Timing Gear Drive

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ne57

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Has anyone used the timing gear drive set from Thunderchicken? I'm told these are Chinese imports. I find goods from China can vary tremendously in quality, not neccasarily all junk.

I see the Milodon set for the LA smallblock has the same part number as for the old 392 Hemi(which I have), and I know regular timing chain sets interchange between the two. So I'm hoping someone has some real world comments about the smallblock Thunderchicken set, which looks like is the same for the 392. They advertize different prices though for the two applications so maybe there IS a difference?

Much appreciated, thanks.
 
ive never heard of them could you post a pic or link..my friend has the mil.in his motor hes happy with it...i just used the tensioner sold by mopar...
 
they do sound nice, but I believe the cat one requires drilling the block or something If I remember correctly
 
It's just 2 holes that need to be drilled and tapped, no big deal. I just bought one off fishy68 for my 360. I ran a Pete Jackson noisy gear drive on a 350 that I built when I was 13 and loved it. Last I heard that motor ended up in a Toyota pick up.


From the CAT website...



INSTALLATION OF GEAR DRIVE TIMING SET

MOPAR 318/331/340/354/360/392 PLATE MOUNT THREE (3) GEARS DRIVE – INSTALLATION GUIDE


1, Place the idle gear mounting plate on the cam retainer and loosely tight the bolts.
2. Place cam and crank gears on the cam shaft and crank snort.
3. Drill additional bolt holes follow by the bolt holes pattern on the mounting plate
with 17/64 bit at engine block from two bolt holes at mounting plate lower side to
0.750” deep.
4. Tap both holes with 5/16-18 tap and clean the holes thoroughly.
5, Install supplied 5/16 bolts at the new bolt holes and torque to 20 ft-lbs.
6. Install cam gear and torque the thrust bolt to 45 ft-lbs.
7. Place a news paper between all gear teeth to ensure proper backlash maintained.
8. Engine Timing:
a. Install damper on crank and set NO.1 cylinder at TDC position.
b. Using Cam maker specification to find No.1 intake opening degree and move
crank to that degree.
c. Place a dial indicator on top of valve to ensure the lift of cam specification has
reached.

For example, if the cam specification indicates the intake opens at 39º with
0.50” lift. Turn the crank to 39º with dial indicator show a 0.050”lift reached.
d. Mark on the cam gear this is a “0º” timing mark for the cam gear. Install
cam gear bolt.

9. You can advance or retard the engine timing by position the crank gear key way
in 5 different positions according to the timing chart supplied by cam maker.
 
Thanks for the input. As to why a gear set...chain stretch. Combine that with how the align boring can change the crank/cam distance and a gear set seems to be the all around answer. OK, thay make undersize timing chains but at roughly the same price point, why not the gears? The Milodons approach $400, the Thunderchicken (CAT, thanks for that tidy bit) about a $100. That $300 difference could be valve covers.

Money is not unlimited so if the CAT quality and durability are OK, I'd rather spend 100 than 400. But if anyone has negatory experience with the CAT(or CAT products in general) then I'll have to decide if the gear concept is THAT important.


yeah well OK. A unique mechanical sound would be cool too. Ya got me on that.
 
ne57 said:
The Milodons approach $400, the Thunderchicken (CAT, thanks for that tidy bit) about a $100. That $300 difference could be valve covers.

Money is not unlimited so if the CAT quality and durability are OK, I'd rather spend 100 than 400.
Click to expand...

Not for nuthin, but.....

Do you REALLY want to "save money" on an un-necessary, inexpensive gear drive in a critical part of your engine? Do YOU want to be the one who posts " Ya know that $100 gear drive I installed? Damn crank gear stripped off and I bent 8 valves and cracked 6 guides. Now I need pistons and my heads re-built....and I need a good double roller timing chain!"

I came *this close* to installing a gear drive, just for the cooool noise, in my engine and thought twice about it. If you really want that cool noise, step-up and buy the known proven product and get the Milodon. Unless, your building a balls-out killer small block, then you don't NEED the Milodon gear drive. Otherwise, it's just an attention getter for the cruise-in.

Just my .02
 
John is right. The gear drive is just not necessary. In fact it may even impart detrimental harmonics into the camshaft from the crank causing more valvtrain harmonics that may influence timing events more than any measured chain stretch. This is why all the Pro Stock and Comp Eliminator engines have gone to a belt drive.

My engine is critically close on valve to piston clearance, .058 int/.076 exh and after nearly 6 years of racing it and twisting it to 7200-7500 rpm's I've yet to bang a valve.

Personally I think you get what you pay for and I wouldn't put a $100 gear drive in my engine. YMMV.
 
In my line of work I've been seeing more and more Chinese imports and some of them are just great quality so I feel I have to discount my natural cynicism in that regard. The Chinese factories will make what the importer wants and if they specify higher quality that's what they give em, if they specify cheap then that's what they get. Its like the old "made in japan' myth. It no longer equates that Chinese goods are necassarily junk. They might be, they might not be. So that's why I was looking for someone to say what their real life experience was with the CAT sets. Very good point though about them being unproven as yet.

I was reading more and while the harmonics thing is valid, there's also the point that heavy spring pressures may wear out a chain prematurely. I remember the 354 hemi I had many moons ago that had spark bounce at the timing marks. Rebuilt the distributor, new intermeadiate bushing, still bounced. Was it the chain? I dunno but I thought I might like to avoid the situation if I could.

If the gears didn't make noise I'd still consider them for the precision and accuracy. This isn't a pretend motor but if it sounded wicked too, well that's OK. I think the whole point of a hemi dart is to generate excitement, no?
 
Well, that's another part of the equation. I haven't measured the spring pressure yet but interpolating from the build sheet(I bought these heads finished) open pressure is likely to be around 325lbs if I go with the .450 lift cam I already have on hand. I know 450 doesn't sound like much but old hemis don't require as much lift as some other motors. I haven't ruled out changing the springs, depends on the cam I end up with. If I go to over .500 on the cam open pressure will increase.

My tentative goal is 6000 rpms or so(seems a safe rpm for the reworked stock 392 rods, which Garlits told me he used up to 6500 rpms on nitro in his swamp rat 1. I've ordered some exhaust rocker reinforcement ribs that get welded on (old school I know but titan rockers just too much $). I'm told that will be strong enough for the springs and rpms, jury still out though.

I'm also told that the harmonics kick in around 7000 rpms. If that's correct the gear drive shouldn't be a problem as far as that goes. But who knows? Most of my info comes from the web, and well...its the internet, you know?

Sorry to be talking hemi here on a smallblock board but I thought since the timing sets are the same between the two motors maybe somebody here had some hard facts that I could apply to my eventual decision.
 
My engine has a .672 lift flat tappet mechanical cam, valve springs are 140 on the seat and 440 over the nose. The chain is still fine however it sounds like you've already made your mind up about running a gear drive, I can't help you with that but wish you luck.
 
I was told by my engine builder that they induce substantial engine harmonics. I had put one on my engine and when I brought it in to the engine builder for a rebuild the first thing he said was remove the gear drive, if you want improved timing accuracy use a belt drive.
 
Trying the Cat Gear Drive on the 318 based 402 I am putting together right now.

Issues that I have found.

1) There is only 1 hole that needs to be drilled and tapped it is on the lower right bottom of the plate.
2) Very hard to degree the cam by skipping teeth on the cam gear only.
3) The plate will need to be clearance'd so the timing cover will go on all the way and mate with the block.
4) You will also have to cut the V out of the cover to clear the drive before buttoning it all up.

For example my cam card says installed ICL @105*

Using the standard key it came in at 103*, skip a tooth and it came in at 115*, put in a Mr. Gasket 2* key "that fits VERY loose in the cam" and is really 3.5* comes in at 106.5*, So I ended up at straight up rolling the cam gear 1 tooth back counter clockwise and using a Mr. Gasket 4* Key to bring the cam back clockwise and ended up at exactly 105*ICL, I found out that the 4* key is actually 5* and it fits very tight in the cam just like the stock key. FWIW

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Hey Mad dart. I have been running one of these cat gear drives on my 318 for a few hundred miles now. I recently pulled the engine to fix an annoying oil leak. While I was in there I looked at the gear drive and it was showing 0 wear. I am very happy with it and it is staying. I kind of like the sound anyway. For some of you that don't know, what do you think every Cummins has that pulls your race cars every weekend? Gear drive.
 
I like the whine of a turbo but not a gear drive. :D It`s sounds like you`ve made up your mind already to get the gear drive but a good Cloyes chain would likely serve you as well. On the flip side, I can understand you wanting something with a little flash to go with the old 392 Hemi engine.
 
Badart said:
Hey Mad dart. I have been running one of these cat gear drives on my 318 for a few hundred miles now. I recently pulled the engine to fix an annoying oil leak. While I was in there I looked at the gear drive and it was showing 0 wear. I am very happy with it and it is staying. I kind of like the sound anyway. For some of you that don't know, what do you think every Cummins has that pulls your race cars every weekend? Gear drive.
Click to expand...

That is good news! Nothing like a big cam, gear drive and exhaust dumping down right before the axle!! Going for the old school on this one! Regardless of what guys are saying, the quality of the gears, bearing, plate and hardware look really good.
 
Mad Dart said:
That is good news! Nothing like a big cam, gear drive and exhaust dumping down right before the axle!! Going for the old school on this one! Regardless of what guys are saying, the quality of the gears, bearing, plate and hardware look really good.
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Is there anything you have about setting up the gear clearance?
Or is this something that is what it is?

I ask because I believe the milodon for example is clearanced with a sheet of paper.

Thanks for posting this I am definitely interested now. I always was interested, but the trash talk on these is knee-deep.
110 bucks is a steal for it and I now see the auctions on ebay for them have better pictures of the parts too. They definitely look up to the task.

This may just be going on my 408.

P.S. Make sure you divert some of that bottomless budget of yours on a camcorder! I would love to hear the mad dart and this new one whining away! Just bought all the stuff I need from brian yesterday, so I need inspiration.8)
 
Badart said:
Hey Mad dart. I have been running one of these cat gear drives on my 318 for a few hundred miles now. I recently pulled the engine to fix an annoying oil leak. While I was in there I looked at the gear drive and it was showing 0 wear. I am very happy with it and it is staying. I kind of like the sound anyway. For some of you that don't know, what do you think every Cummins has that pulls your race cars every weekend? Gear drive.
Click to expand...

Thanks for the input on the wear. Good to know.
Yeah screw this, I'm getting myself one.

I looked at timing sets for hours last night and the one thing they all have in common is stretch. They ALL do it.

This doesnt stretch, and if there is no evidence of wear yet, I'm cool with giving it a try. I feel a lot safer with that than a chain. The idler gear looks like it fastens to that plate pretty strong.
 
I have the Milodon gear drive on my 408. It is cool. I've never hear the engine run, it's still on the stand, but when my dad was at he dyno shop, he said it sounded awesome, and he loved the whine!

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Billet timing cover made by Magnum HP.

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Interesting to see the Milodon and the CAT have the idler on different sides and the hole drilled in diff places. Any input as to the hole drilling...ie hole does or does not hit water/oil or something like that?

You can definitely see the Milodon is engineered more. Is simple good enough?

The CAT is available in noisey and quiet...any input on that?
 
I don't think the whole drilling doesn't matter...On mine, the hole did not go through any oil or water passages...And also the cam gear is adjustable, eliminating all the hassles that MadDart had on his because it isn't adjustable...
 
Umm, pardon what might be a dumb question but...on the CAT don't I see several keyways on the crankgear? Wouldn't you use those for degreeing?
 
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