Tom Tom Turbo
Turbo Goes Woo Woo
- Joined
- Jul 10, 2002
I'm getting ready to order a GN1 crank and they want to know if I want the knurled or plain version for the rear main area. Should I have a preference or does anyone have any input on this?
Knurled or plain GN1 crank?
- Thread starter Tom Tom Turbo
- Start date
- Joined
- May 26, 2001
Just a matter of preference, we have used both type of GN1 cranks and both work fine.
Tom Tom Turbo
Turbo Goes Woo Woo
- Joined
- Jul 10, 2002
Thanks Nick! I need to get in touch with you about some fuel system parts too. Is phone or email better?
Now that they finally offer cranks without the knurling thats all I will use. The knurling was designed to work with the rope seal. The problem with a rope seal is that it cannot exert tension against the sealing surface like a lip seal can. The sealing surface on a rope seal is rather wide and counts on the knurling to act like pump vanes to constantly push the oil back inside the engine. That rope seal is why our engines are famous for leaking at the rear. It is a really poor antiquated design. Lip seals are designed to work on smooth surfaces. The sealing surface of the neoprene lip seal is small and the knurling actually creates a leakage path that allows oil to bypass the seal. The real problem with the knurled eagle cranks is that the knurling is usually deeper and wider that the OEM cranks. Some of them are so badly done that there is no possible way to seal them well. Next time you think you have sealed your motor well try this. Fill the engine with oil and hang it from a lift at a 45 degree angle with the rear lower than the front. This simulates what happens when you accelerate fast--oil moves to rear of the engine. Wait a few minutes and it will start to drip at an alarming rate. The oil flows through the grooves and right past the neoprene lip seal. There is no way to block it if it has the deep wide knurls. Compare the knurling of some of them to the shallow-narrow grooves on the OEM cranks. Another example of Chinese manufacturing not really understanding the function of the product they are making. If a small groove is good a bigger groove must be better. NOT !!! I am glad that they have finally started offering the smooth journal cranks. When they finally figure this out I am sure that they will eventually make all of them smooth.
Last edited:
achalmersman
Well-Known Member
- Joined
- May 28, 2012
Nice post thanks! Is the lip seal an easily sourced part number? I haven't looked up seals yet but am in the process of building a 4.1
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The lip seal is the rubber/neoprene seal thats available from most gasket mfg's
achalmersman
Well-Known Member
- Joined
- May 28, 2012
Awesome thanks. I didn't know if the generic gasket kits still used the rope seals or if they came with this lip seal. Thanks!
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Some do, IE felpro front cover gasket has 2 part numbers. One for rope, one for rubber.
If you're using Fel-Pro on the front get the TCS45930. That one comes with a lip seal and a .007" oil pump gasket. The rear main seal is sold by itself (and waaaay overpriced for what is it). I recommend tossing the side seals and using The Right Stuff with pipe cleaner 'rebar' and a 2 molecule thick layer of Yamabond on the parting line between the cap and the block along the rear.
RmvBfrFlght
Well-Known Member
- Joined
- Sep 28, 2007
Here are some part numbers I've saved over the years:
Kirban's:
NEOPRENE REAR MAIN SEAL #6548
Cometic makes a nice rear main seal. I use them on all my engines (Chris Hogeland).
Cometic C5707 is the number you are looking for. It's a viton seal. Please see the link below for more info.
http://www.cometic.com/catalogs/autodomestic.pdf
Autozone:
Felpro/rear main seal 2 pc rubber
part number: BS40613
RemoveBeforeFlight
Kirban's:
NEOPRENE REAR MAIN SEAL #6548
Cometic makes a nice rear main seal. I use them on all my engines (Chris Hogeland).
Cometic C5707 is the number you are looking for. It's a viton seal. Please see the link below for more info.
http://www.cometic.com/catalogs/autodomestic.pdf
Autozone:
Felpro/rear main seal 2 pc rubber
part number: BS40613
RemoveBeforeFlight
BEATAV8
The Engine Whisperer
- Joined
- Feb 14, 2002
Yep I can see that
I've had good luck using lip seals on factory cranks in Buicks and Pontiacs (with their knurls), but its very true that the knurling was meant for ropes.
Seen it on more than a few China cranks that weren't smoothed out. I've never seen the stock knurl be a problem
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SCOOBY DOO
BASED CANADIAN PATRIOT!!
- Joined
- Feb 18, 2007
No. I race my car every weekend spring to fall with the stock crank and neoprene seal. Engine has been tore down a couple times for freshening...and zero issues in respect to seal damage.
purchased 4340 forged stock stroke good known crank new from vendors
Excessive crank knurling and deep like teeth, this cant be any good for seal and wont last long
having crank polished at machine shop as it is a little tight on the main journal clearances
Running felpro seal Bs40613
My question would be
how much to polish the knurlin down?
Shallow grooved ok?
Excessive crank knurling and deep like teeth, this cant be any good for seal and wont last long
having crank polished at machine shop as it is a little tight on the main journal clearances
Running felpro seal Bs40613
My question would be
how much to polish the knurlin down?
Shallow grooved ok?
