Exotic "SOUNDING", high revving V8! Read "ENTIRE" thread before posting!!!

[kiwi303]

Thanks Gollum.

From my observations of flat plane V8 crankshafts, a standard racing counterweight is in the ballpark of 50%.

Som people may be confused by the percentages I have been talking about, but it is simply how much mass is on one side of the crankshaft compared with the directly opposite side.

 

and so the lighter the piston and rod set, the lighter the counterweight can be? How do you balance rod and piston weights to counterbalance weights when putting together a custom engine? Surely if using lighter than stock racing forged pistons and rods, on a stock crank, or whatever plane, then the crank counterweight is going to be more than 100% then? what happens in that case?

 

The nice thing about the SBF is you can buy a new OEM block from summit for about $500.

 

Nice, the only bare ford block I can find in my copy of NZ Petrolhead's Adverts is a Boss 302W, Siamese bore Splayed 4 bolt with 8.2" deck height. Thats a little pricey at NZ$2632. they do advertise it as being stronger than Original tho, I wonder how one with a flat plane, and twin turbos (one per bank) fitted with ported racing heads would do...

 

 

The flat plane crankshaft that I designed with 100% counterweights actually weighs about the same as the longer stroke cross plane crankshaft that came out of the engine. Reason being that with a shorter stroke you can remove less material inside of the conecting rod journal. With an extra few millimeters of stroke I was able to remove some more weight at the sacrifice of crankshaft durability. (less main-rod bearing journal overlap and less material)

 

so the crank, being more solid with less material removed, would be able to handle higher HP and torque limits?

 

 

 

Now...

Single cam V8 vs. DOHC V8.

 

First of all, you will need custom camshafting, which is MUCH cheaper with a single camshaft.

 

Are there any cams that are made for an Inline 4 that will fit a V8 cam train? since the flat plane runs like 2 I4 engines, then what if a pair of I4 cam sets can fit the cam towers and run the valves?

 

 

does/did Ford use the same valve spacing and design in the I4 and V8s? bearing size, valve spacing etc? Surely it would have made sense to have been able to make their cams for the Sierra and Laser/telsar engines et al on the same cam grinders as the V8 ones, just change the programming of what the cam grind and duration etc is...

[OlderThanMe]

and so the lighter the piston and rod set, the lighter the counterweight can be? How do you balance rod and piston weights to counterbalance weights when putting together a custom engine? Surely if using lighter than stock racing forged pistons and rods, on a stock crank, or whatever plane, then the crank counterweight is going to be more than 100% then? what happens in that case?

 

 

Nice, the only bare ford block I can find in my copy of NZ Petrolhead's Adverts is a Boss 302W, Siamese bore Splayed 4 bolt with 8.2" deck height. Thats a little pricey at NZ$2632. they do advertise it as being stronger than Original tho, I wonder how one with a flat plane, and twin turbos (one per bank) fitted with ported racing heads would do...

 

 

so the crank, being more solid with less material removed, would be able to handle higher HP and torque limits?

 

 

Are there any cams that are made for an Inline 4 that will fit a V8 cam train? since the flat plane runs like 2 I4 engines, then what if a pair of I4 cam sets can fit the cam towers and run the valves?

 

 

does/did Ford use the same valve spacing and design in the I4 and V8s? bearing size, valve spacing etc? Surely it would have made sense to have been able to make their cams for the Sierra and Laser/telsar engines et al on the same cam grinders as the V8 ones, just change the programming of what the cam grind and duration etc is...

 

On a flat plane V8, you do not need to take the connecting rods/pistons into account. They statically balance each other out.

I looked at summit again and I guess they don't carry an OE SBF block any more. They do have a Ford racing 5.4L modular block for $500 though. LINK

 

About the crank being more solid: That is my theory. From what I have read, the more bearing journal overlap that you have, (rod vs. mains) the stronger your crankshaft will be. With more stroke you have more of a lever acting on the crankshaft and are putting more twisting forces on the entire crankshaft.

 

For the I4 cams, I know that most I4 engines have a rather small bore spacing. For example, the VH45 has 112mm bore spacing while most Nissan 4 cylinder engines have around 100mm bore sacing.

 

About the Ford specific stuff, I have no idea. I'm not really much of a Ford guy.

 

I hope that helped.

OTM

[Gollum]

I have “heard†that some of the faster drag V-8s as far back as the ‘70’s will hit 10,000 RPM. Current Pro stock V-8 engines are shifting between 9000-9300 and read on one site that some Pro Stock engines will spin as much as 9800 RPM. Top Fuel 8200 RPM. Of course these drag engines are only seeing these RPM’s for a very brief second or two max.

 

Hey, I might be young, but I've "heard" a lot in my life! (sorry for my poor interweb grammar/spelling)

 

On a flat plane V8, you do not need to take the connecting rods/pistons into account. They statically balance each other out.

I looked at summit again and I guess they don't carry an OE SBF block any more. They do have a Ford racing 5.4L modular block for $500 though. LINK

 

About the crank being more solid: That is my theory. From what I have read, the more bearing journal overlap that you have, (rod vs. mains) the stronger your crankshaft will be. With more stroke you have more of a lever acting on the crankshaft and are putting more twisting forces on the entire crankshaft.

 

For the I4 cams, I know that most I4 engines have a rather small bore spacing. For example, the VH45 has 112mm bore spacing while most Nissan 4 cylinder engines have around 100mm bore sacing.

 

About the Ford specific stuff, I have no idea. I'm not really much of a Ford guy.

 

I hope that helped.

OTM

 

The only I4 I can think of that shares a valve train with a V8 is that GM engine that uses SBC parts, and is basically a SBC cut in half.

 

Oh and also Question for OTM, who seems like the person to ask right now.

 

Does the rod bearing being closer to the main bearing cause more load on the main bearing leading to more severe wear?

 

It seems like the rod will be pushing very directly on the crankshaft and be putting a lot more force on those bearings. If so, much larger main bearings might be REQUIRED, and might rule out many block options as custom bearing sizes would be required.

 

I could be wrong, please say so.

 

Today I'm going to try to find the highest reving street driven Ford Mod motor. They seem like a hopeful option. Their prices have really been falling since the 3 valve debut. They might very well be the next "5.0" engine out there. Given enough time they'll be everywhere, and they're an extremely solid foundation to build on. And the DOHC heads are easy to come by, if we're talking the lincoln and SUV variety.

[OlderThanMe]

 

Oh and also Question for OTM, who seems like the person to ask right now.

 

Does the rod bearing being closer to the main bearing cause more load on the main bearing leading to more severe wear?

 

It seems like the rod will be pushing very directly on the crankshaft and be putting a lot more force on those bearings. If so, much larger main bearings might be REQUIRED, and might rule out many block options as custom bearing sizes would be required.

 

I could be wrong, please say so.

 

You are almost there, but 180 degrees in the wrong direction.

The more the rod journal and main journal overlap, the more rotational strength there will be.

Severe bearing wear is more related to counterweight than stroke, but it does have some effect.

Think of it as a simple beam problem rather than a complex crankshaft, just for a minute. Think of a pair of beams joined t look like a "T". The top part is at the centerline of the crankshaft and the vertical part represents the stroke.

For the same amount of force applied to the bottom of the vertical element of the T, a shorter vertical element will apply less twisting forces on the horizontal element.

 

What I was saying about bearing journal overlap is that the more solid metal that runs the length of the crankshaft, the more stout the crankshaft is, thus improving crankshaft lifespan and less axial twisting.(thus bearing wear too)

A ballpark figure for the amount of twist in a crankshaft while running is around .03 degrees.

[kiwi303]

You are almost there, but 180 degrees in the wrong direction.

The more the rod journal and main journal overlap, the more rotational strength there will be.

 

What I was saying about bearing journal overlap is that the more solid metal that runs the length of the crankshaft, the more stout the crankshaft is, thus improving crankshaft lifespan and less axial twisting.(thus bearing wear too)

 

In other words... the larger the continuous metal through the shaft, the stronger the shaft. The picture below was made in MS paint rather than solidworks or a CAD program, so it's a bit ragged, but lookign at 2 crankshafts, for ease of drawing, rather than dual plane they're single plane, one has the rod journals out beyond the bearing journals and will be weaker than the second one, which has overlap. (the red bits) This seems to make sense I hope the pics make it easier to visualise.

[Gollum]

This is a rough sketch based off the Ford Modular engines. I have bore spacing and journal specs, but I honestly had no clue how wide to make them. So I guess on some of the figures, but the overlap from the journals should be extremely close to what it would be in the real world with a 3" stroke.

 

 

Here's a better image without the rods

 

[Guest Zedintheshed]

Just wondering if any Old CanAm Racing engines used Flat Plane Cranks with American V8's? Also didn't some Formula 5000 engines have flat plane cranks and if so are some of these cars still getting around today in historic racing with these same cranks? Surely these engines would occasionally need new cranks - so someone must make them and have done all the R&D?

[ZROSSA]

There are engines out there......I have posted them before in previous threads.

 

DTM all use flat planes. Merc, Audi and opel(which uses a version of the northstar engine)

 

Every time i go to the local dirt track- not often- i hear at least one small block with a 180 crank.

 

Most of the IRL engine are flat plane.

 

SOMEONE MAKE CRANKS FOR THESE! Probably a case of how bigs your wallet, but they are out there.

 

There is an engineering co in the uk that I think makes these parts. Cant find there name right now but will keep looking. They seem to be able to make anything. Just need to check some back issuies of racecar engineering.

 

Douglas

[OlderThanMe]

The problem isn't finding someone to make the crank, the only problem is finishing a crankshaft design and sending it to your choice crankshaft manufacturer.

And about $2000-$3500 depending on your crankshaft design and how intricate it is.

[Gollum]

My current build =

 

I've made rods that are now to spec. I need to shorten the length of my rod journals on the crank slightly, but I was happy how close my guess came.

 

EDIT:

 

I now have a video with pistons -

[Daeron]

I now have a video with pistons -

 

Me Likey

[OlderThanMe]

Gollum,

Have you measured your critical area in your crankshaft?

Its from the bottom of the rod journal to the top of the main journal. The max stress of the crankshaft moves through this plane.

 

ala critical plane:

 

 

OTM

[proxlamus©]

is that a real picture in post #442 right above this?

 

or is that a computer rendering?! Looks crazy real!

[OlderThanMe]

Its a rendering that I made the other day.

 

I want to learn more of the animation stuff but I still stink at it. lol

[Gollum]

No I havn't. I'll try to get something today or tomorrow posted for ya.

 

I kinda want that ground texture...

 

Anyways, I've already got another crank design on my computer, this time spec'ed to the SBF instead of the Mod motor. I'm getting better at this

 

I'm kinda holding off on rendering a video though, since I'm considering starting over. I've been looking into multipiece crankshafts... I've been looking at too many F1 and other race car crank designs and I'm thinking I could design something much better.

 

Here's a picture of what I've currently got though:

 

[Careless]

is that a real picture in post #442 right above this?

 

or is that a computer rendering?! Looks crazy real!

 

That crank pin cut-away would have to be pretty big to be sitting on bricks that small.

[Gollum]

OTM Here's a cut like you were saying.

 

 

Inventor is calculating an area on this plane of 1503mm^2, which is 59.1732 square inches.

[OlderThanMe]

OTM Here's a cut like you were saying.

 

 

Inventor is calculating an area on this plane of 1503mm^2, which is 59.1732 square inches.

 

Alright... now lets get rid of any stress risers(sharp corners...) and then maximize your critical section area. Use that information I gave you and plug some numbers to figure out if it will hold up to your expected horsepower levels.

Although 59in^2 sounds like you had an error somewhere in your conversion math. 6"X6" only yields an area of 36in^2 and your cross section isn't that big.

 

Just as a comparison, my design has a cross section of 2249.2mm^2.

[Gollum]

Yea I thought that number was fishy too... guess that's what I get for just doing a basic mm to inch conversion... wooops.

 

Ok, I just checked my other crank (not seen in this thread) and I've got this:

 

"1876.846 (square millimeters) = 2.90911712 square inch"

 

That inch figure makes a bit more sense. Still not as much area as yours, but I'll try to figure out how much stress it'll take. Quick question though... in your picture there's quite a bit of material from the main journal in the critical plane. Am I wrong? Is this being calculated? Are you cheating me?

 

Ok, I'm off to try to figure this stuff out.

[OlderThanMe]

Quick question though... in your picture there's quite a bit of material from the main journal in the critical plane. Am I wrong? Is this being calculated? Are you cheating me?

 

Nope. The critical plane contacts the main and rod journals at one point each. Also mind you that I have 34mm for each cheek pad. Yours look offset to one side with different cheek pads. (I'm hoping that your motor is based like that)

It also looks like you cut into the main and rod journals too with your critical plane? What are the rounded parts at the upper and lower portions? Are they radii on the journal?

OTM