Who has a single crank pulley on their 3.6 and have you had any problems as a result?

[JonT]

I'm debating whether or not to remove my patrick motorsports single crank pulley and going back to the stock dual pulley with harmonic balancer on a 1989 3.6 rebuild that is just getting completed. Thanks for any experienced responses.

[Bill Verburg]

Originally Posted by JonT

I'm debating whether or not to remove my patrick motorsports single crank pulley and going back to the stock dual pulley with harmonic balancer on a 1989 3.6 rebuild that is just getting completed. Thanks for any experienced responses.

I've got one on one of my engines, It's a bastard setup, 964 bottom end w/ 993 top end and Motronic. No problems her in 5 yrs of use.

I couple of track acquaintenses run a single non harmonic balancer pulleys of their 964 Cup cars, again no issues.

[ja78911sc]

Bill, do you still recommend using a harmonic balancer or has your opinion changed due to lack of confirmed failures? Thanks, Jim

Originally Posted by mjshira
so I have a 964 engine with a Clewett pulley system on it, it is bigger than the RSR lower pulley but not as heavy as the stock harmonic bal. Issue?

The thing about the 964 crank is that it is not as torsionally stiff as a 993 crank or the earlier 911/930 cranks. Each time a cylinder fires it twists the crank a little bit. All the little bits of twist can resonate w/ each other at a given crank speed(what the resonance rpm is I haven't a clue), think Tacoma narrows bridge though. A harmonic balancer as used on the 964 has a weighted outer ring separated form the inner ring by an elastic medium. The elastic medium absorbs and dissipates the extra twist energy.

Now some do run w/o the harmonic balancer, I have seen several M001 964 Cups w/o one, but personally I wouldn't.

The M001 993 Cups that used the 964 cranks fro theiir increased bearing area also used the h/b in all cases
__________________
Bill Verburg
'76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone)
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[Porsche84]

I have a single pulley on my 964 and it has been fine, 7 or 8 years. I have done about 5 other 3.6 conversions, all with single pulley. Not to worry.

[JonT]

Jerry do you do any work on the cranks before conversions? Rebalance ? Otherwise stock engines? You are talking crank pulley correct? Just confirming thanks.

[Porsche84]

I just replace the stock crank pulley with Patrick's single pulley. All of the cars are DE cars so they get a lot of high revs. No issues on any engine. I'm sureJim Patrick has done many himself. One of the cars I did was a 3.6 into a 914 (what Patrick specializes in). No choice there but to use a single pulley, no room for a double.

[Tom '74 911]

I've been running a single pulley conversion on my 3.6L, but only for a little over a year - so I can't offer much in the way of long term durability testing etc....

I have a Patrick lower pulley and a Rothsport upper hub. . . I did the conversion so I could use a 3.2L engine mount and cross bar.

Tom

[JonT]

Bump to front. Looking for more experienced single pulley crank 3.6 applications.

[skinnerd]

I got a single on my Vram.
Rothsport (Oregon) built the engine.
No problems at all.

They have done many of these 3.6 conversions, most with the single pulley I'm sure.

[Joe Bob]

Been five -six years. Except that it has to get rev to turn the alt light out, no problems.

[RRWood]

I second Joe Bob's comment.

[rattlsnak]

Yep, I've ran them as well with no issues.

[JonT]

not one failure attributed to removing the harmonic balancer?

[JonT]

Bumpity bump