Re: Bla Bla Bla roller cams
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BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: Bla Bla Bla roller cams
Interesting. What are your lift, duration and spring pressures on that cam? What did TA have to say about it? Seems like information that we need to know.
Also if you don't mind my asking, was that the only lobe affected, and what was the condition of the matching lifter? (was it flat spotted?) Jim Edited 1 time(s). Last edit at 02/20/2020 11:43AM by BlownMGB-V8. |
Re: Bla Bla Bla roller cams
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BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: Bla Bla Bla roller cams
Well, it's a lot of lift and about twice the valve lash that I'd expect to see, maybe more. That can't be helping. What is most obvious to me from that photo is the appearance of the metal being displaced, mashed, or smeared, indicating ductility, or insufficient hardness for the operating conditions. A Rockwell hardness test of the lobe surface might have given you grounds for a claim against TA or it might not. This can't be good publicity either way. However, as close to the limitations of the system as you are running, only a small increase in spring pressure might do it, especially with the hammering caused by the large valve lash. You might want to double check to make sure your spring pressures aren't too high and then close up that clearance some. Considering where the damaged area begins that's what I would look at first.
Also, I realize that lash spec is probably from TA, but it really looks like a mistake to me. Jim |
roverman Art Gertz Winchester, CA. (3188 posts) Registered: 04/24/2009 11:02AM Main British Car: 74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L |
Re: Bla Bla Bla roller cams
Your using TA heads ? What king of rpm ? Solid stainless valves ? Big roller cams sometimes benefit from "glass beading the lobes, to prevent "skipping". .650" is a mother-load of lift. Shure you need that much ? All 8620 billet roller cams "should be case hardened to about .080". Art.
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88v8 Ivor Duarte Gloucestershire UK (1041 posts) Registered: 02/11/2010 04:29AM Main British Car: 1974 Land Rover Lightweight V8 |
Re: Bla Bla Bla roller cams
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Re: Bla Bla Bla roller cams
I'm going with that cam was destined to fail from the start. Thats crazy lift and that lash is too big. The rover cam is a small diameter cam. The LS cams went with a huge diameter and thats what allows them to get .600 and greater lift and still maintain reliability. No way I would go above .550 unless it was race engine and I planned on tearing it down frequently. Seriously, how much extra hp was gained going with that much more lift, and did you really need that extra couple of ponies?
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BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: Bla Bla Bla roller cams
To be fair about it, Buick engines have been running up to .750" of lift. Mostly those are purely drag engines but that by itself doesn't explain the failure. Neither does "particles". If you look closely it is clear that the metal was not worn off the lobe, it was displaced. Now that being the case it is not obvious that the lobe would have failed even though it seems likely.
Jim |
88v8 Ivor Duarte Gloucestershire UK (1041 posts) Registered: 02/11/2010 04:29AM Main British Car: 1974 Land Rover Lightweight V8 |
Re: Bla Bla Bla roller cams
Ha!
Particles was too oblique. Was thinking of the particles that are now running around inside the engine, that may go through a standard filter but the Filtermag will capture them. Wonder whether the cam was bedded in at first startup... 2,000rpm for 30 mins, no stops for adjustment or tinkering.. Yes, some may think that elementary but I don't know whether it's a universally accepted practice. Ivor |
BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: Bla Bla Bla roller cams
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MGBV8 Carl Floyd Kingsport, TN (4511 posts) Registered: 10/23/2007 11:32PM Main British Car: 1979 MGB Buick 215 |
Re: Bla Bla Bla roller cams
Ivor,
"Wonder whether the cam was bedded in at first startup... 2,000rpm for 30 mins, no stops for adjustment or tinkering.. Yes, some may think that elementary but I don't know whether it's a universally accepted practice. " Yes, for flat tappet cams. Is that really a concern for roller cams? |
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BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: Bla Bla Bla roller cams
Bryan, could you let us know what the spring specs were (open and seated pressures)? Might help someone else avoid this.
Jim |
Re: Bla Bla Bla roller cams
you'll find a unicorn and talking frog long before TA ever warranties any kind of cam issue even when it's plainly their fault.
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BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: Bla Bla Bla roller cams
To be fair, proving it was actually their fault is a stiff challenge to begin with, especially in an engine built for racing where the builder is pushing all the limits to get maximum power. Probably not a fight worth starting.
Jim |
BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: Bla Bla Bla roller cams
Yeah that's getting up there a ways. Can you tell us what they were at full lift?
Jim |