RB20 Repair Options?

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Stoink
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Tue Jul 28, 2020 2:58 pm

I have a small block rb20. Stock size bore. I have an issue where the spigot on the cylinder is thin from factory and has warped pinching the piston at bdc. I do not want to just hone the cylinder and replate. I do not want to resleeve and use a smaller piston. I have seen the quattrini 200 does not have a spigot, just a small lip to center the cylinder on the case. Can all or some of the spigot on an RB200 cylinder be cut/trimmed similar to a quattrini while still being safe/functional? Any other clever repairs to over come this problem.?
Thanks

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Toddy
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Tue Jul 28, 2020 9:21 pm

Stoink wrote:
Tue Jul 28, 2020 2:58 pm
I have a small block rb20. Stock size bore. I have an issue where the spigot on the cylinder is thin from factory and has warped pinching the piston at bdc. I do not want to just hone the cylinder and replate. I do not want to resleeve and use a smaller piston. I have seen the quattrini 200 does not have a spigot, just a small lip to center the cylinder on the case. Can all or some of the spigot on an RB200 cylinder be cut/trimmed similar to a quattrini while still being safe/functional? Any other clever repairs to over come this problem.?
Thanks

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Grumpy225
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Tue Jul 28, 2020 9:27 pm

the two kits are very similar. I'd think if it was done correctly without damaging the platting it should work just fine.

holty
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Tue Jul 28, 2020 9:47 pm

ive seen damaged spigots used in the past with no issues, just as long as there are no sharp edges, so you could cut away the damaged part, i believe a shorter spigot will cool the piston more, you will not have as much support for the piston if you remove the full spigot, i would mark the inside of the cylinder and work out where the distorted part is and cut it of if it isnt too large, failing that langcourts can repair and replate it.

Warkton Tornado No.1
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Wed Jul 29, 2020 2:38 pm

You first need to deal with the distortion & why it has occurred. If you remove all of the cylinder studs, the cylinder can be placed in position & should freely rotate without catching anywhere. Magneto housings have caught me out before now..... :oops:

Once the cause is addressed, you really can go to town with removing the areas of the cylinder that need it, but chamfer all edges & try to make any slots nicely radiussed. A TS barrel that I acquired had a rod snap & when it let go, crankshaft still rotating with inertia, it caused slotting of the skirt extensively. I simply extended the rough slots to make a nice shape & the inlet side a shallow port connecting into the inlet port as a feed to the boost port. It works fantastically well. So far.....Ha!

Do check what you have (as suggested above) first & if it helps, I will email you images of what I did to the TS barrel. Knowing theory is one thing, but when you can see it for real, it inspires confidence.

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