Prove it to me....Camshaft Gear Drive is a HP Killer

[1980RS]

I have a new gear drive for a BBC with a bunch of parts I bought one time. I didn't use it because it's a noisy version and I don't need my car to sound like a blower car all the time with that kind of noise. I'll just sell it at the swap meet for a few bucks.

[Alaskaracer]

Other than that Roush test I’ve never seen a SHRED of actual testing that showed the GD transferred more harmonics, cost horsepower or anything else.

And you won't because it doesn't exist. Another myth perpetrated on the auto industry in an attempt to sell a certain product. If gear drives were so bad then you wouldn't see them on supercars engines......and they are widely used on many types of engines, not just diesels........

[hoffman900]

Other than that Roush test I’ve never seen a SHRED of actual testing that showed the GD transferred more harmonics, cost horsepower or anything else.

And you won't because it doesn't exist. Another myth perpetrated on the auto industry in an attempt to sell a certain product. If gear drives were so bad then you wouldn't see them on supercars engines......and they are widely used on many types of engines, not just diesels........

All those engines also have the aforementioned camshaft dampers I mentioned. They’re great, but you have to pay attention to the execution and they are not like whatever 60yo design you’re going to get from Summit Racing.

Also, all those engines are heavily focused on OA length, and use the gear drives to run all the accessories as well, with no belts anywhere.

[bill jones]

---here some chat about basically the same thing

viewtopic.php?t=626

[Jeff Lee]

FINALLY got the AMX with its Milodon 3-gear GD running 03/22/2024 and made 9-passes 03/23 and 03/24. Shifting at anywhere from 7K to 8K and the camshaft is still in place, no junk in the filter, and can’t even hear it w/ open headers (although I thought I could hear it in 4th gear?). Amazing, I thought it was supposed to rattle or vibrate itself to death! LOL! This has been a good discussion. Thank you all.

[RW TECH]

What are your valve weights & peak lifts? It'd be great to get the valvetrain optimized so you could lower your open spring loads.

I did a spin rig test on a .700" lift combination with 900-ish lbs over the nose, then 650-ish lbs, and it was 12 ft lbs less to turn it with lower spring pressure. Same combination ran 600-700 RPM higher with lighter springs. Valves weighed a ton but it still got better with a smaller OD, lighter weighr spring with less pressure.

[Jeff Lee]

I don’t know the weights on my Manley Pro-Flow valves. But they are 2.025/1.685 w/ 3/8 stems and bead-lock keepers, Ti retainers. Valve sizes are dictated by rules. Manly would not provide hollow stem’s; said you wouldn’t notice as this size valves are inherently heavy. Last year I ran to 8k every gear effortlessly. I had some carb issue this last weekend debut so I’m not sure of RPM max yet. Will find out next weekend at Arizona Nationals. Thanks for the interest in helping

[RW TECH]

I don’t know the weights on my Manley Pro-Flow valves. But they are 2.025/1.685 w/ 3/8 stems and bead-lock keepers, Ti retainers. Valve sizes are dictated by rules. Manly would not provide hollow stem’s; said you wouldn’t notice as this size valves are inherently heavy. Last year I ran to 8k every gear effortlessly. I had some carb issue this last weekend debut so I’m not sure of RPM max yet. Will find out next weekend at Arizona Nationals. Thanks for the interest in helping

Does Super Stock still require stock stem diameters?

I think JHE can do drilling & plugging to make the valve stems hollow, and I'm betting it'd be significant if the hole diameter is big enough to yield same wall thickness as a typical hollow stem 11/32 or 5/16 valve.

Good luck in AZ!

[Jeff Lee]

Yes on stem diameter. Who is JHE?

[RW TECH]

Yes on stem diameter. Who is JHE?

https://jheinc.com/