Has anyone ever done any testing to see what the horsepower difference is between a timing chain and a Milodon gear drive?

I have heard different opinions on it. Some say that the gears consume 20 more horsepower. Other people say that the steady timing of the gears improves horsepower.

I'm freshening up the early Hemi in the coupe and I have run both a chain and a gear, but have never dynoed it. Trying to figure out which way to put it back together.

Dulcich did a comparison of standard timing chain vs cheap gear drive vs expensive gear drive vs somebody's belt-drive and they came up virtually the same in HP and torque. The belt drive had the advantage of more easily setting the ICL, but that was pretty much it IIRC.

Found it: https://www.motortrend.com/how-to/ccrp-0510-camshaft-drive-comparison/

Milodon fixed 3 gear is the one to get if you want a gear drive to race with. You can hear them at idle if you listen for it, but nothing that you really notice inside the car once it's moving as the exhaust drowns the sound out since they are just not that loud. Not many race cars use the floating 4 gear setup that I have noticed. People still run them, but it's mostly the car show street rod guys who just like the blower sound.

Timing chain setup I'd say the Avon Pro Gear is a good one to look at. Complaints about those seem to be far less than others. Next choice would be the Rollmaster from Australia.

A retired machinist I used to use here has a drag car with a pretty serious SBC that turns 8-9k and he ran a fixed type 3 gear drive for years, and then tried the belt drive out of curiosity and lost a little 60 foot time. Best he could figure was the belt stretched from the rpm shock on the line and retarded the timing a hair for a few seconds. He put the gear drive back on and got his 60 foot times back where they were before.

I have wrecked a double roller timing set or two, and a gear drive you buy once.

Many moons ago, Bill Jenkins found that gear drives transmit all the harmonics (vibration) from the crankshaft to the valve train. While it probably doesn't immediately affect the power output, it can have long lasting affects to longevity of parts. Much has been written about it.

That Dulcich test is one of the greatest and most informational tests of all time. What it doesn't tell you is that even if your grandmother gives you a Jesel belt drive for Christmas, you will spend more on belts over time than a gear drive costs.

If you have a high quality gear drive unit that fits and works then I'd probably use it. They are noisy but I assume you already know that. A high quality gear drive can solve some problems that timing chains have but it has to be a really good gear drive. Cheap gear drives are the worst thing to install on an engine.

Thanks for all the replys so far. Is the Dulcich test on line somewhere?

I had a rollmaster on it with a Mopar tensioner. I had no issue with it, other than that the ignition timing was not real stable. And I don't know for sure if the timing chain was the cause.
So I put in the Milodon single idler gear drive. But on Sick Week, the cap screws that hold the gear mounting plate vibrated loose, one came out. That let the cam walk forward, lobes hit the adjacent lifters and the shavings got into the oil pump shearing off the drive shaft. I'm not sure if it was the extra harmonics from the gear drive that caused the locktighted screws to come out, or if I forgot to locktight them. Or if I even forgot to tighten them? So if I put the gear drive back in, the screws will be safety wired. But i still have the chain too, so I have a choice and need to decide.
I'm going to try to get register for Sick Week 2025 and hopefully redeem myself for my day 4 DNF.

Been running Donovan gear drives for years. The Donovan is not noisy.

Yes, use the Milodon fixed gear drive. You wont believe how easy it is to dial your cam timing in. About 10 minutes or less. It has taken me sometimes hours to get the timing just where i want it using timing chain.

Not my cup of tea.

Pretty sure this was tried on an engine masters episode, IIRC the belt drive came out on top on the day but only marginally. I used to run a Milodon gear drive, I changed it 'cause I didn't like the noise. Switched to a Jesel, real easy to set the timing but spares are expensive.

Years ago buddy was running a small block chevy vega that ran low nines. Started braking cams on a regular basis. He figured out it was his gear drive transmitting harmonics to the cam. Belt drive solved the issue.

I am running the Milodon fixed Gear drive on the 505 in my Cuda. I like it. Easy to install, easy to get the cam shaft where you want it. Isn't as loud as people make them out to be.

Expensive lesson, I doubt you were at fault.

I'm of the opinion if the Factory didn't engineer for it, it isn't meant to be on there especially when it's the cylinder block itself we're talking about.

Can't deny the cool factor of a gear drive, but that idler wheel has to be costing something in the hp department: Maybe 2 hp? Put another way: if it made more power the OEMs would all be doing it and Performance Motorcycles would all be shaft drive instead of chain.

What type of cams was he breaking, flat tappet cast cores or roller steel cores?

Joel, my thinking, for what it's worth, timing chain and crank trigger. I ran a Milodon geardrive in my motors for a long time, and i have a lot of hurt rocker arms and lifters from those motors. I do not know if the geardrive was the cause, but heard it transmits vibrations, etc. So I now run a Jesel beltdrive. I can't speak to power changes, but just the knowledge that a belt drive is the top choice for hi hp motors like Pro Stock, and they will do ANYTHING to gain two horsepower. You may not want to spend the $$$ on the beltdrive or crank trigger, but there must be a way to run the timing chain and reduce any timing fluctuation by shimming distributor, etc?