Gen 6 HR cam in a Mark IV??? - Page 3 - Chevelle Tech
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post #31 of 55 (permalink) Old Apr 7th, 14, 6:49 PM Thread Starter
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Re: Gen 6 HR cam in a Mark IV???

See the pic below (I'm not as think as you dumb I am! )

The depth of the step is .125. It seems this needs to be deeper by a lot. So... if I reduce the thickness of the retainer plate to get the cam to spin freely and get this gear further on the crank somehow, I'll be golden. Easier said than done!


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post #32 of 55 (permalink) Old Apr 7th, 14, 7:45 PM
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Re: Gen 6 HR cam in a Mark IV???

Looks like you have the right crank gear. Lets check one more thing; lets look at the back-set on the cam gear and make sure it's the right one.



I know it's a little hard to see but the step is 7/16".

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post #33 of 55 (permalink) Old Apr 7th, 14, 8:44 PM
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Re: Gen 6 HR cam in a Mark IV???

Lunati steel-core w/ iron distributor drive gear, and a fuel-pump lobe Gen 6-style step-nose cam in my MK IV 454 boat engine. Used the GM timing kit. Thrilled with everything except the amount of slack in the chain.

Camshaft end-play:




I am completely baffled as to why a person would use a Torrington bearing on the cam gear, when the cam retainer plate is already protecting the block.

I did not test my Gen 6 retainer plate, but if the thing is hardened like the cam retainer plates in the 3.4 DOHC V-6 engines in my Luminas, there's no way you're going to sand clearance into it. I sanded my Lumina retainer plates until my arm about fell off, and managed to cut it down by half-a-thousandth. Had to take them to a machine shop to get them surface-ground for added clearance.

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post #34 of 55 (permalink) Old Apr 7th, 14, 9:58 PM Thread Starter
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Re: Gen 6 HR cam in a Mark IV???

Quote:
Originally Posted by steelcomp View Post
Looks like you have the right crank gear. Lets check one more thing; lets look at the back-set on the cam gear and make sure it's the right one.



I know it's a little hard to see but the step is 7/16".
Hey Scott- yep 7/16" is what I get too.
John

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post #35 of 55 (permalink) Old Apr 7th, 14, 10:08 PM Thread Starter
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Re: Gen 6 HR cam in a Mark IV???

Quote:
Originally Posted by Schurkey View Post
Lunati steel-core w/ iron distributor drive gear, and a fuel-pump lobe Gen 6-style step-nose cam in my MK IV 454 boat engine. Used the GM timing kit. Thrilled with everything except the amount of slack in the chain.

I am completely baffled as to why a person would use a Torrington bearing on the cam gear
Schurkey- you said it right there: Thrilled with everything except the amount of slack in the chain. That is why I want a double-roller timing set. I've seen and heard more than a few people mention how fast the chain stretched (wore) on the GM set. And if you're baffled about the Torrington bearing, I guess ask Romac- they are the ones that put the bearing on the gear- not me!

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post #36 of 55 (permalink) Old Apr 7th, 14, 10:40 PM
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Re: Gen 6 HR cam in a Mark IV???

Quote:
Originally Posted by Schurkey View Post
Lunati steel-core w/ iron distributor drive gear, and a fuel-pump lobe Gen 6-style step-nose cam in my MK IV 454 boat engine. Used the GM timing kit. Thrilled with everything except the amount of slack in the chain.

Camshaft end-play:




I am completely baffled as to why a person would use a Torrington bearing on the cam gear, when the cam retainer plate is already protecting the block.

I did not test my Gen 6 retainer plate, but if the thing is hardened like the cam retainer plates in the 3.4 DOHC V-6 engines in my Luminas, there's no way you're going to sand clearance into it. I sanded my Lumina retainer plates until my arm about fell off, and managed to cut it down by half-a-thousandth. Had to take them to a machine shop to get them surface-ground for added clearance.
The bearing works like any other Torrington on a timing gear. Mostly it helps reduce friction. It's not to protect the block. There's more pressure against that surface than one might imagine, especially at higher rpm's.

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post #37 of 55 (permalink) Old Apr 8th, 14, 1:14 AM
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Re: Gen 6 HR cam in a Mark IV???

Quote:
Originally Posted by jburns View Post
See the pic below (I'm not as think as you dumb I am! )

The depth of the step is .125. It seems this needs to be deeper by a lot. So... if I reduce the thickness of the retainer plate to get the cam to spin freely and get this gear further on the crank somehow, I'll be golden. Easier said than done!
John no one is suggesting you are dumb
The only way for any of us to know for sure what you have is to see it & you didn't say you checked the gears just that you changed them

Anyway it sure appears you have the correct gears so I am out of ideas except one
Check the ID of the recess & the OD of the crank shoulder it goes over to be sure it can seat properly on the front face of the shoulder

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post #38 of 55 (permalink) Old Apr 8th, 14, 7:39 AM
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Re: Gen 6 HR cam in a Mark IV???

Maybe compare the cam itself to another GENVI step nose cam. I only used GENVI hyd rollers and never had an issue with alignment. I'd double check the nose of the cam to make sure it has not been cut back. Regarding single timing chain, early on I used the GM set. It did gain slack, although I kinda doubt it was from chain stretch and more from break-in of the cast timing gear. Later went to the Cloyes billet GenVI set in -.005" line honed set for the 454.070 block. This was just as tight after 3 seasons and approx. 5000 miles as when went on. Reused this set on the 540 which surprisingly fit excellent on a new standard spacing block.

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post #39 of 55 (permalink) Old Apr 8th, 14, 8:09 AM Thread Starter
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Re: Gen 6 HR cam in a Mark IV???

Thanks guys- I'll keep checking stuff!

Mike- the gear does seem to be seating properly on the front face of the shoulder- I'll check more closely.

Joe- just to be clear- you ran the GEN 6 cam in a Mark IV? I think yours is the first post I've seen (and I have searched!) about using a Cloyes timing set in this mod. I actually ordered a Cloyes set yesterday.

Does anyone know the "correct" dimension of the step nose on this cam?

Maybe I'm chasing tolerance stack and the gremlins born in the aftermarket world. The answer is here somewhere and we'll figure it out. I appreciate all of the feedback- if this was easy, everyone would do it!

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post #40 of 55 (permalink) Old Apr 8th, 14, 8:55 AM
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Re: Gen 6 HR cam in a Mark IV???

You could call or email cloyes.I did when I was searching for a new timing set for mine.I had a sloppy chain(stock) too at 2400 mile teardown.
They said they prolly make it for GM anyway.They can tell you,or clear it up anyway which gear you have or need.
I couldn't get a definitive answer on what I needed because I had a later 12/2009 454,so I bought a new gm set for the 502.I figured since the cam was interchangeable,the heads were the same,and I had the aluminum timing cover,I was safe.Nope,lol.The gear patterns and chain were the same,but the 502 gears had a weird offset thing going on.
I wound up re using the same gears(they were fine)and the new chain.
The new chain was already sloppy like the old one.So I figure that slop is built in by them(gm)I don't like sloppy chains either,but whatre you gonna do.

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post #41 of 55 (permalink) Old Apr 8th, 14, 9:21 AM
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Re: Gen 6 HR cam in a Mark IV???

The step on the front of the GEN6 cam should have a diameter of 1.565", and a depth of .236". Regards, Chase
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post #42 of 55 (permalink) Old Apr 8th, 14, 9:29 AM
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Re: Gen 6 HR cam in a Mark IV???

Quote:
Originally Posted by jburns View Post
Thanks guys- I'll keep checking stuff!

Mike- the gear does seem to be seating properly on the front face of the shoulder- I'll check more closely.

Joe- just to be clear- you ran the GEN 6 cam in a Mark IV? I think yours is the first post I've seen (and I have searched!) about using a Cloyes timing set in this mod. I actually ordered a Cloyes set yesterday.

Does anyone know the "correct" dimension of the step nose on this cam?

Maybe I'm chasing tolerance stack and the gremlins born in the aftermarket world. The answer is here somewhere and we'll figure it out. I appreciate all of the feedback- if this was easy, everyone would do it!
Yes, absolutely ran GenVI in MarkIV block. As I understand it, MarkIV blocks (454's at least) first came drilled/tapped for reverse drive for marine applications. All GM did was rotate retainer plate orientation 90* when they moved main oiling from pan rail to cam tunnel.

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post #43 of 55 (permalink) Old Apr 8th, 14, 9:36 AM
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Re: Gen 6 HR cam in a Mark IV???

Also, FWIW, cure for the sloppy single chain is to get the crank gear for the -005" set. Chains are the same for all of the sets, all they do is cut the crank gear oversize when they perform the broaching operation for the teeth.

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post #44 of 55 (permalink) Old Apr 8th, 14, 10:46 AM Thread Starter
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Re: Gen 6 HR cam in a Mark IV???

Quote:
Originally Posted by cknight View Post
The step on the front of the GEN6 cam should have a diameter of 1.565", and a depth of .236". Regards, Chase
Thanks Chase- those are numbers I am coming up with too.

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post #45 of 55 (permalink) Old Apr 8th, 14, 9:34 PM Thread Starter
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Re: Gen 6 HR cam in a Mark IV???

Guys- I am oh so close. I had the retainer modified by reducing the thickness .002 and opening the ID of the snout hole to accommodate the 3 little tabs on the torrington (the machinists at work take care of me!). The plate was touching that and also a raised ring feature those tabs are on. The hole's ID is now essentially the same as the torrington race. See the photo below.

Big question- I installed it all and it spins freely, but there is zero end play as described by Shurkey's photos. I can have a couple more thousandths knocked off easy enough- it this recommended?

As for the crank gear... I screwed up- bigger hammer needed. It went all the way in and they line up now. In my defense... no, I got nothin'.

I appreciate the suggestions everyone has given- the retainer plate seems to be the culprit...


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