Cam Lobe Wear Question

[DCIEVE]

The photo below tells the story - are the cams usable or no good? They are apexi 270 11.4mm.

Thanks,

Nick

[DCIEVE]

More

Hard to see here but it's right on the tip of the lobe.

[33GTRV]

I see a bit of surface rust, but the detail isnt much better that i can see mate. Description may help us Id be getting some very fine wet and dry and trying to polish that rust off too, provided its not too deep.

[The Mafia]

All I can say is:

800 grit

Then

1000 grit

Then

1500 Grit.

Then install, and realize they they don't fit and need all sorts of shit changed because of the massive lift.

Also, if they do work, then I'm assuming you have an engine that will rev to 9,000rpm to 10,000rpm because those cams will only be good from about 5,000rpm upwards.

Still surprised at people that think bigger is always better when it comes to cams.

[GTScotT]

you can get them micropolished by a machine shop and they should be fine. I wouldnt risk the sandpaper method on a good set of cams.

i cbf for a keyboard war but there is no simple rule of thumb for cams, the 10,000rpm comment is not accurate. keep on topic.

[DCIEVE]

Piss off Mafia, the thread didn't ask 'are these cams suitable for my build which you know nothing about', did it??

Thanks Allan - still feel smooth to touch, appears to be some discolouration from sitting unused for a period of time. Mainly seeking feedback if people have seen this sort of thing deteriorate rapidly or if it's purely cosmetic. Now I've shown the previous owner he says they've been run as pictured in his race engine with no issues which is somewhat reassuring.

Edit - thanks Scott, I'll speak to the head shop about micropolishing.

Edited December 26, 2011 by DCIEVE

[The Mafia]

Most shops stick them on a slow lathe and use sand paper anyway.

Last thread about the size of cams were mentioned, the guy had no clue and didn't realize that 270s were going to be unsuitable for a standard engine and mid sized turbo limited to 7k. he thanked us and went a pair closer to 256 or 260.

But I have no idea who you are or what you're building so if you're going to be like that then you can jam it right up your ass. Sideways.

P.s. I wet and dried my poncams and they came up like new. Never had an issue.

[33GTRV]

Just be sure they dont have to polish them too far. Thats why i always try a bit of 100 or 1500 wet and dry first. If it comes off easy then keep at it, if its deep and isnt going to budge, send them in to the machine shop. They may even say to grind them back, metal spray them and have them re-ground to original spec's so just be prepared. If you are going to try the wet and dry polish at home remember to not go too hard on it, just light and easy and remember to not concentrate on any one sopt for too long.

Good luck and get beer

Cheers, Allan

[MrStabby]

Piss off Mafia, the thread didn't ask 'are these cams suitable for my build which you know nothing about', did it??

Maf was trying to stop you potentially wasting your time and/or money, because a lot of guys go for cams that are too big. If you're confident with your sizing, you could say "no worries, I've done my homework with cam sizing" and leave it at that.

I'd use fine paper wet with engine oil if you're going to paper them. I used 1200 grit wet with brake fluid on my brake pistons - came up nicely and worked well in service. Sandpaper should be low very low risk if you go slowly with a fine paper and check the surface regularly.

[DCIEVE]

Constructive comments appreciated.

Mafia and Stabby - if the mafia wants to make condescending comments about cam selection in a thread about cam wear then he can expect to get a 'short' reply.

[Hanaldo]

Piss off Mafia, the thread didn't ask 'are these cams suitable for my build which you know nothing about', did it??

+1.

Having seen Nick's car in the flesh... The man knows what he is doing

[The Mafia]

As I said, I had no idea what you were building or who you are.

9\10 threads about cams, the op has no idea.

The fact that you came asking about something as simple as surface rust lead me to believe that you may have been a rookie that was looking at some cheap cams from jimmy around the corner.

Put it all together and it looks as it looks. I was trying to help out a potential rookie.

But, you came out with your chest puffed out and lots of dickhead attitude instead of correcting me.

Anyway, good luck with your surface rust.

[NoFigJamHere]

Mate fact is if you say the "surface rust spots" cant be felt with your finger dont worry about it.... The important thing/part to look at is right on the crest (top) of the lobe...U dont want pits there at all.. Ive used 282deg 11.0m lift cams on a few engines and all being done/setup correctly theyre not that bad.

[NoFigJamHere]

BTW, they look like they have a small base circle, maybe 29,30mm so you'll need special buckets or really thick shims. Cheers n good luck

[GTR_JOEY]

Dude u pulled my stock cams out if my engine in the same if not worse condition in terms of surface rust...

Engine ran fine with them, not sayin it's a good thing at all and I would defiantly clean them up...

How the he'll does this happen by the way? Surely they dont go in clean and come out with surface rust!

[Gerg_R31]

surface rust / heat stains, though they do look a little porus (as in metal sprayed then ground to a large size, not ground from a billet, cheaper to manufacture) but thats all i can get from a picture

but i wouldnt stress about them not looking pretty if you cant feel it

at minimum id recommend a Linish as micro-polishing is a completely different process which takes about a week (but if you got the coin id recommend to get them micro-polished)

this is coming to you as first hand information from someone who is qualified in the engine machining industry

(and go easy on mafia he knows his stuff)

linishing

http://image.turboma...haft+polish.jpg

micro-polishing

http://media.photobu...d/esp_armor.jpg

[GTScotT]

I think linishing can impact tolerances though, whereas I'm of the belief micropolishing wont harm the specs of the bearing section

I'm happy to be corrected there though. I just see it more of a mission to linish then tunnel bore (if needed) than paying a little extra to micropolish. I think phone calls would need to be made before going any further either way, pitting is never good for soft metal bearing sections (IE cast sticks into an alloy head or cast crank into copper bearings).

I did happily use a pitted flywheel recently though (with a brass clutch) lol

[DCIEVE]

BTW, they look like they have a small base circle, maybe 29,30mm so you'll need special buckets or really thick shims. Cheers n good luck

Yes correct, this head & cams have been run on another SAU members race engine and are simply being rebuilt before going on a new short motor. The machinist is shut for Chistmas so I thought I'd get a second opinion.

But, you came out with your chest puffed out and lots of dickhead attitude instead of correcting me.

I had/have no interest in being baited into an e-battle about cam selection so the alternative was telling you to take your advice elsewhere. I would apologise for not being delicate enough but your the one throwing the insults.

[The Dan]

As suggested - rub them lightly with wet and dry sandpaper. If, after that, your fingernail gets caught on any pitting or imperfections, they will be no good for use in any reliable form.

As for camshaft sizes, 270 x 11.4 is nothing. Lift is critical for maximum torque gain. Duration is what will effect the RPM range of its efficiency. And even then, are they 270 at 0.020 or 270 at 0.050? What is the ramp duration? If no one knows the answer to that then speculating what they will and won't do is a silly idea.

[GTR_JOEY]

So effectively all lift does is get more air in/out because the valve opens more but still opens and closes at the same time.... Correct?

Where as a larger duration will extend the time in which a valve is open and there for move the power to a different point in the band... Correct?

Also duration is calculated by the amount of engine degrees that the inlet or the exhaust is open for while LSA lobe separation angle is the amont of overlap of the inlet and exhaust...correct?

These are half startment half question replys btw