V8RRC Posted October 12, 2006 Share Posted October 12, 2006 Ian, Is this the effect of cavitation? Regards, Quote Link to comment Share on other sites More sharing options...
simonr Posted October 12, 2006 Share Posted October 12, 2006 really S****y day Smelly? Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted October 12, 2006 Share Posted October 12, 2006 Erm No.... your on the right track...... S****y ......as in "Probably how O2 feels" from being BBC'd Nige Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted October 12, 2006 Share Posted October 12, 2006 Put 02 down and walk away That's harsh Nige, I don't see why he should have to die for asking stupid questions ! Mo Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted October 12, 2006 Share Posted October 12, 2006 Must be tired ............. Took me a few secs before the true 'droolness' dawned on me . Very sharp Nige Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted October 12, 2006 Share Posted October 12, 2006 Ian,Is this the effect of cavitation? Regards, Yes, that looks like cavitation damage at its best, that is exactly in the correct position. The damage should look like polished corrosion …….. just like something has eaten into the ali. Could you post a real good closeup of the damage ? BTW: I have yet to find an EFI timing cover without this damage………. Some are real bad, leaving the housing paper thin, and others not so bad. Ian Quote Link to comment Share on other sites More sharing options...
Les Henson Posted October 12, 2006 Share Posted October 12, 2006 Seems to me that of late there's a lot of 'we/I am better than you'. A little bit of brain engagement prior to opening ones mouth is all that's needed. Every member of this website has a contribution to make, perhaps we should bear that in mind? Les. Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted October 12, 2006 Share Posted October 12, 2006 Could you post a real good closeup of the damage ? Not V8RRC's timing cover, but mine - I thought this was casting faults, but I'm wondering now: Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted October 12, 2006 Share Posted October 12, 2006 Geoff, That’s the best cover I have seen ……….. that could be the start , however I normally see it a lot worse with a large patch as shown in the other pic…….. on high revving engines it eats right through the casing ............ Ian Quote Link to comment Share on other sites More sharing options...
T1G UP Posted October 12, 2006 Share Posted October 12, 2006 got me paranoid now.v8's are pants. want a v8 diesel instead. Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted October 12, 2006 Share Posted October 12, 2006 That’s the best cover I have seen ……….. that could be the start , however I normally see it a lot worse with a large patch as shown in the other pic…….. on high revving engines it eats right through the casing ............ It's not a particularly old one - it's off a '93 3.9 with roughly 150k on it. It's never been revved that hard as it was attached to an auto box. Won't be getting reused anyway, as I'm going to rebuild the engine with a serpentine timing cover (yes, I do know about the other bits I'll need to change). Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted October 12, 2006 Share Posted October 12, 2006 Geoff, If it will be surplus to requirements ……………… PM me a price and put my name on it . I would like it for a spare. For those who are worried …………….. the cavitation damage was bad enough on mine to cause porosity just below the two outlets. As I see it there are 3 methods of repair, 1) Take out the water pump and build up the damaged area with aluminium weld.(needs a TIG really) 2) change the timing cover ……..PITA job, primarily due to sealing the small sump section without removing the sump. 3) Build up the rear of the waterpump housing with JB weld to a thickness of about 1/8 (3mm in new money). I took option 3 and it has been fine for at least 15K miles………. JB weld is pretty tough stuff and doses exactly what it says on the tin. Come on …………. Anybody got any more pictures of V8 timing cases .? Ian Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 13, 2006 Share Posted October 13, 2006 Dagnammit, the 4.6 has just been bolted together and I didn't take any piccies of the timing cover At least now I know to keep an eye on it, and the EWP has moved up the "to do" list Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted October 13, 2006 Share Posted October 13, 2006 What do you do with the original water pump if you convert to electric? I presume you need to get rid of the impeller somehow? If you lose the whole pump, what happens with the pulleys? Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted October 13, 2006 Share Posted October 13, 2006 That’s the best cover I have seen ……….. that could be the start , however I normally see it a lot worse with a large patch as shown in the other pic…….. on high revving engines it eats right through the casing ............ Interestingly, I just dug out the later serpentine type cover that I bought to replace that one - there's no damage to that (well, maybe the very, very early startings - hard to tell). It's a very different design, though, so maybe they sorted the problem out. Quote Link to comment Share on other sites More sharing options...
pugwash Posted October 13, 2006 Share Posted October 13, 2006 Hey Geoff, thats the same with my serpentine front cover too. My old timing cover was shagged- there was close to a hole all the way through! The serpentine one seems fine- although it could becuase it is younger. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 13, 2006 Share Posted October 13, 2006 What do you do with the original water pump if you convert to electric? I presume you need to get rid of the impeller somehow? If you lose the whole pump, what happens with the pulleys? The manual says either modify the impeller not to impel, or pull the whole lot & block it off. The pulleys I would expect just get bypassed, just get a different length belt and adjust accordingly. Quote Link to comment Share on other sites More sharing options...
Bush65 Posted October 13, 2006 Share Posted October 13, 2006 As most know, increasing pressure in the cooling system increases the boiling point. The opposite happens when the pressure is reduced. When this happens in a pump it is called cavitation. In a pump, if the pressure (at the pump suction) is lower than the vapour pressure of the fluid, the fluid starts to vapourise and bubbles of vapour form. This often occurs if a restriction occurs in the suction line to the pump. It also happens if the pump is driven at too high a speed. Those bubbles of vapour travel with the fluid, toward the high pressure outlet of the pump. When the pressure exceeds the vapourisation pressure, the vapour condenses and the bubbles collapse (they do not burst or explode). It is the rapid collapse of the bubbles, which cause very high stresses on small areas and erodes the material from the surface. Cavitation will destroy a pump in a very short time. If air leaks into a pump suction, the effect is similar but not as destructive, because the bubbles are compressed and don't completely collapse. The pump can be destroyed but will last a bit longer. This makes a very rattely noise, again not as severe as cavitation. Boat propellors can also suffer from cavitation, and from sucking air from the surface. Most outboard motors have a fence to avoid air being sucked from the surface. Quote Link to comment Share on other sites More sharing options...
TJ101 Posted October 15, 2006 Share Posted October 15, 2006 Boat propellors can also suffer from cavitation, and from sucking air from the surface. Most outboard motors have a fence to avoid air being sucked from the surface. ?? Fence ?? Think you mean the Cavitation plate these exist to keep surface air from reaching your prop all outboards and stern drive have them in the leg. bar little ones of about 2hp !! Quote Link to comment Share on other sites More sharing options...
GBMUD Posted October 15, 2006 Share Posted October 15, 2006 So does air being drawn in from the surface have ther same damaging effect as cavitation? Chris Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 16, 2006 Share Posted October 16, 2006 Found this kicking round at the weekend: Yellow tint is due to being on the shelf in the proximity of Jez building/spraying things Quote Link to comment Share on other sites More sharing options...
Bush65 Posted October 17, 2006 Share Posted October 17, 2006 ?? Fence ??Think you mean the Cavitation plate these exist to keep surface air from reaching your prop all outboards and stern drive have them in the leg. bar little ones of about 2hp !! In aero/hydrodynamics the generic name is fence. What you are calling the cavitation plate is a fence. It does as you said, but this has nothing whatsoever to do with cavitation (has similar, but less severe affects as cavitation). So I why should it be called a cavitation plate and not a fence?? Quote Link to comment Share on other sites More sharing options...
Bush65 Posted October 17, 2006 Share Posted October 17, 2006 So does air being drawn in from the surface have ther same damaging effect as cavitation?Chris It can. Quote Link to comment Share on other sites More sharing options...
BogMonster Posted October 19, 2006 Share Posted October 19, 2006 (edited) In aero/hydrodynamics the generic name is fence.What you are calling the cavitation plate is a fence. It does as you said, but this has nothing whatsoever to do with cavitation (has similar, but less severe affects as cavitation). So I why should it be called a cavitation plate and not a fence?? Dunno but Tim is right, that is what they are always called on outboards even if it is technically wrong, but it isn't wrong as it stops cavitation when cornering Edited October 19, 2006 by BogMonster Quote Link to comment Share on other sites More sharing options...
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