stroked small blocks in the race cars?

[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]

Originally Posted by 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.

The overlap is what you have to keep an eye on. It can make or break an engine.

1. Overlap can make/break vacuum, which is necessary for accessories like power brakes.

2. You can have too much overlap (either by narrow LSA or by large advertised durations) which will push the charge right out the exhaust instead of using it for power-making. That's why engines with really large or tight LSA cams sound so radical at idle, they are inefficient.

3. Overlap can be your friend on a large intake port, such as in the case of a 4V 351C head or a Tunnel Port FE head. With the valves open at the same time, the exhaust can scavenge the intake charge on a port which is otherwise too large and too slow on velocity, which will help fill the cylinders.

[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]

It’s a 1.060” piston, so just a hair shorter than a 347 piston. Works fine. I use thinner rings than most guys do though. Most are 1mm/1mm/2mm.

The long rod gives me a torque advantage. They make between 390-400 lbft with factory heads.

[MAStuart]

Originally Posted by blykins

It’s a 1.060” piston, so just a hair shorter than a 347 piston. Works fine. I use thinner rings than most guys do though. Most are 1mm/1mm/2mm.

The long rod gives me a torque advantage. They make between 390-400 lbft with factory heads.

Thanks for some reason this morning I could not picture it. Now its got me thinking about the big end of the rods dimensions. 2 inch or smaller Honda size stuff . Smaller journal same stroke = longer rod.............Just thinking out loud!

[blykins]

Can’t give away all my tricks but I’ll tell you that there’s not a lot of factory parts or dimensions in one of these custom race engines.