Nathan Plemons

One of the benefits of running an electric water pump is being able to run a double roller timing chain or possibly a gear drive. Some of the newer ones are so quiet you can barely hear them as well, so false knock wouldn't be an issue. The question I have is that all of the gear drive sets I've seen say "not for hydraulic roller camshaft" What does it matter?

I have seen a website where some guy did it on his F-body, he just had to grind a little on his timing cover. Any thoughts on why it wouldn't work? What makes a hydraulic roller cam different?

Thanks guys

BrianCunningham

How are you going to drive the opti?

Nathan Plemons

That shouldn't be a problem. On the later models the same pin that drives the cam extends to drive the opti, which shouldn't change with a gear drive setup. Now in my case I suppose that could be a problem, but this is for a 94 F-body that is being converted to the late style opti.

Nathan Plemons

TTT, Nobody?

I'd love to know if this works, if so I'll be doing it next time I have my motor apart.

gsvette

Nathan, there are two very good reasons why NO gear drive manufacturers offer a geadrive for the LT1 or LT4.

The high-frequency harmonics of the gears meshing together cause havoc with the knock sensors and the optispark timing. This problem is compounded by hydraulic roller camshafts.

As an example, the Pete Jackson gear drive apparently develops a resonance frequency (like a tuning fork) in the LT1 at about 6500 rpm. A guy in the local Corvette club discovered this the hard way and was rewarded with pieces of connecting rods in his oil pan after the engine had a high rpm misfire.

If you want blower whine, buy a blower, otherwise go with the GMPP severe duty timing kit for LT1's

MSR

i have assembled a few engines with gear drives. i took the time to measure freeplay, and found that (even when properly set up) the cam has more freeplay than with a chain. also, the freeplay is completely undamped, whereas the freeplay with a chain has some chain friction to resist oscillation.

i'd stay away from them....

ChrisB

Gear drives have been done in LT1 f-bodies. The motor in question had other issues, so I can't say for sure what effect if any the geardrive had in that specific instance.

In general Michael above is dead on. A gear drive will transmit all harmonics directly from the valvetrain to the crankshaft. A chain gives you some dampening at least.

Is there any particular reason you would prefer to use a gear set over a chain?

bogus

you could always get a belt drive conversion! :jester

Nathan Plemons

A friend of mine has his motor apart for a cam swap and we were discussing direct gear drives as opposed to a timing chain. From a timing standpoint I've always heard that the gear drive is the best thing you can get, but because of noise and such it is not recomended on a car with knock sensors, etc. Well enter another friend how installed a gear drive in his pickup truck, it is so queit you can barely hear it, you have to stick your head right over the engine and run it up to WOT to even begin to hear it whine just a little.

Hearing that we started to think if it was possible to install such a drive on an LT1 and what the adverse affects might be. That's why I'm asking.

Pete Jackson? That's the loudest one you can buy?!?! You'll note that a good deal of them say "machined for more noise" just because some people think it's cool to have the noise. Thing is that there ARE queit ones out there, and that's what I'm asking about. Also if I go with a chain I think I'll go with a true double roller, screw the GM piece. Knowing GM it costs the same as a far superior aftermarket one.


[Modified by Nathan Plemons, 1:32 PM 2/10/2002]

bogus

I have heard that the new LT4 heavy duty is a pretty good part... also, you get to convert to the better quality late model Opti...

Nathan Plemons

That's another strange thing. The vented opti seems to have more trouble than the older style. At least that has been what I've seen. No thanks, I'll keep my old style until I am forced to change it due to a different timing chain. Maybe it's just because there are less people running around with the older style, but I drive my car EVERY day rain or shine and it's got over 65k miles on it. Sure it'll go sooner or later but 65k + for a glorfied distributor isn't that bad. Sure it's expensive, but given the proper sources it's not too bad. The hardest part is getting to it to replace it. The opti's placement seems to be the worst flaw, directly under a water pump that is prone to failure, but then I've got the electric one now, so it doesn't really matter.

snaketr

The harmonics off a gear drive are too much. This is not the whining sound. For the price of one you can not beat a chain drive, if you want to spend some money to upgrade over a chain, it is a belt drive.

Nathan Plemons

Alrightly, fair enough. I'll never have a belt drive as long as I live. I like the idea of a metal chain rather than a cheap rubber belt. Just seems like a belt would stretch easier and be more prone to break, and could also slip.

A friend of mine was just driving along in his Dodge Daytona to have the timing belt break on him, so much for that. After he got the car towed home he had somebody replace the belt. Oh he was all cool for like 3 miles until the belt stretched, now his timing is WAY off and the car runs like CRAP.

Next time I'm into mine I'll just go with a true double roller.

bogus

belts are not that bad, Nate... too many of them make it 100k miles before maintenance.. they don't stretch just for giggles... and they don't break out of spite.

ASRoff

Just put some rubberbands on the cam to absorb the harmonics :jester

Bill Reid

gsvette,
Did you confirm this with Pete Jackson? I contacted them directly when putting my motor together because of this very argument on the forum over a year ago. They stated that although they heard some people claim to have a problem with gear drive interfering with the knock circuit they had never been provided with any proof from individuals, professional engine builders, other manufacturers, or otherwise. The gentleman I spoke with stated that gear drive frequencies, at any RPM, are not even close to the set frequency range at which a knock sensor, which is nothing more than a microphone, is monitoring. That said I think maybe they have already determined that this isn't an issue... otherwise they would have added a disclaimor to their product when distributing it to reseller's. If Pete Jackson knew this and did not put disclaimors on their product and people were having problems with them then I could see a class action suit that could easily put Pete Jackson out of business if not permanantly damaging their reputation. I forget if it was PAW or Summit that warned people against its use on engines with knock sensors but I contacted them to and they offered no proof.
Also, in my opinion and although I never discussed it with them during my phone call, it is not economical for Pete Jackson, or any other manufacturer, to develop gear drive for LT1/LT4 motors because of the install base. How many standard small block Chevy's are there out there compared to LT1/LT4's? The numbers are so far apart that its not even funny. They could never recover engineering costs associated with development of a unit that could still be compatible with the Opti/WP.

Gear drive is far superior to chain drive in accuracy of timing. This is not even an argument. Belt drive is better in ways than gear drive no question about it. One of belt drives assets as it does not transfer, but rather absorbs, crank harmonics. Chain drive has its own advantages and disadvantages. Does gear drive transfer potentially damaging crank harmonics to the valve train? Thats an open debate. Gear drives, initially, were never designed for 100k mile engines... but were developed for racing engines torn down on a regular basis.
And I'm not buying the guy in the local club losing his motor because of gear drive... sorry... not intending to flame but I think Pete Jackson wouldn't buy it either. Until somebody can come up with emperical data to confirm beyond a show of doubt regarding gear drives incompatibilities with computer controlled/managed engines my gear drive stays in :yesnod: If I find for some reason that gear drive is giving me problems I'll be the first to post. But I will only post fact... as I do not want to be the one that tips a person in the dirction of buying a gear drive, installing, and suddenly they start dropping rods. All I can say is that it works for me until I can be proven otherwise.
Peace :cheers:


[Modified by billreid1@***.net, 10:43 PM 2/10/2002]

Aggravated4life

Hey Nathan,
I have no other info to add about the gear drives that others have already mentioned,wether positive or negative.
However, youre gonna hate me for bringing up another possible dilemma.
:D

I was told by some engine builders NOT to use a roller chain,to stay away from them double rollers.WHY? Because they told me they stretch quicker over time,even faster then stock chains.
I was told to use a Performer LINK chain over a roller.It suprised me because every car magazine I read with engine build ups always raved about the rollers.

But these guys didnt want to use them on the engines they did.
So I gave in to their advice and stayed with a link chain for hopeful reliabiity.
11 years later,theres still no sign of stretch from that Link chain.It was reused In 2 motor jobs I had.Were they right? Well in my case,they were.No stretching o timing problems.No real wear and the steel sprockets and gears will of course last longer then GM plastic ones or powdered metal POS's.

I Dont want to confuse you, I would believe roller chains have some advantages but be sure to explore all options before you decide what you need.Maybe just being able to say "I have a double roller chain in there" sounds better and makes it sound more trick but is it worth the extra money?What made you decide thats what you needed?

Also,Anyone else have a comment on them roller chains?will they last 50-100K miles with no stretch at all? Or was I fed a BS story?
Is the truth about them having roller bearing failures and ruining a motor a real scenario?

:)

93Polo

As Chris said a few LT1 f-bodies have tried it. I would be in favor of a double roller chain. The Mezier water pump has to be done with either the chain or gear drive. My concern would be the gear drive setting off the knock sensor. Run a search on http://www.camaroz28.com/ and see what you find.

BlueDemon

Well here soon I will be able to clear this topic up. I am installing one in a friend of mine's car. I will have a scan tool to see if he is throwing any knock. I will be trying it on the pete jackson noisy too, so if it does not throw knock none of them will.

GlockLT4

:nono: :nono: