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Jeff G 78

Looking for ATI harmonic balancer users

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I finally got around to tearing my race engine down after it failed the oil pump gear and I found that the root cause was a loose crank damper bolt.  The bolt loosened six hours into a race and allowed the damper to walk out some.  At that point, the crank gear could slide fore/aft on the crank which took out the pair of gears.  Also, the damper began to wobble which beat up the crank snout and ruined the damper bore.

My plan is to buy a new damper, probably an ATI from Summit Racing.  Once in hand, I'll take the damper and the crank to an engine machine shop and see if the crank can be saved.  I've heard they need to be sized anyways, so maybe they can take a few thousandths off the snout and salvage the crank.  After a lot of research online, I see that the ATI pulley is much smaller than the OE pulley.  Has anybody had an issue with cooling or charging due to the ratio change?  It's an endurance racer, so charging wouldn't normally be an issue, but we do need to run several sets of headlights for night races and it will get an electric cooling fan upgrade.  Next question is the bolt.  MSA sells a higher quality bolt from Kameari, but I don't know if the length is right for the ATI damper which I've read requires a longer than stock bolt.  Datsun Spirit sells an ATI kit with a bolt and a belt, but their price is $200 higher than the same damper from Summit and the Kameari bolt from MSA.  I like supporting Datsun shops, but paying $200 more for the same part seems silly.

 

Which ATI damper?  ATI makes three different ones for the Datsun L6.  One is smaller (about the same as stock) and the two larger ones are available in two weights.  It appears Datsun Spirit sells the lighter of the two large diameter dampers.  Summit Racing stocks all three.

What bolt to buy and what is the right length?

Any issues with underdriving the alternator and water pump?

crank1.jpg

crank2.jpg

damper.jpg

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Any idea why yours failed?  Was it a stock Nissan damper?  Wrong bolt length or washer?  Looks painful.

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Bolt came loose.  From what I've read, that isn't super uncommon.  I've never had one loosen before, but now I will be sure to use Loctite and check it often.  The engine had 20 race hours on it before this happened.  

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Since my stock damper is now unusable, I need to get a damper no matter what.  Since the performance dampers are known to be a tighter fit than stock, my hope is that I can salvage the crankshaft.  If not, I have an old engine I can tear apart for the crank, but that one is an unknown and might need work and or bearings too.  This crank is good other than the snout.  My teammate thinks we should upgrade now to a better damper for (hopefully) future reliability.

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Whatever you use Jeff, make sure the crank bolt isn’t too long. I used a Nismo performance crank bolt once and it was a tad too long (for the stock damper) to pull everything up tight. Took me a while to figure that one out. Just make sure you are torquing threads and not the bolt bottoming out, or you’ll go through the same problem again. BTW, my guess is a performance machine shop can weld and machine that snout. If they can change the stroke on a stock crank, don’t know why they can’t fix the snout.

Guy

 

Edited by Diseazd

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Thanks Guy.  Do you still use stock, or did you upgrade on your latest build?  BTW, do you recognize the damper in the picture?  

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In the past, I’ve only used stock dampers.....280 dampers bought new from Nissan. My two Stroker Motors used expensive dampers (ATI Super Dampers)....Eiji built those two motors. My guess is that’s the one I sent to you. If I use stock dampers, I always use the stock crank bolts....lesson learned.

B873DF16-08B2-4A62-AEAF-B0D29502ADB7.jpeg

E14F6D20-9ABB-4604-9D96-8FD92C36FDCA.jpeg

Edited by Diseazd

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So what brand did Eiji use on your strokers?

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Ahh, perfect.  Do you know what model number ATI that is and what bolt you/he used?

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ARP doesn't make one and MSA only lists the Kameari bolt which might or might not be the right length.

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4 minutes ago, Jeff G 78 said:

So what brand did Eiji use on your strokers?

Not sure on the numbers Jeff, but any good speed shop (Summit) will have those numbers and my guess is the bolt came with the damper. It takes a special tool to install as you can see.

DD1608CA-18CB-49F5-A1AD-4F202A83B986.jpeg

E9D7B951-ADAF-46DC-AAA4-DFD2CE364867.jpeg

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ATI lists three different damper for the L series and Summit sells all three.  The bolt is always sold separate.  😞

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Call Eiji.....he’ll be happy to help you out.....tell him I told you to call and you are trying to put a bet down (on my car) to win our Dinwiddie race this Fall! Seriously....Eiji will be happy to give you the right info.

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Cool, thanks.  I always read your posts about Eiji and his great work, but never realized until now, that he is Datsun Spirit.  Duh...

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IIRC the Kameari bolt isn't quite long enough.

Regarding the underdrive on the alternator, at race speed it should be fine, a friend did some calcs on a road use engine, he said at idle and to 1500rpm is it wasn't enough.  Anyway, ended up changing the alternator pully to a smaller one.  Job fixed.

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I bought two ATI's that did not fit.  I would not touch them. Quality is not good.

 

Jeff Priddy, a Datsun super user, has done long term empirical development of an L series turbo for very high and reliable HP. He worked closely with BHJ to develop an exclusive damper for his needs.  They now sell it:

http://harmonicdampers.com/index.php?main_page=index&cPath=74_10

 

http://forums.hybridz.org/topic/58936-standard-bhj-vs-rebello-bhj-damper/

 

Jeff's work is worth looking up on the net.

: http://www.angelfire.com/extreme/280zxt/

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1 hour ago, 240260280 said:

I bought two ATI's that did not fit.  I would not touch them. Quality is not good.

 

Jeff Priddy, a Datsun super user, has done long term empirical development of an L series turbo for very high and reliable HP. He worked closely with BHJ to develop an exclusive damper for his needs.  They now sell it:

http://harmonicdampers.com/index.php?main_page=index&cPath=74_10

 

http://forums.hybridz.org/topic/58936-standard-bhj-vs-rebello-bhj-damper/

 

Jeff's work is worth looking up on the net.

: http://www.angelfire.com/extreme/280zxt/

I think thats the only negative review of an ATI damper?

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Great info, thanks 240260280.  Where is everybody sourcing their bolts?  I see lots of talk about bolts and lengths, but few specifics and very little on sourcing.  The NISMO bolt is NLA and each brand of damper appears to need a different bolt length to maximize the thread engagement.  Is the KA bolt the OE one, or something else?  I appoligize for sounding dumb, but the more research I do, the more questions I have...

As far as installation goes, green Loctite on the bore, red Loctite on the threads and then what torque on the bolt?  "How To Modify..." book states to use the manufacturer's recommendation for non-stock bolts.  

I've been endurance racing with various L Series engines for years and this is my first crank bolt issue.  I plan to learn and eliminate this failure method in the future.

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Maybe it's because I've never had a damper come loose, but I don't think I would use red Loctite on those threads. I'm thinking thread lock blue would be enough?

And when you said green on the bore... Are you talking about their sleeve retainer? If so, I wouldn't do that either. That's like belt, and suspenders. And nails, and screws, and bungee cords, and duct tape. If you use sleeve retainer on the bore and red on the threads, it's gonna take a lot of torch to get that stuff apart if you ever need to.

Of course, all of my opinion might change if I ever had one come loose like you did, but that really sounds like a bit much.  YMMV

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Same here Captain.  I never gave it a second thought until I DNF'd a race, missed another race and caused hundreds to thousands in damage.  After spending a lot of time on various sites including reading the links 240260280 posted, as well as rereading Frank Honsowetz's "How To Modify Your Nissan/Datsun OHC Engine" book, it sounds like the green and red Loctite applications have been in use for decades.  Since the internet began, I've learned who in the Z community to trust and the common theme here is that they all agree on a quality damper, high strength bolt/washer in the right length and Loctite on the shaft and threads.  I never had any idea that the bolts ever came loose, but apparently, it's super common.  I guess I should have been aware and built my engine right in the first place.

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I understand completely, and I'm not telling you not to. Just bringing it up. Do whatever you need to do to finish the race!

On a related note... I wonder how much heat the damper rubber can deal with. According to Loctite:
The red thread lock "For removal, it may require localized heat (>550°F/260°C), hand tools, and disassembly while hot"

And you've got quite a lot of thermal mass there. So hopefully once it's on, you won't have to ever worry about damaging the damper rubber because you just won't have to mess with it!   :beer:

And I hope I never have the problem you did!

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I thought the same thing about the red Loctite, but the experts say it comes apart without heat.  It only takes a few drops to keep everything tight.  I would have gone with blue had I not read that the red comes apart well.

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