline 4s without balance shafts, but the secondary unbalances of each bank may interact. Also, many V8s have much more individual cylinder capacity than most 4s. Even the "large" IRL 3.5L V8 is only about a 214 cubic inch V8, or about the same individual cylinder capacity as a 1.8L I4. If you limit the V8 to ~5L (~305 cubic inches) with a short stroke (~3.0 inches), and rpm in the 7000 range vibration might be acceptable for a street engine. 19000 rpm 2.4L F1 engines don't have much problem with the secondary unbalance. They have strokes in the 1.56 inch range.

AFAIK, there are few if any folks making one-off cast cranks. You'd need a pattern, which isn't cheap in itself. I suggest that a one-off cast crank might cost more than a billet.

Most cast cranks are not made from the same grey cast iron used in cylinder blocks. Noldular or ductile iron is most often used for "cast" cranks. A good cast nodular or ductile iron crank is remarkably non-brittle and tough, and better than some forgings, but ultimately a forging or billet alloy steel (eg 4340 or even VAR steels) is stronger, tougher, less brittle and can be lighter than a cast crank.

ProdriveMS

The benefit to a 180 degree crank is that on one bank, the exhaust valve on one cylinder is closing just as another cylinder's valve is opening. With a properly designed 4-1 header, the exhaust gases from the cylinder blowing down can help create a small vacuum in the cylinder whose valve is in the process of closing. This also takes place during the valve overlap period and the net result is higher VE with a properly designed intake and exhaust system. Basically, a 180 degree crank allows you to extract more power from your intake and exhaust system NA.

It would be of no benefit in a turbo application since you have two exhaust valves open at the same time and the result is that exhaust will want to enter the second cylinder and contaminate the charge.

Btw, you can do the same thing with a two plane crank, but headers would have to cross under the engine from one bank to the other then to the collector. A PITA sure, but cheaper than having a special crank and cam made. In a high revving race engine, it's illegal(NASCAR) or impractical(ferrari) to cross the headers from bank to bank since they must be very short to tune for the high rpm. We keep spools on the shelf here and could have a cam made with the correct firing order in 3 weeks. The crank would be your biggest expense and wait.

Alin

Boosted LS1

I pattern stroker cranks for Rovers and cast them in SG Nodular. They're not that expensive to cast but the machining is a pita. Few people over here seem able to machine them in small numbers. I've thought about a flat plane lsx item but it wouldn't compete on price with the US and would be a dead duck if somebody there produced forgings. A UK billet would cost at least twice the cost of a cast item and there are know UK forgings available.

Boosted.

VYSSWagon

Don't forget:

6. Re-programing the firing order/fuel injection in the PCM. Once again could be done in the 3-4 months while you wait for the crank.

joecar

This is the easiest part... just move the coil/injector trigger wires around (extend/shorten) to suit the new firing order.

VYSSWagon

Not with a flat crank, you'll have two cylinders firing at once all the time.

So you actually have to wire them up in pairs. I don't know how the PCM would like running pairs of injectors and coils (double the current load). Not to mention the missfire codes, etc...

engineermike

I think you have 2 at TDC at the same time, but that's not different from a 90 deg crank. One is on TDC compression, while the other is on TDC exhaust.

Mike

Old SStroker

I don't think so. You have two 4-cylinder "engines" (each bank) connected at 90° . The cylinders on each bank fire at 180° intervals, so there is a firing pulse every 90° due to the bank angle. Here's how:

If you number the right bank 1-2-3-4 (from the front ) and the left bank 5-6-7-8 also from the front, the typical firing order for a single plane crank V8 is: 1-8-3-6-4-5-2-7.

edcmat-l1

iTrader: (10)

Warren Johnson experimented with a 180* motor. Said it was a waste of time.
There's some people you listen to and dont question.
I realize they have their place. It seems that bigger V8s isnt one of them.

Brief Encounter

iTrader: (6)

yes, because people like Smokey Unix and Roger Penske, and companies like Ferrari and BMW and Mercedes and even Chevrolet are all complete idiots and were all wrong.

I dont think so.. WJ was wrong.

edcmat-l1

iTrader: (10)

I didnt say it didnt work at all. Just not in what WJ was doing. It obviously has its place, I just dont know how practical for a 90* V8.
And I guess I should have clarified, WJ said/expressed that he found no clear, distict advantage using a 180* crank. It wasnt worth ditching the 90 stuff.
And with all the engine technology in nhra prostock, if there WAS a clear advantage to using 180* over a 90* I'm sure someone would have at some point been running them. They may be against the rules now, I dont know. But someone would have run one til they outlawed it.

99 Black Bird T/A

iTrader: (4)

Seems like an individual intake runner with it's own throttle body would be a nice for this.

Something like