3.4 DOHC Timing Belt to Gear-Drive Mod

[Myotis1134]

Just watched Furious 6, which always gets me thinking about the beast, and how cool it would be to set whatever mod team they use for that movie series loose on the Lumina.

 

I'm trying hard to get "the job", which will let me start doing a lot of things - including - getting started on the 3.4 project. Can't do much until the job happens, but I can't turn the brain off either, so I'm doing a lot of planning which may or may not work out.

 

Was looking for 3.4 rebuild advice/kits/info, and came across a post somewhere, where some guy was asking about modifications for the GM 3.4 DOHC, which (as usual) turned really negative really fast, with everybody telling the guy how crappy of an engine it is, and he should just give up on the spot and get a 3.8.

 

So I'm going down this thread, getting annoyed at the people who don't get why someone would try to work on this engine, and I keep seeing that one of the most difficult things to maintain on the 3.4 is the timing belt. OK - I've seen this complaint about this engine before, and it is reported to be something like a 5 or 6 hour procedure? So I'm wondering why use a belt for this? why not pull the idler pulleys, swap all the drive and tail pulleys for gears, do a bit of math to figure out the gear ratios involved, and use a gear drive system to transfer rotation to the cams?

 

It seems like having a gear system would be more efficient long term: 1 - The gears aren't going to wear out every 20 - 80K miles (seen recommendations for changing the belt at both mileages). 2 - If this system could be built into the timing belt cover, then it could be easily checked if there were problems. 3 - Belts can and will slip - but it's a little more difficult for gears to do this, so the timing will remain accurate.

 

I work on my car a lot, and have even torn the engine down a few times, but I don't consider myself an expert. Having said this, the list above seems logical to me, but if anyone can tell me why this wouldn't or couldn't work, I'd rather find out now than after I've put some time and effort into making it happen.

 

The part that I'm stumped on is getting lubrication to the gears. It wouldn't take much to keep them nice and lubed, in fact - I believe that too much lubricant would be harmful to such a system. If the area is sealed off when the covering is in place, then a small pump (electric or whatever) could be used to continuously cram some gear oil through a couple of nozzles up near the cam gears, and suction it at the bottom where it converges. Circulate the fluid into a reservoir, through a filter into the pump, etc. One could totally throw a magnetic dip-stick into the reservoir to check for gears getting chewed up too.

 

Took a schematic from a page outlining the timing belt replacement, and threw a gear-drive system on to get an idea. I understand that more calculations would be involved to get an accurate system, but I like lots of pictures in my books so here's a few to get the brain-juice going.

 

First pic is from the replacement procedure.

Second pic is the gear-drive system.

Third pic is the probable retaining shroud that would keep everything nice and lined up.

 

If anyone can trouble-shoot this theory and give me some problems to solve I'd appreciate it.

 

p.s. Apparently the pics don't stay in the same order as uploaded. Shouldn't be too hard to figure out the order though.

Edited July 8, 2013 by Myotis1134

[White93z34]

That is ridiculous

 

Not only would it be very, very noisy, hell SBC gear drives are noisy and and its a total of 4 gears. But it would be extremely expensive to implement and like you said you have logistical challenges such as lubrication of 16+ gears.

[Myotis1134]

Thanks man, making a list. Definitely didn't think about the noise, but that can't be impossible to solve. Expense was not and is not a factor at this point, but probably will be at some point. I hope to be in a position to go for it - despite the cost - when it's time to actually make the thing.

 

There won't be 16 gears in the final product, in fact I have no clear idea of how many gears there will be. The picture is just something to consider, not the actual plan. I hope to reduce the number of gears required by increasing the size of the gears involved. The larger gear that will work, the less revolutions needed (with respect to large vs small gears), but smaller gears will provide more torque - if driven by larger gears. It's a conundrum for sure.

 

I'll be doing research, but the goal will be to use the minimum amount of gears possible.

 

As for the lubrication problem, this is probably the easiest one to solve. Electric pumps are very easy to install under the hood, and there is a multitude of aftermarket reservoir tanks available, as well as filters, hoses, and fluid injection components. Drill a few holes, tap them, and presto. Doesn't have to be complicated, just thought out.

 

I'd like to hear more about the actual ramifications of a gear system, such as - is it actually possible for this thing to work? does anybody actually know? It looks and sounds possible, but I'm no engineer. Will some gears need more stability/reinforcing than others? Should gear size go from large to small or the other way?

 

p.s. Chris you're just calling it ridiculous because you didn't think of it first - you know it's an awesome idea.

[AL]

I think you would be alot better off converting it to a timing chain set up than a timing gear set up, one reason being noise, and two being that a chain will last 100k miles very easily

[Galaxie500XL]

Reminded me of something....

[Galaxie500XL]

You'd need custom EVERYTHING gears... even the cam and driven gear would have to be replaced, since they're made for driving a belt...not to mention fabricating an almost new front cover just to accommodate everything. I believe I'd just stick with the belt.

[RobertISaar]

Not only would it be very, very noisy, hell SBC gear drives are noisy and and its a total of 4 gears.

 

and that's problem #1: gear drives on a SBC with a knock sensor are pretty much a no-go, since even the quietest of setups tend to tickle the knock sensor in a way that you will never be able to work around.

 

 

 

if i were going to change the LQ1 from a belt drive to ANYTHING else, it would be a chain drive. slightly noisier, but a pretty good chance that the chain will never need replaced.

 

even northstars with their 1.25 (+/- .05) mile long drive chain rarely tend to wear it out. and since the timing belt cover is already monster thick to allow for a fat belt to be used, you could use an extremely wide chain and be assured that it will never need replacing.

[Night Fury]

What about retrofitting a LX5 3.5 DOHC shortstar timing chain setup?

[Psych0matt]

[RobertISaar]

What about retrofitting a LX5 3.5 DOHC shortstar timing chain setup?

 

possible, along with a lot of the other DOHC V6 designs GM has put out since ~2002 or so.

 

the only significant workaround i can see is dealing with the fact that the LQ1 starts off with both a timing belt and chain.

[GOT2B GM]

It would have to be sealed and utilize a splash lubrication system......it would be noisy as fuck...........and expensive to make a gear set that will spin at 7k and not tear itself apart.

[Schurkey]

Time spent thinking about a gear-drive conversion is time not spent thinking about something useful.

 

The belt-drive is intimidating...the first time a person dicks with it. The second time it's no big deal. Parts can be had for <$120. What's to improve?

 

GM specs are to change belts at 60K. Works for me.

[Myotis1134]

Thanks for the feedback guys, good to know this stuff before things got out of hand.

[intern8tion9l]

[Myotis1134]

It's on... again! Oldsmobile did a DOHC v8 in the late 60's with a gear drive, and it worked. Got something to work with now.

 

http://www.streetlegaltv.com/news/the-w43-oldsmobiles-dohc-455-v8-that-never-was/

[Galaxie500XL]

Something to work with?

[Schurkey]

Something to work with?

Ditto. There is NOTHING wrong with the OEM belt system if the belt is changed on schedule; and the belt won't need ultra-precision machining to prevent undesireable backlash and timing variation.

 

Converting to gear drive is an exercise in futility, wasted effort, and is likely to result in an undriveable vehicle when the disassembly is finished...and the reassembly doesn't take place due to a surprise realization of how incredibly complex this project is going to be.

[Myotis1134]

Is it that I'm exploring ideas that aren't understood, and therefore feared? Grow a pair people.

 

If I'm willing to try something different, don't mind the noise from a geared timing drive, and am not concerned over the cost, then why throw your own inadequacies at me?

 

So it's never been tried on the 3.4 - I'm willing to give it a shot. So the belt drive works just fine - that's fantastic.

 

Almost thinking this isn't the site for w-body enthusiasts... more like w-body traditionalists.

[rich_e777]

I got the same friendly feedback when I mentioned, RWD conversion, headers, side pipe exhaust, mid to rear mounted engine, exterior LED accent lights, wheel well flares, substituting a JATO system instead of NOS, underglow neon etc. All though I'm sure if the guys who built that dual engine Cutlass would have probably gotten the same responses. Sometimes its better to say fuck it and just go ahead with the plan, then show it off here once its done. I do think its ironic some would bring up engine noise yet have loud exhaust:lol:

[Schurkey]

Is it that I'm exploring ideas that aren't understood, and therefore feared? Grow a pair people.

 

If I'm willing to try something different, don't mind the noise from a geared timing drive, and am not concerned over the cost, then why throw your own inadequacies at me?

 

Just trying to save you from yourself. It's an act of kindness, not an act of fear and loathing.

Let's start from scratch.

I keep seeing that one of the most difficult things to maintain on the 3.4 is the timing belt. OK - I've seen this complaint about this engine before, and it is reported to be something like a 5 or 6 hour procedure?

First wrong assumption. 5-6 hours the FIRST time. Less when you've done it before.

 

So I'm wondering why use a belt for this? why not pull the idler pulleys, swap all the drive and tail pulleys for gears, do a bit of math to figure out the gear ratios involved, and use a gear drive system to transfer rotation to the cams?

Math to figure out the gear ratios? First principle: Assuming you take power from the upper timing gear...one to one. No gear reduction. If you're taking power from the lower timing gear, it'd be two turns of crankshaft to one turn of camshaft. Now, there'd be a hint of math if you want the various gears to spin at different speeds, but the end result at the camshaft is going to be what I listed above. All you really have to worry about is direction of rotation.

 

It seems like having a gear system would be more efficient long term: 1 - The gears aren't going to wear out every 20 - 80K miles (seen recommendations for changing the belt at both mileages). 2 - If this system could be built into the timing belt cover, then it could be easily checked if there were problems. 3 - Belts can and will slip - but it's a little more difficult for gears to do this, so the timing will remain accurate.

But gears can severely wear if the lubrication isn't adequate; if the tooth profile/finish isn't appropriate, and if the metallurgy/heat-treatment isn't done right. And a frayed belt doesn't put metal shavings into the oil.

I work on my car a lot, and have even torn the engine down a few times, but I don't consider myself an expert. Having said this, the list above seems logical to me, but if anyone can tell me why this wouldn't or couldn't work, I'd rather find out now than after I've put some time and effort into making it happen.

Apparently, you lied. You want folks to OOOH and AHHHH over your proposed project, and when that didn't happen, you attack the site and those who responded.

 

Bonus reason:

Since a belt tends to damp crankshaft harmonics, and gear systems tend to create them; from that perspective a belt is BETTER than a gear drive for spinning the camshaft(s).

[White93z34]

And while you might not mind gear noise I can assure you that the knock sensor very much will mind it.

 

However rather then argue with us about it, go do it if you really want to. Just don't think you'll see a bunch of support for "fixing" something that is a 60-80,000 mile maintenance item. But if that's what you really want, then by all means do it.

 

What people are trying to say is for the time, money and effort screwing around with that you could do something way cooler with that same amount of effort, time and money. Think Turbo, Supercharger.

[Galaxie500XL]

Grow a pair?

 

You really want to get rude on this board?

 

Tell you what. I grew up in a hot rodder's home. Started putting things together from the time I was FIVE. I'm 50 now...I'll put my 45 years of experience against yours any day. I've done plenty of stupid things to cars when I was younger, and didn't know any better...and I'd bet a good number on the list have similar experience.

 

You asked for input. You got it. If you had no interest in that input, or you only wanted folks to agree with you, you've come to the wrong place.

 

You'll have to fabricate a new front plate for the engine to accommodate the mounting bosses for all those gears, you'll have to have custom gears fabricated, a lubrication setup, and in the end, even IF it works, the car isn't going to run one bit differently than it does now.

 

Wanna spend 1-2K doing something like that? By all means, it's YOUR car, and YOUR money, have at it.

 

You've been given GOOD advice concerning the project, and to be fair, it's YOUR business whether you decide to proceed--but at least be mature enough to listen without being rude.

 

<end rant>

 

 

 

Is it that I'm exploring ideas that aren't understood, and therefore feared? Grow a pair people.

 

If I'm willing to try something different, don't mind the noise from a geared timing drive, and am not concerned over the cost, then why throw your own inadequacies at me?

 

So it's never been tried on the 3.4 - I'm willing to give it a shot. So the belt drive works just fine - that's fantastic.

 

Almost thinking this isn't the site for w-body enthusiasts... more like w-body traditionalists.

[z34Phoenix]

I think the main issue with the idea is this... the goal is to make the engine simpler and more reliable. the thought of building a prototype from scratch, using a design that is more complex and rarely used on engines is counter productive.

 

the gears will need to be very tight tolerance. the area will also need to be at least half full if not more full of oil/lube to make sure all gears are covered. This is assuming you can fit the correct size and ratio gears needed to make it function and still be able to seal it up. GM had a much larger budget for engine design then anyone one of us can imagine. unless you are J Leno... I don't see this project having the funding to make a more reliable drive system using gears.

[AL]

Like I said before, I could see a timing chain conversion being a much better idea than a timing gear setup