Rod Clearance
 

Installing a Scat 4 1/4”” stroke crankshaft and H beam rods in a 59A block. What’s the minimum clearance I can get away with between the rod and the bottom of the bore. ? I can get a .070 feeler gauge between the rod and block.

Re: Rod Clearance
 

My personal opinion is i would be grinding a spot in the block to the rod will clear and get more clearance
Wish I could tell u how much to take out but more id better than not enough


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Re: Rod Clearance
 

Usually on a stroke that big some lower bore relief is needed. I use a plastic Ty-rap to check clearances the ones I have measure a bit more than the .070 When I can get the Ty-rap in between the rod and bore I stop grinding I like to see at least .100
Ronnieroadster

Re: Rod Clearance
 

I’ll try a ty rap ,haven’t thought of that . My feeler gauge blade is a little wider than the H beam rod so I might have more clearance than I think .

Re: Rod Clearance
 

Just been reading on such items seem to recall a figure of 0.110 quoted for this clearance.
Phil NZ

Re: Rod Clearance
 

Does everything really grow that much when the engine is hot. ??

Re: Rod Clearance
 

Ronnie's 0.100" surely seems to work for him, and I've seen HIS tach buzzing near 8 grand-ish! DD

Re: Rod Clearance
 

Sounds like I need to pull the crank and valve train back out and do some grinding and flushing.

Re: Rod Clearance
 

Its worth the effort I can say from experience rod clearance is extremely important. Just go easy on the cylinders towards the oil pan rail side of the bore that area is not extremely thick. The area towards the inside /center of the block is a bit thicker at the bottom of the bore from what I have learned.
Ronieroadster

Re: Rod Clearance
 

Thank you.

Re: Rod Clearance
 

Assuming you have a 3.312" bore size you will be fine with .050" for a "streeter", it's all you really need!

We've sent dozens out with .050" clearance and absolutely no grinding using the 3.312" bore x 4.250" stroke! It's not an issue unless you "spin" a rod brg!

The only time we've found it necessary to grind in any add'l clearance is when you have the 4.250" stroke and the bores are smaller than the 3.312", e.g., for an .080" o/b you'd be grinding some!

Thanks, Gary in N.Y.

P.S. Due to the limited amount of room in this area it is the main reason we use the Scat rods, they will clear, the Eagle H-beam rods with a 1.100" beam width will NOT go with the 4.250" stroke in the program!

Re: Rod Clearance
 

Gary, what if you used the 21a rods,
Lawrie

Re: Rod Clearance
 

Yes, it’s 3.312 with the Scat rods.

Re: Rod Clearance
 

Hi Lawrie, I would surmise due to the difference in the beam widths on the Scat (.790") and the OEM type rods (.710") you'd have more room with the OEM's?

The Scat rods are reasonably "straight" along the beams from top to bottom while the OEM's are tapered some. The area of contact at the bottom of the bores is about where the sizes are written on the beams?

Thanks, Gary in N.Y.

P.S. Here's a shot of both rods comparing the actual beam widths, you can see there would some slightly add'l room with the OEM's.

Re: Rod Clearance
 

OK , the originals would be better though if using the floaters ?.
Lawrie