Thread: Signs of Detonation???
10-20-2007, 03:40 AM #1
Signs of Detonation???
With your combined knoweledge, hopefuly one of you may have some ideas after looking at the pictures of my cylinder head, has it has suffered detonation? the head is off a 1997 SLTX 1050 that was "reconditioned" but failed after 5 hours running. The engine was never pressure tested and I think it failed due to a poorly sealed mag housing (failed main bearings). The head is off the PTO cylinder, could the crank be out of index? I have read that the centre cylinder on the 1050 runs 15 psi less compression, how is this achieved (different dome volumes)? can this head be succesfuly repaired?
Below are some of group K's words about detonation (this is what alerted me).
many thanks for your help, dave
Detonation seizures - If a modified engine has been prepared with too much compression or spark advance, or if it's run on unacceptably low octane fuel, it will begin to "ping" or detonate. Detonation is a big subject the merits another article of it's own. For now we only need to understand that it causes a terrific amount of internal heat in a very short time, as well as physical damage to the combustion chamber. If you have ever seen the outer diameter of a cylinder head dome that looks as if it's been eaten by termites, you have seen the results of detonation. It packs a physical force that is roughly equivalent to hitting the edge of the piston crown with a full arm swing of a ball peen hammer.
10-20-2007, 05:54 AM #2
Do you have any pics of the pistons? The domes look more like forgin object damage.
10-20-2007, 07:12 AM #3
These are the only pictures of the pistons that I have. It may not show up in the photos but there is very noticable pitting in the head near the ridge into the dome. The rod on the PTO end of the crank was replaced and this is the cylinder the head is from. The darker head in the photo is from the mag end that was damaged (bearing failure) although there is no physical damage to this head.
10-22-2007, 12:48 PM #4
Dave ,Doesn't look like detonation to me .Where are you in Perth ?Was I talking to you last month ?.Give me a call and I will have a closer look and see if we can't find your problem .
10-22-2007, 09:17 PM #5
Hi Dave.You are correct,the 97 1050 had lower compression in center cylinder.Accomplished by using a different head,larger dome.You can identify heads by part #.3022050 on mag & pto. 3022025 center.In your picture,the head on left appears to have smaller squish area/larger dome.
10-23-2007, 01:33 AM #6
Thanks Casey, any ideas on how best to repair the pitted head? the head also has some raised material (alloy) next to where it's pitted almost like what is left after striking an arc with a welder, any ideas/comments?
Thanks everyone, Dave.
10-23-2007, 07:38 AM #7
That head on the left is a higher octane dome than the rest. You can see the squish band is narrower and tigheter. The more I look at it, the more it looks like it is for an 84mm bore, not 81. There could be some light deto going on there, or someone bead blasted the domes at one point. The squish clearance looks very tight, even for 92 oct.
Last edited by PolarisNut; 10-23-2007 at 07:44 AM.
10-23-2007, 10:28 AM #8
Hey Dave,I'm not an engine builder,so I can't say what would work as far as repairing it reliably.In another post John Zigler mentioned having the 050 head & probably the 025 head,Pm him.
10-24-2007, 01:07 AM #9
I have had a closer look at the heads and casey67 was spot on about there being 2 different heads, I do indeed have 2 x #.3022050 and 1 x #.3022025 centre. It was actually the lower comp head that has possible signs of detonation. I always use ultimate98 fuel (98 oct) and Redline watercraft oil in my ski's. The guys that built the engine are unsure about these marks on the head, however they do concede that it may be detonation.
Thanks for all the help Dave.
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