stroked small blocks in the race cars?

[xb-60]

Ed, how did you simulate the areas on the pistons that are stressed differently in your situation by the forced induction ? That must have been a challenge?
Cheers
Glen

[eschaider]

Originally Posted by xb-60

Ed, how did you simulate the areas on the pistons that are stressed differently in your situation by the forced induction ? That must have been a challenge?
Cheers
Glen

The finite element simulation software provides tools to load different portions of the piston as you see fit. In the simplest model you start with a crank slider mechanism dimensioned to mimick your crank, rods, and pistons and then start to increase crank rpm and watch as the stresses build in the model. Red will be high stress, blue typically is low stress. As you add or remove mass from various points in the model you can see the impact it has by the change in color.


Ed

[xb-60]

Double post

[blykins]

Duration would be in the ballpark. Hard to comment on lift and LSA without knowing if any head work has been completed. Porting changes a lot of things including the duration split and even the LSA itself.

For most small displacement road race engines, a tighter LSA will make a huge difference in torque and how much throttle response is available down low.

[PDUB]

Originally Posted by blykins

For most small displacement road race engines, a tighter LSA will make a huge difference in torque and how much throttle response is available down low.

Does the smaller angle increase or decrease torque and throttle response, or do those go in opposite directions?

[blykins]

Originally Posted by PDUB

Does the smaller angle increase or decrease torque and throttle response, or do those go in opposite directions?

Yes.

Not trying to be facetious, but it just depends on the application. There are a lot of camshaft theories that just can't be generalized.

[PDUB]

Originally Posted by blykins

For most small displacement road race engines, a tighter LSA will make a huge difference in torque and how much throttle response is available down low.

Originally Posted by blykins

Yes.

Not trying to be facetious, but it just depends on the application. There are a lot of camshaft theories that just can't be generalized.

Neither am I, Brent, but I was just quoting your generalization about LSA making a huge difference in both torque and throttle response, and trying to gain understanding about the "how and why."

[blykins]

In an optimum situation, a small cubic inch engine with a small intake port volume should gain torque and throttle response. If the overall combination is not optimal, then one could go one way and the other could go the other. Just depends.

[MAStuart]

Ok dont know if this will help at all. If 2 cams were identical except for separation angle. And installed on the same intake center line. The one with the narrower separation angle would open the intake at the same time as the wide one. But it would have more overlap and a later ex opening. The narrower one would also have more valve closed time during the compression and power stroke.

[blykins]

Dart IE heads havent been available for the past year and still aren’t. You’d be best off porting what you have.

I do *really* long rods on my 289’s. Longer than what normal guys do, at 5.700” length. It requires a SBC rod and some rod narrowing with some non-typical bearings.

Be happy to help with the cam when it comes time.

[1795]

Brent,

Ok, looks like we might be porting. He has them in the cleaner right now. Will let you know what we come up with. I believe that the rods that has on order are 5.04" from what I recall. Luckily he has not ordered the valve train parts yet. What would be an estimate of turn around for the cam, once we have the flow numbers?

Jim

[MAStuart]

Originally Posted by blykins

Dart IE heads havent been available for the past year and still aren’t. You’d be best off porting what you have.

I do *really* long rods on my 289’s. Longer than what normal guys do, at 5.700” length. It requires a SBC rod and some rod narrowing with some non-typical bearings.

Be happy to help with the cam when it comes time.

Brent How high up into the ring package does the 5.700 rod put the pin ? Any chance you have a picture?

[blykins]

There are "universal" lobes. Some lobes will tolerate hydraulic lifters or solid lifters. With the lobes that are as such, the lash spec will be very low with solid lifters, such as .005-.010".

In getting back to running solid lifters on hydraulic cams, I've seen guys try that because the hydraulic cam wouldn't rev. Generally, that's not a lifter issue, it's because the cam wasn't spec'd correctly, valvetrain isn't light enough, or things are just not right in general. Putting a solid lifter on a hydraulic lobe in that situation is a band-aid only.

Keep in mind that there are also "aggressive" hydraulic lobes and aggressive solid lobes. The key is choosing the correct one for the application. You don't want hydraulic lobes so aggressive that the lifters can't keep up and you don't want solid lobes so aggressive that they eat valve springs.

[MAStuart]

Brent i think you meant Less overlap gives you vacuum.

[blykins]

Originally Posted by MAStuart

Brent i think you meant Less overlap gives you vacuum.

Well, yes and no. I worded that poorly, I should have said, vacuum depends on the correct amount of overlap. "Correct" will vary from engine to engine. I'll change it.

[MAStuart]

Brent guess i was thinking more overlap at idle the less vacuum.

Hey its been good spending the last couple of day with you guys !

[PDUB]

Originally Posted by MAStuart

Hey its been good spending the last couple of day with you guys !

I couldn't agree more! Y'all are a great bunch. The conversation has been informative, too. The info and expertise is much appreciated!

[1795]

Originally Posted by MAStuart

Hey its been good spending the last couple of day with you guys !

I could't agree more. This is a great thread with a lot of useful information. Keep it coming!

Jim

[blykins]

You aren't wrong, I just worded it goofy and it wasn't clear.

As an aside, increasing the overlap doesn't mean that you lose your brakes, they will remain functional for quite a while. On a 445 FE, 65° of overlap still gives you 14-15" of vacuum if the engine is sealed up tight.

[PDUB]

Seems like I have heard that Webers don't like the LSA to be less than 108-110 degrees... trying to remember where I got that info. Sound right?