SCAT Crank issue

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Wes Bender
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Re: SCAT Crank issue

#31 Post by Wes Bender »

"The AA iron barrel/cast piston sets are good for most street cars but the Shasta durabar barrel/JE piston sets are much better. You get what you pay for."

++1
Some days it's just not worth chewing through the restraints.....

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Mike Smith
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Re: SCAT Crank issue

#32 Post by Mike Smith »

CJ Quote - The AA iron barrel/cast piston sets are good for most street cars but the Shasta durabar barrel/JE piston sets are much better. You get what you pay for.

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Adam Quote - But with that in mind I would recommend anyone using AA pistons to get them directly from AA, not from one of the re-sellers or EBAY sellers who may have an old set, even un-knowingly.

Agreed in Both Cases
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John Brooks
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Re: SCAT Crank issue

#33 Post by John Brooks »

Shasta barrels and JE pistons, the rings on the new Pistons are thinnnnn. But I guess that why they call it technology. Awaiting the heads to come back, but the build progresses
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Bottom end together.
Bottom end together.
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Wes Bender
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Re: SCAT Crank issue

#34 Post by Wes Bender »

The thin rings mandate that you be verrry careful when setting the gaps. Easy to overdo it.
Some days it's just not worth chewing through the restraints.....

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Glen Getchell
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Re: SCAT Crank issue

#35 Post by Glen Getchell »

Ok, I opened up the bottom end to check this whole SCAT Crank / Bearing issue. Yes I can basically see what everyone is talking about. However, I installed new AA aluminum bearings (I have no idea how long they have been available on the market) and they appear to already be angled. I compared one to an old bearing which is basically a 90 degree angle, where the AA's as I said are already angled. The old bearing has a huge gap were it runs into the curvature on the crank. The AA bearing has very little as it follows the curve. I have attached photos of the comparison between the new AA bearing (on the left), and an old bearing (on the right). I also included a picture of the AA bearing on the crank. If you look closely at the photos, you can see that the AA bearing has been angled off at the factory. Do these AA bearings still need to be chamfered even more than they are from the factory? Because honestly, when I look at the AA bearing on the crank, I'm not sure how much more if any should be taken off the bearing. Should you go to it fits square to the crank? Clearly the old bearing would have been an issue. That is obvious now that I know what to look for. But damn, I have to question if this issue applies to the current AA Main Bearings like I purchased. Everybody please chime in. I didn't rip this thing apart because I am all knowing. Thanks!

Glen
64Cx2
P.S. I have edited this post with a photo of the older bearing on the crank. You can clearly see the difference. The first photo is an old bearing with square edges. The second photo is the AA bearing with angled edges. The 3rd&4th are the two together with the AA on the left.
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bearing 4.JPG
bearing 3.JPG
bearing 2.JPG
bearing 2.JPG

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Re: SCAT Crank issue

#36 Post by John Brooks »

Tom picked up the heads today, tomorrow we can finally start measuring volumes and get PC installed. Verified the cam timing and base lift, then went into work stoppage for heads.
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Verifying base lift and timing
Verifying base lift and timing
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C J Murray
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Re: SCAT Crank issue

#37 Post by C J Murray »

John, what cam are you using and what CR do you want?
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Re: SCAT Crank issue

#38 Post by John Brooks »

C.J.

I believe it's an aftermarket SC cam. I forget the base lift bit it's 106 deg intake. Tom bought all the parts, I am just balancing and help assembling

We have heads, are all close just 1.8 cc spread. 58.2 to 60.0cc. A little polish and smoothing we should be good at 60 all the way around. I need to get the Pistons on and measure the deck hight, but we are shooting for 8.75-9.0 CR.

Tom drives this cross country every year to the holidays, parade, and the SOG dragon pig roast. I am shooting for good power, but with flakey varied gasoline quality. Long 6-8 hour days at freeway speed, with no delays.

Cam data from the web cams Inc. website,
426/.361. 273°/273° 233°/233°

http://www.webcamshafts.com/pages/autom ... 71302.html
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Last edited by John Brooks on Wed Mar 07, 2018 2:27 am, edited 1 time in total.
John Brooks

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Tom Olson
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Re: SCAT Crank issue

#39 Post by Tom Olson »

Cliff, John,

The cam is a Web Cam #62. This will be used with cast iron rocker assembly. I believe the cam is 105 deg.

Tom
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C J Murray
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Re: SCAT Crank issue

#40 Post by C J Murray »

That is a stock S, SC, 912 grind except that it is ground with more overlap, 105LC vs stock 108LC. Confirm that the timing card that came with the actual cam says 105/105LC and refer to your notes from when you timed the cam during assembly. If it is a 105/105 cam then carefully check the valve to piston clearance as you proceed. The intake will be ok but the exhaust will be tighter than it would be with the stock 108 cam.
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Vic Skirmants
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Re: SCAT Crank issue

#41 Post by Vic Skirmants »

Isn't a 1.8cc difference a bit much?

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DonCichocki
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Re: SCAT Crank issue

#42 Post by DonCichocki »

From my little bit of experience don't trust the cam card. Install the cam in the bare block and degree it, you'll be surprised at the error. Just my .02 $.
Also, agree with Vic 1.8cc is too much. Get it down to +- .5cc or closer between chambers. Again, my .02$.

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Re: SCAT Crank issue

#43 Post by C J Murray »

John Brooks wrote:A little polish and smoothing we should be good at 60 all the way around.
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Vic Skirmants
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Re: SCAT Crank issue

#44 Post by Vic Skirmants »

C J Murray wrote:
John Brooks wrote:A little polish and smoothing we should be good at 60 all the way around.
I don't think you can "polish and smooth" 1.8cc. Some judicious aluminum "grinding" will be required.

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Re: SCAT Crank issue

#45 Post by Glen Getchell »

Honestly, I don't know when this thread took the sweeping turn away from the Scat Crank / Bearing issue. But if some one knowing could read my previous post and look at the photos showing the angled edge already built into the AA bearings I would appreciate it. I pulled this engine apart based on the forum, and from what I can see, the modification to the bearing appears to have already been done by the AA bearing factory. Am I correct, or am I missing something? Is it still not enough angle? There is a substantial difference of the edges of the AA bearing vs. an older bearing I had laying around to compare. In fact the bearing material on the AA bearing is .15mm narrower at the top than at the base. On the old bearing, it is the same width. That means that the AA bearing angles in from the base .075mm to the top on each side.

Glen
64Cx2

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