62T Detonation issues in 1st gen Proforce

[long beach local]

Wanted to share my experience running a big bore ,86mm pistons stock stroke 885cc in my Proforce . I got 65hours out of this top end running up and down the river which is the best I have gotten.This setup gives me nearly 11gallons of fuel and 3hours run time nonstop. Anyway I screwed up and may have put some 87octane gas in it and noticed my spark plugs had loosened up and knew I had damaged it. I usually run half Av gas or a gallon of 110 in a 5 gallon can mixed with 91 octane ,I have run straight 91 without issue. I run TL Zeel on the Wax curve and believe this ignition has saved detonation and runs amazing. My compression is 160psi and I have a .025 base gasket which gives me .050 squish.You would think this setup would be safe from detonation but it is Not. The pipe I run is a lay down TNT V3 race spec and has a 2” stinger and I love the power this pipe makes the midrange is Very Strong. I’m running a Kawi 145 skat setback with a 10/18 prop which spools up quickly and pulls ok if I want to hold it wide open for a decent top end. My carb is a 49 ATP Dasa intake ,V2 reeds 2.5ns 170m 130p 95g 1.5 turns out both high and low. I think the pipe makes a lot of power at the price of reliability and would like to hear other’s thoughts on this subject as I have gone thru a bunch of pistons learning about this. I have ran dual 48s and 44s the results are the same I think I’m just on the edge performance wise. I will post some pics of the cylinder it’s a big bore sleeved 62t that was port matched by a machine shop. It was a BCW race cylinder that I wanted to bring back to life but maybe the exhaust ports are tooo big and the rings are just going to catch anyways.

 

[long beach local]

More pics of the domes.

 

[veedubs]

Very cool build. I remember seeing your thread when you first got it. Looks like you’ve had some fun with it.


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[TheBuzzard]

Looks like it just snagged a ring on the way down and knocked that chunk out of the piston crown. I've seen that a few times. Detonation is eroded looking , not just a perfect chunk missing like a jigsaw puzzle. I just saw that same thing on the new xs1060 motor that's been nothing but problems

 

[kevbo]

Full throttle mixture must be set rich of peak power and the ignition timing retarded well below the detonation threshold. Ive burned a piston on a 92 octane Superjet by letting the tank get low and running full throttle. This engine was 81mm, 165psi, and 21 degrees advance. A separate header tank and pump has so far prevented a repeat.. It appears that combustion temps are a wild card that can cause problems.