Scat crank and bottom end

[danliveshere]

Anybody using the new scat crank and full rotating bottom end that speedway offers? Do you need to alter the bottom of the barrels if you use their 4 1/4" stroke crank and rods? Considering going this way for a 59A block thanks Dan.

[KiWinUS]

Suggestion. Check with Gofast Gary on here he can supply & answer any questions with years of experience

[JM 35 Sedan]

Dan, I built a 59 series engine using a SCAT 4-1/8" crankshaft in 2007. This was not a Speedway kit, just ordered the crankshaft separately from one of SCAT's Rep's. I used stock 29A rods that were rebuilt, and I definately had to add a very slight relief at the bottom edge of each cylinder bore to make sure the rod nuts had enough clearance. Some of the engine building Gurus here said I should not have had to do this, but the fact remains that it was necessary on my build.
Not knowing exactly what the rod journal diameters on this 4-1/4" SCAT crankshaft will be, or what rods come with this SW kit, but you may not have the same clearance issues that I had with the crank and rod combo that I chose to use.

[Ol' Ron]

I used one from Gary, dropped right in.

[JWL]

Bore size can be a factor for clearance at the block. The only problem I had was with one lobe on a roller cam contacting the rib at the upper half of rod bore housing on a 29A rod just above the stud location.

[tubman]

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I remember reading here that a combination of parts (Eagle rods and Scat crank or vice versa) is the way to go. Hopefully, Gary "GOSFAST" will check in here. Otherwise, do a search here or on the H.A.M.B.

[KGS]

Originally Posted by tubman

I remember reading here that a combination of parts (Eagle rods and Scat crank or vice versa) is the way to go. Hopefully, Gary "GOSFAST" will check in here. Otherwise, do a search here or on the H.A.M.B.

Here is a link to the thread I think you're referring. See Gary's post # 16:
https://www.fordbarn.com/forum/showth...scat&showall=1

[Krylon32]

I've done a couple with the 4 inch Scat kits from Speedway, only thing we did was rebalanced the assembly otherwise it worked fine.

[Ronnieroadster]

I have found when building an engine using a 4 -1/4 stroke crankshaft and H- beam rods a small amount of notching is required. Also depending on the camshaft you might find cam lobe to connecting rod clearance to be very close in a few locations.
Notching for the clearance is not difficult just go easy the material being removed is at the bottom of the bore where the block casting is thick so going threw should not be a problem. Go easy and slow and you will be fine if you decide to use the parts your asking about.

[A bones]

Originally Posted by tubman

I remember reading here that a combination of parts (Eagle rods and Scat crank or vice versa) is the way to go. Hopefully, Gary "GOSFAST" will check in here. Otherwise, do a search here or on the H.A.M.B.

Yeah vice versa is the way he said it. He and others have pointed to the necessity to work over the Scat crank to achieve balance, the Eagle comes in good. While Scat rods are his preference for clearance

[GOSFAST]

Let me go over it one more time, no problem.

We've encountered too many balancing issues with the Scat line of cranks, not only on the Flatheads but with the Chevy's also. For this reason we totally avoid Scat cranks when possible.

Their rods are another story however, on the Flatheads these are the only ones we will use.

Here's how we now order/sell our own kits, Eagle cranks, Scat rods, Ross pistons (with the metric ring packs) and Clevite rod brgs. All these shafts utilize the 2.000" rod journals, the brgs are designated as for a Pontiac/Buick unit.

The largest issue comes into play about using a pre-balanced kit, we do ALL our own balancing but strongly recommend to our kit buyers that they consider allowing their own shop to do the balancing. There's actually a very solid reason for this line of thought! Read on.

Down the road, if a pre-balanced kit is purchased, and there just happens to any noticeable vibration in the unit, there will tend to be a large disagreement between the owner and the builder about who is exactly responsible at that point for the vibration, the same shop that wouldn't have balanced the kit. For this reason we urge our customers to let their guy do this procedure! It just makes absolute sense to us here. It is also reflected in our kit pricing, if we deliver it unbalanced there is obviuosly a price difference. In the end you will pay to have it done, but you will save it on this end. Here it changes the overall kit price by about $150.00 less out the door.

This is important info here, if and when we get ANY pre-balanced kits in our shop to work on (this is very rare here), and we were expected to stand firmly behind the build, at a minimum we would charge the customer to setup all the bobweights, mount them on the shaft, and run the shaft up for checking purposes. At this point they would be charged for the procedure, one they've already paid for initially in the kit price. Sort of like "double-jeopardy"? We would have no choice but to do it this way to at least guarantee a "vibration-free" build.

On a side note we also include the main brgs in all our kits. We stock them for the earlier Flatheads and the later ones.

The chances of having to "clearance" the bottoms of the bores for the rod beams is "slim-to-none" so to speak. This is the MAIN reason we choose the Scat rods over the Eagle's. The Eagles rods will NOT go in under any circumstances without a whole bunch of grinding.

Assuming you're going to use the Ross piston/ring combo, make certain any shop you use has the proper stones to finish the bores for the "moly" rings, they will need to be a fairly smooth finish. We also use a block-plate for our finish honing here but I suspect you won't find too many shops offering this feature??

See the second photo below, it shows the Eagle rod in position, it will NOT clear like I said.

Thanks, Gary in N.Y.

P.S. That ride in my signature has one of the best "Flatties" ever built here, 155 HP & 265# TQ, and now has probably close to 30,000 miles on it. I firmly believe it has a chance to possibly go in the neighborhood of 100,000 miles before any engine issues arise?? I'll have to wait and see, if I happen to be around that long?? Here's another photo showing the difference between the Eagle and Scat beams. You can see why the Scats would be the best choice.

[Pete]

I have built 3 engines with 3 7/16 stroke using Scat ROUGH crank castings. I used SCAT rods with the 2 inch crank pins.
NO grinding anywhere to clear with .488 net lift cam.
The rods cleared as out of the box but I machined them for weight which gave even more clearance.

I happen to know that it is no big deal to clear everything with a one inch stroke.

I am positive the rods would NOT clear with the 2.139 pins.
I run .040 minimum clearance on crank stuff.