66 Roadster 300 HP vs 350 HP

[Michael H.]

Re: 66 Roadster 300 HP vs 350 HP

While the 300 HP is a wonderful engine, I do love the sound of a 350 HP L79, especially through off road exhaust. It's just so.... so... Corvette! Love the look of the engine too.
I really don't think the actual horsepower is a factor. It's just an old car.

[Michael M.]

Re: 66 Roadster 300 HP vs 350 HP

While the 300 HP is a wonderful engine, I do love the sound of a 350 HP L79, especially through off road exhaust. It's just so.... so... Corvette! Love the look too. I really don't think the actual horsepower is a factor. It's just an old car.

Me too. I own one and I love it. I just find this engineering stuff fascinating. I guess I missed my true calling. And I hope to never have to rebuild it, although I'm sure I would enjoy the experience.

[Jim T.]

Re: 66 Roadster 300 HP vs 350 HP

My first Corvette was a 64 327/300 4/speed with factory air and 3:08. Really liked driving the 64. Best trip was San Diego, CA to Glenco, GA in 1969. Still have a 68 327/350 M21 with 3:70 L79. Like it a lot, the sound of its original L79 idling is nice to my ears, just like the sound of the L79. I think either of the two cars would be a great Corvette to own.

[William F.]

Re: 66 Roadster 300 HP vs 350 HP

Gonna throw the BS flag on "never been down in 20 yrs."

[Bob S.]

Re: 66 Roadster 300 HP vs 350 HP

From a cruising viewpoint, can someone tell me what the difference in RPM is at 60 mph for cars with 3:08 vs 3:36 vs 3:70 gears?

thanks,
Bob

[William F.]

Re: 66 Roadster 300 HP vs 350 HP

"Just an old car"??? Please!!! Like saying a Rembrandt is "just a painting."

[Joe R.]

Re: 66 Roadster 300 HP vs 350 HP

Bob,

Try this:

http://www.angelfire.com/fl/procrastination/rear.html

Joe

[Jim T.]

Re: 66 Roadster 300 HP vs 350 HP

I believe Duke can nail this question with his 3:08 experience. I do not remember but will guess about 2100 at 60mph.

[Bob S.]

Re: 66 Roadster 300 HP vs 350 HP

Bob,

Try this:

http://www.angelfire.com/fl/procrastination/rear.html

Joe

This works great, thanks!!

[Joe R.]

Re: 66 Roadster 300 HP vs 350 HP

Jim,

Yes, Duke will nail it if he responds. I was looking for a thread with his thoughts on this, but couldn't find it quickly. He knows the tire diameter and has a simple formula. But the web site I posted should work too.

Joe

[Michael H.]

Re: 66 Roadster 300 HP vs 350 HP

"Just an old car"??? Please!!! Like saying a Rembrandt is "just a painting."

I should have put a smiley face after that statement. I didn't think anyone would take it seriously.

[Duke W.]

Re: 66 Roadster 300 HP vs 350 HP

So, it's a nice cam when rebuilding an L79 as well, correct? The same top end power and a little (or a lot) more low end torque. And a smoother idle too. But maybe not pass the PV? No lumpy idle. Otherwise, no downside right? Sounds like a nice way to go if you can live without the PV. How would you handle the CR on a rebuild like that? Go higher like the L79 or lower like the 300hp engine. Maybe there is a better cam for the L79 rebuild?

The McCagh Special cam would be a good way to tame a 350 HP. Combined with massaged heads it would have the characteristics of the 300 HP engine at the low end - smooth 500 RPM idle and stump pulling low end torque with the same top end power and revs of a Flint-built L-79 - essentially the best of both worlds, and the way most of us drive today, the smooth idle and low end torque of the 300 HP engine is most useful. Plus you have the external visual features of the L-79, which are more attractive than the 300 HP engine.

As far as passing a PV is concerned, one could increase the idle speed to about 750 and lean out the idle mixture to the point of a little idle roughness, and it will probably pass. You can try this out on any 300 HP engine, and if it works with the OE cam it will work with the McCagh Special cam. They have identical overlap, but it's phased a little later with the McCagh Special.

As far as CR goes, since the McCagh Special cam inlet valve close event is nearly as late as the L-79 cam it can run about the same CR as L-79s left Flint with - about 10.5:1, however, I recommend the KB157 hypereutectic piston, which has 0.5 cc net dome volume, and depending on deck height and head gasket thickness will yield a true CR in the range of 10 to 10.5:1.

If someone wants to retain the L-79 characteristics, I recommend using the F-M L2166 pistons (5.3 cc net dome volume) and L-46/82 cam installed four degrees advanced. This cam has essentially the same duration, lift, and overlap as the L-79 cam with better dynamics, but it is manufactured with an IPOML of 114 deg ATC rather than the L-79 cam's 110, so an adjustable timing set will be required.

The other option for the L-79 if you want maximum top end power and revs is the LT-1 cam.

Restoring a L-79 offers several options on the shape of the torque curve and how it's positioned in the rev range, all without affecting visual appearance, and all will likely pass a PV.

Duke

[Duke W.]

Re: 66 Roadster 300 HP vs 350 HP

It's a very simple, easy to rememeber formula.

Revs @ 60 = axle ratio x tire revs per mile.

Corvette speedometers going back to the beginning are set up for 760 revs/mile 6.70-15 tires. From '67 to '72 OE 7.75 and F70-15 tires were actually 775 revs/mile, but speedometer gearing didn't change for most axle ratios. The GR70 and 225/70R-15 radials used from '72 to '82 were 760 revs/mile, same as the 6.70-15.

Duke