360 crank in a 308 block

F1 engines in comparison to the other engines I talked about.
Some of the bores in NHRA got as large as 4.700"!!!

 

It's also contains several errors

"In oversquare engines power does not suffer, but low-speed torque does to some degree, since torque is relative to crank throw (distance from the crank center to the piston pin center)—the leverage, essentially"

This in particular is not true. As long as the displacement is constant, the force on the crank will be constant (rods ratios being equal of course). The reason is the the piston is smaller in tha long stroke engine so there is less surface area for the the combustion gas to push on and therefore less force acting on the crankshaft exactly negating the effect of the longer throw on the crank.

The low speed torque issue is another old wives tale. Short stroke engine are normally build specifically because higher rpm is desired and the combination or lower loads due to the short stroke and the ability to fit larger valve and port are ideal for that application. It's the larger ports and valve that cause any engine to lose low end performance. A short stroke engine fitted with small valve and port will have very similar low end performance as a long stroke engine fitted with the same size ports and valve. The chevy 305 already mentioned is an excellent example with a 1.33 bore/stroke ratio and excellent low end performance, a the 911 engines are another example.

 

I agree the link is not perfect and some verbage could be generic, but on the whole we know what it means. The "air pump" must have all parameters in balance.

 

Whoa went to bed and look what I wake up to . Sorry I'm on the other side of the world so takes time for me to comment . Thank you to all who have posted . I started this by thinking I would try and put a complete 360 motor onto a 308 box ,but realised that the oil pump is on the gearbox side and would need to be moved . With alot of compromises that come with that .I want to build a reliable road car not a race car for the road (no external drysump pumps ).So thought lets increase the stroke with a 360 crank in the original block ,but now after reading all this maybe the complete motor oppotion is not that much more work ? You get the added breathing of the heads with the increased stroke so benefit from both sides .

 

Sorry to post late, but I did look into this with both the shop in California doing this and we looked at this with Norwoods. As mentioned, while it does basically 'fit', there is a lot of modification needed at both ends to make it work.

It is actually cheaper in the long run, and this was a surprise to me, to have a long throw crankshaft made. James at Norwoods said that they have had these done for V-8 Ferraris with success and have existing cnc specs, but it takes a while for the company that makes them to do them. So, stroking a Ferrari V-8 is not entirely new, but like most things Ferrari, not entirely inexpensive.

 

Mark, in reference to the rods, the only reason would be for moving from aluminum to titanium to cut the weight in half. the heads would be an issue for flow but the can be 'worked' to help them. the more 'cost' effective means would be to match up the 348 heads instead. once I sort thru the options and build it then we'll know. but as we know the cost of this first one is going to hurt.

cams are another issue, hence why the 348 would make a better choice in heads. I'd rather start from blanks and have them made then the weld/grind game. yet another big project.

the goal is to ultimately have a stroker motor option that puts out 400hp and costs around $10k.

 

Can't wait to see what you build!

custom pistons are about $1000 and custom liners another $1000 so you could have a 3.2 big bore kit for a 308 for including gaskets (say 85mm and use 348 head gaskets) for under $3000 I'd think. That give you $7k to rework heads and cams. Just a thought.

I'm working on billet cams for my project too btw.

 

the crank is $2k and the rods are another $3500, so that's another $5500. I was also going to go out to 90mm on the bore for a 4.0L build. any good leads on billet blanks?

 

90mm? Your out of control man, even I'm not that crazy

Are you going with coated steel instead of iron so you can thin them out a bit more?

I've never done a billet crank. I backed away from stroking mine as soon as I realized welding wasn't universally accepted as adequate and didn’t do any more looking.

You do know you can just buy a 4.8 or 5.0 liter and “bolt” it in right?

 

Hey guys,
neat-o thread.

BUT,
Raising your RPM was the question,
as RPM goes up (in theory), more fuel is burned, giving more HP (power).
Yes, you need air flow through the heads to maintain 14.7 air/fuel ratio...


All,

Torque is in ft-lbs,, emphasis on the foot part of this property.
Simply, Torque is the ability to change your speed.
Thus,, Torque is proportional to stroke length and cylinder gas pressure.

HP is Power.
Simply,,, Power is the ability to maintain a speed.
Power is proportional to Gas pressure.
Thus, Power is proportional to Compression ratio.

Now,, your thoughts please...?
(Test on Friday,,, tomorrow.)

Edwardo

 

This is what Steve Demirjian the builder/machinist of the 4 liter project wrote on another forum about the custom Ferrari crank.

"I have a custom Crower billet Ferrari flat crank here for a special project I am working on. I thought it would help you folks visualize what Erik was talking about.

The flat or 180 degree crankshaft for a V-8 looks identical to a four cylinder inline crankshaft. The 180 degree crankshaft is balanced independently of the rods and pistons, etc. just like an inline four or six (no bobweights).

As Erik said, these cranks offer no improvement over a conventional 90 degree crankshaft in most applications. They do seem to work better with individual intake runners and only because the exhaust pulse tuning is better with even firing cycles per bank. Intake manifolds for the LS1 and most other V-8 engines were designed for a 90 degree crankshaft. Unless you have a lot of time and money to come up with an intake manifold that will work effectively with a 180 degree crankshaft you will loose power.

Another problem area is the secondary imbalance with these cranks. Other than using a pair of balance shafts there is no easy way to get rid of the imbalance.

Ferrari guys love the sound of the flat crank. Also, the only cams made are for a flat crank so I have no choice in the matter. I am taming down the secondary imbalance by using titanium rods and very light pistons in these engines.

Steve Demirjian
Race Engine Development
Sponsor"
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Group77,

I believe all Chevrolet small blocks are the same,,,,? or "similar. "
the diifferance between a 327 and a 350 is the crank only.

This interchangability was what gave Chevrolet an edge against Big Ford, a 350 block is a 350 block is a..... etc.
Now, how about that 1980 Chevrolet diesel with a 350 block, I believe they lasted 100 mi then booooooomb!
Because, the 350 block wasn't made to be a diesel.

Edwardo

 

Edwardo, please re-read the Horsefly post, he had it backwards. Yes, I know 350 and 327 used the same blocks but I didn't want to confuse this dudes post by introducing another number to digest. So, " smallblocks are all the same,,,,? or "similar" WTF?

 

OOps, ok.

 

Torque is proportional to stroke length and cylinder gas pressure[* piston area].

It needs more, there has to be a force in there and that is way engines with equal displacement are capable of equal torque regardless of the bore or stroke chosen

I'm having trouble with this one.

thermal efficiency and therefore power is:
n=1-1/(r^(k-1))
where
n = thermal efficiency
r = compression ratio
k = constant (1.4 for air)

so power is proportional to the log of compression ratio I guess, there is a quickly diminishing return. Power is directly proportional to rpm I think.

Engine torque tells you how much force is available, but you need an rpm component to use it for anything. HP tells you how much work you can do with the torque is the way I like to say it.

 

.[/QUOTE]

Engine torque tells you how much force is available, but you need an rpm component to use it for anything. HP tells you how much work you can do with the torque is the way I like to say it.[/QUOTE]


Yes, right on Mark.
Piston area is part of the pounds force Lbf on the top of the piston by Cyl. gas pressure.
(usually measured at TDC after an ignition.)
More is needed to use the Torque at hand but not to measure it.

Torque is a instantanious property, usually measured stationary.
At TDC, no Torque is available for piston #1 because your lever arm is zero.
but a lot of potential energy is at hand,
again,"HP or Power."

Nope (sorry), Thermal Efficiency and Power are two very different properties that share some of the same factors.
Motor Torque tells you how much power is available (Cyl. gas pressure)...
AND, how long your lever arm is (i.e. stroke length) ,,
or, in a more proper sense, rod journal offset from center line.

 

Build a crank!!! We did that with our Ducatis, and boy did we ever learn a lot. First thing we learned was make sure that you check the crankshaft, item by item, to ensure it's been machined properly. Every dimension, including those that don't have machined surfaces, every one. Second thing we learned was to make sure that you use the right materials, we ended up using vacuum forged steel. Lastly make sure that you make several. Since most shops use CNC, you've paid for the set up, you might as well make an extra, because you never know when they are going to brake. We went through several before we figured out what was breaking them, and fixing the problem (not the crank shaft directly, it was a balance issue).

Good luck, expect to spend twice what you've budgeted.

Art

 

Now you're just getting it all mixed up...chemists.....

Yes power and efficiency are different, but compression ratio is only present in the thermal efficiency calculation. It ends up in the torque and therefore the power by changing the % of the total energy that is converted into mechanical energy on it's way to becoming torque and power.

The engine torque that is useful and that is always quoted and graphed is average torque. Torque is proportional to cylinder pressure and displacement, not stroke.

But we digress......back to monster 308s

 

Out of interest is it possible to upgrade a 3.0 to 3.2 that easily? Has anyone done it on a carbed motor?

 

Yes, I was bass ackwards. The 302 is a 283 crank in a 327 block. (I'd rather admit that my memory wasn't 100% accurate than pull specs off the internet in an attempt to look like an expert.) But the jist of my posting was still true. You can't simply make a stroker motor by dropping a similar crank in a block. Most longer stroke motors will have larger crankshaft counterweights that won't always clear an earlier engine block, even if it's from a similar make. That's also why 454 Chevy engines use externally balanced flywheels and 427 engines do not. The stroke is so long on a 454 that the counterweights can't be made big enough to balance the crank and still clear the block. Uh,....now back to our regularly scheduled Ferrari program.

 

Nope, CR is in the Torque equation, remember the Lbf on the area on the top of the piston.
Nope again, , You can't use that Ideal Thermal Efficiency equation to predict Real Brake HP or Brake Torque.
(note; no Average HP,, that you made up.)
Anyway, with that equation the assumptions are; ideal gas, and no mass transfer across system boundaries. Now in Reality, improving the mass transfer will increase your efficiency. (see how it works now)

Ex;
Diesel motors have Long strokes and major torque.
Unstroke a 350 with a 327 crank, get more HP.

Q=mc(T2-T1) will give you your energy,
then integrate with time to get your HP.


Back to Monster stuff.

Can I/we get a naked forging, ,
say from Fiat-Ferrari?
or from Dart.?

I know of an FAA shop that can do anything to a Crankshaft, , ,
just don't put it in an aircraft of anykind.

A custom 360 flywheel can be made for about $ 400.00,, I am having one made for my motor now. (a 308)
and I really could use a New crankshaft though. Did my check clear?

 

This is just getting too mixed up to even try straighten out. Some of it's right, some we're talking about different things and some....well.....(hint the only really wrong part are your examples )

Just make a billet crank, I'd guess 8620 but some research might find something better.

I wasn't waiting for that...I saw the letter Saturday then it was gone and I was trying to find where Lana put it (I cna't tell her there's a check in it if I want to actually have the check). I found it this morning and I'll ship the crank tomorrow.

 

A forging would be way too expensive with custom dies and all. And while the forging may have superior grain structure, the trade off is that forgings have inclusions and other defects from the dies during the forging process. The process has a high scrappage rate. The most best is vacuum arc remelt (VAR) billet crank. Call Crower or Moldex for prices and waiting times.

 

I remember reading a while back that a 355 slightly modified 355 crank fits in a 328 without the need of any other modifications. Is this true? (ie can you use the same pistons/rods/etc, as well as not have to machine/modify the block or headers in any way?

 

Also, I might as well add, if the 355 crank does work as a drop in post minor modification to the crank itself, where would be the best place to source a used unit?