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Is anyone out there having any problems with bullet flat tappet cams going flat within first 10 minutes. I know all about good oil and zinc additive. Several of the lobes have a very odd wear pattern. I have built motors for over 20 years and have never lost a cam until now. It has single springs and brad penn oil and comp cams zinc additive. It fired immediately and was ran at 3000 rpm for about 10 minutes until I could hear it loose a cylinder. Just wanting to know if anyone has had any issues with a bullet cam with a very abnormal wear pattern.
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This isn't going to help much and it might be the junky stuff I have to use cause I'm poor but I don't like the CompCams stuff. I use Lucas Break in oil with the inner springs removed and haven't killed a cam with it other than the last one which was the Dist gear broke off.
You might call Bullet and perhaps they can give advice.Last edited by Lizardracing; 03-14-2016, 09:22 AM. -
How much spring pressure did you have over the nose?Comment
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I called bullet today and they had me send cam and lifters to them. Hopefully they will find something. This is a single 1.25 valve spring. Basically the z28 springs. That is the odd part is they are a pretty light spring to have a cam problem. And with these its not like you can take out the inners. As far as the oil and zinc additive bullet said they are both really good stuff so they really didn't think that was the problem.Last edited by r3tracing; 03-14-2016, 05:30 PM.Comment
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You might look at the retainer to seal and spring coil to coil clearance to ensure it wasn't biding up and full lift and damaging the lobe. Check the push rods too as binding on the head and or guide plates create additional stresses.
Just out of curiosity, was it just one lobe or were there others invovled?Comment
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Just one lobe but some very abnormal wear on about 4 othersComment
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What spring part number or what spring pressures was it? Also what rocker ratio?Comment
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Had a similar issue years ago with a custom ground Crane cam. After wiping out several lobes during break-in, we contacted them and sent it back. Their response was that there was not enough taper on the cam lobe to keep the lifters spinning. They sent us the corrected ones and we didn't have any more issues.Turn LEFT, Vote RIGHT!Comment
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The z 28 spring 130 lbs closed pressure 1.5 ratio. Bullet will get it today and hopefully they find something wrong with it.Comment
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Ok bullet agrees that cam has abnormal wear on the rear lobes. They are sending new cam for 25 dollars so hopefully no more problems.Comment
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Get rid of those z/28 springs. They are junk. Keep your open pressure under 280 during break in.Comment
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I have always just used stock springs to break the cam in then switch them out. They are usually around 70 on the seat and 200-240 open.Comment
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Spin the cam /lifters (dry) with a speed handle, make sure they are rotating (the lifters). The cam may need to be moved foward or rearward if it's not centered, or just a hair to the rear.
I always order more taper on the lobes than shelf cams have, also.TBLast edited by TBRE; 03-17-2016, 01:06 PM.Comment
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Something to add to Tony's suggestions is:Originally posted by TBRE View Post
When doing that put dykem on the full bottom surface of the lifter so you can see the pattern of the contact. If you have a super aggressive lobe and you lifter bores are off on angle you can actually have the lobe run off the lifter edge and actually dig into the lobe. You should see a small margin of dykem left around the outside edge of the lifter, if you don't you will likely have issues. Stock lifter bore can be off some and that degree or 2 is enough if off the right way to make the lifter diameter not large enough for that lift per degree of duration and wipe out the cam.
You can probably forget this if you have used that lobe in that block before but a new lobe design or a new un-fixed lifter bore block you might want to check it if you using semi aggressive lobes.Comment
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